Chapter 22* Ecology and the Environment Environment Ecology – study of relationships between organisms and environment. Factors: Biotic – living Abiotic – nonliving The Organization of Ecological Systems The smallest living unit is the individual organism.
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Ecology and the Environment
Ecology – study of relationships between organisms and environment.
Biotic – living
Abiotic – nonliving
The food chain
Sun is primary source of energy for most living things.
Higher trophic levels lose ~90% of energy to space due to 2nd law of thermodynamics.
Carbon cycle – essential for the organic compounds
Nitrogen cycle – essential for formation of amino acids. Often the limiting factor in terrestrial ecosystems.
Kenya-large prereproductive population will grow rapidly in the future. US-large
reproductive population, low prereproductive. Will continue to grow for a time but will
Stabilize in the future. Germany-large post reproductive. Population is beginning to fall.
Natality – added to population by reproduction
Mortality – leaving population by death.
Natality and mortality low.
Natality equals mortality
Presently the human population is growing at ~75 million people per year. All animals reach a carrying capacity.
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Ecology – study of relationships between organisms and environment. Biotic-living, abiotic-nonliving.
The smallest living unit is the individual organism.Populationsare groups of organisms of the same species. Communitiesare interacting groups of populations of different species. An ecosystem is all the interacting organisms in an area and their interaction with their abiotic surroundings.
Those organisms that trap sunlight from inorganic material for photosynthesis are called producers, the first trophic level, like green plants, algae, and cyanobacteria. They convert sunlight energy into the energy contained within the chemical bonds organic compounds. Consumers obtain energy in the form of organic matter.
All animals are consumers. Each time the energy enters a different organism it is said to enter a different trophic level. Animals that are herbivores are primary consumers and occupy the second trophic level. Animals that eat other animals are secondary consumers or carnivores. Animals that eat herbivores occupy the third trophic level and are primary carnivores. Animals that feed on the primary carnivores are known as secondary carnivores and occupy the fourth trophic level. The sequence of organisms feeding on one another is known as a food chain. Omnivores are animals that are both carnivores and herbivores.
The energy in the organic compounds of dead organisms is released to the environment as heat by decomposers that turn them into carbon dioxide, ammonia, and other simple organic molecules and include bacteria and fungi. These can now be used by producers to trap energy again.
There is about a 90% loss of available energy as we proceed from one trophic level to the next higher.
Biomes :temperate deciduous forest-cold, rainy; Grasslands-medium rain, vegetation mostly grass; savannah-rainy and dry seasons, little vegetation; desert-very dry, almost no vegetation; taiga or boreal forest-long cold winters, rainfall; temperate rainforest-mild T, rain, evergreen trees; tundra-very cold, little vegetation; tropical rainforest-warm, rainy, many plants.
Carbon cycle-CO2 from atmosphere intake by plants, photosynthesis converts it to organic materials and O2. Organic materials are taken in by herbivores and use it for energy and to grow through respiration, and this produces CO2 which It is returned to the atmosphere.
Nitrogen cycle-N2 Bacteria convert it to compounds that plants can use and animals obtain it from plants. It is later returned to atmosphere after decomposition of living matter or taken up by plants again.
Population growth based on age distribution and sex. More females-more reproduction. More reproductive age-positive current growth, more post reproductive age-negative growth. More prereproductive age-future positive growth.
Initial lag phase, then natality greater than mortality- exponential growth phase. Later natality equals mortality stable equilibrium phase.
Carrying capacity-the maximum population an area can hold. Can be increased by technological advances. The world as a whole is now in an exponential growth phase.Summary