Influences on Darwin s Thinking: What ideas did each of the listed names below contribute to Darwin s thinking about evolution? (very brief) Georges Buffon: Jean Baptiste Lamarck: Charles Lyell: Thomas Malthus: Alfred Wallace: What two Assumptions did Darwin have to arrive at BEFORE he could form his theories of evolution? 1
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Darwin's Two Main Points 1. WHAT: Descent with Modification: species of organisms living on Earth today descended from ancestral species 2. HOW: Natural Selection is the mechanism for evolution Figure 14-9 In this hypothetical population of snails, inherited shell variations make some snails less likely than others to be attacked by predators. Wide, blunt shells increase the chances for snails to survive and pass their traits to the next generation by reproducing. 3
There are 5 lines of Evidence that species evolved from common ancestors 1. Fossil Record 2. Geographic Distribution of Related Species 3. Comparative Anatomy 4. Comparative Embyology 5. Comparative Biochemistry 1. The Fossil Record Whale s ancestors have pelvic bones Figure 14-11 Fossil evidence suggests that ancient whales evolved from ancestors with hind limbs. This illustration shows an artist's rendition of what an early whale species, Basilosaurus, may have looked like based on fossil evidence. Horse Evolution fossil record shows the loss of toes to a hoof. 4
2. Geographic Distribution of Related Species Example of DIVERGENT Evolution Plant and animal species are discontinuously distributed throughout the world and their distribution tells the story of their evolution. For example, mammals 1 st evolved in the center of the European/Asian land mass approximately 225 million years ago and from there they migrated to every major continent of the world. In Australia, 80% of the mammals are the more primitive type Marsupials, such as the kangaroo, the wallaby, and the wombat. The only Placental mammals (more modern) in Australia either migrated from elsewhere (e.g. bats) or were introduced by human beings (e.g. rabbits). Also, the echidna and platypus, the only living representatives of primitive egg-laying mammals (Monotremes), can be found in Australia and are totally absent in the rest of the world. By contrast, marsupials are totally absent from Africa and are only represented by the opossum in South America and the Virginia Opossum in North America: How does the distribution of related, but different species support Evolution from a common ancestor (Divergent Evolution)? using the mammals as an example. 5
Define: Convergent Evolution (as evidence for Natural Selection): Under similar environmental conditions, fundamentally different structures in different groups of organisms may undergo modifications to serve similar functions. This phenomenon is called convergent evolution. Similar structures, called analogous structures, are NOT evidence of a recent common ancestor. Rather, they are evidence of natural selection choosing similar body plans and adaptations in similar environments. That s why we see marsupial analogues of placental mammals in Australia. Define Analogous Structures: 6
3. Similarities in Physical Structure (Comparative Anatomy) Define Homologous Structures: 4. Similarities in Embryonic Development (Comparative Embryology) Write a statement here that explains how comparative embryology is evidence of evolution from a common ancestor: 7
5. Molecular Biology (Comparative Biochemistry) Write a statement here that shows the relationship between Biochemistry (ie: amino acid sequence of a particular protein) and species relatedness: 8
Darwin's Theory of Natural Selection Summarized Define Artificial Selection: Figure 14-19 This flowchart summarizes Darwin's theory of natural selection. Example 1: Vegetables 9
Example 2: Pesticides Artificial Selection in Action In your own words, summarize how use of pesticides in an example of Artificial Selection in action: Populations and Their Gene Pools A gene pool consists of: Changes in Gene Pools: Microevolution is a change in the frequency of alleles in a population. 10
Figure 14-24 Each plant in this hypothetical population of wildflowers has 2 alleles for flower color. In all, there are 14 red-flower alleles (R) and 6 white-flower alleles (r). The frequency of each allele is calculated as a ratio based on the total of 20. Figure 14-25 Only the alleles of organisms that successfully reproduce in one generation appear in the gene pool of the next generation. In this population of ten plants, the frequency of whiteflower alleles was reduced to zero due to genetic drift. Define Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1 (You do not need to memorize this equation) p = AA + ½Aa q = aa + ½Aa 11
What 4 mechanisms mentioned in the book can change a gene pool? Which is the only one that can lead to ADAPTAION? 1. 2. 3. 4. 1. Genetic Drift The Bottleneck Effect: Founder Effect: 12
2. Define Gene Flow: 3. Define Mutation: 4. Natural Selection and Fitness Only Natural Selection leads to. Give the Biological definition of fitness: 13
Summarize HOW each of the 4 above-mentioned mechanisms changes a gene pool. 1. 2. 3. 4. Natural Selection and Sickle Cell Disease (slide show) Why do many African populations have such high frequencies of an allele with the potential to shorten life (and thus reproductive success)? 14
Evolution of Antibiotic Resistance in Bacteria 15