Hardy-Weinberg Equilibrium and The Process of Speciation Chapter 17.3

Hardy-Weinberg equilibrium Biologists compare data to a model to study how a population is changing. Genotype frequencies in a population stay the same over time as long as certain conditions are met.

Hardy-Weinberg equilibrium Populations that meet these conditions are not evolving. 5 conditions needed for a population to stay in equilibrium. They are said to be in Hardy-Weinberg equilibrium.

5 conditions of H-W equilibrium 1. Very large population No genetic drift can occur 2. No emigration or immigration No gene flow can occur 3. No mutations No new alleles can be added to the gene pool 4. Random mating No sexual selection 5. No natural selection All traits must equally aid in survival

Isolation of populations can lead to speciation Reproductive Isolation: occurs when members of different populations can no longer mate successfully with one another. Sometimes members of the 2 populations are not physically able to mate with each other.

Isolation of populations can lead to speciation Speciation: rise of two or more species from an existing species Reproductive isolation is the final stage in speciation.

Types of Reproductive Isolation: Behavioral Isolation: caused by differences in courtship or mating behaviors. Male and female fireflies produce patterns of flashes that attract mates of their own species.

Types of Reproductive Isolation: Geographical Isolation: involves physical barriers that divide a population into two or more groups. Most common type of isolation. Barriers include: rivers, mountains, and dried lakebeds.

3 Types of Reproductive Isolation: Temporal Isolation: exists when timing prevents reproduction between populations. Reproductive periods may change to a different time of the year or a different part of the day. Breeding seasons are different.

Closing/Homework On a separate sheet of paper: EXPLAIN in a paragraph. Explain how natural selection and behavioral isolation may have lead to reproductive isolation in Darwin’s finches. EXPLAIN in a paragraph. Write the question.

Closing/Homework On a separate sheet of paper: EXPLAIN in a paragraph. Explain how natural selection and behavioral isolation may have lead to reproductive isolation in Darwin’s finches. EXPLAIN in a paragraph. Write the question. Due tomorrow!