Chapter 6 Adaptations Section 1 Ideas about Evolution

Chapter 6 Adaptations

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

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

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 disproved. hypothesis was

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.

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.

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 theory of evolution by natural selection. �Natural selection: �organisms with traits best suited to their environment will survive and reproduce;

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.

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 �Camouflage is an adaptation that causes an organism to blend into its environment and makes it more likely to survive and reproduce.

�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.

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.

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.

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

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

Clues About Evolution �Embryology – study of �embryos and their development �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 �Vestigial structures – structures that are reduces in size an don’t seem to have a function. �DNA – can determine how closely related

Section 3 �Primates � 3 characteristics ◦ Opposable thumb ◦ Binocular vision ◦ Flexible shoulders ◦ Large brain IS NOT �humans, monkeys, apes

�Hominids ◦ share some characteristics of gorillas, orangutans, apes, and chimpanzees, but had a larger 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

�Homo habilis �Homo erectus �Homo sapien ◦ handy man ◦ found tools beside them ◦ larger brains and more human-like features ◦ 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 sapiens, evolved from Homo sapiens