Chapter 6

1. Chapter 6 Adaptations

2. Section 1- Ideas about Evolution Lamarck--Evolution as a result of acquired characteristics (disproved) Darwin-- Natural Selection (current accepted theory)

3. Early Models of Evolution • Evolution occurs in organisms today • Species: Group of organisms that share similar characteristics and can produce fertile offspring (reproduce among themselves) • Evolution:change in inherited characteristics over time • Gradual—slow change • Punctuated—rapid change

4. Hypothesis of Acquired Characteristics • Lamarck proposed a hypothesis to explain how species change over time • He proposed that Evolution was a result of acquired characteristics • Lamarck suggested that characteristics developed by the parent are passed to its offspring. • Lamarck’s hypothesis was disproved.

5. Darwin’s Model of Evolution -Charles Darwin sailed on the HMS Beagle ship and observed characteristics of animals in the Galapagos Islands. -Darwin hypothesized that the species he saw must have originally come from Central and South America.

6. Darwin’s Observations Darwin observed 13 species of finches. All were similar except for differences in body size, beak shape, and eating habits. Finches with beaks that allowed them to eat whatever food was available eventually became different species.

7. Natural Selection • Darwin’s theory is described in the book • On the Origin of Species • Darwin’s Theory • a) After many years Darwin’s theory became known as the theory of evolution by natural selection. • Natural selection: • organisms with traits best suited to their environment will survive and reproduce;

8. Survival of the Fittest The Principles of Natural Selection 1) Organisms produce more offspring than can survive 2) Differences, or variations, occur among individuals of a species. 3) Some variations are passed to offspring. 4) Some variations are helpful. Those with helpful variations will survive and reproduce. 5) Over time, offspring of those with helpful variations may eventually become a separate species.

9. Variation and Adaptations Variation: Inherited trait that makes an individual different from other members of its species a) Results from permanent changes or mutations in an organism’s genes. b) An example would be an albino squirrel in a population of gray squirrels. c) Some variations are more helpful than others. Adaptation: any variation that makes an organism better suited to its environment Camouflageis an adaptation that causes an organism to blend into its environment and makes it more likely to survive and reproduce.

10. Changes in Sources of Genes a) Over time, the genetic makeup of the Galapagos finch changed, and so did the size and shape of its beak. b) When individuals move in and out of an area, they might bring in or remove genes and variations. Geographic Isolation a) Sometimes mountains, lakes, or other geological features isolate a small number of individuals from the rest of the population. 1) Variations begin to form. 2) Gene mutations might occur. 3) Over time, they become so different that they no longer can breed with one another.

11. The Speed of Evolution Scientists agree that evidence supports BOTH gradualism and punctuated equilibrium. Gradualism: Model describing evolution as a slow process or change from one species to another. a) Mutations and variations over time will result in a new species. b) Darwin hypothesized that evolution takes place slowly.

12. Punctuated Equilibrium • Punctuated Equilibrium: • Model of rapid evolution • Rapid evolution with few intermediate forms • Evolution continues to occur in organisms today • Punctuated Equilibrium Today • a) Ex: Many bacteria once killed by penicillin are now no longer harmed by it. • b) When penicillin was used, those with the penicillin-resistant bacteria survived and reproduced and passed this trait to their offspring.

13. Section 2- Clues about Evolution • Clues from Fossils • Fossil – once living remains from an earlier time • Paleontologist – studies fossils • Old stone tools are NOT fossils • Examples of fossils are as follows: • Petrified wood • Plant such as a fern imprinted or imbedded in rock • Animal found in a glacier

14. Types of Fossils • Most fossils are found in sedimentary rock. • Determining a Fossil’s Age: • Relative Dating – • Comparing fossils in sedimentary rock layers can then be used to estimate the age of fossils. • In undisturbed areas, older rock layers lie below successively younger ones • Radiometric Dating • Uses radioactive elements to tell the age of fossils as they give off a steady amount of radiation as they change to a non-radioactive element

15. Clues About Evolution Embryology – study of embryos and theirdevelopment Embryo – earliest growth stage of an organism Tail and pharyngeal pouch fish, reptiles, birds, mammals Homologous structures – body parts that are similar in structure and origin Indicate that species might share common ancestors Vestigialstructures – structures that are reduces in size an don’t seem to have a function. DNA – can determine how closely related species are to each other

16. Section 3 • Primates • 3 characteristics • Opposable thumb • Binocular vision • Flexible shoulders • Large brain IS NOT • humans, monkeys, apes

17. Hominids • share some characteristics of gorillas, orangutans, apes, and chimpanzees, but had alarger brain • ate both meat and plants and walked upright on two legs • Australopithecus • one of the oldest hominids ever discovered • Lucy • Characterized by small brain cavity and humanlike jaw and teeth

18. Homo habilis • handy man • found tools beside them • Homo erectus • larger brains and more human-like features • Homo sapien • wise human • Neanderthals • family groups lived in caves and hunted and used well made stone tools • Cro-Magnon • lived in caves, made stone carvings, buried their dead. Thought to be direct ancestors of humans • Evidence indicates that modern humans, Homo sapien sapiens, evolved from Homo sapiens