BIO311D Extra Credit Assignment (Levin)

Organization of Genetic Variation

Increase in Variation

Adaptive Differentiation

development of different phenotypes from a common ancestor due to adaptations to different environments

adaptation: a trait that enhances survivorship and reproduction

Mutation

random change in genetic code

generates new alleles

ultimate source of genetic variation

95% of all homozygous mutations are harmful

for men, mutation is age dependent

Decrease in Variation

Reproductive Isolation

Mechanisms

Prezygotic barriers

prevents fertiliztion

Temporal Isolation

organisms mate at different times

Ecological Isolation

organisms mate at different locations

Behavioral Isolation

species isolation. potential mates choose to mate with own species

Mechanical Isolation

structural differences in reproductive organs

Postzygotic barriers

reduce viability or fertility of hybrid

Gametic Isolation

cross incompatibility. sperm transfer, but no fertilization

Zygotic Mortality

fertilized egg, but no zygote development

Hybrid Sterility

hybrid is viable, but sterile

Hybrid Inviability

hybrid dies prior to reproductive maturity

Hybrid Breakdown

F1 hybrid viable and fertile, but F2 and backcross generations aren't

Geographical Isolation

races evolve separately because the distance between them is too great

race: groups of populations with similar allele frequencies that are different from other related populations

Founder Effect: loss of genetic variation when a new population is established by a small number of individuals from a larger population (chance deviation)

Intergradation

members of different populations mating with each other

gene flow: movement of individuals between established, existing populations

Subtopic

Main topic

Selection

Natural Selction

properties

Disruptive

favors the extremes

Directional

will skew the distribution in one direction

Stabilizing

favors the mean

Heterozygote Advantage

genes in the heterozygous state are superior to the homozygous state

Sexual Selection

females choosing males and males compete and females choose

Mating Systems

Inbreeding

mating between relatives

self-fertilization is the most extreme form of inbreeding

every generation of self-fertilization (“selfing”), heterozygous decreases by half

products of inbreeding are inferior than products of non-related individuals

Assortative

phenotypic similarities

Negative Assortative

phenotypically dissimilar

Positve Assortative

phenotypically similar

Random Mating

independent of genotype and phenotype

Consequences

if ppl with blue eyes mate with others with blue eyes, homozygosity for eye color would increase

the rest of the genome is not affected

mating for eye color does not change p or q

Asexual reproduction

offspring of asexual reproduction are genetically identical to the last generation

Population Growth

Biotic potential

rate of reproduction

ability to withstade adverse conditions

Defense mechanisms

Environmental resistance

low nutrients, food, water

disease

redation

competition

space

bad weather

Equal amounts of the two factors results in an population equilibrium.

Biological Control

reproductive control

release of sterile insects

use of chemical sterilants

release of incompatible pest strains

Resourece

increase in population

less

decrease in population

Global Warming

rise in the average temperature of Earth's atmosphere and oceans since the late 19th century and its projected continuation

Atmosphere

Biomagnification

The increase in the concentration of alien substances from one trophic level to the next. (The substances can not be metabolized.)

Aerosol

DDT - used to kill insects (crop pests)

DDT has a 95% breakdown time of 10 years.

Invented in WWII to suppress crop pests. (Mosquitos)

Carbon Dioxide

usually in a balanced concentration

but burning fossil fuels contributes to increased CO2 levels in atmosphere

Consequences

more radiant energy stays in the earth’s atmosphere

not a prevention but a reduction of heat escaping into space

Relationship between CO2 and temperature over time

Positive correlation

Predicted that temperatures will increase by 4°C by the end of the century

Greenhouse effect

the trapping of heat in the atmosphere by certain (so-called "greenhouse") gases.Examples: heat trapped in car, glass greenhouse for plants

Projected Emissions

All the greenhouse gases will increase:

Carbon dioxide

Methane – from wet agriculture (rice paddies), cows, and ocean bottom

Nitrous oxide – from fossil fuels

Water Vapo

CFC’s

Consequences

Increase in ocean temperatures

More intense hurricanes/storms

Increase in malaria and other subtropical diseases

The faster global warming, the faster range shifts

Biological Impacts of Climate Change

Altitudinal/poleward shift in species range

Earlier Spring Events

Coral Bleaching

Species Extinction

Responses to Climate Change

50% of species show a response. (Exists on every continent/every ocean)

The spread of parasites and vectors as they’ve shifted northward.

Northern range shifts

Speciation

evolutionary process by which new biological species arise

Allopatric (geographical)

Series

reproductive isolation present without geographical barrier. speciation is complete

selection causes divergence in gene pools

gene flow interrupted variant types appear

two populations experience gene flow

Models

peripheral

in which new species forms from a population isolated at edge of an ancestral species range

dumb-bell

ancestral species is divided into two roughly equal halves, each of which forms a new species

Species

groups of actually/potentially interbreeding individuals

all species arise from previously existing species

Extinction

Major Causes

Habitat Destruction

species are not found in all habitats

deforestation

farmland/asphalt

Overexploitation/Hunting

Species Introduction

bringing a species to a different country

competition

predation

disease

Genetic Contributions

Inbreeding

includes homozygosity

less reproduction

results in loss of genetic variation

Hybridization

minor species always dislves

Process

Contraction

think deflating baloon

Fragmentation

think lightbulb

single populations in range going out

habitat corridor - reduces population fragmentation

Island Size

Small

extinction rate is higher

competition

Large

higher immigration rates

more resources