Reproductive Patterns and Population Density

Questions for Today: What are the different Reproductive Patterns found in Nature? What are the different Reproductive Patterns found in Nature? How can Genetic Diversity affect the size of small Populations? How can Genetic Diversity affect the size of small Populations? Compare and Contrast Density-dependent and Density-independent Population Controls. Compare and Contrast Density-dependent and Density-independent Population Controls. What are the different Types of Population Changes that can occur in Nature? What are the different Types of Population Changes that can occur in Nature?

Review Terms: Immigration Immigration Emigration Emigration Biotic Potential Biotic Potential Intrinsic Rate of Increase Intrinsic Rate of Increase Environmental Resistance Environmental Resistance Carrying Capacity Carrying Capacity

Reproductive Patterns Species have different Reproductive Patterns that can help enhance their chance for survival: Species have different Reproductive Patterns that can help enhance their chance for survival: r-selected species *note that the r is not capitalized r-selected species *note that the r is not capitalized K-selected species K-selected species

r-selected species These species are those that have a high intrinsic rate of increase. These species are those that have a high intrinsic rate of increase. What are the common traits had by those that have a high intrinsic rate of increase? What are the common traits had by those that have a high intrinsic rate of increase? Examples of r-selected species: Examples of r-selected species: Algae, bacteria, rodents, frogs, turtles, annual plants, and most insects Algae, bacteria, rodents, frogs, turtles, annual plants, and most insects r-selected species are opportunists r-selected species are opportunists When conditions are right they have a boom in reproduction. When conditions are right they have a boom in reproduction.

K-selected species K-selected species are also called competitor species. K-selected species are also called competitor species. Reproduce later in life with small number of offspring Reproduce later in life with small number of offspring Develop inside their mother and are rather large at birth and mature slowly. Develop inside their mother and are rather large at birth and mature slowly. They are cared for by the parent species. They are cared for by the parent species. Called K-selected because they live will when the population is near the Carrying Capacity. Called K-selected because they live will when the population is near the Carrying Capacity. Examples of K-selected species: Examples of K-selected species: Large Mammals, birds of prey, large-long lived plants. Large Mammals, birds of prey, large-long lived plants.

Genetic Diversity and Population Size The Size of a Population can affect the genetic diversity in the area. The Size of a Population can affect the genetic diversity in the area. Usually in Large population, Genetic diversity is fairly constant or there is very little change. Usually in Large population, Genetic diversity is fairly constant or there is very little change. There are several factors that can play a role in the loss of genetic diversity: There are several factors that can play a role in the loss of genetic diversity: Founder Effect Founder Effect Demographic Bottleneck Demographic Bottleneck Genetic Drift Genetic Drift Inbreeding Inbreeding

Genetic Diversity and Population Size Founder effect Founder effect Occurs when a few individuals leave the population and colonize a new area that is geographically isolated from the main population Occurs when a few individuals leave the population and colonize a new area that is geographically isolated from the main population Demographic Bottleneck Demographic Bottleneck When a few individuals survive after a catastrophic event. When a few individuals survive after a catastrophic event. Genetic Drift Genetic Drift Random changes in the gene frequencies in a popuationthat can lead to unequal reproductive success. Random changes in the gene frequencies in a popuationthat can lead to unequal reproductive success. Inbreeding Inbreeding Can increase the frequency of defective genes. Can increase the frequency of defective genes.

Population Density Controls Population density is the number of individuals in a population found in a particular area or volume. Population density is the number of individuals in a population found in a particular area or volume. Two types of controls: Two types of controls: Density-dependent Density-dependent Density-independent Density-independent

Population Controls Density-dependent controls limit population growth as density increases. Density-dependent controls limit population growth as density increases. Predation, parasitism, infectious disease, and competition for resources Predation, parasitism, infectious disease, and competition for resources Density-independent controls limit population growth regardless of density. Density-independent controls limit population growth regardless of density. Mostly abiotic Mostly abiotic Weather phenomenon, geologic processes, catastrophes Weather phenomenon, geologic processes, catastrophes

Population Changes The are four general patterns of variation in population size: The are four general patterns of variation in population size: Stable Stable Irruptive Irruptive Cyclic Cyclic Irregular Irregular

Population Changes Stable Stable Very little fluctuation around the carrying capacity of the area Very little fluctuation around the carrying capacity of the area Species found in the tropical rainforest exhibit stable population changes because the weather and climate changes very little from year to year Species found in the tropical rainforest exhibit stable population changes because the weather and climate changes very little from year to year Irrupt Irrupt When population growth occasionally explode to a high peak then crash to a more stable lower level. When population growth occasionally explode to a high peak then crash to a more stable lower level. Algae and insects Algae and insects

Population Changes Cyclic Fluctuations Cyclic Fluctuations Similar to irruptive but the cycle is drawn out much longer. Similar to irruptive but the cycle is drawn out much longer. Lemmings populations rise and fall every 3-4 years Lemmings populations rise and fall every 3-4 years Lynx and hare populations rise and fall on a ten year cycle. Lynx and hare populations rise and fall on a ten year cycle. Predator-prey relationships have cyclic fluctuations Predator-prey relationships have cyclic fluctuations Irregular Patterns Irregular Patterns No discernable pattern in population change No discernable pattern in population change