Evolution and Speciation

Define evolution

• change in heritable characteristics of a population over time

State what causes heritable change

• change in alleles due to mutation

Distinguish between Darwinian and Lamarckian evolution

• Darwin

Explain why acquired traits are not part of evolution

• not passed through DNA

State why evolution is a theory

• widely supported, but cannot be fully proven
• explains many observations

Describe evidence for evolution from DNA

• similar base sequences = shared ancestry
• more differences = more distant relationship

Explain why conserved genes are used in comparisons

• change very little over time
• found in many species
• easy to compare

Outline steps to compare DNA sequences

• extract DNA
• sequence it
• compare base order with other species

State the DNA similarity between humans and chimps

• about 99%

Explain how selective breeding is evidence for evolution

• humans choose traits to pass on
• shows how fast traits can change

Define artificial selection

• humans pick desirable traits
• repeat breeding over generations

State one example of selective breeding

• crops with high yield
• animals with more meat, milk, or wool

Compare artificial selection and natural selection

• both change traits
• natural = nature selects
• artificial = humans select

Define homologous structure

• similar bone layout, different function

Give an example of a homologous structure

• pentadactyl limb (5-digit limb in mammals, birds, etc.)

State what homologous structures suggest

• shared common ancestor

Define analogous structure

• same function, different origin

Give an example of an analogous structure

• dolphin and shark fins
• bird and bat wings

Define convergent evolution

• unrelated species evolve similar traits due to same environment

Explain how convergent evolution causes confusion in classification

• similar traits but no shared ancestry

Define speciation

• formation of a new species from an old one

State what speciation increases

• biodiversity

State what extinction decreases

• biodiversity

Explain the role of gene flow in speciation

• if stopped, genetic differences build up
• may lead to new species

State when speciation is complete

• when groups can’t produce fertile offspring

State why gradual change is not speciation

• must include reproductive isolation

Define reproductive isolation

• individuals can’t breed to make fertile offspring

List types of reproductive isolation

• temporal (timing)
• behavioral (mating rituals)
• geographical

Give an example of geographical isolation

• bonobos and chimps split by Congo River

Define differential selection

• different selection pressures in different environments

Explain how differential selection leads to speciation

• each group adapts differently
• leads to reproductive isolation

Distinguish between allopatric and sympatric speciation

• allopatric

Define adaptive radiation

• one species evolves into many
• each fills a different niche

Explain why adaptive radiation increases biodiversity

• species avoid competition
• more niches filled

Define a hybrid

• offspring from two species

State why hybrids are usually sterile

• different chromosome numbers
• can’t make gametes

Give an example of a sterile hybrid

• mule (horse + donkey)

State a barrier that prevents hybridization

• courtship behavior
• incompatible mating rituals

Define abrupt speciation in plants

• fast speciation by hybridization or polyploidy

Give an example of abrupt speciation

• smartweed (genus *Persicari