Refer to chapter 16 in your textbook

Transcription

1 Refer to chapter 16 in your textbook

2 Learning Goals: 1. Explain how the 6 pieces of evidence support the theory of evolution. 2. Describe the conditions under which natural selection occurs.

3 Evidence of Evolution 1. Biogeography 2. Fossils 3. Anatomy 4. Embryology 5. Genetics 6. Natural Selection

4 1. Biogeography Biogeography: the study of where organisms live (now & in the past) Biogeographical Patterns: 1. Closely related species live in different environments (Ex. Galapagos Oinches) 2. Different species develop similarities (Ex. Birds that don t Oly)

5 1. Biogeography

6 2. Fossils *DNC Many recently discovered fossils form series that trace the evolution of modern species from extinct ancestors. Since Darwin, paleontologists have discovered hundreds of fossils that document intermediate stages in the evolution of many different groups of modern species.

7 2. Fossils *DNC One recently discovered fossil series documents the evolution of whales from ancient land mammals.

8 3. Anatomy Homologous Structures: body parts that are shared by related species and that have been inherited from a common ancestor (Ex. Limbs) Analogous Structures: body parts that have a common function but not structure (Ex. Wings) Vestigial Structures: body parts that have little or no function (Ex. appendix)

9 3. Anatomy

10 4. Embryology The early developmental stages of many animals with backbones (vertebrates) look very similar.

11 5. Genetics The genetic code (DNA) is nearly identical for all organisms.

12 6. Natural Selection Natural Selection: the process where organisms with variations best suited to their environment survive Conditions required for Natural Selection to occur: 1. Struggle for existence 2. Variation & Adaptation 3. Survival of the Oittest

13 Struggle for existence Cause: If more individuals are produced that can survive Effect: Than individuals in a population must compete for food, living space, and other necessities = Struggle for existence

14 Variation & Adaptation Variation: when similar organisms show differences in heritable traits Adaptation: an organisms heritable trait that increases it s ability to survive and reproduce

15 Survival of the fittest Fitness: an organisms ability to reproduce and survive Differences in adaptations can effect an organism s Oitness Survival means that the organism has reproduced and passed the adaptation onto the offspring = Survival of the?ittest

16 *DNC Natural Selection This hypothetical population of grasshoppers changes over time as a result of natural selection. Grasshoppers can lay more than 200 eggs at a time, but only a small fraction of these offspring survive to reproduce.

17 *DNC Natural Selection Certain variations, called adaptations, increase an individual s chances of surviving and reproducing. In this population of grasshoppers, heritable variation includes yellow and green body color. Green color is an adaptation: The green grasshoppers blend into their environment and so are less visible to predators.

18 *DNC Natural Selection Because their color serves as a camouflage adaptation, green grasshoppers have higher fitness and so survive and reproduce more often than yellow grasshoppers do.

19 *DNC Natural Selection Green grasshoppers become more common than yellow grasshoppers in this population over time because more grasshoppers are born than can survive, individuals vary in color and color is a heritable trait, and green grasshoppers have higher fitness in this particular environment

20 *DNC Evaluating the Theory of Evolution It s called the grand unifying theory of the life sciences because it includes research from all scientioic Oields It is supported by numerous scientists with large amounts of evidence, but like any theory there is still uncertainty and it is constantly changing as new information is found

21 Evaluating the Theory of Evolution