Glossary of Biology 101 exam 3
Created by jkadlik
- the phenotype that yields the greatest fitness depends on how common each alternative phenotype is.
- sexual dimorphism
- pattern: seems to act more strongly on males; traits that respond to sexual selection are more elaborate in males.
- types of sexual selection
- male vs male competition
male- female choosy
- Sexual selection in males
- 1. MaledominanceorExtravaganttrait.
2. Needvariabilityamongmalesinthese traits.
3. Traitsconferfitnessadvantagetosome males. For some males in the population the benefit in reproduction must be above and beyond survival cost.
- sexual selection in females
- 1. Femalechoiceofmales.
2. Needvariabilityinfemalesinchoice abilities.
3. Choicemustconferfitnessadvantageto some females. Better choosers will have higher fitness.
4. Variationinchoicebehaviormustbe heritable.
- Evolution from genetic point of view
- population: all of the individuals of a
species in a single place.
locus: a particular location on a particular chromosome; usually a gene.
allele: a variant form of a gene; a locus
typically has two or more alleles.
- evolution from genetic point of view continued
- gene pool: total aggregate of all alleles in a population at any one time.
allele frequency: at a given locus (or loci), the proportion of a gene pool that is made up of a particular allele.
genotype frequency: at a given locus (or loci), the proportion of individuals that have a particular genotype
- The Hardy-Weinberg model
- p2 + 2pq + q2 = 1
Note that if allele frequencies are known, genotype frequencies can be calculated.
And vice versa
- processes that cause evolution
- • non-random mating
• small population size (genetic drift)
• migration (gene flow)
• natural selection
- founder effect:
- colonization of new or isolated habitat by a few individuals. – important factor in evolution on islands
– in humans, can cause high incidence of inherited disorders, e.g. Ellis-van Creveld syndrome in Lancaster County Amish.
- Reproductive isolating mechanisms prevent interbreeding.
- – prezygotic • behavioral • ecological
• temporal • mechanical
– postzygotic • gamete incompatibility • hybrid inviability/sterility • lowered fitness of hybrids
- Conditions necessary for speciation
- • genetic isolation – gene flow restricted or blocked
• evolutionary divergence
– genetic drift, natural selection, sexual selection.
- Allopatric isolation
- a population is sub-divided into two or more geographically separated parts.
– colonization of newly-formed islands.
– rising sea level isolates former part of mainland as an island.
– geological change, e.g. mountain building.
– formation of islands of habitat, e.g. after climate change.
– continental drift – plate tectonics
- Per capita birth and death rates
- per capita birth rate:
1500 births ÷ 10,000 people = 0.15 births/person/year
per capita death rate: 500 deaths ÷ 10,000 people = 0.05 deaths/person/year
- per capita growth rate
(b = per capita birth rate,
d = per capita death rate)
- Per capita growth rate (increase, decrease, stabilize)
- r > 0, population is growing r < 0, population is shrinking r = 0, population is stable
- Exponential growth rate
- population size * growth rate
N * r
- logistic growth
- Population size increases at a increasing rate and then at a diminishing rate, until it reaches a limit called the carrying capacity (K).
dN/dt =rmaxN (K-N / K)
- • density-dependent factors (effects increase as population density increases)
- – predation • including parasitism
– availability of resources • e.g. food, space
– accumulation of wastes – behavior change
- density-independent factors
- – weather
• e.g. annual freezes, periodic droughts/floods, unpredictable storms, etc.
- a form of speciation that occurs when a population is subdivided by a geographic barrier.
- occurs when a subset of a population establishes a new population in a novel location.
- occurs when a subset of a population moves to a novel location.
- four mechanisms that shift allele frequencies
- o natural selection
o genetic drfit
o gene flow
- heterozygote advantage
- when heterozygous individuals have higher fitness than homozygous individuals
- directional selection
- allele frequencies move in one direction
tends to reduce genetic diversity
sometimes results in fixed/ lost alleles
- stabilizing selection
- reduces extremes
no change in average value
genetic variation reduced
- disruptive selection
- eliminates phenotypes near the average value and favors extremes
tends to maintain the amount of genetic variation in a population
can lead to speciation
- Genetic drift
- any change in allele frequency that is due to chance in a population
can lead to random loss / fixation
most pronounced in small pop
- population bottleneck
- when a large population experiences a sudden reduction in size
- gene flow
- the movement of alleles from one pop to another
reduces genetic differences
- production of new alleles due to errors in DNA
mutations restore genetic diversity
evolutionary mechanism for nat selection
- mating with relatives
always violates assumtions of hardy weinberg principle
- inbreeding depression
- loss of fitness that takes place when homozygosity increases and heterozygosity decreases
o many recessive cells represent loss of function mutations
o many genes are under intense selection for heterozygote advantage
You must Login or Register to add cards