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Transcript
Chapter 35 Important Ecological Terms Niche: role, function or boundaries of an organism Habitat: the place where a plant or animal normally lives Population: a group of individuals of one species in an area Community: many populations of different kinds of organisms living in the same place Ecosystem: assemblages of organisms together with their physical and chemical environments Biome: an ecosystem of a large geographic area in which plants are of one formation Population Dispersion Basic Characteristics of Populations The suitability of habitats influences the geographic distribution of a species. Insights can be gained by studying the spatial distributions of populations within habitats. Population Density The total population per unit area. Depends on: Quality of habitat Interactions within the environment Density dependent factors Density independent factors Capacity – the maximum number of organisms that can be supported by an environment. Controlled by limiting factors Population size can be measured by several sampling techniques. Quadrats Indirect counting Mark- recapture Population Growth Models Interactions within the Environment can effect population Competition Niche – organisms habitat, food source, activity time – role in environment. A fight within the niche Predation Symbiotic Relationships Parasitism – one organism benefits, one is harmed Mutualism – both organisms benefit Commensalism – one organism benefits and the other is not harmed or helped Density-Dependent and Density-Independent Effects on Populations In many habitats, the forces that limit population sizes are independent of population density. For example, extreme weather events may decrease populations. For most species, density-dependent factors limit birth rates or increase death rates at least some of the time. This type of population determination often is referred to as “regulation.” Disease outbreaks and starvation are two factors that may increase with population density. Communities Constantly Change Whether change occurs naturally or it is influenced by humans, disturbances are constantly occurring in ecosystems. Ecological Succession Natural, gradual changes in the types of species that live in an area. The gradual replacement of one plant community by another through natural processes over time Two types: Primary Secondary Primary Succession Begins in a place without any soil Sides of volcanoes Landslides Flooding Starts with the arrival of living things such as lichens that do not need soil to survive Called PIONEER SPECIES Secondary Succession Begins in a place that already has soil and was once the home of living organisms Occurs faster and has different pioneer species than primary succession Example: after forest fires Secondary succession takes place following a major disturbance, such as a fire or flood. Farmland that has been abandoned also can undergo secondary succession. Primary succession always begins on a barren surface, while secondary succession begins in an area that already has soil. Climax Community A stable group of plants and animals that is the end result of the succession process Does not always mean big trees Grasses in prairies Cacti in deserts