door Kevin Schlang 11 jaren geleden
198
Meer zoals dit
Species Extinction
Polar bears
76 species of frogs
Largescale destruction of tropical rainforests
Polward shifts of species ranges
Ex Beech trees ranges have already moved north
Earlier spring events
Projected increase of 4 degrees Celcius in next 4 years
Changes in Percipitation
rising sea levels
Melting of arctic ice and glaciers
Sulfuric and Nitric Acids contribute to increase PH in rain in areas from pollution from fossil fuels.
Coolants Contribute to ozone thinning.
Ice Croe from greenland
Pull out core of ice and snow and it will show anual rings with airpockets. Air in pockets can be analyzed and one can look at nitrogen content.
Aerosol Used to spray insects which remains in Atmoshere for a long time
DDT Example
Sprayed during WW2 to get insects away. However in 60's if was found that it results in thinner eggshells which relates to decline in number of bird species during the time.
Biomagnification increases concentration of DDT, and DDT remained in soil for long time.
Example
Darwins Finches
Finches in diferent areas beaks developed changes creating several species.
Sympatric
Def: differentiating and acquiring reproductive isolation within the same area (sym=together, patria=homeland)
Examples
polinating species becoming more keen to one type of plant.
Apple maggot fly
Polyploidy
Allopatric
2 Models of Allopatric Speciation
Peripheral Isolate Model
New Species forms from population isolated at edge of ancestrol species range
Dumb-Bell Model
Ancestrol species divides into two almost equal halves each of which forms a new species.
Def: species formation from a common ancestor in geograpghically separate locations
Def: random changes in allele frequencies in a population from generation to generation.
genetic drift results from sampling error in a population with limitied size.
Effects from Genetic Drift
Bottleneck effect
random changes in allele frequencies in a population due to dramatic reduction of population size.
Reduction in size is caused either by some catastrophic events (density- independent factors) or only the frequencies of those loci are conside
Founder Effect
founder effect occurs within the same generation.
random changes in allele frequencies in a population during colonization.
Facts
the majority of mutations are detrimental in a given environment
mutation is the ultimate source of genetic variation in populations.
mutation rates for many genes vary between one out of ten to one hundred thousand
Def: Random changes in the genetic code
Allele Frequency= Gene Frequency= gametic frequency
The Hardy-Weinberg genetic equilibrium
The allele and genotypic frequencies remain the same from generation to generation in a population in which there is
Equation
p^2+2pq+q^2=1
2pq=frequency of heterozygous genetype
q^2= frequency of homozygous recessive allele
P^2=Frequency of Homozygous Dominant Species
Factors in order for Hardy-Weinberg equilibrium to exist
No migration
No mutations
No Selection
Random mating
Infinite large population size
MN blood type example
Frequencies of Alleles for blood types similar in populations closer to each other
Example used to explain % Frequence
N/total X 100
New Guinea and Australia are similar, but Guatamala almost opposite
Gene Pool: The set of all alleles at all Loci of a population
Def: The proportion of a certain allele within a population
