How Does Evolution Happen?

After making observations and analyzing evidence, Charles Darwin concluded that natural selection is the mechanism of evolution.

Early Ideas on Evolution The first person to do so was the French naturalistJean Baptiste de Lamarck propose ‘how’ species change.

De Lamarck proposed that during their lifetime, organisms change in response to their environment.

Ex. Giraffes had long necks because their ancestors had stretched their necks while reaching for leaves high in a tree.

Useful acquired traits were passed on, unbeneficial traits werenot.

This is how de Lamarck suggested that a reasonableexplanation for how evolution occurs.

I. Charles Darwin

Charles Darwin served as the naturalist, a scientist who studies nature, on the HMS Beagle.

Darwin’s observations during his trips on the Beagle helped Darwin develop his theory on evolution

Charles Darwin

The HMS Beagle

Darwin’s Journey

A. Darwin’s Journey

1. Darwin observed plants and animals on the Galapagos Islands located west of Ecuador, a country in South America

B. Darwin’s Finches

1. Darwin observed that plants and animals were on Galapagos islands were the same as those in Ecuador, but weren’t identical and differed from island to island.

2. Darwin noticed that the shape of finches beaks differed based upon their food.

Darwin’s Finches

A. Darwin’s Thinking

Darwin proposed that the Galapagos finches came from South America

Darwin suggested that the finches evolved adaptations over many generations

Example: Finches with different beak shapes related to their food

A. Ideas about Breeding

1. Artificial or Selective breeding is the practice by which humans select plants or animals for breeding based upon desired traits

2. Traits are inherited characteristics

3. Certain traits can spread thorough populations a. Selective breeding in dogs has produced over

150 breeds

A. Ideas About Population

1. Darwin was influenced by Thomas Malthus. He realized that populations of all species are limited by starvation,disease, competition and predation.

2. Traits that help organisms survive in their environment and are passed on to offspring

A. Ideas About Earth’s History

1. Darwin was also influenced by Charles Lydell, who believed that Earth changed slowly over time.

2. Darwin believed that organisms had time to slowly change.

A. Darwin’s Theory of Natural Selection

Darwin struggled with his theory for 20 years.

Alfred Russel Wallace came to same conclusion about evolution as Darwin. 1859, Darwin published his book ‘On the Origin of Species by Means of Natural Selection’

Charles Darwin

The Origin of Species

Darwin’s Theory of

Natural Selection

Natural Selection

Four Steps process by which organisms are better adapted to their environment.

a. Overpopulation

b. Genetic Variation

c. Adaptation (inherit beneficial traits)

d. Selection (successful reproduction)

A. Genetics and Evolution

1. Darwin knew organisms inherited traits to create variation but not how traits were inherited.

2. We now know that organisms that inherit genes that increase their survival are more likely passed on to their offspring (heredity and genetics)