Ideas That Shaped Darwin's Thinking

Lyell LamarckMalthusCuvier

Learner Targets

At the end of this lesson, I will be able to describe how Darwin’s thoughts about the development of organisms were influenced by the theories and research of other scientists.

Georges Cuvier (1769-1832)

• Developed an understanding of animal extinction by comparing living organisms to fossils

• Determined that mammoths were not the same species as either African or Indian elephants and therefore must be extinct.

• EXAMPLE

Cuvier

Discussion Question 1

How might an extinction of a population of animals influence other surviving animals?

(i.e. The extinction of wolves and the population of deer)

Stopwatch

Discussion Question 1If a predator in an area disappears,

the prey animals have less pressure on them to survive.

This can change the make-up of the population by allowing animals to survive that wouldn’t have if the predator was still present.

Cuvier’s impact on Darwin: Darwin reasoned that populations have the potential to change because of extinctions.

James Hutton (1726-1797)

• Proposed that rock layers form very slowly

• Some rock layers were forced up from beneath the Earth’s surface

Discussion Question 2

Why would Darwin be interested in the age of the Earth?

In other words, What does a large amount of time have to do with evolution?

Discussion Question 2

Large amounts of time would make it possible for large numbers of generations of organisms to live and die.

Hutton’s impact on Darwin’s thinking:

The Earth could be VERY old – much older than was thought at the time.

• Developed a theory to explain how geological features were built up or torn down over long periods of time.

Impact on Darwin:– Reinforced his idea that

if geological things could change, than living things might change as well.

Charles Lyell (1797-1875)

Thomas Malthus (1766-1834)

Thought that if the human population continued to grow unchecked, eventually there would be insufficient living space and food for everyone, leading of large amounts of death.

Malthus

Discussion Question 3

What is a connection between Malthus’s theory and carrying capacity?

(Hint: Think back to semester 1, page 122)

Stopwatch

Discussion Question 3

Malthus’s theory describes what would happen as carrying capacity is reached in the human population.

As the carrying capacity is reached, population growth slows and may even stop.

Malthus’s Impact on Darwin:–If all the offspring of almost any

species survived for several generations, they would overrun the world.

–Since ALL do NOT survive, Darwin reasoned only the strongest or best suited have a survival advantage.

Jean-Baptiste Lamarck (1744-1829)Big idea: Use or disuse of

organs can cause the loss or acquisition of traits during their lifetime.

These traits could then be passed on to their offspring. Given enough time, this process led to change in a species.

• Lamarck's HypothesisA male fiddler crab uses its front claw to ward off predators and to attract mates.

• Lamarck's HypothesisBecause the front claw is used repeatedly, it becomes larger.

This characteristic (large claw) is passed onto its offspring.

Question 4: According to Lamarck, how would this anteater come to have such a long nose?

The Anteater

Myrmecophaga tridactyla

Stopwatch

It is known now that Lamarck’s hypotheses was incorrect

1. Lamarck did not know How traits are genetically inherited.

2. He also did not know that an organism’s behavior has no effect on its heritable characteristics.

Discussion Question 5: Learner Targets

How was Darwin's thoughts on the development of living organisms influenced by:

Cuvier – Hutton – Lyell – Malthus – Lamarck – Competition influences

reproduction

Discussion Question 5: Learner Targets

How was Darwin's thoughts on the development of living organisms influenced by:

Cuvier – ExtinctionHutton – Large amounts of timeLyell – Populations can changeMalthus – Strong surviveLamarck – Competition influences

reproduction