EVOLUTION REVIEW Chapter 16 & 17 Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing © 2006

Traits controlled by two or more genes Polygenic trait Process by which related organisms evolve differences when they are isolated in different environments Divergent evolution OR Adaptive radiation

Measuring lima beans and finding beans come in different sizes is an example of ____________ Natural variation Process by which unrelated organisms independently evolve similarities when adapting to similar environments Convergent evolution

A change in a DNA sequence caused by a mistake in DNA replication or exposure to radiation or chemicals mutation Changes in the allele frequency in a small population that are due to random chance and don’t follow the laws of probability Genetic drift

All the genes, including all the different alleles, in a population Gene pool A situation in which the allele frequencies in a population do NOT change and the population does NOT EVOLVE Genetic equilibrium

A change in relative frequency of alleles in a population Trait controlled by two or more genes Polygenic trait A change in relative frequency of alleles in a population evolution

A change in allele frequencies due to the migration of a small subgroup of a population to a new place Founder effect Idea that allele frequency will remain constant unless one or more factors cause those frequencies to change Hardy-Weinberg Principle

replication Copying DNA is called __________ Exchange of DNA between homologous chromosomes during PROPHASE I of MEISOIS Mixing up of maternal and paternal chromosomes in different combinations during ANAPHASE of MEIOSIS Crossing over SEGREGATION & INDEPENDENT ASSORTMENT

A trait controlled by a single gene with two alleles Single gene trait The number of times a certain allele occurs in a gene pool compared to the number of times other alleles for the same gene occur Relative frequency

caused by mistakes in copying DNA caused by radiation Tell two sources of genetic variation in populations Mutations caused by mistakes in copying DNA caused by radiation or environmental chemicals Gene shuffling during meiosis crossing over independent assortment

Bell-shaped curve (OR normal distribution) Type of distribution curve shown by polygenic traits Bell-shaped curve (OR normal distribution) Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing©2006

Stabilizing selection The effect of natural selection when individuals near the center of a normal curve of distribution have higher fitness than those at the extremes Stabilizing selection Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing©2006

Directional selection The effect of natural selection when individuals at one end of the normal distribution curve have higher fitness than individuals in the middle or at the other end Directional selection Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing©2006

The effect of natural selection when individuals at the extreme ends of the normal distribution curve have higher fitness than those near the center of the curve Disruptive selection Image from BIOLOGY by Miller and Levine; Prentice Hall Publishing©2006

Random mating NO mutations TELL THE CONDITIONS UNDER WHICH THE HARDY-WEINBERG PRINCIPLE HOLDS TRUE: Random mating LARGE population NO mutations NO movement IN OR OUT NO natural selection

independent assortment How does gene shuffling occur during meiosis? Crossing over & independent assortment What are some causes of mutations? Mistakes during DNA copying (replication) Environmental chemicals or radiation

There is NO EVOLUTION hypothesis If all the conditions of Hardy-Weinberg are met, what happens to the population? A possible explanation for a set of observations or a possible answer to a scientific question There is NO EVOLUTION hypothesis

Can all the conditions of Hardy-Weinberg ever be met? In rare populations over long periods of time they may be met (or nearly met) BUT MOST OF THE TIME NO WAY! You can have small & isolated populations (no moving in or out) BUT. . . there is always non-random mating, mutations, & natural selection. So there is ALMOST ALWAYS EVOLUTION HAPPENING !

Punctuated equilibrium Darwin believed in the idea that evolution happened slowly over a long period of time called __________ Pattern of evolution in which long Stable periods of little evolution interrupted by brief periods of rapid change gradualism Punctuated equilibrium

Punctuated equilibrium WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction Horse evolution shows long stable periods of little evolution interrupted by brief periods of rapid change Punctuated equilibrium Biology by Miller and Levine Pearson Publishing

Adaptive radiation WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction The Galápagos finches evolved through natural selection from a common ancestor into a wide variety of different looking species with different kinds of beaks Adaptive radiation

Mass extinction WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction At the end of the Cretaceous period an asteroid hit the Earth causing the loss of many species including the dinosaurs Mass extinction

Adaptive radiation (divergent evolution) http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T014608A.gif WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction The Galápagos finches evolved through natural selection from a common ancestor into a wide variety of different looking species with different kinds of beaks Adaptive radiation (divergent evolution)

coevolution WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction Hummingbirds have a beak just the right length to reach the nectar in a cardinal flower and as they feed their foreheads bump into the pollen structure. Cardinal flowers are red which hummingbirds can see, but bees can’t, and their pollen structure is at just the right height for the hummingbird to pick up pollen as it feeds. coevolution

Convergent evolution WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction Whales, sharks, and penguins all have streamlined bodies and fins/flipper for moving in water even though they belong in different animal groups (mammals, fish, and birds) Convergent evolution

Adaptive radiation OR divergent evolution WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction Beaver NORTH AMERICA Muskrat Capybara SOUTH AMERICA Coypu Beaver and Muskrat Beaver in North America and capybara in South America are closely related species living in very different environments that have evolved to look different over time. Adaptive radiation OR divergent evolution BIOLOGY by Miller and Levine Pearson Publishing

Adaptive radiation OR divergent evolution WHICH PATTERN IS IT? coevolution adaptive radiation divergent evolution punctuated equilibrium mass extinction The tortoises on the Galapagos islands share a common ancestor, but over time they have become adapted for obtaining food in different habitats on different islands by having different neck lengths Adaptive radiation OR divergent evolution

Stabilizing selection WHICH PATTERN of SELECTION IS IT? stabilizing disruptive directional Human babies born smaller than average are likely to be less healthy and less likely to survive. Larger than average babies are likely to have difficulty being born. The fitness of these larger or smaller weight babies is lower than average-sized babies so human babies tend to born of average size. Stabilizing selection

directional selection WHICH PATTERN of SELECTION IS IT? stabilizing disruptive directional Lighter colored peppered moths were more common in England prior to the Industrial revolution. As pollution increased, the darker colored moths were less likely to be eaten. Over time darker colored moths have become more abundant in the population. directional selection

disruptive selection WHICH PATTERN of SELECTION IS IT? stabilizing disruptive directional A population of birds lives in an area where plants with medium sized seeds are wiped out by a fungal infection. Birds with unusually large or small beaks would have higher fitness than those with medium sized beaks. Over time the population splits into two subgroups; one that eats small seeds and one that eats large seeds. disruptive selection

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