Evidence for Evolution:

• Hypothesized Atmosphere: Earth was anaerobic

 

Environmental Conditions Affected the types of Organisms that Developed:

1. First Cells, Prokaryotes and Anaerobic

2. Some had the variation to photosynthesize

3. With Photosynthesize, Oxygen was produced

4. This allowed areobic prokaryotes to survive

5. Evolution of single cell eukaryotes by endosymbiosis

6. Evolution of multicellular eukaryotes

 

Fossil Evidence Informs our UNderstanding of the Evolution of Species:

• All over the world we can find the sam e,ayers of sedimentary rock, in the same order as characterized by the most commonfossilized organisms. As you move up from the bottom, you can see a continuous chnge in these fossils, with the oldest layers showing only primitive species. These layers can be dated by radioactive methods.

 

What do Biochemical Similarities tell us about Evolution?

• All organisms share atleast some parts of their genetic materials, enzymes and structuralconponents the more closely related, the more they will share.

 

Explaining Natural Selection:

Natural Selection- is a mechanism for change in population which occurs when organism with certain variation survuves, reproduces and passes on these variations to next generation.

• Organisms without these variations are less likely to survive and reproduce so as a result each generation consists largely of offspring from parents with those variations that did for survival.

 

Mimicry- the structural adaptation but subtle an d enables one species to resemble another species. Harmless species has adaptations resembling harmful one.

 

Mechanism of Evolution:

• Populations not Individuals. If organisms poorly adapted it may be unable to survive reproduce. Natural Selection acts on a range of phenotypes, genes.

Gene Pool- All alleles of a populations genes as being together in a large gene pool.

• The percentage of specific alleles in gene pool is called Allelic Frequency

 

Changes in Genetic Equilibrium:

• Any factor that affects the genes in gene pool can change an allelic frquency, disrupting a populations genetic equilibrium resulting in process of evolution.

• One mechanism for genetic change is a mutation via environments.

• Another mechanism that disrupts populations genetic equilibrium is Genetic Drift....... Observed in humans when have been isolated due to religions and belief systems.

• Geographic Isolation occurs when there is a barrir that divides population

• Speciation- when one or more species develops form an existing species.

 

Role of Geographic Isoltion in Speciation:

• Geographic Isloation refers to a situation where species/ populations is separated by a physical barrier allowing each group to seperate evolutionary paths.

 

Causes of Natural Selection:

• Species grow exponentially

• Popuation variation due to mutation and genetic recombination

• Finite supply of resources for life

• Changing environment for specific phenotypes

• Organisms with favorable adaptation survive, reproduce, and pass on alleles

• Accumulation and change in favored alleles leasds to change in species over time.

 

Other Evidence:

• Fossils are important source of evolutionary evidence because it provides a record of earlier life and history.

Homologous Structures- Structural features with a common evolutionary origin. Similar in arrangement and function.

Analogous Structures- body parts of organisms that do NOT have a common evolutionary originbut are similar in function.

Vestigal Structures- body structure in present day organism that no longer serves ot's orginal purpose but probably useful to ancestors.

 

Homologous:

• same structure- bone

• same function- movement

Analogous:

• same function

• different structure

 

Vestigal Structures:

1. Appendix

2. Tail Bone

3. Male Nipples

4. Wisdom Teeth 

5. Tonsils

6. Little Toe

7. Ear Muscles

 

Applications:

• when penicillin was discovered 50 years ago. It was wonder drug because it killed many types of disease.

• Today Penicillin no longer affects as many physiological adaptations to prevent being killed by Penicillin.

• Same applies to pesticides- many species of weeds and insects have become resistant to the chemicals

 

Resistence:

• Natural Selection in a bacterial population for resistence to antibiotics

 

Effects on Natural Selection:

1. Environmental Effects on Pheno

   1. 1959: Thalidomide causes limb defects in fetus

2. Weather effect on phenotype expression

3. pH