EVOLUTION

Charles Darwin (Working off the information and data collected from other scientists)

Point 1 Origin of Species- Species were not created in their present forms but had evolved from ancestral species. Point 2 Darwin proposed a mechanism for evolution, which he termed natural selection.

Natural Selection: All species have such great fertility potential that their population sizes would increase exponentially if all individuals that are born reproduced successfully. Fact 1

Example: Alligators

Fact 2 Most populations are normally stable in size, except for seasonal fluctuations.

Natural resources are limited. Fact 3 Natural resources are limited.

Inference 1 from fact 3 Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of offspring surviving each generation.

Fact 4 Individuals of a population vary extensively in their characteristics; no two individuals are exactly alike.

Much of this variation is heritable. Fact 5 Much of this variation is heritable.

Inference 1 from fact 5 Those individuals whose inherited characteristics fit them best to their environment are likely to leave more offspring than less fit individuals.

Inference 2 from fact 5 The unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics to that environment accumulating over generations.

EVIDENCE OF EVOLUTION

1. Comparative Anatomy

A. Fossil evidence helps to show how different kinds of organisms share similar structures.

2. Homologous Structures The forelimbs of a whale, bat, and a human are homologous structures. Structures which come from different organisms yet have the same evolutionary origin are called homologous structures…

Gill slits present in the embryos of fish, reptiles, birds, and humans. - Gill slits in fish embryos develop into gills but in human embryos, gill slits develop into the tube that connects the middle ear with the throat.

Closely related organisms have a nearly identical order of bases. 3. DNA All organisms have DNA. All organisms are composed of the same four bases, A,T,G, and C. Closely related organisms have a nearly identical order of bases.

Evidence of Micro-Evolution (Natural Selection)

A. Color Industrial Melanism Link

B. Climate Adaptation Eskimos Skin Color                                                                         

Species formation begins with Micro-Evolution

The Origin Of Life

First Cells Experiment Producing CO2 Without Free Oxygen.

Eucaryotes: Complex cells… A. The first cells developed on the Earth approximately 3.5-4.0 billion years ago. Prokaryotes vs. eukaryotes… Yeasts: Prokaryotes: simple celled, no nuclear membranes or other complex organelles. Eucaryotes: Complex cells… C. The atmosphere consisted of a large quantity of carbon dioxide. No oxygen was present during this time.

Eventually, these single celled organisms evolved into many celled organisms in the ocean. Examples would be sponges, starfish, and algae.

C. The ability to photosynthesize and create energy from the sun brought about the release of oxygen into the atmosphere from our first autotrophs.

D. As oxygen gradually became abundant, aerobic organisms could evolve. 1. Aerobic respiration allowed organisms to extract more energy from food molecules. 2. This increase in cellular energy allowed for a higher level of organization and complexity in evolving primitive cells, (eucaryotic cells).

In Review...

Darwin's Theory Of Natural Selection 1. Natural Selection: selection of adaptive traits in nature.

Natural Selection Cont’d 2. There is variation among individuals in any population.

3. Because of limited resources, not all individuals will be able to fulfill their potential for reproduction.

4. Those individuals whose traits are better adapted to their environment will reproduce more than others.

5. Thus, the better-adapted traits tend to become more prevalent in the population, and the population as a whole tends to become better adapted to its environment over time.

6. If two populations of the same species evolve along different paths, eventually they can become two separate species.