EVOLUTIONBy: Paul Meringolo

BEFORE WE BEGIN…• 1. Who were the two scientists discussed that proposed theorys about

evolution• 2. Which of these scientists theory of evolution is still accepted today?• 3. What is natural selection?• 4. What type of organism did Darwin study to propose his theory of

natural selection?• 5. What is meant by variation and adaption?• 6. How does geographic isolation affect a small population?• 7. What are the two models of evolution discussed?• 8. What kind of information does DNA provide us with?

EARLY MODELS OF EVOLUTION• Millions of species of plants, animals , and other organisms live on

Earth today. Do you suppose they are exactly the same as they were when they first appeared or have any of them changed?

• Species – A group of organisms that share similar characteristics and reproduce amongst themselves to produce fertile offspring.

• Evolution- Change in a species inherited characteristics over time.

EARLY MODELS OF EVOLUTION• Jean Baptiste de Lamarck- Suggested that characteristics, or traits,

developed during a parent organism’s lifetime are inherited by its offspring. His hypothesis is called the inheritance of acquired characteristics.

DARWIN’S OBSERVATIONS• Charles Darwin observed 13 species of finches on the Galapagos Islands.

He noticed that all 13 species were similar, except for differences in body size, beak shape, and eating habits. Darwin reasoned that the Galapagos finches must have had to compete for food. Finches with beak shapes that allowed them to eat available food survived longer and produced more offspring than finches without those beak shapes. After many generations, these groups of finches became separate species

• Natural selection- Organisms with traits best suited to their environment are more likely to survive and reproduce. Their traits are passed to more offspring

DARWIN’S OBSERVATIONS• After many years, Darwin’s ideas became known as the theory of

evolution by natural selection.

VARIATION AND ADAPTION• Darwin’s theory of evolution by natural selection emphasizes the differences

among individuals of a species. These differences are called variations.

• Variation- An inherited trait that makes an individual different from other members of its species.

• Adaption- Any variation that makes an organism better suited to its environment.

• Variations that result in an adaptation can involve an organism’s color, shape, behavior, or chemical makeup.

GEOGRAPHIC ISOLATION• Sometimes mountains, lakes, or geological features isolate a small

number of species from the rest of the population. Over several generations, variations that do not exist in the larger population might begin to be more common in the isolated population.

THE SPEED OF EVOLUTION• Scientist do not agree on how quickly the process of evolution occurs.

Many hypothesize that evolution occurs slowly over tens or hundreds of millions of years whereas others believe evolution occurs more quickly.

• Gradualism- A slow model of evolution where one species changes to a new species through a continuing series of mutations and variations over time to result in a new species.

• Punctuated Equilibrium- A model of evolution that is rapid and comes about when the mutation of a few genes results in the appearance of a new species over a relatively short period of time.

VARIATION AND ADAPTION

FOSSILS AND EVOLUTION• Fossils provide a record of organisms that lived in the past• By looking at fossils, scientists conclude that many simpler forms of life

existed earlier in Earth’s history and more complex forms of life appeared later.

• From the study of the fossil record, scientists have concluded that more than 99 percent of all organisms that have ever existed on Earth are now extinct.

DNA• DNA- The molecule that controls heredity and directs the development of

every organism.

• In a cell with a nucleus, DNA is found in genes that make up the chromosomes.

• Scientists compare DNA from living organisms to identify similarities among species.

• DNA often provides additional evidence of how some species evolved from their extinct ancestors and DNA can show how closely related organisms are.

THE EVOLU0TION OF PRIMATES• Primates- Humans, Monkeys, and apes belonging to a group of mammals

• All primates have opposable thumbs, binocular vision, and flexible shoulders which indicate they may have evolved from a common ancestor.

• Primates are divided into two groups known as strepsirhines and haplorhines

• Strepsirhines- Lemurs and Tarsiers• Haplorhines- Monkeys, Apes, and Humans

EVOLUTION OF PRIMATES

EVOLUTION OF PRIMATES• Hominids- Humanlike primates that appeared different from other

primates, lived 4 million to 6 million years ago

Hominids shared some characteristics with gorillas, orangutans, and chimpanzees, but a larger brain separated them from the apes.

HUMANS• Fossil record indicates that homo sapiens evolved about 400,000 years

ago• About 125,000 years ago, two early human groups, Neanderthals and

Cro-Magnon humans probably lived at the same time in parts of Africa and Europe.