Artificial Selection In artificial selection, humans have modified other species over many generations by selecting and breeding individuals with desired traits Terminal bud Lateral buds Cabbage Brussels sprouts Leaves Flower clusters Cauliflower Kale Flowers and stems Stem Broccoli Wild mustard Kohlrabi

Differential Predation in Guppy Populations Researchers have observed natural selection leading to adaptive evolution in guppy populations

Pools with killifish but no guppies prior to transplant Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools”

The Evolution of Drug-Resistant HIV The use of drugs to combat HIV selects for viruses resistant to these drugs The ability of bacteria and viruses to evolve rapidly poses a challenge to our society

Percent of HIV resistant to 3TC LE 22-13 100 Patient No. 1 Patient No. 2 75 Percent of HIV resistant to 3TC 50 Patient No. 3 25 2 4 6 8 10 12 Weeks

Anatomical Homologies Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor

Anatomical Homologies Turtle Alligator Bird Mammal Ancient, lobe- finned fish

Comparative embryology reveals anatomical homologies not visible in adult organisms Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo

Vestigial organs are remnants of structures that served important functions in the organism’s ancestors

Molecular Homologies Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide 100% 95% 87% 69% 54% 14% Rhesus monkey Species Human Mouse Chicken Frog Lamprey Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor

Biogeography Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution

The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record Paleontologists have discovered fossils of many such transitional forms

Whales

Modern Tetrapod Lineage They are all Middle–Late Devonian in age, ranging from 385 million years (Panderichthys) to 365 million years (Acanthostega, Ichthyostega).