Vestigial organs Organs or structures 41 Organs or structures They are usually reduced in size.

Vestigial Organs 42 c

DNA sequences in organisms are close 43 Genetics DNA sequences in organisms are close Sources of genetic variation in species: Mutations Gene Shuffling Crossing over during meiosis Sexual Reproduction Things that cause change. Why we are all a little bit different…

GEOGRAPHIC DISTRIBUTION 45 Organisms that are related change/adapt according to their environment.

Adaptive Radiation 46 The evolution of many diversely adapted species from a common ancestor Relatively rapid Usually occurs when a . New niches Each species becomes specialized for a different set of conditions

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50 Speciation Macroevolution

Evolution: change in the allelic frequencies in a population 51 Macroevolution Speciation How do we get new species? Where do new species come from? Species: population whose members can interbreed in nature and produce viable, fertile offspring Evolution: change in the allelic frequencies in a population

52 Speciation In the physical world, natural barriers form and cause the breakup of populations to form smaller populations. Volcanoes, sea-level changes, and earthquakes are a few examples of natural occurrences that affect populations

Speciation Mechanisms 53 Speciation Mechanisms Geographic Separated by bodies of water or mountains. . Isolation Reproduction takes place at different times of the year Different Mating seasons Overtime they can change so much that they become unable to breed as they adapt to their environment.

54 Behavioral Isolation Populations are capable of interbreeding, but have different or other type of behavior. Do not recognizes another species as a mating partner. Sexual Selection Brightly colored male- drab female video clip: Dressing fro desire

Combined genetic information of a particular population. 56 Gene Pool Combined genetic information of a particular population. All the genes present with in a population Can change A is a localized group of individuals that belong to the same species.

Changes in allele frequency with in a population — along with natural selection, mutation, and migration—is one of the basic mechanisms of evolution. 57 Changes in allele frequency with in a population Genetic drift Random changes in allele frequency that occurs in small populations “Lucky” individuals leave more offspring. Also known as the “Founder Effect”

58 Patterns of Evolution

Divergent Evolution 59 Divergent evolution is the process of . The red fox and the kit fox provide and example of two species that have undergone divergent evolution. As they adapted to different environments, the appearance of the two species diverged.

Two or more related species becoming more and more dissimilar Divergent Evolution 60 Two or more related species becoming more and more dissimilar

Convergent Evolution 61 Independent development of similar structures Convergent evolution is the emergence of biological structures or species that exhibit and appearance but that evolved through widely different evolutionary pathways. examples include the multiple origins of wings (bats, birds) and eyes.

Convergent Evolution 62 Independent development of similar structures

Coevolution Predators and their prey Parasites and their hosts 63 Predators and their prey Parasites and their hosts Plant-eating animals and the plants upon which they feed One example of coevolution is between plants and the animals that pollinate them. Coevolution .

Coevolution 64 Bumblebees & the flowers they pollinate have coevolved so that both have become dependent on each other for survival. Some Central American Acacia species have hollow thorns and pores at the bases of their leaves that secrete nectar. These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar. But the ants are not just taking advantage of the plant—they also defend their acacia plant against herbivores.

Evolution at the species level is called microevolution. It results from genetic variation and natural selection within a population of organisms. Small Changes Macroevolution is evolution that occurs between different species. 65

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71 Rates of Evolution

Gradualism & Punctuated Equilibrium 72 Two ways in which the evolution of a species can occur. A species can evolve by only one of these, or by both. CLIP Species with a shorter evolution evolved mostly by punctuated equilibrium, and those with a longer evolution evolved mostly by gradualism.

Change is slow, constant, and consistent. 73 Gradualism Very gradually, over a long time... Over a short period of time it is hard to notice. . Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die. Change is slow, constant, and consistent. Punctuated equilibrium . , often through mutations in the genes of a few individuals.

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The Effects of Selection on Populations 79 The Effects of Selection on Populations

Types of Selective Processes in Natural Selection 80 Types of Selective Processes in Natural Selection Stabilizing Selection Directional Selection Diversifying Selection Balancing Selection Heterozygote Advantage Frequency-dependent

81 Intermediate forms of a trait are favored and alleles that specify extreme forms are eliminated from a pop. Ex: Human birth weight stay between 6-8 lbs. Lower or higher has higher mortality.

Directional Selection 82 . give rise to directional selection, where one phenotype replaces another in the gene pool. Can produce rapid shift in allelic frequencies. Ex: Peppered moth – peppered moths, pesticide resistance, antibiotic resistance Occur in response to: * directional change in the environment * one or more new environmental conditions * a mutation that appears and proves to be adaptive

83 Selection Increases the extreme types in a population at the expense of the intermediate forms. One population divided into two. (bill size in seedcrackers)

Diversifying selection can result in For example, two distinct bill types are present in black-bellied seedcrackers in which larger-billed birds are more efficient when feeding on hard seeds and smaller-billed birds are more efficient when feeding on soft seeds. 84

Heterozygote Advantage Exists when a heterozygote (Aa) has a higher fitness than either homozygote (AA, aa). ex: 85

Frequency dependent 86 The term given to an evolutionary process where the fitness of a phenotype is dependent on its frequency Can arise in systems of mimicry ex: Butterflies ex: Maintenance of a 50:50 sex ratio: If one sex becomes more common, some of its members will not be able to mate