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Transcript
Study of interactions among organisms, and between organisms and their environment. Organism Lowest level of organization studied in ecology Three important aspects of the ecology of an organism are its: Habitat—physical area in which the organism lives Niche—way of life of a species. Includes its habitat, feeding habits, reproductive behavior Trophic level—the relationship between what an organism eats and what it is eaten by, it’s feeding level. Two basic trophic levels are: Producer or autotroph Consumer or heterotroph Two types of autotrophs: Photoautotrophs-manufacture their own food by photosynthesis (sunlight is the main energy source for life on Earth). Chemoautotrophs-manufacture their food by a process called chemosynthesis which utilizes chemicals in their environment. Certain bacteria can do this. Types of consumers include: Herbivores—eat primary producers Types of consumers include: Carnivores—eat other consumers Types of consumers include: Decomposers— break down dead tissues into fundamental elements or compounds Types of consumers include: Omnivores—eat both producers and consumers Types of consumers include: Detritovores (scavengers)— feed on organisms that have recently died Population A group of organisms of the same species that are living in a particular place at a particular time. A population may also be defined as a group of organisms that can interbreed. Characteristics of populations Population density—number of individuals per unit area Growth rate—three factors may affect the population size: 1. Birth rate 2. Death rate 3. Immigration or emigration Geographic distribution—(range) area inhabited by a population Types of growth Exponential growth— occurs slowly at first, and then increases rapidly (J shaped curve on graph). Under ideal conditions with unlimited resources, a population will grow exponentially. Types of growth Logistic growth—occurs when a population’s growth slows or stops following a period of exponential growth (S shaped curve on a graph) Carrying capacity Largest number of individuals that an ecosystem can support. Occurs when the population reaches the limit of what available resources can support. Growth limiting factors—factors in an ecosystem that causes population growth to slow down, stop, or decrease. Density-dependent factors—depend on population size. Include competition, predation, parasitism, and disease. Density-independent factors—affect all populations in similar ways regardless of population size. May include unusual weather, natural disasters, seasonal cycles, and certain human activities (clear cutting forests, damming rivers, etc…). Communities Different populations that live in the same defined area and can interact with one another. Biotic relationships—all relationships among organisms in a community Competition—use or defense of a resource by one organism that reduces the availability of that resource to other organisms Predation—one organism feed upon another. The predator feeds upon the prey Symbiosis—relationship in which two dissimilar organisms live in close association Types of symbiosis include: Parasitism—harmful, close, long-term relationship in which one organism receives its nutrition from another organism. The one receiving the benefit is called the parasite. The providing organism is called the host. Types of symbiosis include: Commensalism— relationship in which one organism benefits and the other neither benefits or suffers harm. Types of symbiosis include: Mutualism—relationship in which both organisms benefit. Ecosystem An ecosystem is a community of living things and their physical environment. *In an ecosystem, matter is recycled but energy is lost.* Two types of factors that influence an ecosystem: Biotic factors—biological (living) influences that shape an ecosystem. Biodiversity refers to the variety of organisms in a given ecosystem. Abiotic factors—physical or non-living influences that shape an ecosystem. Keystone Species—a species that has an unusually large effect on its ecosystem Ecological succession—a series of predictable changes that occurs over time. Primary succession (bare rock succession)—occurs on volcanic islands or on bare rock as glaciers melt Secondary succession— occurs when a disturbance of some kind (fire, land clearing or plowing) changes the community without removing the soil. Begins with grasses and then follows the same pattern as a primary succession. Ecological Succession Pioneer organism—first organism to populate an ecosystem. The pioneer organism in a primary succession is lichen which is a mutualistic relationship between an alga and a fungus.