Evidence of Evolution FOSSILS Fossilsany evidence of life

Evidence of Evolution

FOSSILS Fossils—any evidence of life in the prehistoric past. Can be the actual remains, an impression, carbon residue, or tracks left behind � It is difficult for fossils to form. They generally form in 3 ways. 1. Animals fell into ice or became trapped in snowfields. 2. Insects and other small animals became trapped in tree sap that hardened into amber 3. Animals became stuck in peat bogs, quick sand, and tar pits.

� Most fossils are found in sedimentary rock. As sedimentary rock is being formed a dead organism may become embedded in the lower layers. The pressure from the layers above turn the remains into rocks (preserves them) � The chance process by which organisms are fossilized means that the fossil record is not as complete as we would like it to be. For every organism that leaves a proper fossil, many die and vanish without leaving a trace.

�Three reasons why the fossil record is incomplete 1. Organisms that live in mountains or deserts may not become part of the record (sedimentary rock fossils happen only in certain bodies of water) 2. Finding fossils is difficult 3. The quality of preservation varies.

� Despite missing pieces, paleontologists can tell/get a clear picture of the evolution of many organisms. � Fossils show us that the history of Earth has been change, followed by change…

Biogeography—study of the locations of organisms around the world � Both Darwin and Wallace observed 1. Animals that seemed closely related yet were adapted to different environments in nearby regions 2. Also observed animals that seemed unrelated but had similar adaptations to similar environments in regions that were far apart

Grass finches (Northern Australia) http: //galliform. bhs. mq. edu. au/~simon/Research. html

Anatomy—study of body structures or organisms �Homologous Structures—structures that occur in different species and originated by heredity from a structure in the most recent common ancestor. Have a related structure even if their functions differ.

Each leaf has a very different shape and function, yet all are homologous structures, derived from a common ancestral form. The pitcher plant and Venus’ flytrap use leaves to trap and digest insects. The bright red leaves of the poinsettia look like flower petals. The cactus leaves are modified into small spines which reduce water loss and can protect the cactus from herbivory.

Homologies are not just anatomy �http: //evolution. berkeley. edu/evolibrary/arti cle/side_0_0/notjustanatomy_01

�Analogous Structures—have closely related functions, but do not come from the same ancestral structure • Wings of birds, bats and moths all have very different structures

�Vestigal Structures—body structure that is reduced in function in a living organism but may have been used in an ancestor • Some resemble structures with functional roles in related organisms • Show structures changed over time �Examples: • Molars in vampire bats • leg bones in snakes and whales • ear muscles in humans

Embryology—the study of how organisms develop In many organisms, the embryos are very similar in the early stages of development �Suggests ancestor descent from a common

Biological Molecules SCIENTISTS COMPARE DNA, RNA, PROTEIN AND OTHER MOLECULES. �The greater the similarities, the more closely they are related they are through a common ancestor

� Scientists comparing the genomes of members of the three domains of life—archaea, bacteria, and the eukaryotes (animals, plants, fungi, and protists)—have discovered about 500 genes that all living things share. These "immortal" genes have survived essentially unchanged for over two billion years (including the portion of a protein's sequence seen here, with shared amino acids indicated by shading). Says Brown's Ken Miller: "Despite the extraordinary diversity of life, all living organisms share a nearly identical set of essential genes, reflecting their evolutionary development from a common ancestor. "