Populations

Populations – focus questions How does a change in one population affect another population? What is the biotic potential of a species? What factors affect the biotic potential of a species? What is environmental resistance? What factors contribute to environmental resistance?

Factors which can limit the growth of a population include: Predation Shortage of food Disease Lack of water Lack of space Disaster Contamination of the Loss of habitat Environmental Resistance :

Carrying Capacity “The largest number of individuals in a species that an environment can support” 4 factors that determine carrying capacity: 1.Materials/energy 2.Food Chains 3.Competition 4.Density

Materials and Energy All populations are limited by the availability of resources:  Energy (from the sun)  Water  Oxygen  Carbon  Nitrogen  Other nutrients

Food Chains The Pyramids of Biomass, Energy, and Numbers demonstrate how the population of a given organism is limited by:  its position in a food chain/web  the population size of those populations above and below it Relationships: Producer – consumer - decomposer Predator - prey

Competition Ecosystems have limited resources. Organisms with similar needs must compete to get the resources they need. Supply versus Demand Competition occurs between: MMembers of the same species = Intraspecific competition MMembers of different species = Interspecific Competition

Density An organisms’ need for space depends on their size, environment, and way of life. Different species have different needs for space. This need for space determines how many individuals of a given species can live in the same area at the same time. Factors affecting population size may be: 1. Density-Dependent Factors 2. Density-Independent Factors

Density Dependent Factors If population density increases, it can cause a decrease in the population. Overcrowding leads to:  Increased stress = spread of disease and parasites  Increased aggression = neglect of offspring  Reduced access to resources, mates and habitat Increased death rate/decreased birth rate =decrease in population

Density Independent Factors Events that can decrease population size that are not related to how many individuals are in the population to begin with:  Forest fire  Flood  Volcano  Extreme weather (ex. Hurricane)  Pollution

How do humans manage biological variables to affect the carrying capacity of an ecosystem?

Population Growth Curve Carrying Capacity

Earth as Easter Island What is unique about Easter Island’s location? Describe what the first European explorers encountered upon arrival at Easter Island. How have the biotic factors on Easter Island changed over time? How has this affected the population? How do scientists know that many species of extinct plants and animals used to live on the island? What did the islanders use the trees for? How did the absence of trees affect the soil? Drinking water? Agriculture?

Lessons from Easter Island?

Resources Biotic Potential and Carrying Capacity of a Population Biotic Potential and Carrying Capacity of a Population