Biology - Populations & Community Dynamics: Hardy-Weinberg Equilibrium, Changes in Gene Pools, Analyzing Populations, Succession (copy)

population

the whole # of inhabitants occupying an area and is continually being modified by increases (birth/immigration) and losses (death/emigration)

gene pool

the combination of all the genes (including alleles) present in a reproducing population or species

allele frequency

• the proportion of gene copies in a population of a given allele

• how common an allele is in a population

• how many times times an allele appears in a population

selective advantage

characteristic or trait that gives an organism or a genotype greater chances of surviving and reproducing than the available alternatives

gene flow

• distribution of alleles due to migration of individuals (some genes flowing in, some flowing out)

• immigration and emigration

genetic drift

• change in allele frequency due to chance events (forest fire wipes out half of deer population)

  • most notable in small populations

• change of an existing # gene variant in population due to random chance

founder effect

• reduction in variability that occurs when a small group of individuals becomes separated from larger population

• isolation can lead to speciation

• new population formed by small # of individuals

bottleneck effect

• change in allele frequency due to only some individuals reproducing

• results from rapid decrease in population (disease, overhunting, fire, etc.)

• leaves few individuals to reproduce

genetic equilibrium

• a population that is not changing or evolving, no change in allele frequencies over time

natural selection? does it act directly on phenotypes or genotypes

• environments change over time—putting pressure on species

• individuals w/ traits that help them obtain resources (observable traits) are more likely to breed and pass on those particular variations

  • acts on phenotypes, as they are the observable/desired traits

what is genetic variation? how is it created in popualtions

• the difference in DNA sequences between individuals within a population

• can arise from gene variants (mutations) or from normal processes in which genetic material is rearranges as a cell is getting ready to divide (genetic recombination)

sexual selection? example?

• natural selection arising through preference by one sex for certain characteristics in individuals of the other sex

  • ex. peacock mating or ram mating

intraspecific competition

• competition between individuals from same species

• ex. two oak trees growing too close together fighting for sunlight and nutrients

interspecific competition

• competition between individuals of different species

• may be detrimental to one or both species

can occur in 2 ways:

• interference competition: involves aggression between individuals of different species who fight over the same resources

• exploitative competition: involves consumption of shared resources by individuals of different species, where consumption by one species may limit resource availability to other species

symbiosis

various interactions in which two species maintain close, usually physical, association

includes parasitism, mutualism, and commensalism

3 types of symbiosis

mutualism: interaction is beneficial to both species

commensalism: interaction is beneficial to one species, and the other species is unaffected

parasitism: interaction is beneficial to one species and harmful, but not usually fatal, to the other

resource partitioning

avoidance, or reduction in competition for similar resources by individuals of different species occupying different none overlapping ecological niches

warning colouration and batesian mimicry

warning colouration: bright and conspicuous colours in animals that act as a warning signal to potential predators. it often indicates that the animal is toxic, venomous, or has some other defence mechanism.

batesian mimicry: form of mimicry where a harmless or less harmful organism mimics the appearance of a harmful or poisonous one. benefits the mimic by reducing the likelihood of being attacked, as predators may mistake it for a more dangerous species.

Assumptions of hardy-weignberg equillibrium

1. no selection

2. no mutation

3. no migration

4. large population

5. random mating

if all of these characteristics are true—then allele frequencies wills tay the same, and it is at hardy weinberg equillibrium

if any of those things are untrue, it can cause allele frequency to change, which means population is evolving

• if one or more of those are untrue, population will evolve

• population stays the same if they all stay the same

• essentially: allele frequency changes—>population is evolving

• new species is an indication that equilibrium is unsettled

• as the environment changes, the individuals who do not have the traits that fit the environment will die due to natural selection

changes in gene pool

• the conditions HW equilibrium represent an ideal situation, that rarely, if ever, occurs

• the following processes can cause changes to allele frequency in a population

  • they are the mechanisms behind evolution

• mutations

• gene flow

• random mating

• genetic drift

• bottleneck effect

• founder effect

• natural selection

mutations

• change that occurs in the dna of an individual

  • an inheritable mutation has the potential to affect the entire gene pool

random mating

• uncommon in natural populations due to selection of preferred phenotypes (mates chosen based on physical and behavioral traits)

natural selection

• environments change over time—putting pressure on species

• individuals with traits that help them obtain resources are more likely to breed and pass on those particular variations

  • ones w phenotypes that let them survive, they will reproduce

When analyzing populations, what are 2 characteristics to describe them? What does each mean?

Density and Distribution

Density:

• population density: the number of individuals (N), in a given area (A) or volume (V)

• D=N/A or D=N/V

Distribution:

• 3 main ways

  • Clumped: Close proximity, congregating around food, shelter, common

  • Even/uniform: members spread out evenly over defined area (more territorial) ex. leopard

  • Random: Abundant resources, little competition ex. dandelion

What is population growth? What affects it?

• The change in population; bigger or smaller

• Increased by:

  • Natality (birth rate)

  • immigration (in)

• Decreased by:

  • Mortality (death rate)

  • emigration (exit)

What is Growth rate? whats the formula?

• Change in number of individuals over a specific time frame

  • gr= Delta N / Delta t

• if the answer is negative, then there is a decrease, if its positive, then theres a increase

Per capita growth rate

• useful when comparing populations of different sizes

• determined by calculating the change in the number of individuals and dividing by the original number

  • cgr = Delta N / N. (population change divided by the OG # of individuals)

What is biotic potential

• the highest per capita growth rate for a population is called its biotic potential: growth only possible with unlimited resources and ideal living conditions

  • basically: growing @ max per capita growth