Ecology School Notes

ECOLOGY NOTES (Chapters 2-5) Ecology is the study of the interactions between organisms and their environment. Ecologists study both the living and non-living parts of the environment because they are interdependent. The living factors in an environment are called biotic factors (plants, animals, etc.). The non-living factors of the environment are called abiotic factors (water, amount of sunlight, temperature, humidity, soil composition, etc.) Levels of Organization 1 There are many levels of organization that ecologists may study. An individual living thing is an organism. (Examples: a cat, a bear, a maple tree) A population is a group of organisms of the same species living in the same area. A species is a group of organisms so similar that they can interbreed and produce fertile offspring. (Examples: a maple tree stand, an apple orchard, all of the cardinals in Winston-Salem, all of the grey squirrels in your backyard) A community is all of the different populations of living things that live in the same area. (Example: all of the trees, squirrels, cardinals, blue jays, crows, insects, etc. in your backyard) An ecosystem is all of the living organisms in a particular environment AND the non-living factors that in their environment (water, air quality, humidity, etc.). A biome is a group of similar ecosystems that have the same climate and similar communities of organisms. (Examples: desert, tundra, tropical rainforest) All of the portions of the Earth that support life make up the biosphere (Earth). 2 Ecological Methods To gather information on populations, ecosystems, etc…. ecologists use 3 main methods: observing, experimenting, and modeling. Energy Flow The main source of energy on Earth is the sun. Organisms that capture energy directly from the sun to produce food are called autotrophs or producers. Some autotrophs use inorganic chemical compounds (like sulfur or methane) to produce their own food. Autotrophs that use the sun’s energy directly make food using the process of photosynthesis. Photosynthesis converts carbon dioxide, water and light energy (from the sun) into sugars and oxygen. Autotrophs that use chemicals to produce their food use a process called chemosynthesis. Organisms that cannot make their own food must consume other organisms for their energy and they are called heterotrophs or consumers. There are many different types of heterotrophs: 1. Herbivores: eat plants (producers) only 2. Carnivores: eat meat (other consumers) only 3 3. Omnivores: eat both plants and meat 4. Decomposers (detritivores): break down dead plant and animal remains; recycle nutrients Feeding relationships Energy flows through an ecosystem in one direction from the sun or inorganic chemicals to autotrophs (producers) and then to various heterotrophs (consumers). The relationships between producers and consumers connect organisms into feeding networks based on who eats whom. A food chain is a series of steps that shows how energy is transferred by eating or being eaten. 4 A food web is a more complex diagram that shows all of the possible feeding relationships in an ecosystem. Both food chains and food webs always start with a producer(s). The arrows are drawn to show which way energy is being transferred. 5 Each step in a food chain or food web is called a trophic level. Producers always make up the first trophic level. Consumers make up the second, third, or higher trophic levels. Each consumer depends on the trophic level below it for energy. Producers always begin the food chain, food web, or are found at the base of an ecological pyramid-plants, algae, phytoplankton….Producers have the most energy because they use sunlight directly to make their own food (photosynthesis). Primary consumers come next, they are HERBIVORES that feed on the producers-cows, grasshoppers, caterpillars, deer, small fish… Secondary consumers are CARNIVORES that eat the herbivores-lion, hyenas, dogs, cats… Tertiary or third-level consumers can be carnivores or OMNIVORES that eat both producers and consumers. Decomposers (bacteria/fungi) feed from all levels of a food web or food chain once the organisms die. Ecological Pyramids An ecological pyramid is a diagram that shows the relative amounts of energy or matter in each trophic level of a food chain or food web. There are 3 types: energy pyramid, biomass pyramid, and a pyramid of numbers. 6 Energy pyramids show how much energy is passed from one trophic level to the next. Only 10% of the energy from one trophic level is transferred to the next trophic level. This is because much of the energy that is being consumed is used for life processes: respiration, reproduction, movement. Producers are always found at the base of the pyramid because they have the most energy. Biomass pyramids show the amount of potential food available for each trophic level in an ecosystem. The total amount of living tissue within a given trophic level is called biomass. 7 A pyramid of numbers is based on the number of individual organisms at each trophic level. Cycles of Matter Energy only flows one-way through an ecosystem BUT matter is recycled within and between ecosystems. Matter can cycle through ecosystems because it is not used up but transformed. Every living organism needs nutrients to build tissues and carry out essential life functions. Nutrients are passed between organisms and the environment in cycles. Carbon Cycle Carbon plays many roles in the environment: ingredient in living tissues, part of the skeleton, found in rocks, forms carbon dioxide gas (CO2), used by plants in photosynthesis, given off by plants and animals during respiration. Four main processes move carbon through its cycle: 1. Photosynthesis, respiration, and decomposition take up and release carbon and oxygen. 2. Erosion and volcanic activity release carbon dioxide to the atmosphere and oceans. 3. Burial/decomposition of dead organisms and their conversion to coal and fossil fuels store carbon. 8 4. Mining, cutting, burning forests and fossil fuels release carbon dioxide into the atmosphere. Climate Climate is an abiotic factor that refers to the average yearafter-year conditions of temperature and precipitation in an area. The Greenhouse Effect Temperatures remain within a suitable range for life because of the insulating actions of the atmosphere surrounding the Earth. Carbon dioxide, methane, water and other atmospheric gases trap heat energy and maintain Earth’s temperature range. 9 What Shapes An Ecosystem? Biotic and Abiotic Factors Biotic factors are all of the organisms (living things) another organism may interact with. Abiotic Factors are the physical, or non-living factors that shape an ecosystem-temperature, precipitation, humidity, wind, nutrient availability, soil type, and sunlight. Biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives. The area where an organism lives is called its habitat. A habitat includes biotic and abiotic factors. The niche is an organism’s job or role in its habitat. It includes its place in the food web (trophic level-producer, consumer…), what type of food the organism eats, the physical conditions it needs to survive, how and when it reproduces… No two species can occupy the same niche in the same habitat. 10 Community Interactions Organisms in ecological communities interact constantly. This shapes the ecosystem. Three types of interactions can affect an ecosystem: competition, predation, and symbiosis. 1. Competition: occurs when organisms of the same or different species try to use an ecological resource in the same place at the same time. • A resource can be: water, nutrients, light, food, space, and mates. • Competitive exclusion principle: no two species can occupy the same niche in the same habitat at the same time. 2. Predation: (predator-prey relationship); one organism hunts and kills another for food (energy). The predator is the hunter and the prey is the animal that is killed. 3. Symbiosis: Two different species live closely together. a. Mutualism: (+,+), type of symbiosis where both organisms benefit; example-CLOWNFISH/SEA 11 ANEMONE, ANTS/APHIDS, FLOWERING PLANTS/POLLINATORS b. Commensalism: (+,0), type of symbiosis where one organism benefits and the other is neither helped nor harmed; EXAMPLEBARNACLES/WHALES, ORCHIDS/TREES C. Parasitism: (+,-) One organism lives on or inside the other (host) and harms it, one is helped the other is harmed. EXAMPLES-TICK/DOG, TAPEWORM/DOG. FLEAS, TICKS, LICE… Ecological Succession: Succession occurs when one ecosystem replaces another, for example, a pond gradually fills in and becomes a meadow. 12 Ecosystems can change in response to human and natural disturbances. Primary succession occurs where no soil exists-bare rock, land formed from volcanic eruptions. There is no soil, just ash and rock. The first species to populate such an area are called pioneer species. Lichens and moss are common pioneer species. Secondary succession occurs when a disturbance changes an ecosystem without removing soil-abandoned farmland, fire-destroyed areas. All succession ends in a climax community, a stable, mature community of organisms that changes very little over time. 13 14