Evolution and Speciation

Flashcards reviewing the process of speciation, variation, natural selection, and related concepts.

What is speciation?

The formation of new and distinct species in the course of evolution.

What are the seven steps to become a new species?

Reproductive Potential, Variation, Competition, Natural Selection, Divergence, Isolation, New Species

What is Reproductive Potential?

The relative capacity of a species to reproduce itself under optimum conditions.

What factors differentiate individuals’ reproductive potential?

Genetics and environmental factors (e.g., diseases, resources, mates, competitors).

What is a population?

A group of individuals occupying a given area and belonging to the same species.

What are the three kinds of variable traits?

Morphological, Physiological, and Behavioral.

What is the only source of variation that creates new species?

Genetic mutations.

Besides genetic mutations, what are other possible sources of variation?

Abnormal changes in chromosome structure or number, crossing over and genetic recombination, independent assortment of chromosomes, and fertilization between genetically different gametes.

What is intraspecific competition?

Individuals of the same population competing for resources.

What is interspecific competition?

Two species competing for the same limited resources.

What is the competitive exclusion principle?

Two similar species competing for the same limited resource cannot coexist together indefinitely.

How does the environment limit the growth of populations?

Increasing the rate of death and decreasing the rate of reproduction.

What did Darwin call natural selection?

The different degrees of successful reproduction among organisms in a population.

How does a population adapt to its environment through natural selection?

A population of organisms adapt to their environment as their proportion of genes for favorable traits increases.

What is disruptive selection?

Individuals with both extreme forms are favored.

What is stabilizing selection?

Individuals with the average form are favored.

What is directional selection?

Individuals with an extreme form are favored.

What is an allele?

One of a pair of genes on chromosomes.

What is a genotype?

A pair of alleles in an individual.

What does homozygous mean?

Alleles of a chromosome pair are the same.

What does heterozygous mean?

Alleles of a chromosome pair are different.

What is allele frequency?

The decimal value of alleles in the total population.

What is genotype frequency?

The decimal value of individuals in the total population.

According to the Hardy-Weinberg Principle of Genetic Equilibrium, what two equations must be true for a population to be in equilibrium?

p + q = 1 and p2 + 2pq + q2 = 1

What are the five conditions that must be met in order for a population to be in Hardy-Weinberg equilibrium?

No natural selection, no mutations, no migration, large population, random mating.

What is isolation in the context of speciation?

When two parts of a formerly interbreeding population stop interbreeding.

What are the two types of isolation?

Geographic isolation and reproductive isolation.

What is geographic isolation?

Physical separation of members of a population.

What is reproductive isolation?

The result of barriers to successful reproduction between two groups in the same population.

What is prezygotic isolation?

Isolation that occurs before fertilization.

What is postzygotic isolation?

Isolation that occurs after fertilization.

What is the morphological concept of species?

Uses the external structure and appearance of an organism to classify it as a species.

What is the biological concept of species?

A species is a population of organisms that can successfully interbreed but cannot interbreed with other groups.

What is gradualism?

Speciation requires millions of years and is caused by evolutionary changes that occur gradually.

What is punctuated equilibrium?

Speciation that occurs suddenly by rapid shifts in the form of organisms followed by periods of no change.

What is divergent evolution?

Two or more related populations or species become more different.

What is convergent evolution?

Two organisms that appear to be very similar but are not closely related at all.

What is coevolution?

The change in two or more species in close association with each other.