Unit 3 - Final Review Flashcards
Allele frequency
rate of occurrence of a particular allele in a population for a particular gene.
The total number of alleles in a population is…
twice the number of individuals
Hardy weinberg says that there are 2 competing factors that characterize populations:
The tendency to remain stable and the tendency toward variability
Genetic equilibrium under hardy weinberg requires:
Large populations
Random mating
No mutations
No migration
Equal viability of all genotypes (no natural selection)
when starting hardy-weinberg calculations…
always start by calculating q
Founder effect
few individuals from a large population leave to establish a new population.
bottleneck effect
population size is drastically reduced due to environmental event
Speciation
process by which new species originate
Species
group of similar organisms that can interbreed and produce fertile offspring
Geographic isolation
physical obstables that prevent gene flow causing two groups to evolve differently.
Reproductive isolation
when organisms can no longer reproduce together, even if physical barriers are removed.
Population
individuals of the same species living in the same place at the same time
Community
all species that occupy a given area
Ecosystem
biotic and abiotic components of a specific area
Interspecific
how one population interacts with another population
Intraspecific
how individuals of one species interact with each other.
Ecological Niche
a population’s role in the community (feeding habits, prey, # of offspring,..)
Population Density
number of organisms in a defined area
Clumped Dispersion
individuals are grouped in patches or aggregations.
resources are likely unevenly distributed.
Random Dispersions:
biotic/abiotic factors have little affect; neither an attraction nor repulsion among members.
Habitat likely has abundant resources
Uniform Dispersions
competition among individuals for moisture, nutrients, light, space, etc.
Area has limited resources.
Growth rate:
how quickly a population is increasing or decreasing
Per capita growth rate:
average growth rate per individual
Dynamic equilibrium/steady state:
how populations adjust to changes in environment to maintain equilibrium
4 phases in a growth curve
lag, log/exponential/growth, stationary, death
j shaped curve
exponential growth
s shaped curve
logistic growth
S shaped curves….
level off due to the carrying capacity (K). when the curve levels off, dynamic equilibrium is reestablished.
Biotic potential
the maximum reproductive capacity of an organism under ideal conditions.
Biotic potential is regulated by….
- maximum # of offspring/birth
- chances offspring will reach reproductive age.
- procreation: # of times/year organism reproduces
- maturity: age which reproduction beings
Environmental resistance
factors that limit population growth (both biotic and abiotic)
Density-dependent
(biotic) factors brought on by population size that may limit further growth/reduce population
when do density dependent factors have the greatest impact?
Impacts greatest with increasing population size and density –> greater intraspecific competition.
Density independent
(abiotic) factors that has the same effect on a population, regardless of size
intraspecific competition
between same species. leads to natural selection
interspecific competition
between different species. limits biodiversity. causes species to develop a niche.
r selected species
j shaped growth curve
K selected species
S-shaped growth curve
r selected species: reproductions per lifetime
one
interference competition
involves aggression for the same resource
Exploitative competition
consumption of shared resources. using up resources to prevent others from using it.
Competitive exclusion (Gause’s Principle)
if two populations of organisms occupy the same ecological niche, one of the populations will be eliminated.
resource partitioning
species split up resources, use at a different place or time; no competition. can prevent gause’s principle.
Mimicry
organism develops similar colour pattern, behaviour, etc. that has provided another organism a survival advantage
camoflauge
used to avoid predators
Structural adaptations:
change in the physical appearance of an organism
Physiological adaptations
change in internal and cellular features of organisms
Coevolution:
two different species exert selective pressures on each other to evolve
Symbiosis:
relationships between two individuals of different species
Social parasitism:
E.g. Cowbirds use another bird’s nest to rear her offspring; abdicates parental responsibility
e.g. Ants invade other ant colonies and conscript them into a life of slavery
Succession:
gradual changes in vegetation from a pioneer community to a climax community
Primary succession:
no community existed before
Secondary succession:
results following a destructive event (e.g. forest fire)
Pioneer species
1st to arrive, hardy plants, able to resist direct sun. Their dead bodies provide the initial soil. (e.g. lichen, weeds, grasses, etc.)
Seral/intermediate species
have longer life cycles. Can tolerate fluctuations. Require more nutrients and water. Shade stops undergrowth (e.g. shrubs, softwood trees)
Climax
can tolerate shade, longest lifecycles, high sapling survival rates → stabilizes environment (e.g. hardwood trees)
