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•Answer key posted on the class webpage •Office hours: Th 11:30am-2pm F 12:30-1:30pm •Exam Error Worksheet •Bonus #1 due F 2/15 Evolution: A species’ genetic component changes as the individuals reproduce due to… •Non-random changes (natural selection) •Random changes (genetic drift/bottleneck) •Mutations add new alleles or genes CB 23.7 Evolution can occur randomly, by genetic drift. CB 23.8 Other random evolution, Bottleneck Bottleneck: northern elephant seals… In 24 genes studied, there was no variation (all homozygous). CB 23.8 Evolution: A species’ genetic component changes as the individuals reproduce due to… •Non-random changes (natural selection) •Random changes (genetic drift/bottleneck) •Mutations add new alleles or genes Mutations add new alleles/genes, that are then subject to selection/drift CB 23.13 How could this occur? Coincidence of malaria and sickle-cell anemia Mutations are subject to Drift and Selection Mutation Generation 1 Replication Generation 2 Generation 3 Drift Selection Generation 4 Generation 5 What determines advantageous traits? CB 23.12 Reproduction/ Selection CB 25.3 Environmental changes drive evolution. CB 26.20 250 mya 135 mya 180 mya 65 mya current CB 22.3 The environment is in constant flux CB 24.5 Changing environment can separate populations and lead to new species… Separation does not need to be geographic Flies raised in different environments prefer to mate with individuals from the same environment... Flies raised in different environments prefer to mate with individuals from the same environment... CB 26.8 Evolution does not always occur at the same rate. CB 24.13 Why are intermediate traits sometimes hard to find? What drives evolution? What changes selection criteria? CB 26.8 The rate of evolution depends on the rate of environmental change. CB 26.8 Dinosaur extinction CB 26.9 an Asteroid impact, 65 mya Where did we come from? •Answer key posted on the class webpage •Office hours: Th 11:30am-2pm F 12:30-1:30pm •Exam Error Worksheet •Bonus #1 due F 2/15