Biology Mutations, Gene Flow, Genetic Variation

Why is genetic variation necessary for the basic mechanisms of evolutionary change to operate?

Without genetic variation, some of the basic mechanisms of evolutionary change cannot operate.

What are the three primary sources of genetic variation?

Mutations, gene flow, and sex (genetic shuffling).

What is a mutation?

A mutation is a change in the DNA.

What is gene flow?

Gene flow is any movement of genes from one population to another.

How does sex contribute to genetic variation?

Sex can introduce new gene combinations into a population through genetic shuffling.

A _____ is defined as a random change in DNA.

mutation

What three aspects of an organism's life are affected by its DNA?

Look, behavior, and physiology.

Mutations are random and can be _____, neutral, or harmful for the organism.

beneficial

True or False: Mutations 'try' to supply what an organism 'needs'.

False; mutations are random and do not occur based on an organism's needs.

Why do not all mutations matter to evolution?

Because some mutations, like somatic mutations, occur in non-reproductive cells and won't be passed onto offspring.

Term: Somatic mutation

Definition: A mutation that occurs in non-reproductive cells.

The golden color on half of a Red Delicious apple is an example of what type of mutation?

A somatic mutation.

What type of mutations are the only ones that matter for evolution?

Only mutations in reproductive cells (egg/sperm).

Mutations that occur in reproductive cells like eggs or sperm are called _____ mutations.

germline

Which type of mutation, somatic or germline, can be passed to offspring?

Germline mutations.

What is one possible outcome of a germline mutation that results in no change to the phenotype?

The mutation occurs in non-coding DNA or the protein produced still works the same way.

The development of curled-back ears in a cat is an example of what level of phenotypic change from a single germline mutation?

A small change in phenotype.

The development of DDT resistance in insects is an example of what level of phenotypic change from a single germline mutation?

A big change in phenotype.

What is a potential negative consequence of a mutation that causes a big change in phenotype?

It can also be harmful or lethal.

What is a key limitation of evolution regarding the types of traits mutations can cause?

Mutations cannot cause impossible traits (e.g., pigs with wings), as evolution works within biological limits.

What is one primary cause of 'naturally-occurring' mutations?

The failure of DNA to copy accurately during cell division.

How can external influences like chemicals or radiation cause mutations?

These agents can cause the DNA to break down, leading to imperfect repairs by the cell.

What is another term for gene flow?

Migration.

Define gene flow, also known as migration.

It is any movement of individuals, and/or the genetic material they carry, from one population to another.

What are two examples of events that result in gene flow?

Pollen being blown to a new destination or people moving to new cities or countries.

When does gene flow become a particularly important source of genetic variation?

When gene versions are carried to a population where those gene versions previously did not exist.

The introduction of new gene combinations into a population through sex is known as _____.

genetic shuffling

Besides identical twins, are siblings genetically identical to their parents or each other?

No, because of genetic shuffling.

What is a potential negative outcome of genetic shuffling?

It can break up 'good' combinations of genes.

Term: Development (in an evolutionary context)

Definition: The process through which an embryo becomes an adult organism, during which its genotype is expressed as a phenotype.

What is a major effect that mutations in genes controlling development can have?

They can have major effects on the morphology of the adult organism, such as causing a fruit fly to have two pairs of wings.

How can studying an organism's development aid in understanding evolutionary history?

An organism's development may contain clues about its history that can be used to build evolutionary trees.

How can developmental processes affect the course of evolution?

They can constrain evolution, preventing certain characters from evolving in certain lineages.

The absence of truly six-fingered tetrapods is an example of how development can _____ evolutionary change.

limit

Along with natural selection, mutation, and migration, what is another basic mechanism of evolution?

Genetic drift.

What is genetic drift?

A mechanism of evolution where, by chance, some individuals leave behind more descendants than others.

Which evolutionary mechanism is described as a random process that does not work to produce adaptations, and can be driven by 'lucky' individuals leaving behind more descendants by chance?

Genetic Drift

How does genetic drift differ from natural selection in terms of the traits it produces?

Unlike natural selection, genetic drift is a random process and does not work to produce adaptations.

Which of the following is NOT listed as a primary source of the genetic variation that is necessary for evolution to operate?

Genetic Drift