Biology 30 - Unit 5 Booklet 1: Population and Community Dynamics (Questions)

What are the conditions for the Hardy-Weinberg Principle?

The population is very large, mating is random, no mutations occur, no migration occurs, no natural selection occurs

What does the principle of constant frequencies of alleles from the Hardy-Weinberg Principle tell us about evolution?

Sexual reproduction reshuffles genes, but does not by itself cause evolution because evolution occurs when genetic equilibrium is broken

How can you mathematically express the Hardy-Weinberg equilibrium using single variables?

p + q = 1 (Only dominant and recessive alleles exist. Their frequencies must add up to 1)

How can you mathematically express the Hardy-Weinberg equilibrium using binomal distribution?

p² + 2pq + q² = 1 (Binomial expansion of p + q = 1)

When natural selection occurs, in what ways will a gene pool change?

Individuals with certain alleles will have greater reproductive success than others do, thereby increasing the frequency of their alleles in the next generation

When individuals migrate, in what ways will a gene pool change?

Individuals that migrate will remove alleles from their original population and add them to another

When mutations occur, in what ways will a gene pool change?

New alleles will arise or one allele will be changed into another, thereby changing the allele frequencies in the population

When mating is not random, in what ways will a gene pool change?

Individuals that are preferred as mates will pass on their alleles in greater numbers than less preferred mates

When a population is small, in what ways will a gene pool change?

Chance fluctuations will cause changes in allele frequencies

What determines the success of an allele?

If it contributes to the reproductive success of an organism based on its environment, it will be passed on

How does a mutation change the gene pool of a population? What effect does this have on a large population?

Immediately changes the gene pool of a population by substituting one allele for another. A mutation by itself does not have much effect on a large population in a single generation, but if the mutation gives selective advantage to individuals carrying it, then it will increase in frequency and thus change the gene pool over successive generations

What kind of population does genetic drift affect the most and why?

Small populations are affected significantly because genetic drift that removes a large amount of individuals will as a result remove many gene frequencies, which can decrease genetic diversity greatly

What factors increase population?

Natality, immigration

What factors decrease population?

Mortality, emigration

Which population size should be used to calculate per capita growth rate?

Initial population size

What assumptions are made regarding population growth models?

Immigration is equal to emigration and so only natality and mortality are considered

What are the characteristics of exponential growth, and what factors cause change in population?

Initially unlimited supply of biotic and abiotic resources in a closed population, and thus growth is only limited by biotic potential, resulting in a lag phase followed by a steep growth phase. Environmental resistance limits the population once it gets too large, causing a steep death phase

What are the characteristics of logistic growth, and what factors cause change in population?

In an open population, individuals reproduce and migrate into an environment, resulting in a lag phase followed by a steep growth phase. Once the population passes a certain carrying capacity, the environment can no longer sustain all the individuals, causing a small number of the individuals to die off. The population number will fall under the carrying capacity, meaning the environment will be able to sustain the population again, causing numbers to rise to above the carrying capacity once more. The population number fluctuates above and below the carrying capacity repeatedly

What are the the density-dependent factors, and are they biotic or abiotic?

Intrapspecific competition, predation, disease; usually biotic

Why are predation and disease density-dependent factors?

Dense populations are easy prey because they are packed together, making it easier for predators to find an abundance of prey to kill at once; disease spreads easiest when individuals are packed together closely

What are the the density-independent factors, and are they biotic or abiotic?

Changes in environmental conditions such as weather and presence of unnatural/man-made chemicals such as insecticide; usually abiotic

What are characteristics of a stable environment?

Abiotic and biotic factors remain similar over time, organisms are suited and well adapted (niches)

In general, how can k-selected species be characterized?

Live in predictable, stable environments, allowing them to invest in themselves to extend their lifespan and grow in size; reach sexual maturity late and have modest numbers of offspring in order to be able to have prolonged care of their young; S-shaped population growth curve

In general, how can r-selected species be characterized?

Live in rapidly changing environments, leading them to take advantage of brief but ideal environmental conditions to reproduce before passing very soon; reach sexual maturity early and have very high numbers of offspring with little to no parental care with the sole goal of producing a surviving generation; J-shaped population growth curve

What are the three types of symbiosis?

Mutualism, commensalism, parasitism

Why are predator-prey relationships important in a community?

Predators that specialize in eating a certain prey species play an important role in controlling the population size of the prey species

What is the main difference between primary and secondary succession?

Barren, soil-less land is inhabited in primary succession and soil is created, while soil is already present in secondary succession and a community is rebuilt instead of newly created