Evolution!

What is evolution? A change in inherited characteristics over time

Theories of Evolution

1.Inheritance of Acquired Characteristics Proposed by Jean Baptiste de Lamarck in 1809

Stated that characteristics parents developed over their lifetime are inherited by their offspring Ex: if a bodybuilder with big muscles had a child, the child should have big muscles

Scientists collected data and proved this theory incorrect.

2. Natural Selection Theory proposed by Charles Darwin in 1859 in his book “On the Origin of Species”

In 1831, Darwin, a naturalist, set sail from England on the HMS Beagle to explore the South American coast.

Voyage of the HMS Beagle

During his voyage, Darwin made many observations, took notes, and collected many examples of new plants and animals.

One of the stops was the Galapagos Islands off the coast of Ecuador. Darwin hypothesized that life here originally came from South and Central America.

He noticed many species on the islands that did not exist anywhere else. Ex’s: 1. Giant land tortoises

Giant Land Tortoise                                                                                                                                   

2. Finches- he observed 13 varieties 2. Finches- he observed 13 varieties. He concluded that they had to compete for food and over time developed different beak shapes for the different foods they ate

3. Marine iguanas- only iguana in the world that swims under water to eat algae off the rocks.

Marine Iguanas                                         

After the voyage was over, Darwin went back to England and analyzed his data and specimens. He developed his theory of natural selection.

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 the offspring. 4. Individuals with helpful variations survive and reproduce better than others.

5. Over time, the offspring with the helpful variations make up more of the population and may produce new species.

Natural Selection was a hotly debated topic then and still is now.

Theory of Natural Selection Also known as “survival of the fittest”

Means that organisms with the traits best suited for their environment are more likely to survive and pass on traits to their offspring

Speed of Evolution Gradualism- a slow change from one species to another by mutations and variations, ex: horse

Punctuated equilibrium mutation of a few genes causes the appearance of a new species over a short period of time, ex: bacteria