1. What is the effect of each of the following on population size: birth rate, death rate, immigration, and emigration?
Birth rate is usually expressed as the number of births per 1000 people per year, and the death rate is the number of deaths per 1000 people per year. The growth rate is equal to the birth rate minus the death rate. If individuals in the population are born faster than they die, then population size increases, and if they die faster than they are born, the population size decreases. Dispersal, or movement from one region or country to another is another effect. Immigration is where individuals enter a population and increase its size, and emigration is where individuals leave a population and decrease its size.
2. How do intrinsic rate of increase and carrying capacity produce the j-shaped and s-shaped population growth curves?
The J-curve is created by exponential population growth, which is the accelerating population growth that occurs when optimal conditions allow a constant reproductive rate over a period of time. The S-curve grows exponentially when the population is low, but slows as the carrying capacity of the environment is approached. The carrying capacity is the maximum number of individuals of a given species that a particular environment can support for an indefinite period, assuming there are no changes in the environment.
3. What are two examples of density dependent factors that affect population growth? What are two examples of density-independent factors?
Density-dependent factors are factors whose effects on a population change as population density changes. Predation, disease, and competition are examples. Density-Independent factors are random environmental factors that affect the size of a population but are not influenced by changes in population density. Examples include frost, blizzards, hurricanes, or fires.
4. What are the three main survivorship curves?
Type I: survivorship of species in which death is greatest in old age
Type II: death is spread evenly across all age groups
Type III: death is greatest among the young
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