1 Evolution Chapter 5

2 Darwin Darwin’s observations included diversity of living things, remains of ancient organisms, and characteristics of organism on the Galapagos Islands.

3 Diversity Diversity among species. Species is a group of similar organisms that can mate with each other and produce fertile offspring.

4 Fossils A fossil is the preserved remains or traces of an organism that lived in the past.

5 Adaptations Adaptation is a trait that helps an organism survive and reproduce.

6 Evolution Darwin hypothesized that the species gradually changed over many generations and became better adapted to the new conditions. Evolution is the gradual change in a species over time.

7 Natural Selection Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

8 Evidence of Evolution Fossils. Pattern of early development. Similar body structure.

9 Similarities in Early Development What do an adult fish, salamander, chicken and opossum have in common? During early stages of development all four have a tail and a row of tiny slits along their throats.

10 Similarities in Body Structure What do fishes, amphibians, reptiles, birds and mammals have in common? They all have an internal skeleton with a backbone. Homologous structures are similar structures that related species have inherited.  Dolphin’s flipper.  Dog’s leg.  Bird’s wing.

11 Inferring Species Relationships DNA evidence. Protein structure. Fossils. Early development. Body structure.

12 Branching Tree A branching tree is a diagram that shows how scientists think different groups of organisms are related.

13 New Species A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits.

14 The Fossil Record Fossils form when organisms that die become buried in sediments. Types of Fossils  Petrified fossils.  Molds & casts.  Preserved remains.

15 Determining Age of Fossils Scientists can determine a fossil’s age in two ways:  Relative dating.  Radioactive dating using half-life.

16 Geologic Time Scale Precambrian Paleozoic Era  Cambrian  Ordovician  Silurian  Devonian  Carboniferous  Permian Mesozoic Era  Triassic  Jurassic  Cretaceous Cenozoic Era  Tertiary  Quaternary

17 Cause of the Mass Extinction About 65 million years ago a large asteroid struck the earth. The impact created a large cloud of gas and dust. The dust blocked sunlight, killing many plants. Animals all starved to death.

18 Rate of Evolution Gradualism proposes that evolution occurs slowly but steadily. Punctuated equilibria states that a species evolve quickly during relatively short periods.

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