the theory of evolution

The idea of CHANGE OVER TIME

I. The Beginning of LifeA. Origin of the Universe: Big Bang Theory

> 15 billion yrs. ago

B. Earth’s Origin 1. 4.6 billion yrs. ago out of gases 2. Gases formed our atmosphere

C. Life’s Origin 1. first cells probably resembled anaerobic bacteria 2. Endosymbiotic Theory – Eukaryotic cells arose from prokaryotic organisms

II. Theories of Evolution

A. Lamarck (French biologist)

1. Evolution results from the use and disuse of physical features.

e.g. Birds kept trying to use front limbs for flying that they turned into wings

If didn’t use wings, they would shrink & disappear

2. Traits are passed on to offspring3. He was WRONG, but his ideas showed that living things change over time

B. Malthus (English economist)

1. Stated that human population would increasefaster than food supply and living space

2. This idea would be applied to all species and would influence Darwin’s theory

C. Charles Darwin (British naturalist)

1. The modern theory of evolution has taken shape due to his work

2. Development of his theory a. He sailed around world studying different organisms (Ex: Galapagos Islands - finches)

Galapagos Islands

Darwin’s route

b. Combined what he saw with the ideas of Malthus and made one key association:

Individuals with traits better suited to an env’t are more likely to survive, reproduce, and pass on traits (survival of the fittest) Natural Selection

3. His Theory: NATURAL SELECTION “Survival of the Fittest” - Individuals w/ the best traits are better suited for the env’t and will reproduce more often. this theory incorporates 3 principle aspects:

a. Genetic Variation - differences exists within a species (e.g. some cows produce more milk, some plants bear larger fruit). Caused by: 1. mutations (changes in base sequences) 2. sexual reproduction combines genes from diff. parents 3. crossing-over during meiosis

b. Competition – An interaction b/n two or more species that use the same scarce resources (e.g. food, water, shelter). Organisms produce more offspring than env’t can support (ex. carrying capacity). They compete for the same resources

c. Requires Adaptation

1. organisms respond to their env’t, undergo changes, & increase their chances of survival

2. Thus, evolution can be thought of as:

Descent with Modification “change over time”

Example: Galapagos Island Finches Beaks adapted to diff. seasons (i.e. wet/dry) Diff. plants produce diff. seeds

4. Publication of his work (1859) After years of further research & improvements, Darwin published his ideas in a book:

“The Origin of Species by means of Natural Selection”

D. Darwin’s Ideas Updated1. Natural selection causes change in a pop.

- the frequency of alleles increases/decreases over time

- Genetic Drift – in small populations, a particular allele may become more common by chance (as compared to larger population)

2. Isolation of a population leads to species formation (i.e. speciation) geographic: physical barrier; island/mountain

reproductive: members of 2 pops. can’t interbreed behavioral: two pops. have different habits

3. When one species becomes extinct, it is replaced by another

III. Evidence of Evolution Organisms have changed over time?

A. Fossil Record1. Fossil evidence

a. Fossil – the preserved remains of an organism. Forms imprints/molds in rock and mud.

b. Radioactive dating - Use radioactive isotopes to determine age - decay rate of carbon-14 used to date young fossils

2. Interpreting fossils

a. Paleontologist – studies fossilsb. Geologist – uses fossils to explain earth’s historya. Anthropologist – studies human evolution

3. History of Life on Earth

a. Hadean Eon – 4.5 billion yrs. ago appearance of bacteria/cyanobacteria?

b. Paleozoic Era – 250 mil. yrs. ago plants, aquatic life, 1st land animals

c. Mesozoic Era – 66 mil. yrs. Ago age of reptiles (dinosaurs)

d. Cenozoic – present time age of mammals, flowering plants

Important Note about the fossil record: the fossil record is incomplete

1. Many species lived in unfavorable environments that do not allow for fossil formation

Ex. Grasslands, mountains, deserts

2. Even though it is incomplete, the fossil record still presents us w/ strong evidence of evolution

B. Other Evidence 1. Body structure

a. Homologous structures – Diff. organisms have body parts w/ similar structure, but diff. fxn (suggests a common ancestry)

b. Analogous structures – Diff. organisms have body parts with a similar fxn, but not structure.

Insect wing Bat wing Bird wing

c. Vestigial Structures – body parts are reduced in size and appear to have no fxn

(e.g. appendix, human tail bone, snake legs)

2. Compare embriology and biochemistry --similar embryos show a closer relationship

lamprey turtle chicken cat human

IV. Patterns of Evolution

1. Adaptive Radiation – diff. species evolve from one ancestral species. Each has a diff. niche Ex. Finches

2. Convergent Evolution – Natural selection produces similar adaptations in diff. organisms in response to similar envt’s. Ex:

Sharks (fish), penguin (bird), dolphin (mammal) Wings/flippers perform the same fxn

3. Divergent Evolution – When two species gradually become increasingly different. Can be linked to one species having a new habitat.

ex. humans & apes polar bear & brown bear

4. Coevolution – Species that interact closely often adapt to one another. Ex. Hawk moth and Orchids

5. Punctuated Equilibrium/Gradualism a. Punctuated Equilibrium – organisms change rapidly, over a short period of time. There are also periods of no change b. Gradualism – change occurs slowly, over a long period of time

Example: Giraffe necks

Cladogram (a.k.a. phylogenic tree)A diagram that depicts how organisms are related to one another by showing how evolutionary lines evolved and branched off from common ancestors over time

Vocab:1. Clade – a group of species that includes a single common ancestor and ALL descendents of that ancestor

1. A common ancestor of species E and C?

2. What two species are most closely related?

a) A and B c) C and Db) B and C d) E and A

3. What are the three clades in this picture?

Refer to Cladogram Practice Packet

Cladogram #1

Cladogram #3