2/8/2012. How do populations and communities interact and change? Do you agree or disagree? Populations. Populations

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1 How do populations and communities interact and change? Do you agree or disagree? 1. Some life exists in the ice caps of the North Pole and South Pole. 2. A community includes all organisms of one species that live in the same area. 3. Some populations decrease in numbers because of low birthrates. 4. An extinct species has only a few surviving individuals. 5. No more than two species can live in the same habitat. 6. A cow is a producer because it produces food for other organisms. Populations What defines a population? What factors affect the size of a population? Populations biosphere population community competition population density biotic potential carrying capacity limiting factor 1

2 The Biosphere Biosphere is the parts of Earth that contain life. This includes all the land, bodies of water, ice caps at the North Pole and the South Pole, and the surrounding atmosphere Ecosystem Community Population Review of Chapter 20 An ecosystem includes all the biotic and abiotic factors in a given area. A community is all the populations of different species that live together in the same area at the same time. The study of all ecosystems on Earth and the and the interactions within them is ecology. A population is all the organisms of the same species that live in the same area at the same time. A species is a group of organisms that have similar traits and are able to produce fertile offspring. 2

3 Competition is the demand for resources, such as food, water, and shelter, in short supply in a community. When there are not enough resources available to survive, there is more competition in a community. Population Sizes Changes in environmental factors can result in population size changes. A limiting factor is anything that restricts the size of a population. What do you think some of these are? Examples of limiting factors Sunlight Without sunlight, green plants cannot make food, which effects animals that eat plants. Food Temperature When the temperature drops below freezing, many organisms die because it is too cold to carry out their life functions. Disease Predators Natural disasters ex. Fires, floods, volcanoes, hurricanes Shelter Population densty is the size of a population compared to the amount of space available. One way of estimating population density is by sample count. Sample- a count of part of a community taken as a representative of a whole group or species Capture and release method- radio devices Population Sizes (cont.) population from Latin populus, means inhabitants density from Latin densus, means thick, crowded A population s biotic potential is the largest number of offspring that can be produced when there are no limiting factors present. No population on Earth ever reaches its biotic potential because no ecosystem has an unlimited supply of natural resources. 3

4 The largest number of individuals of one species that an environment can support is the carrying capacity. A population grows until it reaches the carrying capacity of an environment. What factors affect carrying capacity? Disease, space, predators, and food are some of the factors that limit the carrying capacity of an ecosystem. The carrying capacity of an environment is not constant because it increases and decreases as the amount of available resources increases and decreases. Overpopulation- when the size of a population becomes larger than the carrying capacity of its ecosystem. Problems- each population effects other populations within a community as there is competition for resources The number of individuals in a population varies as the amount of available resources varies. Carrying capacity is determined in part by limiting factors. The population density of organisms, including green plants and algae, varies throughout the world. A community is all the populations of different species that live together in the same area at the same time. Which term refers to all the populations of different species that live together in the same area at the same time? A. a population B. a biosphere C. a community D. an ecosystem 4

5 Population Sizes (cont.) What factors affect the size of a population? 5