Download Evolution and Classification

Evolution and
Classification
Unit 9
How could life have begun on a
lifeless Earth?
• Early atmosphere was similar to gases given off by
volcanoes  carbon monoxide, carbon dioxide, and
nitrogen
• Notice: NO OXYGEN
How could life have begun on a
lifeless Earth?
• Aleksandr Oparin = Russian biochemist;
developed a theory that the chemicals in
the early atmosphere and energy from
lightning could have formed simple
organic compounds
• Earth was mostly covered by water  life
probably began in the oceans, a
“primordial soup”
Miller and Urey Experiment
• Conducted in 1952 by Stanley Miller and
Harold Urey
• They took a vial of water and gases similar
to those of the early atmosphere and
shocked it with electricity (like lightning)
• They discovered amino acids had formed
• Since proteins are a major building block
of cells, they concluded that this could be
how life began
• http://www.youtube.com/watch?v=79o6xz
MfzKg
Biogenesis vs Abiogenesis
• Abiogenesis = the idea that life can come from non-living
things, also known as spontaneous generation
• Biogenesis = the idea that life must come from other life
Redi Experiment
• Performed by Francesco Redi in 1668
• At the time people believed in spontaneous
generation
• Fish came from mud in rivers
• Maggots came from rotting meat
• Redi decided to prove that life must come from
other life
Redi Experiment
Open Jar
Sealed jar
Cheesecloth jar
Open to the air?
Yes
No
Yes
Flies able to get
in?
Yes
No
No
Rotting meat?
Yes
Yes
Yes
Maggots present? Yes
No
No
Conclusion:
Maggots come from flies, not from meat. Therefore,
life must come from other life  spontaneous
generation is wrong
But wait, there’s more…
• After the discovery of the microscope and microscopic
organisms, people wondered “Is biogenesis true at all
levels of life?”
• Louis Pasteur (a French microbiologist) performed an
experiment that proved that it was
Pasteur’s Experiment
• Pasteur made a “broth” of nutrients that he boiled until he
was sure nothing was alive in there
Pasteur’s Experiment
• The flask was specially designed to be open to the air, but
not let any dust touch the now sterile broth
Pasteur’s Experiment
• Pasteur saw that nothing grew, so he repeated the experiment, but now
he snapped off the neck of the flask and exposed the broth to dust
• The broth was soon filled with microorganisms
• Therefore, spontaneous generation was proven wrong again
So where do cells come from?
• Miller and Urey had proven that amino acids could form on
their own, but what about cells?
• The first cells were probably anaerobic, prokaryotic,
heterotrophic, and unicellular
• Anaerobic = no oxygen in atmosphere
• Prokaryotic = no nucleus (developed later)
• Heterotrophic = don’t make own food  too hard
• Unicellular = small and simple
How did we get oxygen?
• Over time, photosynthetic cells developed
• RECALL: Photosynthesis produces glucose and
oxygen
• All of this oxygen resulted in the ozone layer and
allowed aerobic organisms to develop
Endosymbiont Hypothesis
• Developed by Lynn Margulis in 1966
• States that eukaryotic cells came from prokaryotic cells that lived
together in symbiosis
• Mitochondria and chloroplasts have their own genetic material and
reproduce on their own  probably bacteria absorbed by the cell
• Endosymbiosis = when one organism absorbs another and they live
and work together
Ok, so now we have cells…
Where did all this life come from?
• Charles Darwin (1809-1882) is credited with creating the
theory of evolution, although his ideas were based on the
ideas of many others
• Developed his ideas as he sailed on the HMS Beagle,
especially as he sailed around the Galapagos Islands
Theory of Evolution
• Darwin originally decided to keep his ideas to himself
• In 1859, Alfred Russel Wallace discovered the same things as Darwin
and was going to publish his ideas
• This made Darwin decide to go ahead and publish his findings
Theory of Evolution
• 1. There is a variety of traits in a population.
• 2. There is competition in the population for limited
resources.
• 3. Natural selection favors the individuals with a certain
trait. This doesn’t mean that everyone else dies, but they
won’t have as many offspring.
• 4. Over time, this trait will be more frequent in the
population, because nature has selected that trait.
Theory of Evolution
• What makes a trait useful?
• That depends on the circumstances of the population
Adaptations
• An adaptation is any heritable trait that suits an organism
to its natural function in its environment (its niche)
• Three major types:
• Structural adaptations = physical traits like defensive
structures, camouflage and mimicry (looking like a more
dangerous animal)
• Behavioral adaptations = behaviors (learned or instincts)
that help an organism survive, such as herding, schooling,
growling, etc.
• Physiological adaptations = physical/chemical traits such as
sight, enzymes, and hemoglobin
Evidence for Evolution
• Fossils = any evidence of life, including imprints and
remains of organisms
• The fossil record is incomplete  very few organisms
become fossils
• However, the fossil record indicates that life began in the
sea and moved to land
Evidence for Evolution
• How can we tell how old a fossil is?
• Relative dating = where the fossil is compared to other
fossils; fossils near the top are more recent than those below
 not very accurate
• Radioactive dating = uses the rates of decay of various
radioactive isotopes to determine when the organism was
fossilized  much more accurate
Evidence for Evolution
• Biochemical similarities = similarities in DNA, amino
acid sequences, proteins, etc.
• The more similarities there are, the more closely related
two species will be
Evidence for Evolution
• Shared anatomical structures = physical similarities
between species
• Similar bone structures (even if the function is different)
indicate a common ancestor = homologous structures
• However, structures that perform the same function but have
different anatomical structures DO NOT come from the same
ancestor  evolved separately = analogous structures
Evidence for Evolution
• Vestigial structures = structures that are not functional in
an organism, but indicate a link to a previous ancestor
• Examples: Human appendix, human tail bones, foot bones in
whales and dolphins, etc.
Evidence for Evolution
• Embryology = comparing how organisms look at different
stages of embryonic development and looking for
similarities
So if there is all this evidence, why
is evolution just a theory?
• In science, a law tends to describe a relationship in nature,
a theory explains why that relationship exists.
• If a better explanation is discovered, a theory can be
discarded or replaced
• Right now, the theory of evolution is the best scientific
explanation for life
When did different organisms
evolve?
• Life began in the ocean  unicellular (simple protists,
algae, etc.)
• Eventually, life got complicated (multicellular plants,
invertebrate animals like jelly fish, etc.)
How did animals evolve?
• From jellyfish, animals developed backbones  fish
• Some animals grew legs and lungs and moved out of the
water  amphibians and insects
• Amphibians still need to return to water to lay their eggs
How did animals evolve?
• Eventually, harder shells and dry skins or feathers develop
 reptiles and birds
• Mammals then evolved  live birth, produce milk, hair
follicles
• Some mammals returned to the ocean  whales, dolphins,
manatees, etc.
How did plants evolve?
• Aquatic plants moved onto the land  bryophytes =
seedless, non-vascular (they can’t move water through a
stem)
• Mosses, liverworts, hornworts
• Must stay low to the ground for water  osmosis
• Need water to reproduce
How did plants evolve?
• Seedless vascular plants developed next
• Now capable of growing taller  can move water against
gravity
• Xylem = carries water up from roots to rest of plant
• Phloem = transports nutrients and carbohydrates (food) to rest
of plant
• Reproduce using spores instead of seeds
• Ferns, club mosses, horsetails
How did plants evolve?
• Plants then developed seeds  Gymnosperms (“naked
seed”)
• Have vascular tissue and seeds, but no flowers
• Not as dependent on water = wider variety of habitats
• Palm trees, conifers, ginkgoes, gnetophytes
How did plants evolve?
• Finally, flowers developed  Angiosperms
(“enclosed seed”)
• Roses, oak trees, daisies, maple trees, etc.
• Two kinds:
• Monocots = one seed leaf, parallel veins,
floral parts often in multiples of 3, vascular
bundles scattered throughout stem, fibrous
roots
• Dicots = two seed leaves, branched veins,
floral parts often in multiples of 4 or 5,
vascular bundles arranged in a ring, taproot
Types of Plants:
Vascular Tissue?
(able to move
water?)
Seeds?
Flowers?
Bryophytes
No
No
No
Seedless
vascular plants
Yes
No
No
Gymnosperms
Yes
Yes
No
Angiosperms
Yes
Yes
Yes
How does evolution work?
• Jean-Baptiste Lamarck = (1744-1829) the man who got it
wrong
• Thought that acquired traits could be passed from parent
to offspring  now we know that is not true
How does evolution work?
• Individuals don’t evolve, populations do
• Populations are the smallest unit of evolution
• Evolution occurs when the gene pool (all of the genes of a
population) changes
• A change in genotype may lead to a change in phenotype
• Evolution acts on the phenotype
How does evolution work?
• Mutations = random changes in DNA; may lead to a new
phenotype
• If the mutation is favorable, the organism will have an
advantage to survive and reproduce
• The environment also plays a role  environmental
changes are nature’s “selection forces”
• Example: Lots of snow makes a mutation for white fur
favorable
Types of Selection:
• Stabilizing selection =
favors the “average” or
“middle” phenotype
• Directional selection =
favors ONE of the extreme
ends of the phenotype
spectrum
• Disruptive selection =
favors BOTH of the
extreme ends of the
phenotype spectrum, but
not the middle
Co-evolution
• The evolutionary effect of one species on another
• Example: Hummingbirds with longer beaks are better able
to collect nectar from long, narrow flowers.
Hummingbirds prefer brighter colored flowers. Therefore,
there is an increase in frequency for long-beaked
hummingbirds and bright flowers.
Geographic Isolation
• Speciation = the formation of a new species
• Geographic isolation = two populations of a species are
physically separated from each other and unable to
interbreed  eventually become new species
• Therefore, geographic isolation leads to reproductive
isolation
How quickly does evolution
happen?
• Two different rates:
• Gradualism = evolution that takes a long time, happens
gradually and slowly
• Punctuated equilibrium = evolution that happens over a
relatively short period of time, happens in rapid bursts
after long periods of stability, probably due to
environmental change
Does evolution happen today?
• YES!
• As long as variation, overproduction, competition,
natural selection, and mutations occur, evolution will
happen
• Since most evolution takes so long to occur, it can be hard
to see in a lab
• However, there are some forms of evolution we can
observe…
Does evolution happen today?
• Resistance evolution = insects become resistant to
pesticides, bacteria become resistant to antibiotics
• Artificial selection = humans select desirable traits and
breed animals who have those traits (ex. Different dog
breeds)
How do we organize organisms?
• Aristotle = Ancient Greek philosopher who developed the
first classification system
• Two main categories = plants and animals
OR
Carl Linnaeus – Father of
Classification
• Further divided plants and animals into smaller and
smaller groups
• Used Latin because it was a “dead language” and would not
change
Linnaeus Classification
• Linnaeus first grouped related organisms into a genus
• Example: All dog-like creatures are grouped into the genus
Canis
• Every different type of organism within the group gets its
own name  a species
• Example: A domesticated dog is grouped into the species
familiaris, while the wolf is grouped into the species lupus
• Genus is always capitalized, species is not
• Italicized or underlined  Canis familiaris or Canis lupus
Scientific names
• Binomial nomenclature = two names (genus + species)
• Why use scientific names?
• Avoid confusion due to common names  same name for
an organism all over the world
• Question: What is the difference between a cougar,
mountain lion, panther, puma, and a catamount? What
about a cottonmouth and a water moccasin?
• Answer: In North America, they are the same animal!
Modern Classification
• Even after the microbial world was discovered, the 2
kingdom system continued to be used
• Science can be very slow to change
• In 1969, Robert Whittaker expanded classification to
include 5 kindoms: Animals, Plants, Fungi, Protists, and
Monera
Modern Classification
• Taxonomy = the science of classification
• Today, we have seven levels:
Kingdom
Phylum
Class
Order
Family
Genus
Species
King
Phillip
Came
Over
For
Great
Sex
Modern Classification
• A kingdom is a more general, broad group and will
therefore have more organisms
• We now have 6 kingdoms
• A species is much more specific, and will therefore have
less organisms  only one
• A species is defined as a group of organisms which can
interbreed and produce fertile offspring
But wait… There’s more!
• We now have 3 domains that we organize the 6 kingdoms
into:
• Bacteria
• Archaea
• Eukarya
Organizing Life…
• So what happens if you come across an organism, and you
don’t know what it is?
• There are several tools you can use, but one of the easiest
is the dichotomous key
Dichotomous Key
• Uses a series of paired statements about the physical
appearance of the organism
• Only useful if the organism has already been classified and
given a scientific name
• 1. Always start at statement 1 (or the beginning point)
• 2. Decide which path best describes the organism
(Statement A or Statement B)
• 3. Follow that path to find the next choice (Go to …)
• 4. When you can go no further, you will find the name!
Dichotomous Key
But what if it is an organism that
hasn’t been classified yet?
• Scientists use many methods to classify new organisms:
• Morphology = classifying organisms based on their physical
characteristics  usually enough to get the correct domain and
kingdom
• Example: Having a nucleus will place the organism in the domain Eukarya
• DNA and biochemical analysis = scientists will look for genetic
similarities to other classified organisms or other less visible (but
still testable) characteristics
• Example: In a Gram-stain, prokarya will stain pink (gram-negative) while
archaea will stain purple (gram-positive)
But what if it is an organism that
hasn’t been classified yet?
• Scientists can compare embryology (how organisms look
during early stages of development)
• Evolutionary phylogeny = describes relationships between
organisms based on shared traits, which can be physical (does
the animal have a jaw?) or genetic (shared genes)
• Phylogenetic tree = tool used to show phylogenetic
relationships
Don’t get the wrong idea…
• Humans are not at the top of the “evolutionary ladder”
• We are just another branch on the tree!
1) German Shepherd, Great Dane, parrot,
Irish setter, canary, husky, robin, pigeon
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2) apples, peas, orange, banana, carrot, lettuce,
turnip, pear, grape, potato
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The Six Kingdoms: Bacteria
• Prokaryotic, unicellular
• Food: Can be autotrophic or heterotrophic
• Cellular energy: Can be aerobic or anaerobic respiration
• Reproduction: Asexual
• Can be beneficial (making food like yogurt) or harmful
(causing disease) to humans
The Six Kingdoms: Archaea
• Prokaryotic, unicellular
• Food: Can be heterotrophic or autotrophic
• Cellular energy: Can be aerobic or anaerobic respiration
• Reproduction: Asexual
• EXTREME bacteria  live in areas with very high
temperatures, salinity, guts of animals, etc.
The Six Kingdoms: Protista
• Eukaryotic, can be unicellular or multicelluar
• Food: Can be autotrophic or heterotrophic
• Cellular energy: Aerobic respiration
• Reproduction: Asexual
• Some protists (like algae) form the base of food webs and
produce most of our oxygen
The Six Kingdoms: Plantae
• Eukaryotic, multicellular
• Food: Autotrophic
• Cellular energy: Aerobic respiration
• Reproduction: Sexual and asexual
• Very important  form the base of many food webs, used
for many products (lumber, food, cloth, medicine, etc.)
The Six Kingdoms: Fungi
• Eukaryotic, can be multicellular or unicellular
• Food: Heterotrophic
• Cellular energy: Aerobic or anaerobic respiration
• Reproduction: Asexual or sexual
• Act as decomposers (break down dead stuff) and can be
used to make alcohol and food
The Six Kingdoms: Animalia
• Eukaryotic, multicellular
• Food: Heterotrophic
• Cellular energy: Aerobic (occasionally anaerobic)
• Reproduction: Sexual
• Important consumers in food webs, humans are animals