Download Chapter 22 Descent With Modification

Chapter 22 Descent With
Modification
Classification of Species, a history
• Aristotle (384-322B.C.E.)
– Species fixed, unchanging, eternal world, absolute
– Scala natura
• Life forms arranged in linear order of perfection
• Carolus Linnaeus (1707 - 1778)
– Binomial nomenclature
• Homo sapiens
Carl von Linné
– Nested classification based on similarities
• Birds/bats
• Systema Natura book
Fossils
• Remains or traces of organisms from the past
• >10,000 years old
• Organism dies  sediment  compression 
 rock strata
• Paleontology = study of fossils
Fossils buried in strata
• Charles Lyell, geologist (1797- 1875)
– Uniformitarianism, Earth changes slowly and
continually
– Change NOT due mainly to catastrophes
– Examples of slow processes
– Wind, erosion, water flow
• Lamarck (1744-1829)
– Evolution explains change in fossils over time
• Theory of use and disuse
• Theory of inheritance of acquired
characteristics
– Both not correct
This is a big tree dwarfed by many years of cutting
What size plant will seeds from this Bonsai produce?
Charles Darwin (1809-1882)
Descent with modification (evolution)
Alfred Russel Wallace came to same conclusion just before Darwin published
The Origin of Species
Voyage of the Beagle
Observed plants, animals
Darwin’s observations and inferences
• 1. Adaptations
– Characteristic of organisms enhance survival
– Adaptations could lead to new species
• Galapagos finches
Each on a different island
• 2. organisms descend from a common
ancestor
– Unity of life
– Can be represented as a tree
– Millions of years
Species grouped
by evolutionary
relatedness!
Mechanism of Natural Selection
A. Members of a population vary in traits
Genetic diversity
B. Traits are inherited from parent to offspring
C. More offspring produced than environment
can support
D. Those with beneficial traits survive AND
reproduce successfully
(survival of the fittest)
E. Populations change over time
F. Can lead to speciation
Note:
• Individuals do not evolve, populations do
• Only heritable traits are passed on
• Environmental factors vary!
Evidence for Evolution
I. FOSSILS
document change in living organisms over time
Example
Whales have a
terrestrial , 4
legged, ancestor
Bones suggest a
cow- like animal
50 mya
II. HOMOLOGOUS STRUCTURES
Reflect a common ancestry
Shared features
1. Skeletal structures
common mammalian ancestor
Function/name?
Homologous structures (cont.)
2. embryology- shared developmental plan
Homologous structures (cont.)
3. Vestigial structures
served function in ancestor, function lost, but
structure remains
Snakes retain vestige of pelvis
Ancestor to snakes had legs
Homology (cont.)
4. Genetic homology
universal genetic code
supports evidence for relatedness of species
Beta globin amino acid sequence
DEVGGEALGRLLVVYPWTQRYFDSFGDLSSASAI Mus musculus
DEVGGEALGRLLVVYPWTQRYFDSFGDLSSASAI Rattus norvegicus
DEVGGEALGRLLVVYPWTQRFFESFGDLSTADAV Bos taurus
• Convergent evolution
– Sometimes distantly related species have similar
structures
– Evolved separately (arose more than once)
– Example: mammals
marsupial
Rodent (placental)
III. BIOGEOGRAPHY
Geographic distribution of species
Affected by continental drift
slow movement of continents over time
250 mya Pangaea
As continents move, species disperse,
environmental changes
Example: endemic species found in one location
BUT, have relatives nearby
Island species colonized by mainland species
IV. Direct documentation of evolution
Peacock sexual selection
http://www.youtube.com/watch?v=T7ftXEQvnyU
Direct documentation
– Predators influence natural selection
– Prey adaptations to avoid predation
• Male guppies
• Color genes expressed in males only
• Predators attracted to color
• Sexual selection
– Females attracted to colors
Observations
Pool 1 with few predators:  brightly colored males
Pool 2 with many predators  drab males
Add brightly colored males to pool 2  over 15
generations, males more drab
Why?
Rosemary and Peter Grant, Princeton University
• In 1981 an unusually large male finch from Santa Cruz arrived on
Daphne Major.
• The biologists tagged the bird number 5110, and followed him and
his offspring through seven generations total.
• In the fourth generation drought killed off all descendants except
one male and one female.
• These offspring can only breed with each other because they have
strange bird song. Finches learn their songs from their father, and
the Grants suggest that 5110 sang the songs from his birth home of
Santa Cruz then modified his mating song by roughly copying the
Daphne Major birds’.
• This imperfect copying has, over time acted as a barrier to
breeding with other finches . So the immigrant bird’s descendants
have bred only with each other for three generations.
• New species?
The Grants won the Kyoto prize for their life work
Theory
• Unifies many observations
• Supported by all evidence
• Predictions stand up
Chapter 23
The Evolution of Populations
0rganisms do not evolve
• Microevolution
– Change in allele frequencies in population over
time
– Affected by
• Natural selection
• Genetic drift
• Gene flow
23.1 Genetic Variation
A. Genetic Variation: Variation within a
population
Discrete characters
one gene
Quantitative characters
vary along continuum
two or more genes
• Gene variability in a population
average heterozygosity f (Aa)
information about genetics of a population
• High heterozygosity = high genetic variability
• Can range from 0 to 1
Fruit fly has ~ 13, 700 genes
On average 1,920 are heterozygous (14%)
• Very low heterozygosity in cheetahs indicate
severe effects of small population sizes
Originated about 4 million years ago and was
common in Europe, North America, Asia ,
Africa. They disappeared about 10,000 years
ago from North America when major climatic
changes took place. Also disappeared from
Europe and most in Asia and Africa
vanished. Present populations derived from
inbreeding by very few surviving and closely
related animals. Every one is nearly identical.
B. Genetic Variation: Variation between Populations
• Geographic variation, ex. Mus musculus
Islands of Madeira – mice brought 15th century
several populations have evolved in isolation
Portugal
Populations descended from single ancestral
population, changes in chromosomes (not genes)
Geographic cline
Graded change along
geographical axis
Mummichog fish cline in cold adaptive allele
Mutation
Ultimate source of new alleles
Relevant only if in sperm/egg
Mutation: Point mutations
one base pair change in DNA
possible effects:
-none – does not change amino acid sequence of
protein
-harmful – protein function compromised
-beneficial - rare
Mutations that alter gene number or
sequence
• Gene duplication
– May expand the genome with no negative effects
– Mammal ancestor had 1 odor gene  duplication
• Humans have 1,000 olfactory receptor genes
– 60% inactivated in later mutations
• Mice have 1,300
Jianzhi Zhang and colleagues
(Univ. Michigan)
• Paper (handout)
• Homework – article analysis
Sexual reproduction
• Leads to genetic diversity
– .crossing over during meiosis
– . Random segregation of alleles into gametes
– . Independent assortment
– (and mutation)
Hardy Weinberg Principle
• A population that is NOT evolving :
(hypothetical population)
– No mutations
– Random mating
– No natural selection
– Extremely large population
– No gene flow
• Change in any one of these  change in allele
frequencies  evolution
23.3 Allele Frequencies (cont.)
• Affected by:
1. Natural Selection
• Differential success in survival and
reproduction
• Allele frequencies different in each generation
• Adaptive evolution
– Some alleles favored over others
– These increase in frequency with time
 Adaptation (at population level)
DDT is a pesticide used beginning 1940s
banned in 1972
• Example: Drosophila
• 1930s wild strain – no DDT resistance gene
– zero tolerance to DDT
Adaptive evolution
Figure: increase in frequency of pesticide resistance in mosquitos after spraying
with DDT. A sample of mosquitos was captured at each time indicated and the
number that were killed by a standard dose of DDT (4 % DDT for 1 hour) in the
laboratory was measured. From Curtis et al. (1978).
2. Genetic Drift
• Chance events can cause allele frequencies to
vary
The founder effect
A. A few individuals become isolated from
population
B. The new population has different allele
frequencies than the main population
• Founder effect examples:
• Few individuals wind up on island during
storm
• A few individuals are cut off by an earthquake
Founder effect
Bottleneck effect
– Sudden drastic population reduction
– Lessens genetic diversity
– Example: greater prairie chicken
• 1800s – millions in Illinois
• 1993 - 50 birds in 2 populations
– Low genetic diversity
– 50% of eggs hatch
Genetic Drift, summary
• Significant factor in small populations
• Allele frequencies can change wildly with
generations
• Genetic variation is lost
• Harmful alleles may become fixed in
population
23.4 Natural Selection is a mechanism
that causes adaptive evolution
• A blend of chance and sorting as natural
selection favors certain alleles.
• Relative fitness
– Relative contribution individual makes to gene
pool of next generation
• Note: the organism is subject to natural
selection, populations evolve
• Directional selection
– extreme phenotype
most fit
– f(alleles) in
population shifts in a
direction
• Example: deer mice
– Dark favored, live
among dark rocks
– Why is this a
beneficial trait?
Disruptive selection
– Individuals of both
extremes most fit
• Some mice colonized
white rocks, some
dark
• What happened to
the intermediate
color mice?
• Stabilizing selection
– Intermediate
phenotypes favored
Example: birth weight in humans
Examples of adaptations
• Cuttlefish
• Adaptation?
Snake
adaptation
• Sexual selection
– Individuals with certain inherited characteristics
more likely to obtain mates
• Can lead to sexual dimorphism
– Differences between males and females
• Intrasexual selection
– Individuals of same sex compete for mate
• Intersexual selection
– Mate choice
– Showy tail in peacocks advertises fitness to female
– Showiness may be risky
• Ex. guppies
Preservation of genetic variation
• Diploidy
– Allows recessive alleles to be maintained in
population in heterozygotes
– Maintains genetic diversity
The heterozygote advantage
– Sometimes a heterozygote has greater fitness!
– Beta globin gene encodes subunit of hemoglobin
Genotype
Phenotype
SS =
Ss =
ss =
Heterozygote advantage
• Frequency of s allele highest in areas with
malaria
Why natural selection cannot fashion
perfect organisms
1. Selection can only act on existing variation
2. Evolution builds on what is present in organism
already
Ex. terrestrial lineage of whales, bats
3. Adapations are compromises
Ex. shoulder joint (human)
4. Evolution based on interaction between chance,
environment
Ex. wind storm kills many insects, including most fit
Chapter 24
Origin of Species
Speciation
• Process by which one species splits into two or
more
• Unity of life – species evolutionarily related
• Microevolution
– Change in allele frequencies in populations
• Macroevolution
– Change over geological time  speciation
Biological species concept
• Species is a group whose members can
interbreed (and produce fertile offspring)
• Share a gene pool
• Reproductive isolation
• Pre-zygotic barrier
– Sperm from one cannot fertilize egg from another
– Why?
• Habitat isolation, temporal isolation, behavioral
isolation, mechanical isolation
Different sperm proteins
Mates late winter
Mates late summer
Misalignment of genital openings
• Post-zygotic barrier
– Hybrids are infertile
– Example: mule
May not survive
Mechanisms of speciation
• Allopatric speciation
– A population is divided geographically
– Each group continues to evolve, but separately
salamanders
• Natural selection
– Selects for different traits depending on environment
• Genetic drift
• Speciation occurs - When populations are
reintroduced – do not interbreed (reproductive
isolation)
Sympatric speciation
• Gene flow reduced between members of
same population/same geographical area
• Ex. Polyploidy
– Extra set(s) of chromosomes
– Not uncommon in plants
Sympatric speciation (cont.)
• Can be driven by habitat
– North American maggot fly lived in hawthorn tree,
then, some colonized apple trees. These flies
developed faster, now, temporally isolated (mating on
apple tree flies is 3 wks earlier)
Rhagoletis pomonella.
Hybrid zones
Both frogs found in the hybrid zone
Hybrids have high embryonic mortality and anatomical abnormalities
• Hybrid zone outcomes:
1. Reproductive barriers strengthened
• Limits hybridization
2. Barriers weakened
• Species fuse into single species
3. Stable hybrid zone
Genetics of speciation
• Identify genes that control traits involved in
reproductive isolation
• Ex. Japanese snail, Euhadra
– Single gene controls shell spiral direction
Chapter 25
• History of Life on Earth
The Fossil Record
• Record of life on earth over time
• Incomplete record/limited
• Radiometric dating of strata
– Decay of radioactive isotopes
– Half life = time for 50% of isotope to decay
C-14 half life = 5,730 years
C-14
C-14 dating not effective > ~75,000 years
Measure C-12/C-14 ratio
• For older fossils in rocks
– Use K-40 (1.3 billion year half life)
Key Events in Life’s History
Geological eras of life
1. Paleozoic
2. Metazoic
3. Cenozoic
The first single celled organisms 3.5 bya
Stromatolites
Microbes bind thin layers of sediment
Large amount of biomass/communities
Algal biscuits
fossils
May have contained cyanobacteria, algae, eukaryotic cells……
Oscillatoria
• The first eukaryotes 2.1 bya (older?)
– Single celled
– Nucleus
• Multicellular animals > 535 mya
– Soft bodied, small
– <1 meter
The Cambrian explosion
• 535 mya
• Cnidaria, Porifera, Mollusca fossils
Cambrian explosion lasted ~40 my
• Larger animals
• Hard shells
• Predator/prey evolution
500 mya trilobite
The colonization of land by animals
• 500 mya
• Adaptations to prevent dehydration
• Tetrapods ~ 365 mya
Mass Extinctions (5)
• >50% of animals extinct in “short” period of
time
1. Permian extinction
– 250 mya
– 95% of marine species extinct
– Most terrestrial species
Cause: Oxygen deficit?
– Neil Tyson DeGrasse
2. Cretaceous extinction 65 mya
Most marine and terrestrial species including
dinosaurs
Cause: asteroid 
hot vapor, debris
blocked sunlight?
10 km
Consequences of mass extinctions
• Once a species is extinct, it does not return!
Adaptive radiation
• Periods of evolutionary change in which new
species adapt to fill different ecological roles
• Occurred after each mass extinction
• Example: Cretaceous mass extinction 65mya
– Mammal radiation
Evolution is not goal oriented
Chapter 52 Ecology and the
Biosphere
Ecology
• Study of the interactions between organisms
(biotic factors) and the environment (abiotic)
• Environmentalism
– Advocating for the protection of nature
• Red kangaroo (Macropus rufus)
– Abundant in interior
Australia – dry climate
– Not found along coast – wet
– Hypothesis? Abiotic factor?
Biotic?
• Moisture, predator,
temperature, food,
competition, disease
Rachel Carson
• “ The ‘control of nature’ is a phrase conceived
in arrogance, born of the Neanderthal age of
biology and philosophy, when is was supposed
that nature exists for the convenience of man”
• Efforts led to a ban on DDT
• Silent Spring (1962)
Factors affecting species distribution
1. Dispersal and distribution
A. Range expansion
Movement of individuals away from area of origin
B. Transplants
– Intentional or accidental
Kudzu, a Japanese invasive vine growing in
Georgia, US
Brown tree snake (from Australia)has eaten all
Guam Flycatcher, Rufus Fantail, Bridled WhiteEye and Micronesian Honeyeater eggs, now
eating the Mariana Crow, the Guam
Micronesian Kingfisher, the Island Swiftlet and
the Mariana Fruit Bat.
• 2. Habitat selection and behavior
A. Behavior
An individual may avoid a certain habitat even though it is
suitable
Corn borer moth prefers to lay eggs on corn even though
larvae can feed on other plants
B. Biotic factors that affect species distribution
– Parasitism, competition, pollinators, predators,
food source…
• C. Abiotic factors
– Temperature, water, salinity, sunlight, soil
– Vary spatially and temporally
• Temperature
– Cells rupture <OoC
– Proteins denature>45oC
– Metabolic rate may be affected by T
• Water
– Dehydration
• Salinity
– Osmosis
– Example: freshwater fish gains water -it is adapted
to excrete water.
• Sunlight
– Photosynthesis
• Rocks, soil
– pH, minerals, substrate
Chapter 54
Community Ecology
1. Competition
• Interspecific competition
– Individuals of different species compete for a
resource
– Limits growth and survival
• Canadian lynx and fox compete for snowshoe hare
Outcomes of competition
• Competitive exclusion
– Paramecium experiment (G.F. Gause, 1934)
P. aurelia + P. caudatum
Competition for food source
P. caudatum dies
Even a slight advantage will lead to
disappearance of less fit species
P. aurelia
P. caudatum
• Niche development
– Niche = species use of both abiotic and biotic resources (habitat is
“address” niche is “profession”)
– Example: Anolis lizards in DR
Niche (continued)
2 similar species can coexist in same community if niches are
different
Resource partitioning in Anolis lizards
A. distichus prefers sunny twigs
A. insolitus prefers shady branches
Hypothesis: competition in the past selected for individuals
using different sets of resources
The fundamental niche of distichus may be sun and shade,
but its realized niche is sun – how could this be tested?
Anolis lizards, resource partitioning
Fundamental and realized niches in
barnacle species (Joseph Connell, Scotland, 1961)
Balanus cannot survive on high rocks, it dries out during low tide – compare
fundamental and realized nice
• Character displacement
– Observed in sympatric populations (overlapping ranges)
– Divergence of body structure and resource use
Twig anole
Bahamas and Cuba
Trunk anole
Trunk ground anole
2. Predation
• Predator adaptations
smell, sight, claws, stingers, teeth, aggressive mimicry
• Prey adaptations
hiding, herds, alarm calls, cryptic coloration aposematic
coloration, Batesian mimicry, Mullerian mimicry
Zebra
Vervet monkey
Aposematic and cryptic coloration
Golden poison frog A warning
coloration to indicate a toxic defense
(alkaloid toxin –batrachotoxin in skin
- one frog could kill 20 humans)
• Batesian mimicry
– A harmless species mimics a harmful one
Hereroplanes ornatus (hawk moth larvae)
• Mullerian mimicry
– Two or more unpalatable species resemble each
other
– Each species gains additional protection
Both untasty
• Aggressive mimicry
– Predator shares feature with harmless model to
attract prey
“flower“
lantern
tongue “worm”
3. Herbivory
• Interaction in which organism eats plant or
algae
• Adaptations – smell, teeth, digestion
• Plant defenses
– Chemicals – peppermint, strychnine, nicotine
– Spines, thorns
4.Symbiosis
• Two that live in direct contact
• May be harmful, neutral, or helpful
• Parasitism
– One organism (parasite) derives nourishment from
another (host)
– Endoparasite lives within host
– Ectoparasite – lives on host
plant root
• Parasites affect:
–
–
–
–
Survival
Reproduction
Population density
Behavior
•
•
Lake Superior Island
70,000 ticks per moose  hair damage,
blood loss  increase chance of cold
stress, wolf predation
• Mutualism
– Benefit both species in a relationship. Ex. acacia
and ant
Central America, ant hollows out large
thorns of the acacia plant for nests,
feed on secretions from four nectaries
at the base of each petiole and on the
protein rich tips of the leaves, which
together provide an almost complete
diet for the ant.
The ants protect trees from
invertebrate as well as vertebrate
herbivores. With movement of the
branch, the ants emerge releasing a
nasty odor and physically attack the
herbivore.
• Commensalism
– One species benefits, the other is not, but is not
harmed
Cattle Egret often seen in the company of
grazing animals. The grazers stir up insects,
which the egret eats. There is no apparent
benefit to the cattle.
The birds will also follow mowers……
The clownfish slowly accustoms the anemone to the chemical makeup of the
fish's skin; this gradual acclimatization prevents the anemone from stinging the
clownfish. The fish gets a safe habitate and some food; the anemone gets cleaned
clownfish chasing away fish that would harm the anemone, may attract
prey. Some scientists do not see any benefit for the anemone and classify this as a
commensalism.
Each sloth can host 100 moths and 1000 beetles. The entire life cycle
of beetle and moth is connected with the sloth, each spending its
larval period in sloth dung, and their adult period eating the algae.
?
Costa Rica. Tree sloth has algae growing in its
fur. Algae help to camouflage the sloth against
the lichen-covered tree (note brown fur of
baby, not covered with algae).
Xenarthra
A moth lives only in the sloth's fur and
consumes the algae. What is the relationship
between the moth and the sloth?
Effect of Interaction On:
Type of Interaction
Species 1
Species 2
(-)
(-)
Predation
Predator ( )
Prey ( )
Parasitism
Parasite ( )
Host ( )
Herbivory
Herbivore ( )
Plant ( )
Commensalism
( )
( )
Mutualism
( )
( )
Competition
Species in communities
• Species richness = the number of different
species in a community
• Relative abundance = number of each
Community 1: 25A, 25B, 25C, 25D = 4 species of
same relative abundance
Community 2: 80A, 5B, 5C, 10 D……..?
• Trophic structure
– Feeding relationships between organisms
Food chain
Primary producers  primary consumers 
secondary consumers  decomposers
Food web
Linking food chains
• Food web links
food chains
• A species may be
in web at
different trophic
levels
Species with a large impact
• Dominant species
– Most numerous
– More biomass
In temperate bogs the dominant vegetation is
usually species of Sphagnum moss
Foundation species
primary producer
Kelp in kelp forest , CA
• Keystone species
Beaver are well-known for building
dams. These dams create relatively large areas
of still water where there once was a small
stream. For organisms that live in such still
waters the beaver is a wonderful keystone
mutualist; for animals that like flowing water
it's not such a good deal.
•
The American Alligator, left, excavates depressions in its habitat that fill with
water. During dry times, these gator holes may be the only places with
water. Thus, to all the organisms whose survival depends on the water in those
holes the alligator is a keystone mutualist. Of course, the gator might eat a few of
those things that come to live in its wallow.
Community Ecology is useful for understanding
pathogen life cycles and controlling disease
• Pathogens can alter community interactions
• Coral reef communities
– White band disease kills corals
• Zoonotic disease
– Transferred from animals to humans
– Direct contact or vector
– Parasite life cycle
– River blindness and black flies
– Avian flu tracking