Transcript Ecosystems
Ecosystems Ecosystems An ecosystem is all living and nonliving things in an area. Ecosystem is derived from the Greek word oikos, for “house,” eco-is the combining form meaning “environment or habitat.” An Ecosystem may be very small such as: A backyard A pond A playground Some may be very large like: The deserts of Africa The rain forest of Brazil The saltwater oceans All ecosystems have the same parts: Abiotic Factors Biotic Factors Abiotic Factors The nonliving parts of an ecosystem. They include water, minerals, sunlight, air, climate, and soil. Biotic Factors The living parts of an ecosystem. They include animals, plants, fungi, protists, and bacteria. Key Terms Population ecology the study of how natural processes affect the size, composition, and dynamics of populations. Population - a group of interacting individuals of the same species. Community - a group of interacting populations. Ecosystem - a functional environmental unit, consisting of a biotic community and the abiotic (nonliving) factors on which the organisms depend. Biosphere - the total of all ecosystems. In other words, all the area on Earth where life is found. Ecology - the study of relationships between organisms and their environment. Biome- very large ecosystem. 9 biomes exist Describe your own community and the population you will find there. Focus on your school What living things do you see? What nonliving things help you survive? Biomes Population Density Density - the number of individuals per area unit. Density-Dependent Factors - In general, densitydependent factors are biological factors, such as diseases, parasites, competition for resources, predation, and stress. Density-Independent Factors - In general, density-independent factors are physical factors, such as weather factors (severe winter), natural disasters (floods and fires), or the presence of harmful chemicals. Population Patterns Distribution patterns describe distribution within the area being studied and give a better picture of actual population density. Many animal populations will have different distribution patterns at different times. Random distribution - each individual has an equal chance of being found at any place in a given area. This is a hypothetical condition that might never occur in nature because resources are not randomly distributed. Uniform distribution - animals are evenly spaced throughout the habitat. This can at least be approached in nature. Clumped distribution - animals are found in areas where resources are found. This is by far the most common distribution pattern in nature. Population Growth Models Exponential Model A population could reach its biotic potential, the maximum growth rate – environmental conditions are ideal – there are no restrictions on reproduction – mortality rate is kept extremely low Realized intrinsic rate of growth (r) is measured by the difference between natality (birth rate, n) and mortality (death rate, m). r=n−m Since environmental conditions are rarely ideal, the maximum growth rate is almost never achieved in nature. The realized intrinsic rate of growth more closely represents the actual growth of organisms in nature than does the biotic potential. Zero population growth is reached when r = 0, natality equals mortality, and population size remains constant. Population Growth Models Logistic Model Environmental resistance - the combination of many factors that tend to prevent exponential growth. Exponential growth begins to slow because of a combination of declining birthrate and increasing death rate. Eventually, the population stops growing as it fluctuates around zero population growth at the habitat's carrying capacity the maximum population density that the environment can support for an extended time. Restricted or logistic population growth can be expressed by the following equation: d N / d t = r N x (K − N) / K – d - means an instantaneous change in – N - the number of individuals already in a population – t - a unit of time – r - realized intrinsic rate of population growth – K - carrying capacity Population Growth Graphs Growth Generalizations Population density varies from habitat to habitat. No population increases indefinitely. Population Laws Law Of Minimums - essential material available in amounts most closely approaching the minimum needed by an organism will tend to limit the organism's growth and development. Limits Of Tolerance - organisms can only tolerate certain extremes in environmental factors. Populations cannot exist outside the tolerance limits of its individuals. Competitive Exclusion Principle - competition between populations of two species for the same limiting resource eventually leads to the elimination of one of the species populations. Relationships An animal's niche is determined by all the ways the animal interacts with its environment, including what it eats, how it obtains its food, what physical and chemical conditions it will tolerate, what conditions are optimal for its well-being, and how it interacts with its predators and parasites. – – Predator-Prey Foragers