GENES AND VARIATION OBJECTIVES: 16.1 Explain what a gene pool is.

1. GENES AND VARIATION OBJECTIVES: 16.1 Explain what a gene pool is. Identify the main source of inheritable variation in a population. State determines the numbers of phenotypes for a given trait.

2. Genetic ________ is studied in a population (a group of individuals of the same ______ that interbreed). The individuals share a common group of genes called a ____ _____. A gene pool consists of ___ genes, including all the different _______, that are present in a population. The relative frequency of an _____ is the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.

3. _________ is any change in the relative frequency of alleles in a population. The two main sources of genetic variation are __________ and the genetic _________ that results from sexual reproduction. A mutation is any _______ in a sequence of DNA. They can occur because of mistakes in ________, radiation, or chemicals in the environment. Many mutation do not produce changes in the _________ of the individual.

4. Human _____ mutation. They believed that this man was born with the ___ virus that causes the growth of all these ______ that cover his body and creates the illusion that branches are covering his skin

5. Most _______ differences are due to gene shuffling that occurs during the production of _______. Another process, ___________, also occurs during ________ which increases the number of different _________ that can appear in offspring.

6. The number of _________ produced for a given trait depends on how many ______ control the trait. Among humans, a widow’ peak – a downward dip in the center of the hair line – is a ______-gene trait. The allele for the widow’s peak is _________ over the allele for the hair line with no widow’s peak.

7. Many traits are controlled by two or more genes and are, called _________ traits. Each gene of a trait has two or more ______.

8. EVOLUTION AS GENETIC CHANGE OBJECTIVES: 16.2 Explain how natural selection affects single-gene and polygenic traits. Describe genetic drift. List the five condition needed to maintain genetic equilibrium.

9. The _______ of an organism is measured in its ability to _____ its genes on the next generation. _______ _______ never acts directly on _____. Because it is an entire _______ – not a single gene – that either survives and reproduces or dies without reproducing. If and individual produces many ________, its alleles stay in the gene pool and many increase in frequency.

10. Natural selection on single-gene traits can lead to changes in allele frequencies and thus to _______. During the ________ Revolution a lot of soot was put into the atmosphere and it collected on trees. The soot making the ______ peppermoth more visible. Because of this the _____ peppermoth became predominant over it white cousin. Peppermoth of England

11. Natural selection can affect the __________ of phenotypes in an of three ways. • __________ selection – when the individuals at one end of the curve have higher fitness than those in the middle or the other end. • ________ selection – when individuals near the center have higher fitness than the individuals at either end of the curve. • _________ selection – when the individuals at the upper and lower ends of the curve have higher fitness than those near the middle.

13. In _____ populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurrences of this type can cause an _____ to become common in a population. _____ ______ is the random change of allele frequency. A situation in which ____ frequencies change as a result of the ________ of a small subgroup of a population.

14. The ____________ principal states that the allele frequencies in a population will remain _______ unless one or more factor cause those frequencies to change. • Genetic ________ is the situation the allele frequency remains _______. • ____ conditions are required to maintain genetic equilibrium from generation to generation: • There must be _______ mating; all members of the population must have a equal opportunity to produce offspring.

15. 2.The population must be very large; genetic drift has less ______ on a large population 3.There can be no movement ____ or ___ of the population; new individuals may bring in new _____ in to a population. 4. No _________; if genes mutate from on form into another form, new alleles may be introduce into the population. 5. No ________ selection; all genotypes must have the same probabilities of _______ and __________.

16. THE PROCESS OF SPECIATION OBJECTIVES: 16.3 Identify the condition necessary for a new species to evolve. Describe the process of speciation in the Galapagos finches.

17. __________ is the formation of new species. A _______ is a group of organisms that breed with one another and produce ______ offspring. As new species evolve, population become reproductively ________. When the members of two populations cannot _________ and produce ______ offspring, reproductive isolation has occurred. At that point the _________ had different genic pools.

18. _________ isolation occurs when two populations are capable of interbreeding but have difference in courtship _____ or other reproductive strategies that involve behavior. __________ isolation occurs when two populations are separated by geographic barriers such as rivers, ________ or bodies of water. _______ isolation occurs when two or more species reproduce at different times.

19. Geographic isolation

20. Speciation in the _______ finches occurred by founding of a new population, geographic isolation, changes in the new population’s gene pool, and _______ competition.

21. A few finches (_______) from the South American mainland – species A – flew or were blown to one of the Galapagos Islands. Later a few birds of species A cross to another island (________). Over time, populations on each island become _______ to their local environment. One island may have produced a _____ with a thick husk and the birds adapted by growing _____ beaks, resulting in species B.

22. A few birds from species B fly over to the island inhabited by species A. Species A will not mate with species B because species A prefers _____ beak size. The gene pool of the two species are now ______. The two are now _______ species.