Unit 4 Module 2 - Evolution and Viruses

Evolution

A change in allele frequencies in a population over time

Darwins Observation from his Voyage on the Beagle

Observation #1: island species have a strong resemblance to species on nearby mainland

Observation #2: Extant (living) species have a strong resemblance to extinct species discovered as fossils

Theory of Evolution by Natural Selection

Overtime species that colonize new habitats gradually change to a new form but similar species. Only individuals that are best suited can reproduce so overtime that species becomes better adapted to environment.

Darwins Postulates that must be true for Natural Selection

1. There must be variation in a trait

2. Heritability - trait must be passed from parent to offspring through genetic information

3. Differential reproductive success - individuals posses one version of a trait must produce more offspring that those with different version of a trait

Survival of the fittest example in class

wolf and elf

• elk with lease amount of good traits dies

• but cant reach peak performance because of fitness tradeoffs

Directional Selection

is a type of natural selection that favors one extreme phenotype over the others, leading to a shift in the population's allele frequency in a specific direction.

ex. Farmers only allow turkeys w big breasts to mate

Stabilizing selection

is a type of natural selection that favors average phenotypes, reducing variation and maintaining the status quo.

ex. Baby birth weight

Disruptive Selection

is a type of natural selection that favors extreme phenotypes at both ends of the spectrum, leading to increased variation within a population.

Examples include species where individuals with either very large or very small traits have better fitness than those with intermediate traits.

Fossil Record

-Physical record of organisms that lived in the past

-biased in favor of abundant organisms

Comparative Embryology

-growth, development, and body structures of major groups of organisms

-Homologous structures

Molecular Biology

• DNA similarities in more closely related organisms

• All living organisms has the same genetic code

Lab and Field Experiments

• use of scientific method to study evolutionary mechanism

• multigenerational experiments show evolution in progress

vestigial structures

apparently useless anatomical features reveal evolution past

convergent evolution

the process where unrelated species develop similar traits due to adapting to similar environments. (analogous structures)

Developmental regulatory genes

genes that activate protein coding genes early in development

• tell protein coding genes where to build body parts but not how to build them

Hox (homeobox) genes

virtually no variation because all members of species want bodies arranged in similar manner.

-small genetic changes can cause enormous morphological changes

antigens

spikes on virus capsid notify body that pathogen is present

Antigenic Drift

Small changes in surface spikes on virus makes it harder for immune system to recognize it

antigenic shift

two forms of virus infect the same cell, causing hoist cell to produce viral particle from both viruses causing a new strain.