Download Lecture 2 and text (pg. 1,2,12-14) 1. What are some properties of life

Lecture 2 and text (pg. 1,2,12-14)
1. What are some properties of life?
Adaptations
Growth and Development
Order - ordered structure
Energy processing
Reproduction
Regulation of body processes
Response to environment
Evolutionary adaptation
2. Evolution is the "overarching theme in biology".
3. Why do biologists pose questions and then try to answer them, rather than simply setting out to "study"
some phenomenon?
By asking questions, forming hypotheses, we have a focused topic that can be experimented on.
4. What is a hierarchical system of classification?
Linnean classification is a kind of taxonomy which names individuals based upon levels of similarity.
The
following are also examples of classification:
Taxonomy, Emergent Properties, Levels of organisms and life on earth
5. The terms Ursus and genus (Fig. 1.14) are not synonymous but they are
linked. How are they similar and how are they different?
Genus is the classification name, Ursus is a one of those names and is a genus
6. What are the three domains of life?
Archaea, Bacteria, Eukarya
7. What is the difference between a prokaryotic and a eukaryotic cell (check
your glossary)?
Eukaryotes have a nucleus enclosed in a membranous sac
8. What are the four traditional kingdoms of eukaryotes? Which one is now
thought to comprise numerous kingdoms?
Protists are now numerous
Anamalia
Plantae
Fungi
Protists
Things to think about
Think of this course as the diversity and UNITY of life
However, we consider viruses as non-living because they cannot replicate on their own
Insects are arthropods, which is the largest group of living organisms whereas Mammals are a
relatively inconsequential and diverse grouping in terms of size/numbers
Two complementary approaches to our studies
•Diversity of Life
•Unity of Life
Classification
Classification shows connections/unity through similarities and diversity through differences
Characters are any attribute which is considered separately from the whole organism for the purpose of
comparison, identification, or interpretation
Character/ expression of character can be used to find the state. For example, our hand has the character of
digits. The state of fingers is yes or no (either you have fingers or you don't). The state is usually four
fingers, one thumb.
Characters are chosen by distinction - characters vary.
Groups
We define groups in different ways.
Hierarchical Grouping - you can have groups within groups
Can be shown through tree diagram
Hierarchical Systems
Aristotle - species as fixed and arranged on scala naturae
- classified animals into two groups
Blood - born
Bloodless - insects shelled animals
*Now called vertebrate and invertebrate
Aristotle's Basic Questions
What is the vital principle (life)?
Is it the same for all creatures?
What is required to maintain life (physiology)?
How does "like" beget "like"?
What is responsible for the diversity of creatures?
What can account for the similarity among creatures?
Linnaneus
Used artificial classification
Binomial Nomenclature - all species have a latin name of genus and epithet (adjective) or species
Linnaeus - Species Plantarum
Post Linnaean Systems
Strove to be "natural" systems based on overall similarity
Lecture 3 (453, 537-538,1246-1250)
1. How did Aristotle view biodiversity?
Life-forms could be arranged on a ladder of increasing complexity: the scala natura or scale of nature.
2. What is binomial nomenclature and how does it relate to Linnaeus's views of classification?
Linnaeus grouped similar species into increasingly general categories. Similar species were grouped into
a
similar genus, but had their own specific epithet, making a binomial name.
3. What is a taxon?
The named taxonomic unit at any level of the hierarchy
4. What components make up a species' scientific name?
Genus and specific epithet
5. Provide an example of a category, as the term is used in Linnaean classification.
Kingdom, phylum, class, order, family, genus, and species are categories
6. What are the three main levels at which biological diversity can be described?
genetic, species, ecosystem
7. Identify three main threats to biodiversity.
8. Describe an example of a benefit to humans derived from biodiversity
9. What is meant by the term ecosystem services?
Modern Views of Biodiversity
Current Hierarchical System
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
P
P
E
Binomial Name
Both genus and epithet and in the species name
eg) Canis lupus - wolf
Zea mays - corn
Hierarchical Systems can be shown as tree diagrams
Darwin and the Galapagos
Recent volcanic origin - important bcuz species on island came there by dispersal, islands were
never
connected to another land mass
Most species were unique
Most were similar to species in South America - consistent with idea that species on Galapagos got
there from long distance dispersal from nearest land mass
Finches showed diversity based on different islands and habitats - spatial isolation supported Darwin's
idea of the roles in natural selection and adaptation in evolution
What is Biodiversity?
Genetic Diversity - differences in DNA and traits
Species Diversity - human diversity
Ecosystem Diversity - differences in climates
Loss of Biodiversity
Genetic diversity
Genetic variation is diminished with population extinction
Species diversity
Numerous species endangered or threatened
Species loss has escalated dramatically in the recent past
Ecosystem Diversity
Highlights interactions among species and environment Some keystone species in danger
of
extinction (pollinators) Some habitats are disappearing quickly (wetlands, riparian systems)
Why preserve biodiversity?
Species and genetic diversity
o biophilia
o plants are sources of many economic products including medicines
o Taq polymerase example
Ecosystem services
o The notion that we benefit from proper operation of the ecosystems we inhabit
o Example of New York City
Loss of Biodiversity
Genetic variation is diminished with population extinction
Numerous species endangered or threatened
Species loss has escalated dramatically in the recent past
Highlights interactions among species and the environment
Some keystone species in danger of extinction (pollinators)
Some habitats are disappearing quickly
Why preserve biodiversity?
Species and genetic diversity
- Biophilia
Humans like diversity and feel it is a tragedy to lose species
- Plants are the sources of many economic products including
medicine
Taq polymerase - the enzyme that allows the polymerase chain
reaction to occur for DNA replication
Ecosystem Services
Lecture 4 (14-18, 452-458)
1. Evolution is the process that best explains the unity of life.
2. The character that reflects the overall unity of life is DNA.
3. In Darwin's view, the source of the selective force acting on populations over many generations was
Natural Selection.
4. How are the broad sense and narrow sense definitions of evolution (pg.
452) directly related to each other?
5. How did the Linnaean system of classification support the theory of
evolution?
6. Distinguish between catastrophism and uniformitarianism and identify the
major proponents of each theory.
7. How were Lamarck's ideas of evolution different from our current
understanding of the process?
8. Darwin's observations of South American species (both extant (living) and
extinct (fossil)) provided important insights. What were his conclusions?
9. Darwin's observations of Galapagos species provided important insights.
What were his conclusions?
10.Who was A.R. Wallace and what were his contributions to evolutionary
biology?
11. Darwin adopted the analogy of a "tree" or branching diagram as a means
to present evolutionary relationships. How do these trees show both descent and modification?
The Greatest Threat to Biodiversity
A. Habitat Loss
agriculture, cities, industrial processes, global warming
B. Introduced Species
global travel, species freed from natural constraints
Zebra mussels, purple loosestrife
C. Overexploitation
Over-harvesting
Conservation Biology
Protect genetic, species, and ecosystem diversity
Darwin and Evolution
Embraced idea of gradualism
Geology - change over time
- Gradualism and Uniformitariansim - earth changes slowly
Hutton and Lyell
- Catastrophism - periodic catastrophes explained evolution of the earth
Cuvier - species occurred at one time then became extinct
Lamark - biologist - species could change
- inheritance of acquired characteristics
- use and disuse
Darwin
Descent with Modification
Natural Selection explains modification
Darwin and the Galapagos
•Recent volcanic origin
•Most species were unique
•Most were similar to species in South America
•Finches showed diversity based on different islands and habitats
Propinquity of Descent
Kinship/ relationship: offspring look like parents
Common Ancestry explains similarity
Used a classification system to come up with this idea
Hierarchy exists because of this
Credits Linneaus - Characters do not make the genes, BUT genes make
characters
- Something more is included in this classification than mere resemblance
Unity and Diversity of Life
Descent with Modification
is based on the 'Malthusian struggle'
is similar to artificial selection
Lecture 5 (458-461)
1. What is artificial selection and how does it work?
2. How does natural selection differ from artificial selection?
3. What contribution did Malthus make to Darwin's ideas on natural selection?
4. What were Darwin's four observations and two inferences, relating to his
theory of natural selection?
5. How does natural selection result in adaptation?
6. What biological entity responds to natural selection? (i.e. what is it exactly
that evolves over time?)
7. In the studies of guppy natural selection, two important selective forces
were identified. What are they and how do they work?
8. What were the results/conclusions of the guppy study?
9. How long does it take for HIV resistance to evolve in a patient taking HIV
drugs?
Natural Selection
- based on "Malthusian struggle"
- similar process to artificial selection (practiced in agriculture, breeding)
Overproduction of Offspring
Occurs to sustain population
Unchecked, over reproduction results in an extraordinary number
Artificial Selection, Natural Selection, and Adaptation
•Darwin noted that humans have modified other species by selecting and breeding individuals with desired
traits, a process called artificial selection
•Darwin then described four observations of nature and from these drew two inferences
Darwin's Observations
1. members of a population often vary greatly in their traits
2. traits are inherited from parents to offspring
3. all species are capable of producing more offspring than the environment can support
4. owing to lack of food or other resources, many of these offspring do not survive
Darwin's Inferences
1. Individuals whose inherited traits give them a higher probability of surviving and reproducing in a
given environment tend to leave more offspring than other individuals
2. This unequal ability of individuals to survive and reproduce will lead to the accumulation of
favorable traits in the population over generations
see ch 1 review p. 25 population of organisms flow chart
Biology 1020 Lecture 6 (468-471, 478-481, 483-484)
1. What is the smallest unit that evolves?
Populations. Microevolution is evolutionary change below the species level; change in the allele
frequencies in a population over generations.
2. Who discovered genetics and when?
Mendel 1865, after Darwin's 1859 Origin of Species
3. What is a "cline" in geographical variation?
A graded change in a character along a geographic axis.
4. Define mutation.
A change in the nucleotide sequence of an organism's DNA, ultimately creating genetic diversity.
5. How does a point mutation differ from a gene duplication?
6. How does sexual reproduction generate variation among organisms?
7. How does gene flow between populations shape patterns of genetic variation among populations?
8. What is relative fitness, and why is it important?
9. Is relative fitness a characteristic of the gene, the genotype or the individual?
Individual
10. Distinguish between directional, stabilizing and disruptive selection.
11. Describe two examples of balancing selection.
12. Why, in spite of natural selection, are organisms not perfectly adapted to their environment?
Descent (Unity) with Modification (Diversity)
Natural Selection explains diversity, therefore diversity would be maintained between populations.
However, it would reduce variation within a population.
Evolution - the change in the genetic composition of a population from generation to generation
Arguments against Natural Selection
1. Darwin embraced Lamarckian inheritance which was disproved
2. Lacked any explanation of inheritance
Darwin vouched for "blended" inheritance
3. Difficult to explain the evolution of complex characters
Mendel and Modern Synthesis
Mendel's work published in 1865 (Darwin's was same time, 1859)
Hugo Devries rediscovered Mendel's work in 1900
Genetics is incorporated into evolutionary theory in the 1940s (Fisher and Wright)
Genetic and Non-genetic Variation
Biology 1020 Lecture 7 Text Reading questions (487-498)
1. What is the biological species concept?
Definition of a species as a population or group of populations whose members have the potential to
interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring
with members of other such groups.
It highlights the importance of gene flow as a unifying force
2. What is the importance of gene flow in the evolution of species?
Diversity and variation
3. Reproductive isolating mechanisms can be classified into two groups.
What are the two groups?
4. What are the kinds of isolating mechanisms in each group?
5. Why is the presence of Allele 1 in Population B (Fig. 24.3) evidence of a
gene flow event?
6. What are two limitations of the BSC (biological species concept)?
7. What are three alternative species concepts? How do they differ from one
another?
8. Distinguish between the two main speciation models (allopatric vs
sympatric).
Allopatric Speciation - geographical isolation
Sympatric Speciation - same country
9. What is the evidence that reproductive isolation evolves as a by product of
divergence, rather than via direct selection for the trait itself?
10.What is polyploidy and how does it result in sympatric speciation?
11.What are two other factors that may lead to sympatric speciation?
Species - A population or group of populations whose members have the potential to interbreed in nature
and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other
such groups.
Speciation - an evolutionary process in which one species splits into two or more species.
Microevolution - evolutionary change below the species level; change in the allele frequencies in a
population over generations.
Macroevolution - evolutionary change above the species level, including the origin of a new group of
organisms or a shift in the broad pattern of evolutionary change over a long period of time. Examples of
macroevolutionary change include the appearance of major new features of organisms and the impact of
mass extinctions on the diversity of life and its subsequent recovery.
Population - group of individuals that interbreed -- gene flow occurs
Cline - a graded change in a character along a geographic axis.
Selection requires genetic variation
How does genetic variation arise?
- mutation
o point mutations
o macromutations
like mouse example where chromosomes change
doubling genome
we have 46 chromosomes
- sexual reproduction
o mixes genes into new combinations to maintain diversity
Gene Flow affects variation patterns within and between populations
To prevent gene flow in plants near or further from a mine, a wind breaker could be set up. Copper
tolerance is important in plants nearest the mine.
Natural Selection
From a populational standpoint
When we look at a phenotype, we can describe them quantitatively to show the numbers expressing each
trait.
Directional selection - selection of one or the other extreme of a trait
either white or black color)
cows that produce most milk
Disruptive selection - selects against the mean of a trait
Stabilizing selection - selects for the mean
- the average is the best and reduces the extremes
Natural Selection Results in Adaptation
The Preservation of Genetic Variation
- Diploidy
o One haploid genome may compensate for harmful mutations in other
o Heterozygote advantage
- Balancing Selection
o maintains two or more phenotypic forms in a population.
- Frequency dependent
o decline in the reproductive success of individuals that have a phenotype that has become
too common in a population
The existence of anti-malarial drugs:
Increase disadvantage of heterozygote
Heterozygotes are malaria resistant
The sickle-cell allele is most common
Adaptation is imperfect
1) works on existing variation
2) historical constraints
a. different groups have different traits
b. design based on what was there before
3) Time lag
a. Environment changes first, characters change after
4) Trade-offs
a. compromises
b. A character may be functioning in two different ways that may be contradictory
c. Call of the frog attracts mates, but also notifies predators therefore the mating call is
also bad
5) Chance
a. Cataclysmic events
b. Plays a role in evolution
Biology 1020 - Text Questions Lecture 8 Hybridization (498-504)
1. What is a hybrid zone?
2. What are the possible outcomes of a hybrid zone once it has formed (Fig. 24.14)
3. What is reinforcement and why does it occur?
4. What factors might promote fusion of two species?
5. What factors might promote the formation of a persistent hybrid swarm?
6. What is the average time required for speciation to occur? What is the fastest time recorded?
7. Does speciation require divergence among a large number of different genes or can it occur with minimal
genetic divergence?
Two patterns of evolutionary change
(1) Anagenesis - populations replace each other over time
(2) Cladogenesis - divergence: change that involves a branching path
Speciation causes divergence
Species Concept
How species are looked at
Biological Species Concept
Morphological species concept - species are fundamentally the same
Phylogenetic species concept - branch of a tree
Ecological species concept - species occupies unique niche
Reproductive Isolation Mechanisms
Prezygotic Barriers
Postzygotic Isolation
Example: donkeys and horses interbreed but have infertile offspring
Habitat Isolation
Two species never interbreed or exchange genes because they have different habitats
Temporal Isolation
Reproductive patterns separated by time
Behavioral Isolation
Based upon mate selection
Example: mating dances in birds
Mechanical Isolation
Genetalia do not align correctly
Gametic Isolation
Example: sea urchins project spores/ gametes into water
Postzygotic Barriers
Reduced hybrid viability
Reduced hybrid fertility
Example: donkey and horse produce a mule
Barrier to gene flow
Hybrid breakdown
First hybrid is viable but generations become weaker
Gene Flow
Allopratric Speciation - physical separation
Isolating mechanism is geographic
Sympatric Speciation - even though gene flow is possible, some factor prevents
Habitat differentiation
Polyploidy
Sexual Selection
Gene flow is a barrier to sympatric speciation
Biology 1020 - Lecture 9 (461-466, 536-540)
1. What two major evolutionary phenomena are well documented in the fossil record? Extinction and
change
2. How does the fossil record provide a means of testing evolutionary hypotheses? Age of different fossils =
what evolved from what
3. Define homology?
Similarity in characteristics resulting from a shared ancestry.
4. Why do homologies show a nested pattern?
5. How can ontogeny (=developmental patterns) provide evidence of evolutionary relationships?
6. How does the evolution of analogous structures by convergent evolution differ from the evolution of
homologous structures?
7. How does our understanding of continental drift provide evidence supporting evolution?
8. What is a phylogeny?
the evolutionary history of a species or a group of species
9. What are sister groups (=sister taxa) in a phylogeny?
10. How is classification linked to phylogenetic trees?
branching diagram that represents a hypothesis about the evolutionary history of a group of organisms
Sympatric Speciation
Polyploidy - doubling of the genome
Autopolyploidy
Doubling of the chromosomes
Failure of cell division after chromosome duplication gives rise to tetraploid tissue
The gametes that are produced are diploid or 2n
Offspring with tetraploid karyotypes may be viable with others of this kind and fertile and
would have 4n genome
Allopolyploidy
Doubling of the chromosomes
More common, although more complex than autopolyploidy
Functions as a gamete with twice as many chromosomes
New species is a hybrid
Allopolyploidy Example - Fast speciation event
Species A: 2n = 6
Normal gamete: n = 3
Species B: 2n = 4
Unreduced gamete: n = 4
Hybrid Species 2n = 10
Habitat Differentiation
Often relates to host shift
The environment of the parasite is a host, sometimes it can shift from one host to another host. For
example: parasite moving from hawthorne tree to apple tree. The individuals on the apple tree will
interbreed. The parasites on the two trees are ABLE to interbreed because gene flow is possible. However,
the habitats now differ.
Sexual Selection
Mate selection
Female chooses a specific type of male
Gene flow is possible, but females choose against it
For example, female could chose different appearance, causing divergence
Possible Hybrid Outcomes for species:
Reinforcement
o hybridization is disadvantageous
oMore difference between sympatric populations than allopatric ones
oPre-zygotic isolation mechanism in overlapping areas to prevent hybrids
oHybrid zone lessens
Fusion
o Potential in a hybrid zone where convergence occurs back to one species
Stability
o Stable Hybrid Swarm
- 3 species involved
o status quo relatively maintained
Hybrids could backcross with their parents and dilute the parental gene pools. This implies the ability of
selection into the future.
Why might reproductive barriers.?
If the hybrids are unfit or sterile, they only have so much reproductive potential. This is a disadvantage.
Hybrids reduce the reproductive capacity of their parents.
You would expect pre-zygotic isolating mechanisms to be:
More common between sympatric species pairs
Because hybridization can only occur within sympatric species pairs
How fast can speciation occur?
6 million years average
But speciation CAN happen very fast
Patterns of Divergence in the Fossil Record
Provides evidence of speciation and evolution
(a) punctuated pattern
a. quickly at the beginning, becomes stable
(b) gradual pattern
a. change is slow
Biology 1020 - Lecture 10 text questions (540-548)
1. •What is a homoplasy?
Similar (analogous) structure or molecular sequence that has evolved independently in two species.
2. •How/why do homoplasies evolve?
Convergent evolution
3. •What is a clade?
A group of species that includes an ancestral species and all its descendants.
4. •Distinguish among mono, para and polyphyletic groups.
Monophyletic: group of taxa that consists of a common ancestor and all its descendants. A monophyletic
taxon is equivalent to a clade.
Paraphyletic: group of taxa that consists of a common ancestor and some, but not all, of its descendants.
Polyphyletic: group of taxa derived from two or more different ancestors.
5. •What is the difference between a shared ancestral homology and a shared derived
homology?
6. •What is an outgroup? What is an ingroup?
7. •What information does an outgroup provide in phylogenetic analyses?
8. •What is the principle of parsimony? What information does it provide in
phylogenetic analyses?
The principle states that when considering multiple explanations for an observation, one should first
investigate the simplest explanation that is consistent with the facts.
Phylogenies are a simple as possible
9. •What is the principle of maximum likelihood?
States that when considering multiple phylogenetic hypotheses, one should take into account the
hypothesis that reflects the most likely sequence of evolutionary events, given certain rules about how DNA
changes over time.
10. •What is phylogenetic bracketing? On what principle is it based?
Anagenesis: speciation over time without branching
Cladogenesis: speciation with branching
Speciation builds the tree
Common ancestor - > speciation - > divergence
Homology
How do we recognize homology?
Similarity in characteristics resulting from shared ancestry
Similar structure, same ancestor
If it is a complex structure and still similar, it is likely homologous (underlying bone structure of limb in
human, cat, whale, and bat)
Similarity = homology
1. Complex structures
2. Development
3. Genes
Developmental processes
In early stages of development of an organism, we see shared characteristics that are not observed in
adults. This suggests developmental processes have evolved only in later stages and therefore later stages
are more derived (early stages are conserved). Human embryo and chick embryo are similar with
pharyngeal pouches and post-anal tail.
Since humans and chickens have similar developmental processes and underlying bone structure, they
are
likely homologous
Ontogeny recapitulates Phylogeny
Development (repeat evolutionary stages as embryo) Phylogeny
Embryological homology
Analogy
Similarity resulting from convergent evolution
Analogy: wing of bats and birds
Common ancestor did not have wings
Wings evolved at different times and after divergence from ancestry
Flying is a result of convergent evolution
Homology: forelimb of bats and birds
Far back ancestor had a forelimb before divergence occurred
Analogy: Fish with fins and Whale has a swimming forelimb
Phylogenic Trees
In constructing a phylogenic tree, we ignore analogies
There is one true evolutionary tree of the history of life forms on Earth.
The history predates humans, so it is hard to know it is true.
How do we find it?
Our classification should reflect it
TREE TERMINOLOGY
Common Ancestor is represented by a node of the tree
We construct the tree to be dichotomous
A polytomy is more than two branches from a node
A taxon - species, genus, or family depending on what level you are constructing your tree
Sister taxa - arise from the same common ancestor and are therefore each other's closest relative
Molecular Homologies can be very detailed
Tree Constuction - based on two main concepts:
(1) The principle of parsimony
based on the assumption that evolution proceeds by a smaller rather than a larger number
of events
Occam's Razzor
way of reasoning when have little information
where you don't know, go for the simplest hypothesis/ fewer steps
Can be used to construct a tree with characteristics
Can demonstrate evolution reasonably and helps us choose the best tree
(2) The use of shared derived homologies
Ancestral trait that changed into a derived trait
Homology must be traceable - talking about same character
Derived Homologies are important because they represent change
Change is what defines a phylogenic tree
How do we know what is derived?
Fossil evidence - more complete the fossil record is, the better a source
Outgroup Comparisons
Sister group of the Ingroup, assume outgroup has ancestral trait
Use parsimony - the simplest way for a trait to have been derived
Construction of Phylogenetic Trees
Choose a study group - ingroup
Designate the outgroup - the closest relative
Choose characters (homologies)
Polarize the characters
(ancestral vs. derived through outgroup comparisons)
Score the characters (A, B, C, )
Construct the most parsimonious tree
If you are building a phylogeny of cats in the broad sense, you need an outgroup that is NOT in the ingroup
as a comparison to the felines
Ingroup: lion, tiger, leopard, domestic cat
Outgroup: wolf
How do we translate phylogeny into classification?
Monophyletic - We look mostly for monophyletic groups based upon shared derived characters
- common ancestor and all of its descendants
Paraphyletic - shared ancestral homologies, not consistent with the tree (if you have to cut away twice to
separate the group)
- common ancestor and some descendants
Polyphyletic - based on shared analogies, not what we want to classify on
- does not include common ancestor
Fundamental Questions on the
Origin of Life
How could complex organic molecules form abiotically?
How could metabolism and replication evolve simultaneously?
How could cell membranes develop?
How could all of this happen so fast?
Life arose about 3 to 4 billion years ago
When?
• Earth formed about 4.6 bya (billion years ago).
• BUT: Planet continued to be bombarded by asteroids and comets for at least 500 million years.
• Evidence suggests life originated at least 3.8 bya.
• Either life originated fairly quickly (< 500 million years) or it originated in "Hadean" conditions.
cyanobacteria - photosynthetic bacteria in a filamentus form
3.4-3.5 billion years ago evidence of Bacteria
we believe that something came before these bacteria because photosynthesis was not the first source of
energy and there are simpler forms
How?
• Abiotic synthesis of small organic molecules such as amino acids and nucleotides - provided
building blocks of life.
• Joining of these small molecules into macromolecules (proteins and nucleic acids)
• Packing of these molecules inside a membrane.
• Origin of self-replicating molecules.
Abiotic synthesis on earth
• Miller-Urey experiment in 1953 showed that organic molecules could be produced abiotically, under
conditions plausible for the early earth.
• Early atmosphere may have been composed of methane, hydrogen, water vapour, and amonia. Organic
molecules can be created from these compounds.
Abiotic synthesis in space
• Evidence from meteorites shows organic synthesis is common in space.
Meteorites contain carbon.
• Murchison Meteorite showed bases found in nucleosides, and also amino acids.
• Found L forms of amino acids slightly more common than D - basis for homochirality.
They are mirror forms of each
Living cells only use the L-form
• THEORY:
Organic molecules may have rained down on earth during its early history.
What conditions?
Conditions that favour the formation of molecules essential to life on Earth
• Many different hypotheses because different organic molecules seem to require different conditions for
abiotic synthesis.
• Boiling temperatures aid synthesis of cytosine and uracil.
• Freezing conditions aid the synthesis of adenine and guanine.
• Freezing may also aid polymerization of RNA - a macromolecule
Joining of these small molecules into macromolecules
(proteins and nucleic acids)
Polymer formation
• Generally polymerization is energetically unfavorable reaction.
• Some conditions may have favored polymerization:
- On a drying clay surface.
- Using energy from redox reactions, perhaps using high energy sulphur compounds from volcanic
processes.
A problem
• Proteins require DNA as a template for synthesis.
• DNA requires proteins as a catalyst for synthesis.
• How could either be formed without the other?
So which came first? Neither! RNA came first because it can do both jobs.
RNA World Hypothesis
• Ribosymes can act as both a template and as a catalyst, and therefore could potentially act as a catalyst for
its own production - autocatalysis.
Peptidyl transferase, a ribosyme which forms part of the ribosome
Road to replication
•Autocatalysis
•Natural Selection
A+B=C
>C - the catalyst additional presence
Packing of these molecules inside a membrane.
Droplets and vesicles
• Lots of evidence that a variety of lipids can spontaneously form small droplets with a bilayer at the
surface.
• These can be relatively stable and even split to form "daughters".
• Phospholipid bilayers are highly impermeable to large organic molecules.
• Simpler lipids such as fatty acids or monoglycerides are more permeable, and allow nucleotides and
amino acids to enter.
• Mansy et al. (2008) created simple vesicles with a single-stranded DNA template inside.
Origin of self-replicating molecules.
Where did the origin of life take place?
Places where self-replicating molecules occurred
• Drying coastal beaches or pools.
• Deep sea vents.
• Deep in the earth's crust.
• In outer space - meteorite from Mars, where conditions for life at one time
Three Domains of Life
Domain Eukarya Domain
Bacteria
Domain Archaea
- extreme environments
single celled
more closely related to Eukarya than other prokaryotes (bacteria)
Great Moments in Evolution
•Virtually all important metabolic pathways evolved in Bacteria and Archaea.
•Photosynthesis - 2.7 billion years ago
•Aerobic respiration - 2.1 billion years ago
Evolution of Eukaryotes About 2.1 bya
•Nuclear envelope
•Membrane- bound organelles
•cytoskeleton
Closing thoughts
• Experiments and fossil evidence has begun to suggest some plausible pathways for abiotic synthesis of
monomers and polymers, and eventual evolution of protobionts.
• The RNA Hypothesis has gained much more credibility based on Lincoln and Joyce.
• By 2 bya, most important metabolic pathways had evolved, and life had diverged into 3 main branches.
Sex and Multicellularity
(More Great Moments in Evolution)
Mitosis
Meiosis
Sexual life cycle with
alternation of haploid
and diploid stages
Evolution of sex
Sex provides more recombination, which spreads favorable mutations faster.
• First step is evolution of mitosis.
• Problem: Mitosis is a complex process: How could it evolve?
Organs of extreme perfection
To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for
admitting different amounts of light, and for the correction of spherical and chromatic aberration, could
have been formed by natural selection, seems, I freely confess, absurd in the highest degree.
-- Charles Darwin
"Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect
can be shown to exist, each grade being useful to its possessor... then the difficulty of believing that a
perfect and complex eye could be formed by natural selection, though insuperable to our imagination,
should not be considered as subversive of the theory."
•Cytoskeleton evolved first in Eukaryotes, likely as ameoba-like locomotion.
•Microtubule-organizing complexes (MOC) evolved initially to control flagellae.
•MOC incorporated into nucleus for separation of chromatin.
•MOC later function in both nucleus and controlling flagellae (not at the same time)
•Evidence for this evolution based on examination of oddball single-celled Eukaryotes which don't have
mitosis, or have non-standard mitosis.
Gamete production
• Isogamy
- All gametes are identical.
- May be flagellated or unflagellated
• Anisogamy
- Gametes differ in size or appearance
- May be flagellated or unflagellated
• Oogamy
- Large unflagellatd egg and small flagellated sperm
Gametic Meiosis Fig. 13.06a
Sporic Meiosis Fig. 13.06b
Zygotic Meiosis Fig. 13.06c
Alternation of Generations
• Characteristic of Sporic Meiosis
• Two generations may be identical
- Isomorphic
• Two generations may look very different
- Heteromorphic
Benefits of diploid-dominance
• Greater genetic variability within offspring (or gametes) because many more gametes are potentially
produced from each zygote.
Benefits of Haploid dominance
• Faster growth of vegetative stage.
• May reduce mixing of vertically transmitted (gamete to zygote) parasites.
Benefits of Alternation of Generations
• Haploid and diploid stages may be selected for different environments or functions.
• But - what about isomorphic life cycles?
Evolution of Multicellularity
Benefits of Multicellularity
• Recall our plucky little eukaryotic cell.
• It's MOC can run flagellae or cilia giving the cell mobility, OR they can produce the spindles used in
mitosis. But NOT both at the same time.
• A colony of cells can get around this problem with cell specialization. Some cells specialize in motility,
while others carry out mitosis.
How?
• Multicellular individuals seem to be "organs of extreme perfection."
• Need to understand the transitional steps which allowed multicellularity to evolve.
What about cheaters?
• Multicellularity requires some cells to reduce or halt reproduction.
• Cells that "cheat" will increase their own reproductive success, and so may be favored by natural
selection.
• Mechanisms to prevent cellular "cheating" are common, particularly in animals. E.g. germ- line
sequestration, early determination of cell fate.
Closing thoughts
• Large innovations such as mitosis and multicellularity evolved through a series of small transitional steps,
each providing a benefit.
• The costs and benefits of different lifestyles and life cycles are likely specific to individual lineages,
producing the high degree of variation we see in nature.
• Sex likely evolved to provide greater recombination rates, perhaps as a way to combat parasitism.
PROTISTS
Pages 575-589
What are protists?
• Eukaryotes which aren't animals, plants or fungi.
Survey of the Protists
Diversity
Modes of Nutrition
• Photoautotroph
• (chemo) Heterotroph
- Predators (Herbivores/Carnivores)
- Parasites
- Decomposers/Detritivores
Modes of Locomotion
• Cytoplasmic streaming or amoeboid motion
• Flagellae or cilia
Life Cycles
• Gametic, Zygotic and Sporic Meiosis
• Simple and complex (mainly parasites)
• Sexual and Asexual
SUPERGROUP EXCAVATA
• Some members have grooves or "excavations" on their body
Euglenozoans
• Metabolically extremely diverse.
• Some members are predatory or parasitic heterotrophs. Others are autotrophs
• Some are mixotrophic - can shift between p/s and heterotrophy.
-
long flagellum
eyespot
short flagellum
contractile vacuole
nucleus
chloroplast
plasma membrane
pellicle
Chromalveolata
Dinoflagellates
Apicomplexans
Aid in digestion
Ciliates
Phagocytosis and food vacuoles
Oral groove
Cell mouth
Food vacuole
Contractile vacuole
Macronucleus
Micronucleus
Cilia
Diatoms
Brown Algae
Dominant sporophyte (2N)
Oomycetes
Diploid (2N) Hyphae dominant
Asexual Reproduction
Zoosporangium
Zoospore
Cyst
Germ tube
Hyphae
Sexual Reproduction
Hyphae undergo Meiosis
Oogonium contains egg nucleus (N)
Antheridial hyphae with sperm nuclei (N)
Fertilization
Zygote
Zygote germination
Hyphae
Closing Thoughts
• Protists show tremendous diversity in structures and behavior.
• While they may often go unnoticed in our day to day lives, they form critical parts of the biosphere (more
on this next week).
• The protists can be organized into five supergroups, but members of the groups are extremely diverse,
and some groups are not universally recognized yet.
SUPERGROUPS
Pages 589-599
Excavata
Euglenia - photosynthetic
Chromalveolata
Autotroph or photosynthetic
Rhizaria
Forams
Pseudopodia projecting from shell are slender
Slender openings in the shell from which pseudopodia extend
Heterotroph
Fossilize when sink to bottom of ocean
We can use them as markers to date particular sedimentary layers
Radiolarians
Shelled amoeba
Plasma membrane is outside of shell
Slender pseudopodia
Delicate shell made of silicon (like diatom shells)
Archaeplastida
Red Algae
Can be single celled or multicellular
Photosynthetic
Most have cell walls made of cellulose
Mostly chlorophyll a and accessory pigments
No flagellated stage
Red algae are red because
Physiology:
They contain accessory pigments that absorb blue and green light
Phylogenetic: Their ancestors were red
Functional:
So they can live in deep water
Green and blue light penetrate deeper through water
Life Cycle
Sporic meiosis
Carposporophyte
Also have a cystocarp which is an intermediate
Tetrasporophyte
Nori red algae are used to wrap sushi
Land Plants
Green Algae
Chlorophytes
Charophyceans
Chlorophyll a and b
Cell wall made of cellulose
Large surface area: gases exchange or light collecting area
Life Cycle
Zygotic meiosis
Some few examples of sporic meiosis
Morphology can be
single-celled
colonial/ filamentous
multicellular
Unikonta
Fungi
Animals
Plasmodial Slime Molds
Cytoplasmic Streaming
Similarity to fungus, are mobile through cytoplasmic streaming
Live off of rotting vegetation or logs
Live in damp terrestrial conditions
Multinucleid
Not multicellular
One common cytoplasm that flows down the veins
Plasmodium - feeding structure
Like animals, Diploid is the adult part of the life cycle
Gametic meiosis
Spores are produced through meiosis
Diversity of sporangium
Life Cycle:
Zygote (2N)
Feeding Plasmodium
Mature Plasmodium (preparing to fruit)
Young sporangium
Mature Sporangium on a stalk
MEIOSIS
Spores (N)
Germinating spore
-Flagellated cells (N)
-Amoebid cells (N)
FERTILIZATION
Cellular Slime Molds
Asexual
Haploid dominant amoeba (N)
Spend most of time as single-celled amoeba
Spread spores
Sexual
Zygotic meiosis
Diploid Zygote (2N)
Produce haploid amoebas
Cells secrete cAMP
Gymnamoebas
Naked amoeba
Unshelled amoeba
No cell wall, just a cell membrane
Contractile valve
Food vacuole
Heterotrophic
Feed by phagosytosis
Move by cytoplasmic streaming which is done through cytoskeleton
Fresh water
Entamamoebas
Parasite
Live in guts of host
Choanoflagellates
We think the earliest animals were closely related to Choanoflagellates
Found in colonies
Colonies have similar structure to a spinal column
Cell body, microvilli, and flagellum
Ecological and Economic Role of Protists
Algae are the largest component of photosynthesis in the oceans
Diatoms and Dioflagellates
Protists are important to marine and fresh water food chains, recycling CO2
Open ocean:
Surface waters teem with microscopic protists, such as diatoms.
Shallow coastal waters:
Gigantic protists, such as kelp, form underwater forests.
Intertidal habitats:
Protists such as red algae are particularly abundant in tidal habitats.
PATHOGENS
Malaria is caused by Chromealveta
Toxoplasmosis
Dianoflagellates
Non-pathogenic
Archeaplastida - photosynthetic
Rhizaria - shelled
Protist Symbionts
• Symbiosis means "living together"
• Can be parasitic or mutualistic
Corals
Symbiotic dinoflagellate cells produce sugars from photosynthesis
Supply corals with sugar
Closing Thoughts
• Protists show immense diversity of metabolism, habitat and life cycle, which is not surprising, given how
long many of the lineages have been diverging.
• Protists are essential to global food chains and carbon cycling, and have huge impacts on human health
and wealth.
• Protist taxonomy and phylogeny remain controversial, and a subject of active research.
Lecture 16 (590-592, 600-601)
1. What characters unite the members of Archaeplastida?
Red algae, green algae (chlorophytes and charophyceans), and land plants:
Monophyletic group descended from an ancient protist that engulfed a cyanobacterium for
photosynthesis
2. What are the characteristics of red algae?
Reddish colour from accessory pigment, can live in very deep water, some are heterotrophic
parasites, most are multicellular, diverse life cycles of alternation of generations, no flagellated
stages, depend on water currents for fertilization.
3. Why are green algae currently a paraphyletic group?
Common ancestor: Archeaplastida
Land plants and red algae are not part of the group containing green algae
4. What are the two main groups of green algae?
Chlorophytes - mostly fresh water, can be unicellular or exist in colonies
Charophytes - complex life cycles, alternation of generations
5. Provide examples of chlorophytes you have seen in lab.
Volvox
6. What characterics define the Streptophyta?
Charophyceans and Embryophytes
7. What challenges needed to be met as plants evolved to inhabit a terrestrial environment?
Water and nutrients
PROTISTS
There are many paraphyletic groups that remain well accepted in our classification.
Paraphyletic groups help to highlight major adaptive shifts that have occurred in evolution.
Archaeplastida
The Archaeplastida is a monophyletic group including only:
Red Algae
Green Algae (Chlorophytes, Charophyceans)
Land plants
Rhodophyta - Red Algae
Mostly marine
Cell walls of cellulose and alginic acid (agar)
No motile stages
Parasites - mostly parasitic on each other
Complex Life Cycles
Pit Connections
Porphyra
Source of traditional Japanese food
Seaweed grown on nets
What is a Pit Connection?
There are two types relating to how cells connect with each other
Primary - cells connected by cytoplasm when daughter cells do not
entirely split after division
Secondary - formed between two cells which are not sister but still
end up connected by protrusions to connect cytoplasm
How parasitism takes place in red algae
Parasitic Red Algae
Parasite uses secondary pit connections
Parasite sends nuclei into the host
Revs up metabolism of the host
Parasite harvests what is being grown by the host
Life Cycle of Red Algae
Sexual Reproduction
Male and female gametophytes (2n)
Spermatangia (n) and egg (n)
Fertilization occurs
Zygote nucleus migrates to auxiliary cell through secondary pit connection
Zygote nucleus (2n)
Red Algae - Deep Water algae
Where is the compensation point where photosynthesis and respiration are
equal? As long as plant is consuming more CO2 than respiring - it will grow.
0.005% of 1% of surface illumination
Red Algae are extraordinarily efficient
268 meters deep
Green Algae
Green Algae are a paraphyletic group of Chlorophytes and Charophyceans
Just like plants, green algae have:
Chlorophyll A and B
Cellulose cell wall
Storage product: starch
Motile via flagella
Chlorophytes
Chlamydomonas
Small single cell with two flagella
Volvox
Colony shows multicellularity
Division occurs inside parent colony
To become motile, volvox must grow and then turn itself inside out because
to begin with, all flagella are pointing inwards
Sea Lettuce
Large sea animal like seaweed
Charophyceans
Closest algal relatives to land plants
Relatively small, microscopic
Spirogia
Micrasterias
Derived characters of Charophyceans and Land Plants
Mode of cellulose synthesis
Peroxisome enzymes
Sperm structure
Phragmoplast present
Spindle fibers outside of chromosomes
Characteristic of cell division
Fundamental to show sister taxa
Archaeplastida
Ancestral Algae
Red Algae, Chlorophytes, Charophyceans,
Embryophytes
Viridiplantae
Chlorophytes Charophyceans Embryophytes
Streptophyta
Charophyceans Embryophytes
Plantae
Embryophytes
Why are the plants not classified as green algae?
There are clear characters that separate them
Embryo retention
Grows in a chamber on the gameotophyte
Sporic meiosis
ALL plants have it - not just some
True alternation of generation
Terrestrial
Adaptive shift
Movement to land
Green algae
Can have alternation of generation
Not all are aquatic
Needs to survive: light, oxygen, CO2, water, nutrients,
PLANTS
The movement to land
Requirements for plant life
Light
Water
Nutrients
CO2 / Oxygen
Temperature
Reproduction
Lecture 17 (600-604, 612, 738-745)
1. What are four derived traits shared among plants?
alternation of generations
walled spores
multicellular gametangia
apical meristems
2. What is xylem and phloem? How do they differ?
Vascular tissue made of schlerenchyma cells
Xylem - water and mineral transport
Includes tracheids (tube-shaped cells)
Phloem -transport sugar, amino acids, and other organic products
3. What is lignin and how is it important in the evolution of vascular plants?
Lignin - phenolic polymer that strengthens cell walls making them inflexible
4. What are the three cell types and how do they differ from one another (744)?
Parenchyma - thin and flexible primary cell walls
Collenchyma - unevenly thick primary cell walls for support
Sclerenchyma - dead at maturity, and empty straws, with lignin inflexible
5. What is a tissue?
6. What are the three tissue systems (regions)?
Dermal tissue - epidermis, cuticle
Vascular tissue - transport
Ground tissue - everything else
Requirements for Plant Life
Water
Light
Nutrients
Carbon dioxide/ Oxygen
Temperature
Reproduction
Nutrients
C. HPKNS CaFe Mu An Mo Bo Cu Cl
Carbon, hydrogen, phosphorus, potassium, nitrogen, sulfur, calcium, iron etc
Survival Strategies on Land
Absorption and Retention
Water Light and Nutrients require absorption and some require retention as well
Absorption
Water and nutrients
Large below ground surface area
Light
Large above ground suface area
CO2 and O2
Large above ground
Retention
Water and nutrients
small surface area
above ground
Conflict between small above ground for water retention vs. large above ground for light and CO2 and O2.
Plants have cuticle to retain water
The First Plants
Vegatative
Simple prostrate structures
Flat, protected photosynthetic surfaces
Rhizoids for absorption and anchoring
Selection for support/water retention leads to structural complexity
Kingdom Plantae
Many homologies are shared with the green algae
Differences relate to:
-Selection for structure/ water retention
-Selection for protection and dispersal
Plant Anatomy
Cell types versus tissue types
Cell Types
Based upon cell wall structure
Relates to selection for support
All plants are made of three main cell types:
(1) Parenchyma
cellulose in primary cell wall
cell wall is relatively elastic - expand and stretch a little
basic plant cell
living cell capable of biological processes
(2) Collenchyma
uneven thickening of primary wall
some portions thicker than others
provides more support
living cell capable of biological processes
(3) Sclerechyma
Two cell walls
Primary(outside) and secondary (inward) walls
Lignin - hardening component of secondary wall, impenetrable by water
In most cases, these cells are very mature, and dead
Plant Tissue
Tissue - integrated group of cells with a common function or structure
Simple Tissues
Made up of one cell type:
Parenchyma
Collenchyma
Sclerenchyma
Complex Tissue
Made up of more than one cell type
Xylem
Phloem
Three Tissue Regions
Dermal Tissue - outside layer
Epidermis
Ground Tissue - everything else
Cortex
Pith
Vascular Tissue - transport /support
Xylem
Phloem
VASCULAR TISSUE
Vascular Tissue region containing two complex tissues which each contain two different cell types. Both
Xylem (transport water hard for support) and Phloem (transport sugars) are involved in transport.
Xylem: many sclerenchyma cells for hard support
Tracheids - has pits
Functions in both support and water transport
Tracheids diverge to form vessel elements (conduction) and fibres (support).
Vessel elements - perforated end walls
Specialized for water transport
Fibre Cell - specialized for support
Phloem: parenchyma cells
Transports sugars
From where it is produced to where it is needed
Sieve-tube elements
Clicker Question
Vessel elements are sclerenchyma cells that are part of the xylem and function in transport of water.
Lecture 18 (600-604, 612-613, 746-751)
1. What is an organ?
A specialized center of body function composed of several different types of tissues.
2. What is a stele?
A vascular cylinder, with core of xylem and phloem
A root has a protostele that is hard
3. How did leaves evolve?
4. What is an apical meristem and how does it relate to indeterminate growth?
It is embryonic plant tissue in the tips of roots and the buds of shoots. The dividing cells of an apical
meristem enable the plant to grow in length.
5. What is primary growth?
Growth produced by apical meristems, lengthening stems and roots
6. What is the structure of a root apical meristem?
7. What is the structure of the root stele (Fig. 35.14a)?
8. How do lateral roots form?
9. How is the shoot apical meristem different from the root apical meristem?
10. What is the structure of the shoot stele (Fig. 35.17 a and b)
11. What are stomata and where are they normally located?
Holes controlled by guard cells on the underside of a leaf for gas exchange
12. Why is the leaf mesophyll separated into two layers? Name the layers.
13. How is the vascular tissue arranged in leaves?
Dermal Tissue Region
Epidermis
Outer layer or covering of the plant
Usually consists of a single layer of cells
No intercellular spaces
Interface - between plant and environment
Controls transfer: gas exchange
Stomata: holes in epidermis can open and close
Leaves:
Cuticle covering - prevent water loss
Roots:
Water absorption is much more important
Epidermis has root hairs to increase surface area
Root Hair Region can be regenerated after time, but consists of most of absorption region of the
plant
Ground Tissue
Everything else in the plant not vascular tissue or dermal tissue
Basic cell type
Unspecialized
Organ Development
Shoot - includes stem and leaves
Bud
Leaf: blade and petiole
Root - underground portion of the plant
Shoot Apical Meristem
Between leaf primordia
Branches off developing vascular strand
Tips of plants never get old - it is still embryonic
As it divides, it grows taller
Produces leaves from apical meristem
Leaf primordium on either side of apical meristem
Axillary bud meristems occur beside apical meristem
However, these produce branches, which in turn will have apical meristems
Each meristem is like an individual, which reacts to environment through differential growth in order to
maximize light or water absorption etc.
Leaf is below a branch (or a bud)
Opinion Clicker Question
Roles of the stem/branches in order of importance:
1. Support
2. Transport
3. Reproduction
4. Photosynthesis
5. Storage
Stele - the pattern of vascular tissue in stem or root
Eustele - scattered bundles
vs.
Protostele - sclarenchyma tissue is central core
Rhizome - an underground stem
Mostly functional in vegetative production
Underground storage
eg) potatoe
Above ground: photosythentic stems
Cacti - stem is photosynthetic
Leaves are sharp and protective
Leaves are part of the Shoot Region
Mostly have a role in photosynthesis
Leaves are below the axillary bud
Node - leaves attached to a stem at the node
Internode - the gap between two nodes on a stem
Simple Leaf
Petiole is central vein of leaf
Compound Leaf
Pertiole looks like a smaller stem
Has individual leaflets
Double Compound Leaf
Has grouped leaflets
We know the difference between leaf and leaflet by the placement of bud
Veins include both xylem and phloem
Vascular tissue is arranged with xylem on the top, phloem on the bottom
Think of the stem: Xylem stays in middle
As these bundles move out into branches, the xylem is on the top
Further stratification in the leaf
Palisade mesophyl - light absorption
Larger surface area, photosynthesis occur both sides of elongated cell
Spongy tissue - gas is moved throughout the leaf
Less surface area, big holes are to allow gas movement
Guard cells are at bottom of leaf
Root Apical Meristem
Has a root cap
Root cap protects embryonic cells from soil as roots grow down
Stele - protostele in the roots
Root does not need extra support
Lecture 19 (604-610)
1. What two evolutionary events are highlights in the evolution of land plants?
Vascular plants and bryophytes
2. Land plants can be divided into two groups. Which one is paraphyletic?
Non-vascular bryophytes are paraphyletic
Vascular plants have derived traits and are monophyletic
3. How many phyla of land plants are there?
numerous
4. Name the three phyla of non-vascular plants or bryophytes.
Phylum Hepatophyta - liverwort
Phylum Anthocerophyta - hornworts
Phylum Bryophyta - mosses
5. What is distinctive about the non-vascular plant life cycle?
Roots begin growth at the base NOT at the tip, even though the apical meristem is at the root tip near the
root cap, utilizing an active zone
Branches in roots/ lateral roots are of endogenous origin
Stems have exogenous origins
Potato
A potato is a stem, not a root
If the potato is left to germinate they grow buds from the eye
If you look into the eye of a potatoes you find an external origin = proves a stem
Shoot meristem - apical
Exogenis origin
Root meristem - sub-apical
Endogenesis origin
THE FIRST PLANTS
Vegetative
Simple, prostrate structures
Flat, protected photosynthetic surfaces
Rhizoids for absorption and .
Reproductive
Antheridia and archagonium

Sexual Reproduction on land requires protection
Gametes
Gametes must be able to fuse
Fusion of gametes occurs in fluid/water
However, a cell covering is needed for protection
Multicellular gametangia
A multicellular structure
Males: Antheridium - cellular structure around with sperm inside
Females: Archegonium - cellular structure with pore and single egg inside
Retention of the egg
Sperm released into water
Zygotes and Embryos
Need protection until can develop own protection
Retention on gametophyte
Sporophyte embryo develops on the parent plant called the gametophyte
Effective dispersal on land requires a new strategy
Sperm need another stage in the life cycle to promote dispersal (not open water)
Gametes cannot be protective because they need to fuse
So, we find on land:
- increased spore production
- increase dispersal in dry or terrestrial environment
- how can this be accomplished?
- After meiosis of the zygote from 2N to haploid N, repeated mitosis of spores occurs for
many identical haploid cells
- Mitosis of zygote increases diploid cells, which then each undergo meiosis,
producing
more spores that are genetically diverse
Heteromorphic Alternation of Generation
Haploid and diploid stages look different
Isomorphic Alternation of Generation
Haploids and diploids appear the same
Non-Vascular Land Plants
Bryophytes
Bryophyte Vegetative Traits
Light and CO2 absorption
..
Bryophyte Reproductive Traits
Swimming sperm
Increased dispersal
Need to know life cycle:
Lecture 20 Questions from the text (610-616)
1. When does the fossil record indicate that vascular plants originated?
Present-day vascular plants date 420 million years
2. How does the life cycle of vascular plants differ from that of non-vascular?
Vascuar plants have branched sporophytes that are not dependant on the gametophyte for
nutrition.
3. How and why did leaves originate?
Leaves increase the surface area of the plant body and serve as the primary photosynthetic organ of
vascular plants.
4. How are the lycophytes related to the rest of the vascular plants?
Sister taxa
Lycophytes are the oldest lineage of present-day vascular plants. Only lycophytes have
microphylls,
which are small, usually spine-shaped leaves supported by a single strand of vascular tissue.
Almost all other vascular plants have megaphylls, which are leaves with a highly branched vascular
system; a few species have reduced leaves that appear to have evolved from megaphylls.
Microphylls originated from sporangia located on the side of the stem.
Megaphylls, by contrast, may have evolved from a series of branches lying close together on a stem.
Lycophytes are a sister group to the rest of the vascular plants.
Lycophytes are seedless; so are some vascular plants.
This is why we separate lycophytes from everything else (of vascular).
5. Where does meiosis occur in ferns?
6. What characters unite horsetails and ferns on the same clade?
Homosporous
7. What is peat moss and where does it grow?
"Sphagnum" is a wetland moss that forms extensive deposits of partially decayed organic material
known as peat.
Clicker questions
(1)The plant gametophyte produces gametes via mitosis.
(2)Alternation of generation refers to:
Alternation of sporophyte and gametophyte ONLY.
This is two multicellular stages. One haploid, one diploid.
(3) The bryophyte life cycle has a:
Dominant gametophyte, dependent sporophyte
Sporophyte meiosis
Meiosis - movement from diploid to haploid (N)
Fertilization - two haploids make a diploid (2N)
Mosses
Fig 29-8-3
Meiosis occurs in sporangium in the sporophyte
They germinante to generate protonemata (haploid = N)
Gametophyte (haploid = N) includes both the gametophore and protonemata
Male gametophyte vs. female gametophyte
Antheridia male vs. archegonia female
Raindrop transfers male spore INTO the female archegonium for fertilization.
Zygote grows up the archegonium, sometimes pushing up haploid remnants.
The female gametophye supports the sporophyte (diploid = 2N) until it grows up.
The gametophyte supports mature sporophyte
Method of dispersal:
When cap comes off, teeth push into spore mass so when it gets drier the spores are dispersed into the dry
air.
*Must know comparison of bryophyte phyla:
Liverworts, hornworts, and mosses
All have dominant gametophyte and dependent sporophyte
Peat Mosses
"Sphagnum"
Specialized leaves
Live in very acidic environment - bogs
Commercially important
Living cells of peat leaves are small. Most cells are empty and dead. The dead cells take up and hold
water
to keep moss moist. The increased acidity also provides a wound dressing as an anticeptic.
Peat fills in lakes
Peat in pushed down to the bottom
A peat bog is a highly acidic filled in lake
People have found perfectly preserved bodies in peat bogs
Excellent source of fossil information
Peat is an excellent, clean-burning fossil fuel
Peat is more difficult to transport, so it is really only useful small scale
In Canada we harvest peat by strip mining
Some people are concerned we are destroying peat bogs about to lose them
Vascular Plants
Monophyletic group
Dominant sporophyte (2N) and dependent or independent gametophyte (N).
Plant life in the Devonian
Vascular plant occurs first in fossil record: believed they preserve better.
Psilophyton
Oldest vascular plants
Kidney shape structure on side of stem = lateral sporangia
Flaps of tissue on stems
Enations - these flaps of tissue do not have vascular tissue
Cooksonia
Looks different in that it has swellings the tips which are terminal sporangia
No enations
The first vascular plants
No leaves
No roots
Simple, small
Two main groups:
Terminal sporangia
Lateral sporangia and enations
How did leaves evolve?
Two theories: evidence that both happened
(1) Enation Theory - Microphylls
Vascular tissue > sporangia > microphyll
(2) Telome Theory - Megaphylls
Overtopping growth > other stems become reduced and flattened > webbing develops in the
megaphyll leaf
Modification of the branches
LIFE CYCLE THEORY
What is the nature of the sporophyte?
(1) Sporangium
antithetic theory
(2) Same as gametophyte
homologous theory
Isomorphic alternation of generation is an ancestral trait in plants according to the Homologous Theory but
a derived trait according to the Antithetic Theory.
Comparison of bryophyte phyla
All have dominant gametophyte and dependent sporophyte
Liverworts (Hepatophyta)
Gametophyte prostrate thallus with gametangia (antheridia and archegonia) often on stalks
Small sporophyte (sporangium)
Hornworts (Anthocerophyta)
Gametophyte Similar to liverworts, gametangia embedded in gametophyte
Larger photosynthetic sporophyte
Mosses (Bryophyta)
Gametophyte Axial gametophores plus protonemata
Complex sporophyte
Lecture 21 (618-621)
1. What important innovation in the plant life cycle did reduction in gametophyte size facilitate?
Tiny gametophytes can develop from spores retained within the sporangia of the parental
sporophyte. This protects the female gametophytes from environmental stresses.
2. What kind of spores produce male gametophytes and what kind of spores produce female
gametophytes?
Seed plants are heterosporous.
Megasporangia produce megaspores that give rise to female gametophytes.
Microsporangia produce microspores that give rise to male gametophytes.
3. What are the layers that make up an ovule?
Integument - sporophyte tissue envelops and protects megasporangium
Gymnosperm megasporangia are surrounded by one integument
(whereas those in angiosperms usually have two integuments)
The whole structure: megasporangium, megaspore, and their integuments
4. What, in a bryophyte life cycle, is homologous to a pollen grain?
A microspore develops into a pollen grain that has a male gametophyte enclosed within the pollen
wall, which protects the pollen grain in pollination.
Bryophytes have flagellatted sperm to travel short distance.
5. What is the relationship between an ovule and a seed?
The ovule is the stage before complete fertilization.
Fertilization of the ovule initiates the transformation into a seed.
6. How are spores and seeds different? How are they similar?
Similar: Protective
Dispersal
Tiny size
Different:
Spores are unicellular; seeds have multicellular layer of tissue
Seeds have a supply of stored food
The seed can then germinate on its own
Lycophytes (Phylum)
.. (Phyum..)
eg) lycopodium obscurum
Longitudinal Section of Strobilus consisting of a central stem supporting a cluster of 
Leaf and sporangia are associated in location
Lateral sporangia
Cones are terminal
Homosporous: produce spores that are all the same
Typically a bisexual gametophyte that produces both sperm and eggs
Heterosporous:
Megasporangium/ megasporophyll > produces megaspore
> female gametophyte > eggs
Microspoarangium/ microsporophyll > produces microspore
> male gametophyte > sperm
All emerged from enations
Phylum Pterophyta (Ferns and relatives)
Leaves - megaphylls
Sporangia - terminal - tips of "branches"
Includes both ferns and horsetails
Horsetails - Sphenophytes
Sporangia on sporangiophores, in cones
Leaves are small and whorled (they come off in a ring/ collar of leaves around stem)
silica in cell walls
Non-photosynthetic reproductive stem
Vegetative, photosynthetic stem with branches
Sporangia on cones is made up of modified branches
No leaves in the cone - all little stalks
What theory explains this branch modification?
Telome theory: modification of branches
Ferns
Sporangia on megaphylls
Sporangia clustered in sori (sing.= sorus), not in cones
Modification of the stem
Considered so similar even though they look very different
Rhizome - underground stem
Frond - the leaf in the fern
Rachis - the stalk (like a petiole)
LIFE CYCLE OF FERNS
Must know how it is similar and different to bryophyte
Fern gametophyte is independent
Does not require sporophyte for nutriets
Homosporous
Telome Theory:
Where would you expect the ancestral position of sporangia to be?
The tips of veins
Veins are homologous to branches
Sporangia are terminal
As ferns have evolved, this may not always be true
The underside of the leaves of ferns
Sori are located under leaf
Sorus: cluster of sporangia
Inside a sporangium are many spores
Dominant independent sporophyte
Mosses and other Nonvascular Plants
Constraints on the Life Cycle
Necessity of water: gametophyte needs water for sperm dispersal
How can this problem be solved?
Two issues
(1) Where would the gametophyte live?
What clues to strategy do bryophytes provide?
The sporophyte lives on the gametophyte
Moist inside sporangium
Germinates inside sporangium
(2) How will the sperm be transferred?
Text questions (621-625, 751-754)
1. What important characteristics link Archaeopteris to the evolution of seed plants?
The heterosporous Archaeopteris had characteristics of seed plants such as a woody stem. It is called
a progymnosperm - an extinct seedless vascular plant that may be ancestral to seed plants.
2. When (geological period) did seed plants begin to dominate in the fossil record?
360 million years ago, which is about 200 million years before angiosperms
3. Where are ovules located in a pine tree? How does fertilization occur in a pine tree? Is it unisexual or
hermaphroditic?
-Ovules are in cones: most conifers have both ovulate and pollen cones
-Pines are heterosporous.
-Pollination occurs when a pollen grain reaches the ovule. The pollen grain then germinates, forming
a pollen tube.
-Fertilization does not occur until the eggs are mature. By this time, two sperm cells have developed
in the pollen tube, which extends to the female gametophyte. Fertilization occurs when the sperm
and egg nuclei unite.
4. How does secondary growth affect the development of the mature plant body?
Secondary growth is the growth in thickness produced by lateral meristems and adds girth to stems
and roots in woody plants. The secondary plant body consists of the tissues produced by the
vascular cambium and cork cambium, which thicken the stems and roots of woody plants.
5. What are the two main secondary meristems?
(1) Lateral meristems (2)
vascular cambium
6. Where is the vascular cambium located and what does it produce?
It is in between primary xylem and primary phloem in the center of a stem or root. The vascular
cambium is a cylinder of meristematic cells, often only one cell thick, which thickens roots and
stems. It increases in circumference and also adds layers of secondary xylem to its interior and
secondary phloem to its exterior. It increases vascular flow and support for the shoot system.
(1) Elongated initials of the vascular cambium produce cells such as the tracheids, vessel elements, and
fibers of xylem, as well as the sieve-tube elements, companion cells, parenchyma, and fibres of the phloem.
(2) Shortened initials produce vascular rays - radial files of cells to connect
7. What is the difference between heartwood and sapwood?
Heartwood layers are older and closer to the center, no longer transporting water and minerals (xylem
sap). Sapwood is the newest outer layers of secondary xylem.
8. What is periderm and how is it related to cork?
Each cork cambium and the tissues it produces comprise a layer of periderm.
Dispersal
How will sperm be transferred?
Retain gametophyte in the sporangium, to provide a moist environment
Intermediary
Wildlife
Insects
Raindrops
Splash sperm to female gametophyte
Retain moisture so sperm can swim
Gametophyte
Antheridium and archegonium are on gametophytes
You could move the whole gametophyte if it is small
Could use wind to disperse male gametophyte to stationary female
Egg is larger than sperm, so it stays stationary
Division of labour
A heterosporous plant is more successful!
Both sexes are produced in a heterosporous plant
Fertilization
Male gametophyte lands on female sporangium and then can grow through the sporangium and
deposit sperm
Conifers: cones and pollen grains
Packaging your own water
Pollen grain - male gametophyte
Not spores because are more than one cell
How will the sperm be captured?
An ovule
Ovule - an integumented megasporangium
Sporangium contains megaspore that germinates into female gametophyte
Integument is a layer of tissue derived from branches
Female structure of layers around the female gametophyte that include the sporangium, and lobes
of integument
Ovule: Integument > sporangium wall > female gametophyte
Fig 30-3-2
Textbook is wrong in this figure
Spore wall is not living and does not expand
That is the megasporangium wall
Sporangium wall become nucellus
Seed - fertilized ovule
Development of seeds is a major evolution in plants
The seed shows homologies with other plants: gametophyte and sporophytes
Monophyletic group
Gymnosperms "naked seeds" mostly cones
Angiosperms "enclose seeds" mostly flowers
Seed Plants
Heterospory
Eusteles
Presence of bifacial cambium
o Xylem to the inside, phloem to the outside
o structure that produces wood
Where did seed plants come from?
Progymnosperm ancestor
Heterosporous
Megaphyllous
W oody
Vascular Cambium
Division into xylem and phloem
Secondary tissue is produced by vascular cambium
Wood = secondary xylem
How would you characterize bark?
When you peel off bark on a tree trunk you are left with secondary xylem
The boundary between bark and wood must be the cambium
Everything outside wood
Mostly parenchyma cells
Bark includes: secondary phloem (closest to cambium),
primary phloem (further out)
cortex
cork cambium
cork (tissue harvested from surface of tree)
Rings in tree trunks
Cambium divides in spring and summer
Grows quickly and grows large cells in spring, small cells later fall
It is dormant in the winter
Growth rings are the difference in cell size between end of last year and spring.
Asymmetrical growth can occur for the tree to adapt and grow in a direction
Periderm - refers to cork and cork cambium
Lecture 23 Text questions (625-630, 801-804)
1. Name the parts of the four rings of floral structures that make up the flower.
Carpels
Stamens
Petal
Sepal
2. What are the floral organs derived from?
3. What is a fruit?
A mature ovary
4. How many cells (or nuclei) make up the male and female gametophyte (respectively) of the angiosperm?
5. What is endosperm and what is its function?
6. What is double fertilization?
7. What is an embryo sac?
8. Distinguish between the terms carpel, ovary and pistil as used in describing an angiosperm flower.
Gymnosperms
Four phyla
Phylum Cyc
Phylum Ginkgophyta
Only contains one species
Ginkgo biloba
Two big lobes on leaf
Pollen-producing tree in China
Separate male and female trees
Phylum Gnetophyta
3 very distinct genera
Gnetum
Source of ephedrine - strong stimulant - good for tea
Welwitschia
Phylum Coniferophyta
Confirs: Fir, Larch, Pine, Sequoia, Juniper
Megaphyll Leaf
Sporangia is on underside of leaf
Female Cone
Bract
Scale (branch) - ovules located here on top of scale
(leaf)
Bud (becomes branch) is located above the leaf
Angiosperms = Phylum Anthophyta angio = container for sperm = seed
Bisexual reproductive structures
Eg) barley, water lily, oak trees, birch trees, poplars, most are wind-pollinated
FLOWERS
Calyx - sepals
Corolla - petals
Androecium - stamens (leaves with microsporangia on them)
Anther filaments
Gynoecium - female - made up of carpels
Ovaries, stigma, style
Four parts of the plant
Carpels
It is a leaf unit that makes up the ovary
Stamens
Petal
Sepal
Ovules are in an ovary
Seeds are in a fruit
A fruit is a mature ovary
Lecture 24 (630-632, 804-805, 809-811)
1.Which of the two angiosperm groups (monocots or dicots) is paraphyletic?
Monocot - member of a clade consisting of flowering plants that have one embryonic seed leaf, or
cotyledon.
Dicot - a term traditionally used to refer to flowering plants that have two embryonic seed leaves, or
cotyledons. Recent molecular evidence indicates that dicots do not form a clade; species once
classified as dicots are now grouped into eudicots, magnoliids, and several lineages of basal
angiosperms.
2. What is the major constraint relating to pollen dispersal that is less of an issue with seed dispersal?
3. What are the characteristics of wind pollinated flowers?
4. How do bee pollinated flowers differ from bird pollinated flowers?
5. What develops into the pericarp (fruitwall)?
The ovary wall becomes the thickened wall of the fruit, or pericarp
6. Distinguish among simple, aggregate, multiple and accessory fruits.
simple fruit - a fruit derived from a single carpel or several fused carpels.
aggregate - derived from a single flower that has more than one carpel.
multiple fruit - a fruit derived from an inflorescence, a group of flowers tightly clustered together
7. What are two main types of abiotic and two types of biotic seed dispersal?
Abiotic:
wind
water
Biotic: animals
insects
Derived characters defining angiosperm
Flowers
Closed Carpels
Fruits
Vessel members in the xylem
Reduced gametophytes
Double fertilization
Xylem cells in angiosperms
Tracheids diverge to form vessel elements (conduction) and fibres (support)
Reduced Gametophyte
Male Gametophyte
Microsporangium is the anther pollen sac
Produces microsporocyte (2N)
meiosis
POLLEN GRAIN
4 microspores (N)
Each of 4 microspores
Generative cell (N)
Female Gametophyte
Megasporangium (2N)
Megasporangium wall
Megasporocyte (2N)
Integuments (2N)
Micropyle
meiosis
Surviving megaspore (N)
EMBRYO SAC
Ovule
3 antipodal cells (N)
2 polar nuclei (N)
1 egg (n)
2 synergids (N)
TOTAL: 8 cells
highly reduced gametophyte
Clicker
The closest relative to an angiosperm is a gymnosperm
A reduced angiosperm female gametophyte is beneficial because less maternal commitment prior to
fertilization and less weight for the sporophyte to carry and detrimental because another food source for
the embryo must be found.
Life Cycle of Angiosperms
Mature flower
Meiosis in the anther
Pollen grain lands on stigma, pollen tube grows down stile
Release sperm into ovule
Fertilization occurs
Double fertilization
Fertilization of both the egg and the polar nuclei in the ovule
1. Endosperms nucleus (3N) 2 polar nuclei plus sperm
2. Zygote (2N) egg plus sperm
Coevolution
Angiosperms use animals to aid their dispersal
Two different dispersal stages
Seed dispersal syndromes
Abiotic: wind, water
Biotic: animals
Active: sometimes involves attraction/reward
brightly colored fruit
food sugar around seed in ovary wall
seed has oils that are not attractive to animal
Passive biotic dispersal such as burrs
latch onto animal
Pericarp (fruit wall) is often involved in promoting dispersal
It acts as an intermediary, and offers protection
eg. coconut - strong fibrous pericarp would float in salt water ocean
Wind dispersal
Dandelion "parachute" white hairs break off of flower stem
Tumble weed
Animal dispersal
Seed caches
Excretion of whole seeds
Simple Fruits
Peas are an example of a simple fruits
Strawberries
Yellow things are fruits/ ovary walls
Red part is stem
Accessory Fruit: red part attractive portion are not ovary
Aggregate Fruit: single flower, aggregation of fruits from single flower
Multiple Fruits
Pineapple
Many flowers, one carpel
Pollination syndromes
-Biotic/Abiotic dispersal of pollen grains
-Biotic involves attraction and reward
Attraction: color of flower
Reward: fruit, nectar
-Precise destination of the pollen to a stigma of a receptive flower
Clicker Opinion Question
True: Flowers should evolve to attract as many different pollinators as possible so that
reproduction is maximized.
False: precise destination, need specialized subset of pollinators otherwise
pollen is wasted going to places where there are no receptive
Pollination syndromes and strategies
Wind
Insect
Bird
Introduction to Fungi
pages 636-643
Fungi are absorbtive heterotrophs
Fungal Characteristics
• Absorbtive heterotrophs.
• Cell walls of chitin (protein found in insect and crustacean exoskeletons)
• Life cycle with zygotic meiosis (except a few chytrids)
• Decomposers, parasites (and predators)
• Multicellular - mycelium made of hyphae
• Or Single-celled (yeast)
Fungal Morphology
Fungus can be very large, extending underground and can be colonial
Fungi have hypha to absorb nutrients
Fungi can be predatory (on nematodes)
(a) septate hypha - discrete cells divided by a septum
(b) coenocytic hypha - all nuclei float around in common cytoplasm (also aseptate)
Movement of Cytoplasm allows for fungi to grow quickly
Fungal Life Cycles
Asexual Reproduction
Germination
Mycelium - haploid dominant mycelium organism
Spore-producing structures
Spores
Sexual Reproduction
Plasmogamy (fusion of cytoplasm)
Heterokaryotic stage (unfused nuclei from different parents)
Karyogamy (fusion of nuclei)
Zygote
Meiosis
Spores
Germination
Heterokaryotic Stage
Gametangia containing multiple nuclei
Two hypha grow together
Compatible + and Two parents have nuclei float around in cytoplasm
Dikaryotic Stage
In septate, we get a single nuclei from each parent in same cytoplasm
Fungal sex, sexes and parasex
• Some fungi can sexually reproduce with themselves.
• In those that don't, different "sexes" consist of individuals with different alleles at one or two loci.
May be many "sexes" in population.
• Often these genes are responsible for forming the dikaryotic phase.
• Asexual fungi can also produce recombination through a strange process called parasex.
Fungal Ecology
Decomposition
Fungi can break down cellulose, lignin, karatin, etc. that are hard compounds
Fungal mycelia convert cellulose and lignin (from wood) into sugars and other small organic
compounds
Fungi can also attack living trees
Adaptations in Fungi
Adaptations for dispersal of spores
-Shoot spores out by building up hydrostatic pressure
-Spores land in grass
Can be eaten by herbivores, and deposited in a new habitat
Economics of Fungi
Plant parasites
Important fungal disease agents
Leaves toxins on our food and harm our plant-life
Grains: mildews, black rust on wheat, corn light
Trees: white rot, dutch elm disease
Fruit: mold
Rye: ergots causes hallucinations (Salem witch trials)
Fungi as Food
Mushrooms
Molds (to flavour cheeses)
Truffles
Brewing and baking
Yeast
Wine and Beer
Pharmaceuticals
Penicillin comes from a mold called penicillium
Fungi for Biological Control
Protect plants by killing off insect parasites
Fungi have an ability to secrete enzymes that break down chitin in the body
of the insects
Evolution of Fungi
Fossil Record
Suggests animals and fungi separated before we see them in the fossil record
Very little evidence
Linked to the evolution of land plants in movement to terrestrial environments
Symbiotic relationships
Chytrids
• 1000 spp. Found in freshwater and soil.
• Single celled and multicellular.
• Decomposers, parasites, and mutualists. •
Likely the first fungal lineage to diverge.
- Only group with flagellated stages.
Chytrids can be parasitic
Can contribute to the decline of amphibians by causing skin diseases
Digestion
Chytrids can help break down grass in the stomach of cows
Closing thoughts
• Fungi are absorbtive heterotrophs with unique lifestyles, metabolism and life cycles.
• Fungi have important roles in the global nutrient cycles, and major economic importance, particularly as
plant pathogens.
• Fungi evolved from flagellated protists.
• The primitive Chytrids, a paraphyletic group, are the only fungi which retain flagellae.
• Chytrids are an inconspicuous group, but contain some important pathogens and mutualists.
Fungi
pages 643-646
Zygomycota (Glomeromycota) Ascomycota
Only zygotic meiosis
No flagellated stages
Adapted for terrestrial life
Zygomycete
Member of the fungal phylum Zygomycota, characterized by the formation of a sturdy structure
called a zygosporangium during sexual reproduction.
Phylum Zygomycota
• 1,000 species.
• Aseptate fungi.
• Almost all decomposers (molds)
• Small and short-lived heterokaryotic stage.
• Asexual reproduction more common than sexual.
Life Cycle
Mating type + and mating type Gametangia with haploid nucleus
PLASMOGAMY
Young zygosporangium (heterokaryotic)
Sexual reproduction
KARYOGAMY
Diploid nuclei
MEIOSIS
Sporangium
Haploid spores
Dispersal and germination
Mating type + and mating type Asexual Reproduction
Spore dispersal and germination
Mycellium
Sporangia
Ecology of Zygomycetes
• Mainly decomposers
reason why not to put bread in refridgerator: grow in cool damp conditions
Parasitic zygomycetes
Colonize insects, spreading throughout body and killing insect
Predatory Zygomycetes
Makes rings to catch nematodes
Spore dispersal mechanisms of zygomycetes
Live in cow dung and shoot spores several meters into grass
Asexual spores attach selves to fly, reproduce, then explode out of fly body
Spirodactylon spores in rat pellets disperse by rats carrying them, the spores
are spiral "burrs" that latch onto rat fur, rats lick, ingest, excrete, smell pellets
Glomeromycota
• Only 160 species
• Aseptate.
• Sexual reproduction unknown.
• Extremely important as mycorrhizae (we will discuss this next day).
• Reproduce asexually though sporangia at ends of hyphae.
Ascocarps
Ascomycota
• 65,000 species.
Most diverse group of fungi
• Septate hyphae
• Some unicellular forms (yeasts)
• Terrestrial, marine and freshwater.
• Sexual reproduction through ascospores produced in asci.
• Longer lived and larger dikaryotic stage.
Life cycle
Sexual Reproduction
Two hypha come together
Mating type (+) and mating type (-)
Plasmogamy
Dikaryotic hyphae
Ascus (dikaryotic) - small clear sac, plural asci, each containing 2 nuclei
Karyogamy
Diploid nucleus zygote
Meiosis
Four haploid daughter nuclei
Mitosis
Eight ascospores
In an ascocarp, many asci, may be both haploid and diploid
Dispersal
Germination
Mycelia
Asexual reproduction
Haploid spores
Dispersal
Germination
Hypha
Mycelium
Conidiophore
Haploid spore on end of hypha (conidia)
Mycelium is the dominant part of the life cycle
Relatedness to parent in Ascomycota:
Conidia is exactly 100% related to parent (asexual reproduction)
Ascospore average 50%
Types of ascocarp
Related to method of spore dispersal:
• Apothecium - Open. Cup or saucer shaped
wind dispersal
• Perithecium - Small opening (ostiole). Flask or pear shaped.
can act like a canon to fire out spores
wind dispersal
• Cleistothecium - no opening. Spherical.
animal dispersal
ascocarp provides protection for spores
Asexual reproduction via conidia
• Produced entirely by mitosis.
• Often produced "naked" on the end of a specialized hypha - a conidiophore.
• Sexual and asexual reproduction often occur at different times and on different substrates, leading
to confusion and delay.
• Typically produced in huge numbers.
Survey of the Ascomycota
About 700 molds
Grain infection: ergots
Infect insects
Powdery mildew
Athlete's foot is caused by fungi
Penecillium
Can grow with little water present
Yeasts
• Unicellular fungi.
• Not a monophyletic group.
Description of morphology, not a taxonomic group
• Reproduce mainly by budding.
Budding = asexual reproduction
• Some can reproduce sexually by asci.
Closing thoughts
• Ascomycota are extremely diverse but monophyletic group.
• Defined mainly by sexual reproduction, but evidence suggests many asexual species
are
Ascomycetes.
• Contains many of the most important plant pathogens.
Fungi and Fungal Friends
Basidiomycota, Lichens, and Micorrhizae
pages 646-652, 795-797
Ascomycota and Basidiomycota
The two most similar phyla of fungi
Basidiomycota
• 30,000 species.
• Septate hyphae
• Mainly terrestrial
• Sexual reproduction through basidiospores produced on a basidium
• Even longer lived and larger dikaryotic stage.
Structure of septa
Ascomycetes and basidiomycota have a wararin body to block pores between cells
Function seems to be to ensure that nuclei do not move between cells
Life Cycle
Sexual Reproduction
Haploid mycelia
Mating type (+) and (-)
Plasmogamy
Dikaryotic mycelium
Gills lined with besidia (bottom ribbing on a mushroom)
Basidiocarp - dikaryotic (n+n)
Basidia (n+n)
Karyogamy
Diploid Nuclei - zygote is short-lived
Meiosis
Basidium
Basidium with four basidiospores
Basidium containing four haploid nuclei
Basidiospores (n)
Dispersal and germination
Haploid mycelia
(1) Class Hymenomycetes
• Spores exposed at maturity.
• Many have mechanisms to shoot them, but usually only a very short distance.
Commonly called "gill-less" fungi
Shelf fungi (important decomposers of wood) appear as half circles on logs
(2) Gill Fungi
• Mainly decomposers or ectomycorrhizae, especially with conifers.
• Basidia produced on gills or lamellae.
Toadstool mushroom
Anatomy of a mushroom
Cap - umbrella like structure on top that keeps spores dry
Gills - underside of cap
Annulus - veil that covers stipe, falls off at maturity
Stipe - grows up out of ground, like a stem
(3) Class Gasteromycetes
Distinguished by their spore dispersal
Puff-balls
(4) Rusts and Smuts
• 6000 rusts and 1000 smuts.
• All parasitic on plants, and include many common crop diseases.
• No basidiocarps.
• Different septal pores from other Basidiomycetes.
The odd ones of fungi, most are parasitic
Complex life cycle between wheat and barberry
dikaryotic spores infect wheat plant
basidiospores grow into barberry
Some structures similar to land plants
Fairy rings
Produced by a fungus living underground
Middle of fairy ring no longer has enough nutrients
Basidiocarps are produced around the entire perimenter
Mycophagy
Edible fungi are mostly found in basidiomycota
Lichens
• Lichens are symbiotic associations between a fungus and a green algae (or
cyanobacteria).
• Most common with Ascomycota (98%) which form lichens,
but Basidiomycota, Zygomycota and Glomeromycota are all known to form lichens.
• About 20,000 lichens known.
Three layers in a cross section of a lichen (Fungal hyphae is most of body)
(1) Fungal layer
Asci produced by fungus
(2) Algal layer
Soredia - Asexual reproduction through soredia
Fungus may be parasitic to algae
(3) Fungal layer
Substrate
One organism or two?
Three Morphologies of Lichen
1. Crustose (encrusting lichens that live on rocks)
Extract minerals from rock
Absorb moisture from air
2. Foliose (leaflike)
Often grow on trees
3. Fruticose (shrublike)
Lichen Ecology
Long lives
Can live in extreme cold or hot environments
Arctic - cold environment, lichens grow on rocks
Lichen as Bioindicators
Sensitive to acid rain and air pollutants
When lichens disappear, we need to be concerned about air quality
Mycorrhizae
• Mutualistic association between plant roots and fungi.
Plants grow better with Mycorrhizae
Expansion of root system of plants
Improve ability to absorb minerals, nutrients, and water
Some evidence of protection from pathogens
• Probably date back to the earliest land plants and fungi.
• Two main types:
- Ectomycorrhizae
EMF form sheaths around roots and penetrate between root cells, providing a new route for
sugar transport
Basidiomycota and a few Ascomycota
- Arbuscular Mycorrhizae
AMF Contact to plasma membrane in root cells
AMF penetrate cell walls, but not plasma membrane
Glomeromycota
(1) Ectomycorrhizae
• 2000 plants and 5000 fungal partners.
• Many commercially and ecologically important tree species included.
Development and morphology
Seeds grow on plant root, mycorrhizae colonize root
Form sheath around root
Greater surface area
Plant no longer needs to put energy into producing root hairs
(2) Arbuscular Mycorrhizae
• 300,000 plants but only 160 fungi, all in the Glomeromycota.
• Penetrate cell walls of root cortex, and form tree-like arbuscules which are completely surrounded by the
plasma membrane of the cells.
• Roots are also surrounded by fungal hyphae growing in the soil and extending the volume and surface
area for absorption.
Development and Morphology
Reproduction
• Almost entirely asexual reproduction.
• Produce very large, thick-walled spores filled with storage lipids. These can survive for long periods until
conditions are suitable for growth. (Grow under similar conditions to partner plant seeds).
Spores often spread with seeds
AM in agriculture
Use mycorrhizae fungi to help plants grow
Other fungal mutualisms
Endophytes reduce presence of pathogens
Ants take leafs to fungi inside nest
Closing thoughts
• Basidiomycota are less morphologically and metabolically diverse than the Ascomycota, but still very
common decomposers and ectomycorrhizae.
• Lichens are a common and diverse association between fungi and algae, which behave like single
organisms despite their dual nature.
• Ecto and arbuscular mycorrhizae are almost universal in plants, and go back to the earliest invasion of
land by both kingdoms.
Introduction to Animals
Characteristics of animals
Multicellular, ingestive heterotrophs
No cell walls
Many have muscles and nerves
Genome contains Hox genes
Main Lineages in Animals
See Ch.32 Lineage figure
Protostomes
Grades - basic similarities (eg) worm-like bodies
No longer used
Clades - branches on evolutionary tree
Discovered from biological evidence
Body Symmetry
Assymetry - no symmetry, sponges
Radial Symmetry - jellyfish
Bilateral Symmertry - lizard, human, have an anterior and posterior end
Tissue Layers
Sponges
• Some animals have no true tissues (sponges)
Eumetozoa
• Diploblastic animals have two tissue layers
- Ectoderm
- Endoderm
• Triploblastic animals have three tissue layers
- Ectoderm
- Mesoderm
- Endoderm
Fate of Tissue Layers
Ectoderm - epidermis, nervous system
Mesoderm - notochord, skeletal and muscular system, reproductive system
Endoderm - inner organs
Body cavities
Example: Flatworm
Body covering from ectoderm
Tissue-filled region from mesoderm
Wall of digestive cavity
Example: Pseudocelum
Body covering
Muscle layer
No inner layer of muscle, rather a fluid cavity
Digestive tract from endoderm
Example: Hydrostatic skeleton of a nematode
Fluid-filled pseudocoelom (under pressure - creates tension in the body wall)
Example: Coelomate
Tissue layer lines the coelom and suspends internal organs (from mesoderm)
Function: Peristalsis
Peristalsis allows food to move through gut independent of body movement
Refer to:
Animal Phylogeny from Campbell 5th ed. is no longer correct
Animal development
Sexual Reproduction
Gametic Meiosis with oogamy (egg and sperm)
Asexual Reproduction
Mitosis
Animal development
Zygote
Cleavage
Eight-cell stage
Cleavage
Blastula (hollow ball of cells)
Gastrulation
Gastrula
Blastopore (opening)
Archenteron (developing gut)
Ectoderm
Blastocoel
Endoderm
Protostomes vs. Deuterostomes
Early stages of cleavage can help distinguish between Protosomes/ Deuterostomes in the eight-cell stage.
We can also look at the fate of the blastopore and coelom formation.
Protostomes
spiral and determinate
eight-cell stage of cleavage
Deuterostomes
Radial and indeterminate
eight-cell stage of cleavage
solid masses of mesoderm
split and form coelom
folds of archenteron form coelom
mouth develops from blastopore
anus develops from blastopore
Form and Function in Animals
• Gas exchange
• Digestion
• Osmoregulation
- balance of ions, excretion of metabolic waste
• Move to land
Is bigger better?
• Not all animals are big
• But generally, multicellular animals are bigger than the single celled protists from which they evolved.
• What problems has this created, and how has natural selection produced answers?
Cube - Square Law
As size increases, surface area does not increase at the same rate as volume
Surface to volume ratio decreases as animal gets bigger
Gas Exchange - larger animals needs to increase surface area for gas = development of high surface area
lungs
Animals then evolved circulatory systems to carry oxygen to muscles and other areas of the body
Digestion (esp. Absorption) - intestine is folded and has villi to increase surface area for nutrient and water
absorption
Cube-square law affects more than just diffusion
• Heat exchange with the environment.
• Muscle strength
• Friction and terminal velocity.
- "You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight
shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse
splashes."
JBS
Haldane
Closing thoughts
• Animals are multicellular ingestive heterotrophs.
• Animals are a diverse and species rich group. Most of the species are in a few phyla.
• Cleavage, a blastula and gastrulation, and fundamental and almost universal elements of animal
development.
• Much of animals' organ structure can be explained as ways to increase surface area.
Sponges
Water is drawn into the interior cavity, called the spongocoel.
Feeding by phagocytosis
Silicea
Protein - spongin
Sponging is elastic
Sponges
Water is drawn into the interior cavity, called the spongocoel.
Feeding by phagocytosis
Silicea
Protein - spongin
Spongin is elastic
Histoincompatibility - body's rejection of foreign tissues
Reason for organ transplant rejection
Same individual can be separated, then fused back together
You cannot make two different sponges grow together
Sponges Gas Exchange
Choanoflagellates are sessile protists; some are colonial.
Sponges are multicellular, sessile animals. Water current out of sponge
Sponge feeding cell - choanocyte
Phyla Calcarea and Silicea
• Marine & a few freshwater
• 5500 species
• No muscles, organs or nerves
• Filter feeders.
• 5mm to >1min length.
Body wall of sponge
EXAMPLES
Calcarea - spicules of CaCO3
Silicea -- spicules of silica
Silicea - spongin
Functions of choanocytes
• Generate the currents that draw seawater into the interior of the sponge.
• Capture small food particles.
• Capturing incoming sperm during mating.
Functions of amoebocytes
• Digest food collected by choanocytes.
• Store food.
• Give rise to eggs and sperm (most sponges)
• Eliminate wastes
• Become specialized to:
- secrete sponge skeleton
- become epidermal cells
Sexual Reproduction
• Usually hermaphroditic.
• Eggs and sperm produced by amoebocytes (usually).
• Eggs (usually) retained, while sperm is released.
• Incoming sperm is captured by choanocytes and transferred to mesohyl for fertilization.
• Embryo (usually) develops internally to free- swimming stage.
Development
Develop into flagellated free- swimming larva. Larvae quickly settles onto substrate and develops into adult
sponge.
Asexual reproduction
Simple but sophisticated and efficient
• Sponges show histoincompatibility, an animal characteristic.
• A + A : Fuse and grow
• B+B: Fuse and grow
• A + substrate : Grow
• A+B: Death
Gas Exchange
• All animals are aerobic heterotrophs.
• Require oxygen in and carbon dioxide out.
• Gas exchange depends on surface area.
• Because of cube-square law, bigger animals need more elaborate gas exchange organs.
• Metabolically active animals will need more gas exchange as well.
• Larger animals also need to transport oxygen throughout the body - circulatory system.
Basal animals use diffusion
Closing thoughts
• Sponges are simple congretations of cells, but function as efficient filter feeders.
• Gas exchange mechanisms maximize surface area, minimize distance between water/air and cells, and
often connect to circulatory systems.
Cnidaria and Ctenophora
Feeding
Animals formerly known as Radiata
Phylum Cnidaria
• 10,000 species, marine and a few freshwater.
• All predatory with stinging tentacles.
• Have nerves and muscle.
• <5mm to >2m in diameter.
• Four classes.
Morphology
Cnidocytes
Thread shoots out and into the prey animal from the tentacle
Movement
Bell moves down and contracts to push body through water
Development
Polyp - asexually reproducing
Mitosis produces many medusa (2N)
Medusa produces egg and sperm by meiosis
Female egg and male sperm (N)
Fertilization
Zygote (2N)
Mitosis grows zygote into a polyp
Planula larva
Senses and Nerves
• Nerve net.
No centralization.
Sensory information is sent throughout entire body, no brain to receive it
• Balance organs.
Statoliths used for knowing orientation of body
• Light receptors.
• Touch receptors.
FOUR CLASSES
(1) Class Scyphozoa
• ~200 species, all marine
• No true polyp stage.
• Include some of the largest sea jellies.
• Four gastric pouches.
Circular canals (outer edge)
Mouth
Radial canals
(Water flows from mouth at center and radiate out to edge)
(2) Class Hydrozoa
• 3,000 species, mostly marine.
• Polyp and medusa equally prominent.
• Jet propulsion aided by a velum.
• Some form colonies with specialized polyps.
Velum
Opening in the bell is controlled by the circular skin called the velum
Bottom opening in bell has water that is forced out for movement
Specialized colonies
Portugese Man O War has three types of polyp attached to a float made from a medusa.
Cubozoa
Few species, all marine.
Small, but with deadly toxins.
Complex nervous system and eyes.
Anthozoa
• Sea anemones and corals.
• 6,000 species, all marine.
• Medusa reduced or absent.
• Some symbiotic with algae.
Phylum Ctenophora (Comb Jellies)
100 species, all marine.
Swim using ciliated combs called ctenes.
Catch prey with sticky tentacles.
No larval stage.
Hermaphrodites with external fertilization
Feeding
Extracellular digestion
Closing Thoughts
• Cnidarians have a life cycle which alternates between sexual medusae and asexual polyps.
• Cnidarians and Ctenophora are both diploblastic and radial, with a simple gastrovascular cavity.
Cnidarians have cnidocytes and Ctenophora have ctenes.
• Digestive systems can be understood as adaptations to the diet and lifestyle of the organism, and a way to
increase SA for absorption.
LOPHOTROCHOZOA
• Diverse group of Bilaterians
• Some have a Lophophore or a trochophore larva. Some have neither, grouped mainly by molecular data.
• 18 phyla - we will look at 4
- Platyhelminthes
- Rotifera
- Mollusca
- Annelida
Platyhelminthes and Rotifera
Platyhelminthes are triploblastic
Locophores function in suspension feeding in adults
Trocophore larva feed and swim via cilia
Phylum Platyhelminthes
• 20,000 species in 3 classes.
• Free-living or parasitic.
• Simple excretory system.
• Acoelomates with a marine flatworm flattened bodies.
Osmoregulation
Excretion - getting rid of metabolic wastes
Managing ionic balance inside body
Maintain homeostasis
Class Turbellaria
• 3000 species, freshwater and marine.
• 2mm to 60cm
• Mostly freeliving, a few parasitic.
• Hermaphroditic with internal fertilization.
• Larval stage rare.
Morphology
Mouth
Pharynx - used in feeding, can be extended out of body
Gastrovascular cavity
Eyespots - light sensitive
Ganglia - gathering of nerves: processing of nerve information
Ventral nerve cords
Fairly well-developed muscle system
Adaptations for Internal Parasitism
• Reduction of feeding, sensory and locomotory organs.
• Expansion of reproductive organs.
• Internal parasites don't need to hunt for food or avoid being eaten.
• Biggest problem is finding a new host.
Class Cestoidea (Tapeworms)
• About 1000 species
All internal parasites.
• No head or gut.
Absorb food from intestine of host through body wall
• Segmented body consisting of proglottids.
Proglottids - repeating segments of egg and sperm-producing factories
Scolex (head) - attach to gut wall with hooks and suckers
The largest tapeworms can be up to 40m long!
Tapeworm life cycle
Adult tapeworm in definitive host.
Eggs or gravid proglottids released in host feces.
Eggs consumed by Intermediate host
Egg develops into Oncosphere larva
Larva encysts in organs of intermediate host.
Cyst reaches definitive host & grows into adult.
Adult tapeworm in definitive host
Tapeworm myths and misinformation
• Tapeworms won't come up into the host's mouth if you hold a piece of food close to mouth.
• Tapeworms can't be used to lose weight (by any sane person).
Class Trematoda (Flukes)
• About 16,000 species, all parasites.
• All have complex life cycle (intermediate host).
• Responsible for serious human and livestock diseases.
Fluke life cycle
Motile larva
Human host
Ciliated larva from feces get into water
Snail host
Motile larva can penetrate skin of human to end up in kidneys
Morphology
Schistosomiasis and other diseases
• Caused by several species in genus Schistosoma.
• Intestinal and urinary forms of disease.
• 200 million people have chronic symptoms, up to 800,000 deaths a year from complications.
• Most common in Africa, SW Asia and South America.
Monogeneans
• Ectoparasites on skin or gills of fish.
• Closely related to Trematoda.
• Simple lifecycles (no intermediate hosts).
Phylum Rotifera
• About 2,000 species, mostly freshwater and a few marine.
• < 50m to 2mm in length (among the smallest animals).
• Mostly predatory with a few parasites on invertebrates.
Morphology
Crown of cilia
Jaws
Stomach
Anus
Pseudocoelomates have an enclosed body cavity partially lined with mesoderm.
Mastax organ - rigid structures to grind up prey
Well developed sensory organs
Light receptors
Concentration of nerve cells at anterior end (ganglion)
Sexual reproduction is either rare or unknown
Asexual for at least 40 million years
In drought, can form a cyst that can remain dormant for 50 years
Closing thoughts
• Platyhelminthes is a phylum of acoelomate worms which include some specialized and
dangerous
parasites.
• Rotifers are mainly freshwater predators feeding with a corona of cilia.
PHYLUM ANNELIDA
Which worms are Annelids?
• Segmented worms.
• 16,500 species found in marine, freshwater and terrestrial envts.
• Three classes.
• Closed circulatory system and complete digestive system.
Segmentation
Worms have repeating units or segments with the same organs
Open and Closed Circulatory Systems
Closed - blood pumped through Heart and stays in circulatory system
Open - blood vessels open into cavities called sinuses (eg) grasshopper
Digestive System of Worms
Mouth
Muscular pharynx draws food in
Esophagus
Crop (storage)
Gizzard (mechanical mashing of food)
Intestine (runs to back of earthworm)
Typhiosole - provides more surface area in the intestine
(1) Class Polychaeta
• 11,000 species, nearly all marine.
• Body features: parapodia, setae, and head appendages.
• Include active predators, and filter and deposit feeders.
Parapodia and setae (chetae)
Parapodia are for locomotion and digging tunnels
Parapodia are highly vascular and can function in gas exchange
Parapodia move together like oars
Setae are the small hairs branching off of the parapodia
Head appendages
Two well developed eyes
Jaws
Tentacles - filter feeding, gas exchange, or sensory
Burrowing
Filter feeders tend to burrow partially and stay in the same place to collect food with tentacles
Reproduction
They send their reproductive organs off to mate while main body stays to eat
They produce an epitode which swims off to the breeding grounds
Gametes are released into the water in a swarm
Fertilization takes place in the water
Active or "Errant" Polychaetes
Active predators
Sedentary Polychaetes
Burrowers
Can form their own tube
Tentacles around head - used for collecting food in seawater
Christmas tree and feather-duster worms have a coral-like lifestyle
Feather-duster worms are filter feeders
Worms that live in hot areas such as underwater volcanoes can have symbiotic relationship with
bacteria
(2) Class Oligochaeta
• 3,500 species, mainly terrestrial (earthworms).
• No parapodia, little encephalization, but do have setae.
• Distinctive clitellum
Morphology
Outer waxy cuticle - retain moisture; may be porous for gas exchange
Epidermis
Circular muscle (can make worm longer and thinner)
Longitudinal muscle (can make shorter and thicker)
Setae are embedded in the muscle so they can be extended for anchorage or retracted to glide
Clitellum
Three layers form the cocoon
Mucus sheath
Secrete proteins that form actual wall
Secrete food for egg
Eggs laid into this cocoon
Cocoon is pushed off of worm's body and left in soil
Movement
Contracting circular muscles gives a wave of movement
Front part stretches forward; back is anchored to not move backwards
Front and back anchor; middle stretches and moves forward
Reproduction
Worms simultaneously exchange sperm
Worm A sends some sperm into B; then worm B returns sperm
This mechanism has allowed hemaphrodidism to continue
Diversity and Ecology
Some earthworms can be very long
Earthworms are good for soil and plants
Aeration - open airways in soil
Less surface litter
More topsoil
More organic carbon, nitrogen, and polysaccharides
In hardwood forests, worms can be harmful if heavily infested
(3) Class Hirudinea -- leeches
• 500 species, mainly freshwater and terrestrial.
• Parasitic and predatory.
• Have clitellum, but lack setae and septa (no internal divisions).
Morphology
-Jaws, Pharynx, Crop, Crop cecum, Intestinum (short intestine), Posterior suction
-Body walls would prevent suction of maximum blood
Predation
-on small minnows
Mouthparts
-Salivary glands secrete anti-coagulates to keep blood from clotting
Leeches in medicine
-bleeding
Parental care
-among the best parents in the invertebrate world
-keep young in a pouch
Leech removal
• Option 1: Let it feed and drop off by itself.
• Option 2: Find the anterior (skinny) end. Push sideways with a nail next to skin.
Remove posterior sucker the same way.
Closing thoughts
• Annelids are one of many vermiform or "wormlike" phyla.
• Annelids are segmented.
• Polychaetes dominate the marine envt., Oligochaetes the terrestrial, and Hirudinea freshwater.
Phylum Mollusca
Phylum Mollusa
• 90,000 species, marine, freshwater and terrestrial.
• Highly varied body plans in each class.
• Open circulatory system (mostly).
• 7 classes, we'll look a 4 main ones.
Most intelligent invertebrates: squids and octopus
Morphology
Shell - secreted by the mantle
Mantle
Mantle cavity
Visceral mass - (organs)
Nephridium
Heart
Coelom
Intestine
Stomach
Gonads
Radula - scraping organ of herbivorous used to scrape algae off of rocks
Mouth
Anus Gill
Foot - large and muscular
Nerve
Esophagus cords
Mollusc Circulatory system
Open circulatory system
Blood circulates in blood vessels
Blood opens into cavities called sinuses (in the foot and gills)
Radula
New rasping parts always growing
Similar to teeth
Mollusc Development
• Most have a trochophore stage, but this is usually short- lived.
Veliger Larva
Large velum used for gas exchange
Cilia for locomotion and feeding
Gut is protected by the shell
Class Polyplacophora (Chitons)
• 800 species, all marine.
• Shell of 8 dorsal plates - 8 plates running up the back
• Large foot used for locomotion and attachment.
Do not move very much, so mostly foot is for suction
• Use radula to feed on algae.
Chiton morphology
Underside: mouth and ventral foot
Shell top: dorsal plates
Class Gastropoda (slugs and snails)
• 70,000 species, marine, freshwater and terrestrial.
• Shelled (snails) and unshelled (slugs on land and nudibranchs in ocean)
• All display torsion.
Most are herbivores using radula
Gastropod body plan
Mantle cavity
Stomach and Intestine in shell - twists around
Anus - sticks out above head from shell
Mouth on underside
Move by muscular contraction of foot
Gastropod Torsion
In early larval stages have straight body
During development, torsion or twisting occurs so that anus and mouth end up on the same side of the shell
The benefit of this is in adult form for entire animal to retreat into shell
Gas exchange
Marine: Gills inside mantle cavity, some have terrestrial lungs used underwater
sea slugs have large external gills
Terrestrial: lung gas exchange to blood vessels, or gills by maintaining water in shell
Diversity
Carnivorous gastropods
Sea snails - think of shell diversity you see wash up on beach
Nudibranchs - large external gills, extremely colorful, carry toxins
Land snails and slugs
Class Bivalvia (clams)
• 7000 species, freshwater and marine.
• Hinged shell with two valves.
Gives ability to clamp shut, or to open shell
• No head or sensory organs.
• No radula.
• Filter or deposit feeders.
Muscular foot is used for digging into sediments
Morphology
Shell
Hinge area of shell
Mantle
Mantle cavity
Coelom
Gut
Gonad
Heart Adductor muscle
Digestive gland
Mouth
Palp Foot - used for burrowing
Anus
Excurrent siphon - draws water in
Gills - filters water and provides gas exchange
Most clams burrow into soft subtrates and suspension feed.
Gills are thin structures for gas exchange. They also trap food particles as water passes through them. Cilia
move the particles to the mouth.
Scallops live on the surface of the substrate and suspension feed.
Symbiotic Bivalves
symbiotic bacteria living in gills for protection
provide ATP and NADPH to the clams
bacteria are chemoautotrophs
Carnivorous Clams
use siphon to suck up small arthropods
Class Cephalopoda
• About 600 species, all marine.
• Mainly active carnivores.
• Big brains and lots of sensory organs.
• Highly modified gills, radula and foot.
(include squid and octopi)
Cephalization
Eye of the octopus are large and complex
example of analogous/ covergent evolution with vertebrate eye
The brain is in a modified foot
Motion
Jet propulsion
Squid has a siphon used for water movement
Octopus can use tentacles for propulsion
Shell Diversity
Nautilus - uses gas in the shell for buoyancy
Cuttle bone - skeleton of cuttle fish
Squid pen
Octopus has lost its shell
Modifications
Radula modified to beak
Skin can change colour and texture (muscles can contract or relax to change skin from bumpy to
smooth) for camoflage
Bioluminescence
Ammonites
Group of extinct cephalopods
Gem-stones are many from colourful fossils
Diversity in Cephalopods
Blue ring octopus - highly poisonous
Squid sizes - long tentacles for catching prey
Closing thoughts
• Molluscs are a diverse, species-rich phylum occupying marine, fw and terrestrial habitats.
• Most have a basic body plan featuring a mantle, mantle cavity, visceral mass, shell and radula.
• The body parts are modified for different functions in the different classes.
Phylum Arthropoda
Phylum Arthropoda
• The most successful and diverse phylum of animals.
• Segmented body.
• Exoskeleton (or cuticle) made of chitin.
• Paired, jointed appendages.
Exoskeleton/cuticle
Use external skeleton to attach muscles
Legs move separately from body
Cuticle - waxy layer preventing water loss
Open circulatory system
Tublular heart
Large blood sinuses
(1) Subphylum Cheliciformes
• A few marine species, and many terrestrial, mostly in Class Arachnida.
• Head appendages called chelicerae.
• Lack antennae.
• Usually have simple eyes.
Class Arachnida
• 70,000 species mostly terrestrial.
• Half are spiders
most of the rest are mites and ticks.
•Also includes scorpions
Morphology
Head and thorax have become fused
Abdomen behind thorax
Chelicerae of spiders are fangs used for feeding
Reduced celum
Blood sinus
Continuous duct from mouth to anus
Fluid feeders
Blood and sap from plants and animals
Canivores, parasites (ticks),
Gas exchange via book lungs or tracheae
Gas exchange in thin air chambers
Filters
Lung slit
Blood space
Spiders - prey on insects
Spider bites are fairly rare
Spiders are not generally dangerous
Mites - spider mites are destructive on greenhouse crops
Dust mites in your household eat dead skin that falls off your body
When you are allergic to dust, you are actually allergic to the mites in it
Ticks - blood feeder parasite on animals
Carry many diseases
Slow steady pressure is the prescribed method for tick removal
Scorpions
Larger scorpions are less venomous because they can use their pincers
The most venomous scorpions could kill a small child, not an adult human
(2) Subphylum Myriapoda
•Antennae and several pairs of mouthparts.
•Uniramous (unbranched appendages).
•Gas exchange by trachea.
•Excretion by Malpighian tubules.
•Cuticle not waxy.
•Simple eyes or no eyes.
•Many have repugnatorial glands (excrete sticky and smelly chemicals).
Class Chilopoda
Maxilliped
Centipede
Single pair of legs on each body section
Predatory on other insects
Class Diplopoda
Millipede
Two pairs of legs in each body segment
(3) Subphylum Crustacea
• 50,000 species.
Large and diverse group
• Mostly marine and freshwater.
• Biramous appendages.
• Two pairs of antennae.
• Lots of diverse groups.
Lobster
Pincers, swimming appendages under each abdominal segment
Gas exchange by gills
Osmoregulation by glands
Decapods - large group
Includes crabs and shell fish
Mostly marine
Some freshwater
Isopods - terrestrial
Most are fairly small
Copepods and Krill
Marine
Small and numerous
Important part of zooplankton group; major food source
Barnacles - crustaceans that have sedentary life
Calcium carbonate shell
(4) Subphylum Hexapoda
• Body of head, thorax and abdomen.
• Six uniramous legs on thorax.
• One pair of antennae.
• Compound eyes.
• Mainly terrestrial.
Not true insects: descended from wingless ancestors
Class Insecta Morphology
Compound eye
Antennae
Heart
Cerebral ganglion artery
Crop
Abdomen
Thorax and Head fused
Wings attached to thorax
Anus
Vagina and ovaries in female
Malpighian tubules
Tracheal tubes - gas exchange;
characteristic rings; breathing by pressure system (like humans); draw air in; tubes require
rings for support
Nerve cords
Mouthparts
Reproduction and Development
• Sexual reproduction common, with internal fertilization and separate sexes.
• Incomplete metamorphosis: Juveniles look similar to adults but go through several moults as they grow in
size.
• Complete metamorphosis: One or more larval feeding stages that do not resemble adults.
Wings and Flight
Evolutionary hypotheses: Perhaps derived in aquatic environment from excess gills could be used
for locomotion
Wings could have been for thermal regulation
Coevolution with Angiosperms
Bees and flowers
Insect Social Systems
Ants, bees, wasps
Separation into non-reproductive and reproductive individuals
(Think queen ant and the queen bee: for reproduction)
Insect Pests
Mosquito bites and Bee stings
Only a problem when insects are carrying diseases
Insects eat about the same amount of crops each year as humans do
Closing Thoughts
•Arthropods, esp. insects, are the dominant group of terrestrial animals, by almost any measure.
Vertebrates are a very distant second.
Osmoregulation; Move to Land; and Phylum Nematoda
Osmoregulation/Excretion
Two main functions:
1. Maintaining osmotic balance of body.
2. Excreting metabolic waste products - mainly nitrogen compounds.
Two main trends to remember:
• Larger and more metabolically active animals will require more sophisticated excretion system.
• Problems in maintaining osmotic balance are different in salt water fresh water and air.
Wastes:
Urine is most concentrated in salt water fish and mammals
Salt water fish excrete ammonia - most toxic
Mammals excrete urea
Invertebrates move to land
•Fossil tracks from about 490 mya.
•Arthropods with 8+ pairs of legs and a tail.
Arthropod adaptations for land
• Rigid support structures.
• Waxy cuticle.
• Internalized gas exchange surfaces.
• Regulatible pores.
• Internal fertilization
• Use of urea or uric acid rather than ammonia for excretion.
Phylum Nematoda
• At least 25,000 species, terrestrial (soil), marine,freshwater and parasitic.
• Most quite small with a similar body plan.
• Tough cuticle of collagen.
Morphology
Development
Movement
Not very efficient
No circular muscles
"waggle" back and forth
poor swimmers
Parasitic Nematodes
• Can be parasitic on invertebrates, especially arthropods (the good).
• Can be parasitic on plants (the bad).
• Can be parasitic on vertebrates, including humans (the truly revolting).
Closing thoughts
• Osmoregulation/excretion involves four basic processes: filtration, reabsorption, secretion and excretion.
Excretory systems must be more elaborate in larger and more metabolically active animals.
• The arthropods were the first animals to invade the land, and have many adaptations for terrestrial life.
• Nematodes include some of the vilest parasites you are ever likely to encounter. Let's all go wash our
hands.
Phylum Echinodermata
• 7000 species, all marine.
• Most display secondary, pentaradial symmetry.
• Have a unique water vascular system.
• Internal CaCO3 skeleton.
• Six classes.
Pentaradial symmetry
Star with 5 arms
Reproduction and Development
No internal fertilization
Bilateral symmetric larvae
Broadcast fertilization in water
Internal skeleton
Calcium carbonate elements
Stick out of body wall in a spine
Ossicles are internal
If packed close together, hard shell
If loosely packed, more flexibility
Pedicellariae
For defense and protection
Two pronged
Cleaning upper surface to remove debris from gas exchange surfaces
Water vascular system
Madreporite - sucks water in from outside body
Stone Canal - draws water into middle
Ring Canal - circle
Radial Canal - one down each arm
Ampullae - bladder on inside of body
Tube feet - outside of body, extended by ampullae contracting and pushing
water into tube feet for locomotion
1. Class Asteroidea (sea stars)
• 2000 species,
• Predators
• Slow moving, using tube feet.
• Found in intertidal to moderate depths.
• Five (or multiple of five) arms.
Sea Star Digestion
Cardiac stomach ejected from body through mouth
Pyloric Stomach
Morphology
Central disk
Digestive glands
Anus
Stomach
Gonads
Spine
Gills
Madreporite
Radial nerve
Ring canal
Ampulla
Podium
Radial canal
Tube feet
Gas exchange
Dermal Branchia
Extensions that go outside of body wall to increase surface area
Regeneration
Regrowth; one arm can regrow the entire body
Asexual reproduction
Defense
Sea star diversity
Colours, sizes, and shapes
Sun-stars have multiple arms
2. Class Ophiuroidea (brittle stars)
• 2100 species, mainly deep water.
• Predators, scavengers, deposit and filter feeders.
• Digestive system in disc, with no anus.
• No ampullae
More flexible, slender limbs
Tube feet are more used for gas exchange, limbs for locomotion
Look like a "spider" in the way they move with their limbs
Basket Stars - sedentary filter feeders
3. Class Echinoidea (sea urchins and sand dollars)
• 1000 species, mostly shallow water.
• Feed on algae (urchins) or detritus (sand dollars)
• Spines and pedicellariae may be poisoned (urchins)
Spines can be used in locomotion
Feeding
Feed on algae and detritus
5-part symmetric digestive morphology: mouth, stomach
Ecology
Sea Urchins can be devastating to kelp forests
Sea otters eat sea urchins and keep urchin populations down
Sea urchin eggs are considered a delicacy
4. Class Crinoidea (Sea lilies and feather stars)
• 600 species, mostly deep water or coral reef.
• Most ancient class - fossils go back almost 600 million years.
• Filter feeders with oral surface on top.
Feather Parts
Crown: Arm
Calyx
Pelma: Stem
Radix
5. Class Holothuroidea (sea cucumbers)
• 1000 species.
• Soft-bodied, may be bilaterally symmetrical.
See an anterior end, tube feet all on one side
• Oral tube feet modified as feeding tentacles.
• Filter or deposit feeders.
• Internal gas exchange structures called respiratory trees.
For defense, a sea cucumber would spill his guts for distraction
If attacked, digestive tract is spilled out so sea cucumber can get away
Cost may not be large during inactive feeding periods
6. Class Concentricycloidea (sea daisies)
• Only three species known, living on submerged wood.
• Biology not well understood.
Food may be directly absorbed
Closing thoughts
• The Echinoderms are an ancient phylum in the Deuterostomes, with a unique water vascular system used
in locomotion, feeding, gas exchange (and probably waste excretion).
Phylum Chordata
• > 50,000 species, most in Craniata (Vertebrates).
• Deuterostomes.
• Humble origins, but now the largest animals on earth.
• Three subphyla
Phylum Chordata includes the Vertebrates, along with some smaller and simpler members of the phylum.
Chordate characteristics
1. Dorsal, hollow nerve cord
2. Notocord
3. Pharyngeal slits or clefts
4. Tail
Spinal column
Dorsal, hollow nerve cord
Notochord
Body parts
Muscle segments
Mouth
Pharyngeal slits or clefts
Filter feeding or gas exchange
Anus
Tail: Muscular, post-anal tail
Subphylum Cephalochordata (lancelets)
Filter feeders
Bury into bottom of ocean
Considered to be basal group; closest to ancestral
Subphylum Urochordata (Tunicates)
Simple, sedentary life as adults
Filter food through Pharyngeal slits
Larvae mobile; active stage; has all four characteristics
• Cranium (braincase)
• Encephalization and increased mobility.
• Neural crest
• Heart with 2+ chambers.
• Hemoglobin
• Kidneys
• Doubling of Hox genes.
Subphylum Craniata
Neural Crest Formation
Skull Formation and neural tube important
Notochord
Migrating neural cells form eyes and nerves in head
Myxini (Hagfish)
• Lack vertebrae although are craniates.
Primitive eyes.
• Notocord retained as adults.
• No bone or jaws.
• 30 species.
Bottom- dwelling scavengers.
• Produce slime.
VERTEBRATES
Petromyzontida (lampreys)
• Vertebrae are small cartilage elements.
• Notochord retained as adult.
• No jaws or bone.
• 35 species, marine and freshwater.
• Most are parasitic.
Mineralized tissues
• Bone is made of calcium + phosphate mineral (apatite)
- Dermal bone
Humans: jaw and skull
- Endochondral bone
Mammals: large internal bones that anchor muscles
Development: Cartilage acts as a template and is laid down first, then
bone, then cartilage dissolves
• Cartilage
- Sharks have only cartilage and have jaws of cartilage
• "Tooth minerals" (enamel, dentine, cementum)
Extinct jawless fishes
Have complex skeletal structures
Evolution of jaws
• Allowed new ways of feeding, defence and manipulation of environment.
• Gnathostomes also have two pairs of fins.
• Also associated with changes to vertebrae, muscles, sensory system.
Stronger vertebrae for attachment of muscles
Adaptations seem to be associated with becoming more active
Increasing number of Hox genes could have allowed for changes to occur
Evolution: Jaws evolved from the gill arches
Are jaws "organs of extreme perfection"?
Jaws likely evolved in stages, with different functions at each stage.
1. Improved gill ventilation by active movement of water through mouth.
2. Suction of water used to draw in prey.
3. Teeth evolve to keep prey from escaping.
4. Toothed jaws used for biting and tearing prey.
Extinct jawed fish - Placoderms
Large and heavily armoured
(size of a bus - 10m long)
Extinct jawed fish - Acanthodii
Look like modern sharks and rays
More closely related to the bony fish
Strong spines
Chondrichthyes
• 750 species, mostly marine.
Diverged from the bony fish:
• Sharks
• Skates and rays
• Ratfish (chimeras)
• Secondary loss of bone.
May have lightened themselves
• Skeleton of calcified cartilage.
• Vertebrae have largely replaced notochord.
Sharks
Powerful swimmers
Predatory
Internal fertilization
Many give birth to live young
Heavier than water, and will sink
Have a much larger upper part of the tail fin to give lift
Have light oils in organs for bouyancy
Shark sensory systems
Olfactory systems are sensitive
"Nostril" does not connect to gills, only sense of smell to detect blood
Ampullae sense electrical fields in water; temperature gradients
Strong low-light vision
Detect pressure changes in water from vibrations
Olfactory > Vision > Electrical
Jaws and teeth
Teeth are not very well attached, snap off easily
Regenerated teeth often and quickly
Skates and Rays
Feed on molluscs and crustaceans
Jaws for crushing hard shells
Ratfish
Deeper water
Single gill opening
LUNGS or LUNG DERIVATIVES
Ray-finned fishes
• 27,000 species, marine and freshwater.
• Most in a derived group called the Teleosts.
• Found in almost every aquatic environment.
Swim bladders
Associated with gut
Retains buoyancy
Can extract gases from the gut or through the stomach
Operculum forces water past the gills; so fish can sit and still breath
Fin specializations
LOBED FINS
Lobed-finned Fish
Lung fish
Fleshy fins
Closing Thoughts
•Craniates evolved greater body size and complexity than competitors, perhaps because of multiplication
of the Hox genes.
•Evolution of traits such as increased encephalization, jaws and mineralized skeletons has often been
followed by adaptive radiations.