The Evolution of Evolution

Historic ideas about organisms and how they change over time

Aristotle(384 - 322 B.C.)

● “Ladder of life”● Nature is ordered from

lower to higher

● No vacant rungs

● No movement up or down the ladder

● Included living and non-living things

Jean-Baptiste Lamarck (1744-1829)

● First scientist to propose a mechanism for how organisms change (1809)

● His idea: “Inheritance of Acquired Traits”● Greater use of a body part

would change it, and the change would pass on to the organism’s offspring.

Use and DisuseUse and Disuse Organisms could alter

the size or shape of organs

USE: giraffe stretching its neck to reach taller trees

DISUSE: if a bird did not use its wings, then they would decrease and disappear

Lamarck’s Assumptions

1. Organisms have a desire to change. They have an inborn urge to better themselves for their environment.

Ex: Birds tried to fly and eventually grew wings because of their efforts.

Lamarck’s Assumptions

2. Organisms can change shape by using or not using their bodies.

Ex: The wings of a bird that does not fly would get smaller from generation to generation and the wings would eventually disappear.

Lamarck’s Assumptions

3. Organisms can pass on acquired traits to their offspring.

Ex: If an animal developed muscles from lifting weights during its lifetime, it could pass those muscles on to its offspring.

Charles Darwin(1809-1882)

● English naturalist● Traveled around the world on

the Beagle (1831); famously stopped in the Galapagos Islands

● Observed many species and fossils

● Particularly studied finches, tortoises, blue-footed boobies

Galapagos IslandsGalapagos Islands

Small islands of the western coast of S. America

Close together but different climates Smallest/lowest were hot, dry,

barren Higher ones had more rain and

greater diversity of life

The Galapagos Islands (Ecuador)

Patterns of Patterns of DiversityDiversity Darwin was puzzled by species and

where they lived No kangaroos in England No rabbits in Australia

Collected fossils Why did species disappear? How are they related to living

species?

WildlifeWildlife Tortoises- the shape of the

shell could be used to identify which island a particular tortoise inhabited.

Finches – birds on different island with different beaks

“Darwin’s finches”

● Darwin noticed that finches were different on each Galapagos Island.

● He concluded that the different finches had descended from a common ancestor and had changed to be able to do and eat different things.

“Descent with Modification”After his studies, Darwin came up with 4 main ideas…

1. Individuals differ, and some of this variation can be inherited.

2. Organisms produce more offspring than can survive; thus they have to compete for resources, and only the most fit will survive and reproduce.

3. The most fit organisms pass on their heritable traits to their offspring.

4. Species alive today are descended with modification (change) from their ancestors.

Natural Variation: differences among individuals of a species

Artificial selection: humans select those variations that they find useful (dogs)

Descent with modification: change in organisms over time (many generations)

Natural Selection: pressure the environment puts on the specific traits that affects their ability to survive

Evolution: change over time Common Descent: All living organisms are related to

one another Differential Reproduction: individuals that have certain

traits are more likely to survive and pass on those traits (they become more frequent)

Therefore we now call Darwin’s idea ‘biological evolution”

DEFINITIONS

Lamarck’s explanation for the giraffe’s long neck:

Darwin’s explanation for the giraffe’s long neck:

Thomas Malthus(1766-1834) British clergyman and scholar

His prediction: the human population

would grow faster than the space and food supplies needed to sustain it.

The only checks on the human population would be war, famine, and disease.

Influence of Malthus on Darwin

Malthus’ theory of population growth was observed by Darwin in other animal populations as well.

In nature, Darwin saw many organisms that produced many offspring. Most died.

Darwin wondered, what determines which individuals survive and reproduce?

James Hutton and Charles LyellBritish Geologists

Hutton is considered the “father of modern geology”

Based on layers found in rock structures, Lyell proposed that Earth is millions of years old

Lyell proposed that geological features could be built up or torn down over long periods of time stressed that scientists

must explain past events in terms of observable processes (volcanoes, erosion)

Grand Canyon, Arizona

Influence of Geology on Darwin

After reading Lyell’s book, Darwin was convinced that Earth was old.

Darwin reasoned that if geological phenomena could change the earth, then life on Earth could change as well.