Biology | Unit 6 Test

What is artificial selection?

Artificial selection is when humans intentionally choose which traits a species should have by selecting which individuals get to reproduce. For example, breeding dogs for specific traits like size or coat color.

What is it when species are separated and can no longer interbreed?

This is called Reproductive Isolation – when two populations are separated (usually by geography) and can no longer breed with each other.

What does it suggest when species have very similar DNA sequences?

It suggests they share a Common Ancestor – meaning they descended from the same ancestral species and are closely related.

Which type of selection favors the average (middle) in a population?

Stabilizing selection favors individuals with average traits, reducing extreme variations in the population.

Who proposed the theory of evolution by natural selection?

Charles Darwin proposed the theory of evolution by natural selection.

What is an adaptation? (example)

An adaptation is an inherited trait that increases an organism's ability to survive or reproduce in its environment. Example: a polar bear's white fur helps it blend into the snow (camouflage).

What are the Galapagos Islands famous for?

The Galapagos Islands are famous for inspiring Charles Darwin's theory of natural selection. He observed how different species (especially finches) had adapted differently depending on the island they lived on.

Which term describes the process where organisms with favorable traits are more likely to survive and reproduce?

This is called Natural Selection – individuals with advantageous traits survive and reproduce more than others.

What is it called when a group of individuals colonizes a new habitat?

This is called the Founder Effect – when a small group of individuals leaves a larger population and starts a new population in a new habitat. This can reduce genetic diversity.

What does 'fitness' mean?

Fitness is the ability of an organism to survive and reproduce in its environment. A 'fit' organism is one that successfully passes its genes on to the next generation.

What is a bottleneck effect?

The bottleneck effect is when a population is drastically reduced in size due to a disaster (like a natural disaster or disease), leaving only a small number of survivors. This reduces genetic diversity in the population.

Which genetic processes produce variation for evolution?

Mutation (random changes in DNA) and Gene Flow (movement of alleles between populations) are the main genetic processes that produce variation. Sexual reproduction also shuffles existing alleles.

What are analogous structures? (examples)

Analogous structures are body parts that have a similar function but come from different ancestry. Example: the wings of a bird and the wings of an insect – both are used for flying, but they evolved separately and are not related.

Natural selection that favors individuals with extreme traits?

This is called Disruptive Selection – it favors individuals at both extremes of a trait, rather than the average.

What are homologous structures?

Homologous structures are similar structures found in different species that are similar due to shared ancestry. Example: the arm of a human, the flipper of a whale, and the wing of a bat all have the same basic bone structure.

What is the ultimate source of 'new' alleles in a population?

Mutation is the ultimate source of new alleles. Random changes in DNA create brand-new genetic variations that didn't exist before.

What is a 'vestigial structure'?

A vestigial structure is a reduced body part that has little or no function in the current species. It is a leftover from an ancestor where it did have a function. Example: the human tailbone (coccyx) or the small back legs found in some snakes.

What is the result of 'speciation'?

The result of speciation is the formation of new species. When populations become reproductively isolated long enough, they evolve into separate species.

If a color of a species provides better camouflage, what will happen to the frequency of the allele for that color?

The frequency of that allele will increase over time. Because that color helps the organism survive (selective pressure), those individuals are more likely to survive and reproduce, passing the allele on to more offspring.

What can be learned from the fossil record?

The fossil record (preserved remains or traces of past life) teaches us about what ancient organisms looked like, how species changed over time, when species went extinct, and how life on Earth has evolved.

What is required for natural selection to occur?

For natural selection to occur, you need: Variation (differences among individuals), Overproduction (more offspring than can survive), Competition (struggle for limited resources), and traits that are heritable (passed down to offspring). Individuals with favorable traits survive and reproduce more.