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Chapter 16: The Evolution of Populations

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1 Chapter 16: The Evolution of Populations
Section 16-1 Genes and Variation 1. Is the Following sentence true or false? Mendel’s work on inheritance was publish after Darwin’s lifetime. False 2. Which two important factors was Darwin unable to explain without an understanding of heredity? The source of variation and how genes were passed from generation to generation 3. List the three fields that collaborate today to explain evolution a. Genetics b. Molecular Biology c. Theory Gregor Mendel

2 Gene Pools 4. A collection of individuals of the same species in a given area is a population 5. The combined genetic information of all members of a particular population is a gene pool 6. Is the following statement true or false? A gene pool typically contains just one allele for each inheritable trait False 7. The number of times that an allele occurs in a gene pool compared to the number of times other alleles occur is called the relative frequency

3 Source of Genetic variation
Sources of Genetic Variation 8. Complete the concept map Source of Genetic variation Include Mutations Gene Shuffling 9. What is a mutation? Any Change in the sequence of DNA 10. Why do mutations occur? As a result of mistakes in the replication of the DNA or as a result of radiation or chemicals in the environment

4 11. Circle the letter that is true about mutations
They can be limited to a single base of DNA They always affect lengthy segments of a chromosome They always affect an organism’s phenotype They always affect an organism’s fitness 12. Is the following statement true of false? Most inheritable differences are due to gene shuffling that occurs during the production of gametes 13. Circle the letter of each choice that is true of sexual reproduction It is a major source of variation in many populations It can produce many different phenotypes It can produce many different gene combinations It can change the relative frequencies of a population

5 Frequency of Phenotype
Single- Gene and Polygenetic traits 14. Is the following sentence true or false. ?The number of phenotypes produced for a given trait depends upon how many genes control the trait 15. Is the following sentence true or false? Most traits are controlled by a single gene 16. Label the two graphs to show which one represents a single gene trait and which one represents a polygenetic trait Single gene trait Polygenetic Trait Frequency of Phenotype Frequency of Phenotype (%) Phenotype (height) Widow’s peak No widow’s peak Phenotype

6 16-2 Evolution as Genetic Change
Natural Selection on Single-Gene Traits 1. Is the following sentence true or false? Natural selection on single gene traits cannot lead to changes in allele frequencies 2. If a trait made an organism less likely to survive and reproduce, what would happen to that trait? Fewer copies would be passed onto the next generation and the trait could, possibly disappear from the gene pool 3. If a trait had no effect on an organism fitness, what would happen to the allele for that trait? The allele and its frequency would remain unchanged

7 Directional Selection
4. List three ways that natural selection can affect the distribution of phenotypes Directional Selection Stabilizing Selection Disruptive Selection Match the type of selection with the situation in which it occurs Type of Selection ____ 5. Directional ____ 6. Stabilizing ____ 7. Disruptive Situation Individuals at the upper and lower end of the curve have higher fitness than those in the middle B. Individuals at one end of the curve have higher fitness than those at the other end Individuals in the middle have the highest fitness b c a

8 8. An increase in the average size of beaks in Galapagos finches is an example of
Directional Selection

9 9. Is the following sentence true or false
9. Is the following sentence true or false? The weight of human infants at birth is under the influence of disruptive selection 10. Draw the missing graph to show how disruptive selection affects beak size Disruptive Selection Largest and smallest seeds become more common. Key Low mortality, high fitness Population splits into two subgroups specializing in different seeds. Number of Birds in Population Number of Birds in Population Number of Birds in Population High mortality, low fitness Beak Size Beak Size

10 Genetic Drift 11. Is the following sentence true or false? Natural selection is the only source of evolutionary change. 12. Random change in allele frequencies in small populations is called 13. A situation in which allele frequencies change as a result of migration of a small subgroup of a population is called The Founder Effect 14. What is an example of the founder effect? The evolution of the 6th finger on the hands of the Old Amish people of Pennsylvania

11 Evolution verses Genetic Equilibrium
15. What does the Hardy Weinberg Principle state? Allele frequency in a population will remain constant unless one or more factors cause them to change 16. The situation in which allele frequencies remain constant is called Genetic Equilibrium 17. The 5 conditions required to maintain genetic equilibrium Random mating Large population No migration No mutations No natural selection 18. Why is large population size important in maintaining genetic equilibrium? Genetic Drift has less effect on large populations

12 16-3 The Process of Speciation
What is Speciation? The formation of a new species 2. Is the following sentence true or false? Individuals in different species can have the same gene pool 3. What does it mean for two species to be reproductively isolated from each other? They cannot interbreed and produce offspring 4. What must happen in order for a new species to evolve? Populations must be reproductively isolated from one another

13 5. List three ways that reproductive isolation occurs
6. When does behavioral isolation occur? Species do not interbreed because of different courtship rituals 7. Is the following statement true or false? Eastern and Western meadowlarks are examples of behavioral isolation a. Geographic Isolation b. Temporal Isolation Nocturnal Eye & Diurnal Eye c. Behavioral Isolation

14 8. When does Geographic Isolation occur?
When populations are separated by geographic barriers, such as mountain ranges, rivers, or oceans 9. Abert and Kaibab Squirrels in the south west are an example of Geographic Isolation 10. Is the following sentence true or false? Geographic barriers guarantee the formation of new species. 11. What is an example of temporal isolation? Three Similar species of orchids release pollen on different days

15 12. Is the following sentence true or false
12. Is the following sentence true or false? The basic mechanisms of evolutionary change cannot be observed in nature 13. Circle the letter of each hypothesis about the evolution of Galapagos Finches’ beak that was tested by the Grants The finches’ beak size and shape has enough inheritable variation to provide raw material for natural selection b. The different finch species are the descendants of a common ancestor c. Differences in the finches beak size and Shape produce differences in fitness and Cause natural selection to occur d. The evolution of finches is proceeding slowly and gradually

16 14. Circle the letter of each
Observation that was made by the Grants Differences in beak size were more important for survival during the wet season When food for finches was scarce, individuals with the largest beaks were less likely to survive Big beaked birds tended to mate with small beaked birds Average beak size increased dramatically

17 Reproductive Isolation
15. Complete the flowchart to show how speciation probably occurred in the Galapagos finches Founders arrive Separation of species 16. How could difference in beak size lead to reproductive isolation? Birds with the same beak size mated. Birds of different beak size did NOT mate and the gene pools of the different beak sized birds remained isolated. Changes in gene pool Reproductive Isolation Ecological Competition Continued Evolution 17. Is the following sentence true or false? During the dry season individual birds that are most different from each other have the highest fitness

18 Reproductive Isolation
Concept Map Reproductive Isolation results from Isolating mechanisms which include Behavioral isolation Temporal isolation Geographic isolation produced by produced by produced by Behavioral differences Different mating times Physical separation which result in Independently evolving populations which result in Formation of new species

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