The Evolution of Evolution

Why are there so many species of life on Earth?

Where did all the species come from? Why did some species go extinct? _________________________________ _________________________________ _________________________________

Time Line of Ideas

1) Creationism:

• supernatural being created each type of species at the beginning of the world

• modern organisms are unchanged from the original ancestors

• supernatural, not a natural explanation (not science)

2) Plato / Aristotle (400-300 B.C.)

• species are unchanging forms

• there is an increasing degree of perfection between species with humans at the top

3) Leclerc (Comte de Buffon) (1707-1788)

• original creation provided a few species which gave rise to modern species

• unconvincing because:

1. no mechanism for change

2. not enough time for it occur (Earth believed to be 4000-6000 yrs. old)

4) Cuvier (1769-1832)

• many species

originally created

• subsequent catastrophes produced rock, destroying / fossilizing species, therefore, modern species are survivors of catastrophes

•Why are there no fossils of modern organisms in the oldest rocks?

5) Agassiz (1807-1873)• a new creation occurred after each catastrophe, therefore, at least 50 separate catastrophes and creations

6) Hutton (1726-1797) & Lyell (1797-1875)

• geologists who developed uniformitarianism: natural processes produced Earth’s features [Ex: layers of sedimentary rock produced by effects of floods, volcanoes, wind, erosion, etc. The results occur very slowly, so Earth must be VERY old

• provided time frame for organisms to change, but still no mechanism of change

7) Lamarck (1744-1829)

•“Inheritance of Acquired Characteristics”

•organisms can modify their bodies through use or disuse of structures or organs and pass those modifications on to offspring

8) Mid 1800’s

• similarities between fossil forms and modern day species could be explained if present day species evolved from pre-existing ones

• BUT HOW??

Charles Darwin (1809-1882)

5 year, world wide journey as a naturalist aboard H.M.S. Beagle (1831-1836)

Witnessed a diversity of plants, animals and landscapes never seen before

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Voyage of H.M.S. Beagle

© Darwin and the Beagle

How were we formed?

© Dorling Kindersley Nature

http://volcano.und.nodak.edu/vwdocs/volc_images/img_volc_darwin.html

Why are our trunks so tall?

(© Audesirk & Audesirk)

Why do we have wings?

King PenguinsA colony of king penguins gathers on South Georgia, an island near the southern tip of South America. King penguins may stand about 1 m (about 3.3 ft) tall, making them the second-largest penguin species.

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Why are there so many varieties of us?

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Whoever heard of marine iguanas?

http://www.leler.com/galapagos/

What influenced Darwin?

Huge variety of species, some with subtle but important differing features

Increasing complexity of organisms through the fossil record

Earth is very old (Hutton & Lyell) Populations do not grow unchecked; more

offspring are produced than survive (Malthus) What determines who lives & who dies?

The Theory of Evolution by Natural Selection Populations have the potential to increase at a

geometric rate, but in the short run the number of individuals in a population remains fairly constant

The conditions of life are limited Most environments change constantly throughout

geologic time Only a fraction of offspring in a population will

live to reproduce

Individuals in a population are not all the same: some have variable traits that can be inherited

The “struggle for existence” determines which traits are favorable or unfavorable by determining the success of the individual who possesses the traits

Individuals with favorable traits produce more offspring than those with unfavorable traits

Natural selection causes the accumulation of favorable traits and the loss of unfavorable traits to the extent that a new species may arise

Life evolved from one kind or a few “simple” kinds of organisms

Each species arose from another species that preceded it in time

Each species originated in a single geographic location

The greater the similarity between two groups of organisms, the closer their relationship and the closer in geologic time is their common ancestral group

The Theory of Evolution from a Common Ancestor

Extinction of old species is a consequence of the production of new species or of environmental change

Once a species has gone extinct, it never reappears

Evolution continues today in generally the same manner as during preceding geologic eras

The geologic record is very incomplete

Evolution Today

A change in gene frequency within a population over time (population = all the individuals of a species living in a given area)

Species = similar organisms living in an area that can interbreed under natural conditions

Peppered moths (Light & dark genes) Antibiotic resistance by bacteria Pesticide and herbicide resistance by insects

and plants

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