NOTES : CH 16 – Darwin’s Theory of Evolution by Natural Selection / Evidence for Evolution

DEFINITION OF EVOLUTION:

change over time: the process by which organisms have descended from organisms.

The Life of Charles Darwin

• (England)

• Completed college after studying to become a doctor but could not stand sight of blood …

• Set sail on 5 year voyage on H.M.S., Beagle in 1831 as the natural historian for expedition.

• Made extensive drawings and notes on the trip but also collected many species of plants and animals.

• Began to OBSERVE that ;

• He collected fossils:

-noticed some

-others looked like nothing he had ever seen before

• Were these related to the living (present day) organisms?

• Why did some organisms disappear altogether?

Organisms Darwin Observed on the Galapagos

• Land Tortoise = different shaped carapace (shell) depending what island they inhabited.

• Finches = depending on environment in which they lived.

• he realized that characteristics of many animals and plants varied noticeably among the different islands of the Galapagos.

• On the journey home he began to pose the question…

-Could animals on the different islands once have been members of the same species?

Those Who Influenced Darwin

Hutton (Geologist)

-Geologic processes operate extremely slowly (take millions of years!)

-therefore, .

Lyell (Geologist)

-Scientists must explain past events in terms of processes that they can actually observe

è processes that shaped the Earth millions of years ago continue to shape present day Earth

è this explained how geological features can be built or torn down over long periods of time.

Malthus (Economist)

-proposed that war, famine, disease, limit the growth of human populations

-if populations continue to grow unchecked, they will ( )

2 IMPORTANT CONCEPTS TO HELP US UNDERSTAND THE PROCESS OF EVOLUTION:

Variation & Adaptation

VARIATION:

ADAPTATION: inherited characteristic that

EVIDENCE FOR EVOLUTION

1) Fossils:

● (shells, casts, bones, teeth, imprints)

● show a succession of forms through a vast span of time

● progressive changes based on the order they were buried in sedimentary rock

fossils/ species à fossils/ species

organisms à organisms

2) Biogeography and age of the earth:

●

è 13 species of finches on the 13 Galapagos Islands

è 57 species of kangaroos…all in Australia!

● Radioactive dating tells us the earth is about

● Rate of motion of tectonic plates

3) Adaptations: Evidence for Evolution

● MIMICRY:

● CAMOUFLAGE: enables species to blend with their surroundings

● PHYSIOLOGICAL: ability to resist disease or drought

4) Applied Genetics ("artificial selection"):

● Darwin noticed that farmers “selected” the best crops, animals – he wondered if there could be a “selective” force in nature

● today we see DDT-resistant insects;

5) Homologous and Vestigial Structures

Homologous Structures =

ex: " ”

• structures that develop from the same clumps of cells

-later develop into structures that have different forms and functions

• arms, flippers, & wings look very similar at the

beginning of development, but differ as

the animal matures

-the function differs as well!

Vestigial Structures: in an organism

è ex: , , appendix, nictitating membrane, some pythons & boa constrictors have tiny leftover leg bones(and whales!)

è koala's have a large functioning appendix (eat primarily plant materials)

6) Embryological Development

• Similarities of vertebrate organisms in

• All animal development begins in the same way (from the same ball of cells)

-BUT recognizable features for that species develop as the organism grows

7) Cellular and Molecular Evidence:

Cellular Evidence

•

-consist of membranes filled with water containing genetic material, proteins, lipids, carbohydrates, salts

and other substances

Molecular Evidence

• the DNA code to a common ancestor

-DNA and RNA = simple four-base code that provides the recipe for all living things

• Transfer genetic material from the cell of one living thing to the cell of another

-the recipient would follow the new instructions as if they were its own

-EX: Roundworms share 25% of their genes with humans.