APES: Bio evo: description of how earth’s life changes over time.Darwin (gathered evidence) and Wallace (proposed idea) proposed the concept that nat selection was a mechanism for bio evo. Nat selection: survival traits would become more prevalent through natural selection. Not a complete theory because there are other ways a species can form. Life on earth developed over two phases:

1. Chem Evo of organic molecules, biopolymers and systems of chem reactions needed to make 1st cells. Took 1 billion years. Evidence comes from radioactive elements in rocks and fossils. Followed by:

2. Bio evo: Through nat selction we got single celled organisms to multi-cellular protists, plants, fungi, and animals. First in the sea then on land. So far its been around for 3.7 billion years.

Fossils: petrified replicas of skeletons, bones of past living things. We get info on how they work. Glacial ice allows scientists to see the different kinds of life at different layers. Fossil record: world’s cumulative body of fossils found. Bio evo by nat selection states that a population’s genetic makeup changes through generations. Pops not individuals change by becoming genetically different.

1. First step in bio evo is: Developing genetic variability- Occurs through mutations

a. Mutations: random changes in structure or number of DNA molecules that can be inherited by offspring. Can happen in 2 ways.

i. Exposure to radioactivity, X rays, and nat and man made chems (mutagens)

ii. Mistakes in genetic instructions when cells divide or organisms repro. Only those mutations in repro cells are passed down to offspring.

b. Most mutations are bad but sometimes beneficial ones occur. 2. 2nd step in bio evo is: Nat selection

a. Occurs when some organisms have traits that are better suited for survival. Those who survive pass on the traits. Explains how populations survive and adapt through environmental changes.

b. Three conditions necessary for Nat selectioni. Genetic variability: there needs to be enough for a trait to

exist.ii. Heritable

iii. Must lead to Differential Reproduction: Individuals with trait must leave more offspring than those without.

c. Adaptation: Any trait that allows one to make it through nat selection, and repro better under conditions.

d. Three possibilities when a change in environmental conditions occurs:

i. Adapt ii. Migrate

iii. Extinctione. In short bio evo by nat selection:

i. Genes mutate ii. Individuals chosen

iii. Pops evolve that are better adapted to survive and reproduce.

Coevolution: Changes in the gene pool of one species can lead to change in another specie’s gene pool. Genetic race to see who can make the most offspring. Each gains temp genetic advantage over the other. Nat selection states that differently reproducing species can’t produce fertile offspring.

1. Sometimes through hybridization two distinct species can form a new species that may be better adapted to survive.

2. Some species, mainly microorganisms, can swap genes through horizontal gene swapping.

a. Can occur when one species feeds upon, infects, or gets to close to another species transferring genetic info from one species to another.

b. Hybridization and gene transferring is generally faster than nat selection.

Limits on Adaptation through natural selection1. need to have the necessary genes in pool to adapt. 2. Adaption may be limited by repro ability. 3. Bad news for most is that even though a gene may lie present, many of

the others would have to die prematurely so those with the trait could predominate. Many would have to die prematurely for many years until a new genetic trait predominates.

4. Limits don’t apply to hybridization or gene swapping. The fittest individuals leave the most descendants. Fitness based on repro ability. Species don’t develop traits because they need them, but those with the best traits survived and produced more offsprings. There is no master genetic plan for genetic perfection.