HardyWeinberg Equilibrium and The Process of Speciation CHAPTER

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 � 2. No emigration or immigration � No genetic drift can occur � No gene flow can occur � 3. No mutations � No new alleles can be added to the gene pool � 4. Random mating � 5. No natural selection � No sexual 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 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 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!