Biology: Bacteria and Natural Selection Essay example

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Natural Selection 1. Variation of traits 2. Variation affects the ability to survive and reproduce 3. These traits are heritable and are passed to future generations

* Natural Selection is the mechanism that allows for evolution
Evolution=a heritable change in one or more characteristics of a population or species across many generations.
Species= group of related organisms that share a distinct form and can interbreed with one another. * genes in a natural population are usually polymorphic * polymorphism- many traits display variation w/in a population * Due to 2 or more alleles that influence phenotype
Why does microevolution occur? * characteristics that give a survival advantage * if organism is better adapted it is more likely to survive and reproduce
Darwinian Fitness- relative likeliness that a genotype will contribute to the gene pool for future generations
AA, Aa, aa
AA- 5 offspring
Aa- 4 offspring aa- 1 offspring

Fitness of AA= 5/5=1
Fitness of Aa=4/5=0.8
Fitness of aa=1/5=0.2

* Mutations are the main cause of genetic variation * Substitutions (most common) * Deletions, additions, and rearrangements may also occur * Causes of mutation * Random copying errors * Highly reactive chemical agents * Ionizing radiation * UV light * Free Radicals * Most mutations are detrimental

* Rapid changes happen from recombination (crossover)

Patterns of Natural Selection 1. Directional Selection – favors individual at one extreme of phenotype a. Fur color of mice 2. Stabilizing Selection- Favors the individuals with intermediate phenotypes 3. Disruptive Selection- Favors the survival of two or more different phenotypes b. Most likely to occur in a diverse environment 4. Balancing Selection- Two or more alleles are kept in balance and therefore are maintained in a population.
Convergent Evolution = resemblance among organisms belonging to different taxanomic groups resulting from adaptation to similar environments
*see powerpoint for other terms.

Cells and Evolution
Basic parts of a cell 1. Outside 2. Inside a. DNA: Instructions for building the cell
DNA ->RNA ->Protein RNA is translated to protein using ribosomes 3. Barrier b. The plasma membrane: i. Barrier between outside and inside ii. Communication between outside and inside iii. Adherence molecules located in plasma membrane. iv. Lipids- barrier “stupid part” v. Protein selectively allow molecules through * Some proteins are in the membrane, some in cytoplasm (inside of a cell) * Proteins are multifunctional
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