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48 Cards in this Set

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Population
a localized group of individuals that are capable of interbreeding and producing fertile offspring
(a localized group of individuals belonging to the same species Ex. Black racer snake in
,Bears in Alaska)
Species
a series of pop. in which significant gene flow occurs under natural condition
but which is genetically isolated.
Hybrid
a cross between two species
Ex. Lion + tiger= Liger
Dorkey + Horse= Mule
Gene Flow
movements of alleles between population thru interbreeding
Population Genetics
The study of how populations change genetically over time.
(The study of gene pools and genetic variations in the biological population.)
Gene Pool
All the genes in a population or species
“Genetic Constitution”
The smallest unit of evolution
= population evolve
One common misconception about evolution is that individual organisms evolve, in the Darwinian sense, during their lifetimes.
It is true that natural selection acts on individuals
Evolution
a change in the prevalence of inheritited traits in a succession of evolution
The population, not its individual members, evolves
**some traits become more common within the population, while other traits become less common.
Jean Baptist De Lamark
(Pre-Darwinian)
He gives wrong explanation about species change
Inheritance of acquired characteristic (charteristics that are acquired during life time of an organism)
2)Use and Disuse Ex. Giraffe elongates the neck
(this is a somatic change not genetic change)
August Weismann
(Pre-Darwinian)
disproves Lamarckian evolution
Ex . cut mice tail off, we might predict that next generation wont have tail , but it does.
Hardy-Weinberg Theorem
A law of population genetics stating that in the absence of selection, nonrandom mating, and other conditions heredity tends to stabilize allelic frequency in a population.
“no evolution takes places”
Genetic Equilibrium
or H.W. Equilibrium
These equilibrium models, provide a base line form which evolution departures take place.
5 conditions to maintain H.W. Equilibrium
1)Pop. is very large
2)Pop. has to be totally isolated(no immigrate or emigrate)
3) No net changes in gene pool due to mutation
4)Mating is random
(No sex selection)
5)All genotypes are equal in reproductive success
(No natural selection)-same allele forever
homozygous individuals
have two identical alleles for a given locus
Ex. TT(homo. dom.)
or tt(homo.rec.)
heterozygous individuals
have two different alleles at that locus Ex. Tt
use p and q represent the two alleles frequency
p= freq. of dominant allele
q= freq. of recessive allele
(p+q=1)
frequency of gamete cell in the gene pool
will be the same as in the original.Provided that gametes are contributed to the next generation at random, allele frequencies will be unchanged.
Hardy-Weinberg Equation
(binomial expansion)
(p+q)^2= p^2+2pq+q^2=1
Freq.of TT, 2Tt, tt
Causes of Micro evolution
(Disrupting H.W. equil.)
1)Natural selection
2)Mutation
3)Genetic drift
4)Gene flow
1)Natural Selection
Reproductive differential - not all individulas will produce viable, fertile offspring
Ex.Pesticide Resistant Insect(cockroaches),antibiotic resistant bacteria
2)Mutation
A change in the DNA of a gene, ultimately creating genetic diversity
(Rare random, but they do take place causing directs changes in gene pool.)
3)Genetic Drift
a change in the gene pool of a small pop. from generation to the next tha result from chance.
Ex.small wildflower pop. has a stable size of ten plants. Only five plants of generation 1 produce fertile offspring. Then recessive allele falls to zero in generation 3.
Bottle neck effect
Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population
(A natural disaster may drastically reduce the size of a population killing its victim unselectively)
Bottlenecking a pop. tend to reduce genetic variation
Ex. Northern Elephant Seals in CA that were hunted nearly to extinct
Founder effect
Genetic drift that occurs when a few individuals are seperated from a larger population perhab on Island or in Land. The smaller seperatinf pop. is unlikely to have the same proportion of gene as the larger pop.
4)Gene flow
when a pop. gain or lose its allele from the migration of further individuals or the transfer of gamete between pop Ex. Human freely moving around the world& reproducing
Genetic Variation
Natural selction ~ enzyme
Genetic Variation~ substrate
enzyme remain unchange after making substrate complex
two source of genetic variation
1)mutation-rare,produce new alleles, but most are harmful
*2)recombination
or sex.recomb.(most)
Recombination or sexual recombination
Nealy all gen.variation in a pop. result from new combination of alleles produced by sexual recomb. Recall synapsis and crossing over
Genetic variation
between population
A cline = a geographic variation that's a gradual change in some traits along a geographic transect Ex. clinal varia.-climate differ.
Clinal rules in
warm blood animal(Homeotherms)
1)Bergman's rule
2)Allen's rule
3)Gloger's rule
Bergman's rule
**Ex.White Taile deer from
Maine to FL.
the further away from the equator, the larger the body size become.(SurfaceArea-Vol)
Small cube has much more surface area per unit vol. than large cube
White dear in FL. has smaller size coz it has bigger surface-vol ratio, so lose heat easier
Allen's rule
Homeotherms away from the equator have a shorter appendages than those in warmer **Ex. BlacK Tailed Jack Rabbit in Tx has longer ear than Snowshoe Hare in Canada. coz larger THINER ear haS a large surface area to vol ratio to dissipate heat
Gloger's Rule
Organism in warm more humid region are darker in color than those in colder and drier region Ex. Protection from UV (melania)
Genetic Variation within pop.
1) Balanced polymorphism
2) Transitional
or Transient Polymorphism
Polymorphism
Two or more distinct forms that regularly occur in a population Ex.Blood types in human,***Cepaea nemoralis(Snails have diff. pattern@ diff.location called cryptic coloration)
Camouflage
Blending with environment
Balanced Polymorphism
The steady state presevation of a variation in a pop.
Ex. Snow Goose(white&blue moths),**Calif. Kingsnake(striped&banded)
Transitional or Transient
Polymerphism
a particular form is in the process of spreading thru pop. causing the relative pop. of phenotype to alter
***Ex. English Pepper Moth(Briton Betularia)
Quatitaive variation
Traits that show a continuous variation with no obviuos pattern of Mendelian segregation in their heritances. Values of the trait in the offspring are intermediate between the values in the parents
Ex. Medium phenotype
(not T or t)(such as hieght)
Polygenic traits
Traits that are controlled be many genes
Ex. Tail length & fur color in mice, Height in humans
Selections can act on Quantitative traits to produce three diff. kinds of evoltionary response
(Fur colors in mice)
1)Stabilizing selection
2)Directional Selection
3)Disruptive or Diversifying
Selection
**1)Stabilizing Selection
Keyword is Most
Phenotype in the middle of the range are favored and disfavored the extremes
" Average individual's are the best adapted"-It's how Nat.Sel acts on ***most pops most of the time
Ex.Storm Mortal lift on birds
**2)Directional Selection
favor extreme value of the phenotype. This is how Nat.Sel. produce evolution change
Ex. Just Dark or light
**3)Disruptive or Diversifying Selection
Keyword is both colors
"Brimodal distribution"-***Balance polymorphism
EX. both Dark and light