Evolution Overview

Evidence for Evolution

A. Biogeography1. Geographical

distribution of species

Evidence for Evolution

B. Fossil Record1. Evolutionary transitions

2. New forms appearing/disappearing

Evidence for Evolution

Transitional Forms

Evidence for EvolutionC. Comparative Anatomy

1. Anatomical similarities between species grouped in the same taxonomic categories

Evidence for Evolution

2. Homologous structures

a. Similarity in characteristics from common ancestor

Evidence for Evolution

3. Analogous structurea. Look similar because of environment

b. No common ancestor

Evidence for EvolutionD. Comparative Embryology

1. Closely related organisms go through similar stages in embryonic development

Evidence for Evolution

View comparative embryology

Evidence for Evolution

E. Molecular Biology1. DNA, RNA, Protein Analysis, mitochondrial DNA

Evolution is Descent With Modification Evolution only occurs when there is a

change in gene frequency within a population over time.

Beetles and Drought Beetles of a different color

Why are the beetles smaller the next year? Evolution or environmental influences?

1st Year

2nd Year

Why are there less green beetles the next year? Evolution or environmental influences?

I. Basic Mechanisms of Evolutionary Change

A. Mutation

B. Migration

C. Genetic Drift

D. Natural Selection

A.

C.

B.

D.

II. Genetic VariationsA. Mutations (Genetic Variation)

1. DNA copies incorrectly

2. External influences

B. Gene Flow (migration) any movement of genes from one population

to another

C. Sex (genetic shuffling) can introduce new gene combinations into a

population

III. Genetic DriftA. Some individuals leave more descendants

B. Chance

C. Founder effect

IV. Natural SelectionA. Variation in traits

B. Differential reproduction

C. Heredity

D. Fitness how well an individual contributed its genes

to the next generation

E. Stabilizing Selection

Types of Natural Selection

F. Directional Selection

Types of Natural Selection continued

G. Disruptive Selection

Types of Natural Selection continued

V. Coevolution• two (or more) species reciprocally affect each

other’s evolution

I. Microevolution (You can see change) Evolution on a small scale within a single

population A change in generation-to-generation

gene frequency within a population.

Detecting Micro-evolutionary Change WHY?

A. Mechanisms of micro-evolutionary change1. Mutation

2. Migration

3. Genetic Drift

4. Natural Selection

Example of Microevolution

The size of the sparrow (originally introduced in the East in 1852…)

Why are sparrows now larger in the north?

http://evoled.dbs.umt.edu/images/modes.gif

II. Speciation a lineage-splitting event that produces two

or more separate species

A. Species a group of individuals that actually or

potentially interbreed in nature.

•these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator.

The scene: a population of wild fruit flies minding its own business on several bunches of rotting bananas, cheerfully laying their eggs in the mushy fruit...

Disaster strikes: A hurricane washes the bananas and the immature fruit flies they contain out to sea.

The banana bunch eventually washes up on an island off the coast of the mainland. The fruit flies mature and emerge from their slimy nursery onto the lonely island. Has speciation occurred yet???

Types of Reproductive Isolation (behavioral, geographic, temporal, mechanical… pre/post zygotic???

So we meet again: When another storm reintroduces the island flies to the mainland… what will happen now?

B. Prezygotic Barriers Prevents mating and formation of zygotes

1. Habitat Isolation

2. Behavioral Isolation

3. Temporal Isolation

4. Mechanical Isolation

5. Gametic Isolation

6. Geographic Isolation

C. Postzygotic barriers Prevents zygotes from developing into

fertile offspring

1. Reduced hybrid viability

2. Reduced hybrid fertility

3. Natural selection

III. Macroevolution evolution of groups larger than an

individual species. encompasses the grandest trends and

transformations in evolution, such as the origin of mammals and the radiation of flowering plants

The basic evolutionary mechanisms— mutation, migration, genetic drift, and natural selection—

can produce major evolutionary change if given enough time.

The History of Evolutionary ThoughtA. James Hutton 1726-

17971. Geologist

2. Gradualism = Profound change is

the cumulative product of slow but continuous process

The History of Evolutionary Thought Geology

The scientific study of the origin, history, and structure of the earth

Geologic Time Scale Used to represent

evolutionary time

Geology

The History of Evolutionary ThoughtB. Charles Lyell (1797-

1875)1. Geologist

2. Uniformitarianism Geological processes

have not changed throughout Earth’s history

The History of Evolutionary ThoughtC. Jean Baptiste Lamark

(1744-1829)1. Proposed theory of

evolutiona. Change Through Use

and Disuse

b. Organisms Driven to Greater Complexity

The History of Evolutionary ThoughtD. Thomas Malthus (1766-

1834) 1. Economist

2. Population Growth vs. the Food Supply

The History of Evolutionary ThoughtE. Charles Darwin

(1809-1882)1. Naturalist

2. 1831-1836 voyage on H.M.S. Beagle

3. Mission: chart south american coast line

F. Darwin’s Finches1. Galapagos formed

from volcanoes (young)

2. Species live nowhere else

3. Resemble South American

4. Different islands, different environments

5. Today – each island has own species

6. Finch ancestors came from South America

a. “islands had been colonized by plants and animals strayed from mainland and then diversified”

7.Different islands, different environments

a. Adaptation

G. Darwin’s Theory of Natural Selection

1. Obs. #1: Population size

would increase exponentially if all offspring reproduced successfully

2. Obs. #2: Populations tend to

remain stable in size

3. Obs. #3: Environmental resources

are limiteda. Inf. #1: more individuals =

struggle for resources. Only a fraction of offspring survive

4. Obs. #4: Individuals of a population vary

in characteristics

5. Obs. #5: Much of variation is heritable

b. Inf. #2: Survival is not random but depends on heredity. Individuals most fit for environment will produce more offspring

c. Inf. #3: unequal ability of individuals to survive and reproduce = gradual change in a population,

with favorable characteristics accumulating over generations

H. Key Subtle Points1. Individuals don’t evolve,

populations evolve

2. Adaptations an organism acquires from its own actions is different from inherited adaptations that evolve in a population over time

3. Specifics of natural selection are situational

Origin of Primates

Lemurs 55 mya

Tarsiers 50 mya … check out the fingers…and massive eyes

New World Monkey (note tails, side facing nostrils) 35 mya, all arboreal

Woolly spider monkey golden lion tamarin

Old World monkey: ~22 mya (down ward facing nostrils, no prehensile tail)Some arboreal

Some ground dwelling

Macaque Monkey

Gibbon (ape not a monkey)

~15 myaHominoids:larger brains

than monkeysno tailssmaller ranges

Hominoid: (ape) Orangutan diverged ~12 mya

Largest arboreal hominoid

Vegetarian

Gorilla (~8 mya) largest ape- live in groups up to 20 individuals Knuckle walkers

Can walk upright

Shorter legs than arms

Sexual dimorphism

More closely related to humans and chimps than other apes

Pan paniscus, Pan troglodytes… chimps… (diverged ~5 mya)

Bonobos chimps (dwarf chimpanzees) regular chimpanzees (male (female dominate society) dominate society)

Human vs. Gorilla

Hominin family tree…

http://www.youtube.com/watch?v=w1Lu4VggDH0

Laetoli footpath

Lucy

3.6 mya

Evidence of bipedalism

Homo sapiens neanderthalensis vs Homo sapiens sapiens

http://www.youtube.com/watch?v=doF4sNrQtmg&feature=related

Out of Africa… modern humans