Evolution

What is evolution?

A change in heritable characteristics or allele frequencies in populations across generations.

What is the main mechanism of evolution?

Natural selection is a major mechanism, but mutation, gene flow, genetic drift, and nonrandom mating/sexual selection also matter.

What is natural selection?

Individuals with heritable traits that improve reproductive success in a particular environment tend to leave more offspring, changing trait frequencies over generations.

What is a population?

A group of individuals of the same species living in the same area and capable of interbreeding.

What is a change in an individual called?

A change in an individual during its lifetime is not evolution; evolution refers to heritable change in populations across generations.

Population vs. community?

A population is one species in an area; a community includes populations of different species in that area.

What is the context for Alfred Russel Wallace?

Wallace independently developed an idea of evolution by natural selection and communicated it to Darwin, prompting their ideas to be presented together in 1858.

Why is Darwin credited for the theory of evolution?

Darwin developed a detailed argument supported by extensive evidence and published On the Origin of Species in 1859; Wallace independently reached a similar natural-selection idea.

What were Darwin's two key observations and inferences?

Individuals vary, and organisms produce more offspring than can survive; therefore, heritable traits associated with greater survival and reproduction become more common.

What is an adaptation?

A heritable trait shaped by natural selection that improves reproductive success in a particular environment.

What determines which traits are favorable?

The environment and their effects on survival and reproductive success; favorability can change when conditions change.

What time scale does evolution occur on?

Across generations; it can be rapid or slow depending on the organism and conditions.

What is microevolution?

Evolutionary change within populations, often measured as changes in allele frequencies.

What is macroevolution?

Evolutionary patterns at or above the species level, including speciation and large-scale diversification.

What are five sources of evidence for evolution?

Fossil record, observed evolution/adaptation, anatomical evidence, biogeography, and molecular homology.

Why are observed adaptations evidence for evolution?

They show heritable traits and populations changing in response to environmental pressures.

Can evolution be observed in a lab? How?

Yes. Researchers can track changes across generations, such as bacteria evolving antibiotic resistance or changes in experimental populations.

How do you interpret a finch beak-size graph before and after drought?

Compare the beak-size distribution before and after; if birds with larger/deeper beaks survived better because they could eat available seeds, the average beak size may increase. Use the graph's actual data.

How do you interpret an antibiotic-resistance graph?

If resistant bacteria survive treatment and reproduce, the proportion of resistant bacteria can rise; antibiotics select among existing variants and new mutations.

Why is the fossil record useful evidence?

It documents organisms through geological time and shows extinction, change, and transitional combinations of traits.

Why is the fossil record not perfect evidence by itself?

Fossilization is rare and biased, many organisms leave no fossils, and the record has gaps.

How can science go wrong?

Through bias, poor methods, data manipulation, unsupported claims, or conclusions that exceed the evidence.

How do we know some fossils are fake?

They can be exposed by geological inconsistencies, anatomy that does not fit, chemical/material analysis, or evidence of fabrication.

Why don't we have fossils of fish turning into frogs?

Evolution is branching and gradual, not a single fish transforming into a modern frog; fossils preserve only a small fraction of past organisms, though transitional forms exist.

How was Tiktaalik found?

Researchers predicted the geological age and environment where a transitional fish-tetrapod fossil might occur, then searched rocks from that period in the Canadian Arctic.

What is artificial selection?

Human-directed breeding that increases desired heritable traits.

Give examples of artificial selection.

Dog breeds, domesticated crops such as corn, and selectively bred livestock.

What is anatomical evidence for evolution?

Comparisons of body structures that reveal shared ancestry or similar selective pressures.

Can evolution build things from scratch?

Evolution generally modifies existing variation and structures over generations; new structures can arise through changes and co-option of existing parts.

What is mammalian anatomical evidence for evolution?

The similar arrangement of bones in human arms, whale flippers, bats' wings, and other mammalian forelimbs.

What are homologous traits?

Traits similar because they were inherited from a common ancestor, even if their functions differ.

What are analogous traits?

Traits with similar functions that evolved independently rather than being inherited in that form from a recent common ancestor.

What is strong anatomical evidence for evolution?

Homologous structures and transitional combinations of traits; your instructor may emphasize a particular example.

What are homeobox genes?

Genes containing a homeobox sequence that help regulate development and body-plan formation.

What is biogeography?

The study of where organisms live now and lived in the past; distribution patterns can reflect common ancestry, plate tectonics, dispersal, and isolation.

What is convergent evolution?

Independent evolution of similar traits in different lineages because of similar selective pressures.

What is molecular homology?

Similarity in DNA, RNA, or protein sequences due to shared ancestry.

What would you hypothesize when comparing similar genes across species?

More closely related species will generally have more similar gene sequences, though mutation rate and gene history can affect the pattern.