Adaptations Over Time Chapter 6

Ideas about Evolution Evolution-changes in inherited characteristics of a species over time. -A species is a group of organisms that share similar characteristics and can reproduce among themselves.

Jean Babtiste Lamarck Developed a hypothesis to explain how species change over time. He traveled through the Galapagos Islands collecting data on species of animals and their acquired traits.

Charles Darwin- model of Evolution In December 1831 Charles Darwin, a young naturalist, sailed from England on a journey to South America on the HMS Beagle. He recorded observations on plants and animals. He was amazed by what he found on the Galapagos Islands.

He observed the beaks of finches are related to its eating habits. He also noticed the finches were similar to a finch species he had seen on the South American Coast. He found they had to compete for food, and those with beak shapes that allowed them to eat available food survived.

Darwin’s model of Evolution He hypothesized that plants and animals on islands off the coast of South America originally came from central and South America. He observed that the species of finches on the islands looked similar to a mainland finch species. He reasoned that members of a population best able to survive and reproduce will pass their traits to the next generation; over time. Differences can result in separate species. He published - THE ORIGIN OF SPECIES in 1859 Darwin’s hypothesis became known as the the theory of evolution by NATURAL SELECTION-organisms with traits best suited to their environment will more likely survive and reproduce

How do Lamarck’s theory and Darwin’s theory differ?

VARIATION- an inherited trait that makes an individual different from other members of its species Adaptation- a variation that makes an organism better suited to its environment. Many environmental factors can cause change in the source of genes.

Geographic Isolation- can make two populations so different they become different species.

Two models explain the speed of evolution 1.Gradualism- describes evolution as a slow, ongoing process 2.The Punctuated Equilibrium model says gene mutation can result in a new species in a relatively short time.

CLUES ABOUT EVOLUTION Fossils found in Sedimentary rock show evidence that living things evolved. Fossil age can be determined by two basic methods. 1.Relative dating- looks at the fossil location in a particular layer or rock; older rock layers are under newer rock layers.

2. Radiometric Dating- compares the amount of radioactive element with the amount of nonradioactive element in a rock

Fossil records have gaps. Incomplete rock record; most organisms do not become fossils Enough fossils have been discovered for scientists to conclude that complex organisms appeared after simpler ones. Most organisms that have ever existed are now extinct

Direct evidence- such as the development of antibiotic resistance in bacteria; support evolution. Indirect evidence supporting evolution: 1. Embryology- the study of embryos and their development, shows similarities amongst all vertebrate species

2. Homologous body parts- body parts that indicate two or more species share common ancestors

3. Vestigial structures- structures that don’t seem to have a function but might have once functioned in an ancestor.

DNA can provide evidence about how closely related organisms are.

THE EVOLUTION OF PRIMATES PRIMATES- groups of mammals with : 1. Opposable thumbs 2. binocular vision 3. flexible shoulders

Hominids- appeared 4 to 6 million years ago and had larger brains then apes. Fossils such as Australopithecus, point to Africa as the origin of Hominids. Homo-habilis and Homo erectus are thought to be early human ancestors Lucy

Lucy- australopithicus

Homo- Sapiens- Began evolving 400,000 years ago Neanderthals – had short heavy bodies with thick bones, small chins, and heavy brow ridges. Disappered about 30,000 years ago Not thought to be direct ancestors of modern humans Cro –Magnon fossils date from around 10,000 to 40,000 years ago; are thought to be direct ancestors of early Homo Sapiens.