Adaptation and Extinction

Mass extinction

an event in which many species become extinct over a relatively short period of time

Background extinction

species becoming extinct over long periods of time through natural selection

rate of evolution: gradualism

slow steady change of species over time, evidence seen in fossil record

rate of evolution: punctuated equilibrium

organisms undergo rapid bursts of evolution follow by long periods of time when there is no change

adaptive radiation and example

process by which a species or small group of species evolves over a (relatively) short time into __several different forms that live in different ways__

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example: galapagos finches

convergent evolution

different/unrelated species in similar environments evolve similar structures/characteristics

coevolution and example

two species evolve in response to changes in each other over time. example: fig plants and fig wasps

Miller and Urey- what did they do?

developed an experiment which replicated the early Earth’s atmosphere (experiment was incorrect)

endosymbiotic theory definition

prokaryotic cells entered ancestral eukaryotes and created a symbiotic relationship that created chloroplasts and mitochondria

Evidence for endosymbiotic theory

mitochondria and chloroplasts both have:

* double membranes
* DNA and ribosomes similar to bacterial DNA and ribosomes

and they both reproduce via binary fission (how bacteria reproduce)

relative dating

using the location of rock layers to determine if a fossil is older or younger than other fossils

index fossils

distinct fossils used to establish and compare the relative ages of rock layers

radiometric dating

uses radioactive isotopes which break down at a steady rate

geological time scale

by using rock layers, early paleontologists placed earth’s rocks and fossils in order based on age

gene pool

combined genetic makeup of all the members of a population

the three main sources of genetic variation

1. mutations: any change in the DNA sequence
2. gene shuffling: homologous pairs of chromosomes move independently of each other during meiosis
3. chromosomes crossing over during meiosis 1

directional selection

individual at one end of the curve has higher fitness than individuals in the middle or other end

stabilizing selection

when individuals near the center of the curve have higher fitness than individuals at the ends

disruptive selection

individuals at the outer ends of the curve have higher fitness than individuals near the middle

bottleneck effect

a change in allele frequency following a dramatic reduction in the size of the population

founder effect

allele frequencies change as a result of the migration of a small subgroup of a population

speciation

when a new species evolves from a single ancestor species

what is speciation caused by?

1. geographic isolation
2. reproductive isolation
3. competition
4. changes in new population’s gene pool

geographic isolation

two populations are separated by geographic barriers- rivers, mountains

reproductive isolation

when the members of two populations can no longer interbreed and produce fertile offspring

temporal isolation

two or more species reproduce at different times of the year

changes in the new population’s gene pool

eventually over time changes in the DNA of the two populations is significantly different from each other

homologous structures

different in function, similar in fundamental structure, common ancestry, example: pentadactyl limb in vertebrates

analogous structures

same function, different fundamental structure, different ancestry, example: wings in birds, bats, butterflies

vestigial structures

a structure that is small and useless in one organism but useful and well developed in another

Lamark’s theory

use, disuse, and acquired characteristics

What did Malthus realize?

That if the human population went unchecked, there wouldn’t be enough resources for everyone

natural selection

organisms with variations most suited to their local environments survive and have more offspring

artificial selection

nature provided the variations and humans select those they find most useful

evidence of evolution (5 things)

1. Biogeography
2. Fossils
3. Comparative anatomy and Embryology
4. Genetics and Molecular Biology
5. Testing natural selection

Criteria for Darwin’s theory of natural selection (5 things)

1. struggle for existence
2. variation in all traits of all organisms
3. struggle and competition for resources
4. offspring with suitable variations survive, mate, and have offspring
5. new offspring will have more individuals with suitable variations