- Slides: 22
Ecology and Interdependence � Ecology is the study of the interactions between organisms and their environment. ◦ Interdependence is a key theme found throughout ecology. ◦ Living things depend on each other in complex ways for survival. ◦ Ecological models can be used to study this complexity.
Levels of Organization � The hierarchy of environmental organization from largest to smallest is: Biosphere, Ecosystems, Communities, Populations, and Organisms. ◦ Biosphere —thin zone of the Earth that supports life. ◦ Ecosystem —all living and nonliving parts of an ecosystem �Biotic factors—living organisms �Abiotic factors—nonliving parts.
Communities and Populations ◦ Community—all the organisms living in a certain area. Example: pond community ◦ Population—all the organisms of the same species living in the same area. Example: frogs in a pond
Strategies for Tolerance � Two strategies exist to deal with fluctuations in environments. ◦ Conformers—organisms who do not regulate their internal conditions; they change with the environment. Ex: ectothermic animals ◦ Regulators—organisms that use energy to control some of their internal conditions. Ex: endothermic animals
Escaping Unfavorable Conditions � Sometimes, adjusting isn’t possible and organisms must temporarily escape. Ex: Lizard hiding in the shade Seed dormancy or animal hibernation Migration
Energy and the Environment � Sunlight is the main source of energy in most ecosystems � Energy flows from sunlight through producers (make food) and consumers (eat food)
Types of Producers � Photoautotrophs— use solar energy (photosynthesis) to produce sugar � Chemoautotrophs— use energy stored in inorganic molecules (chemosynthesis) to produce carbohydrates
Consumers � Consumers—get food by eating other organisms or organic wastes. (Heterotrophs) � Four types: Herbivores—eat producers Omnivores—eat producers and consumers Carnivores—eat other consumers
� Detritivores--feed on “wastes” (dead plants, animal wastes, and dead animal carcasses. ) ◦ A few are specifically classified as decomposers because they cause decay and return important nutrients to the soil. Detritivores Decomposing Detritivores
Energy Flow � Energy flow through an ecosystem can be illustrated using trophic levels (shows an organism’s position in a sequence of energy transfers) � 1 st level = producers � 2 nd level = herbivores � 3 rd and higher levels = predators
Consumers are also grouped into feeding or trophic levels according to the foods they eat. � Many organisms feed at more than one level, especially omnivores. � C 1—first level consumers: eat plants C 2—second level consumers: eat C 1 consumers C 3—third level consumers: eat C 2 consumers
A food chain is a model of the flow of energy through the Organisms of an ecosystem. C 1 C 2 C 3
Food Webs � Food web —many food chains combine to form a food web. � Gives more information. ◦ The members can be identified by their trophic level. ◦ Many organisms function on more than one trophic level. Which is a producer? Which are C 1 consumers? Which are C 2 consumers? Which is a C 3 consumer? Which is a C 4 consumer?
A complex food web from an aquatic ecosystem
Energy Pyramid � An energy pyramids --show the amount of energy available decreases at each level of the food chain.
Cycles in Nature � Many of the abiotic factors in an ecosystem pass through cycles that allow the substances to be used and reused. � Four important cycles of abiotic substances include: ◦ ◦ Water cycle Carbon cycle Nitrogen cycle Phosphorus cycle
Water Cycle � Water passes through both living and nonliving parts of the environment. The water cycle is maintained by evaporation, transpiration, condensation and precipitation.
Carbon Cycle � Photosynthesis and cellular respiration form the basis of the carbon cycle. � In the past 150 years, atmospheric carbon dioxide has risen more than 30%. . mostly due to the burning of fossil fuels
Nitrogen Cycle � � � Air is 78% nitrogen gas. Most organisms cannot use nitrogen in this form. Nitrogen-fixing bacteria change nitrogen gas into nitrates which can be used by living things to make proteins and nucleic acids. ◦ Live in the soil and on the roots of certain plants (beans, peas, clover and alfalfa). ◦ Receive carbohydrates from plants and produce nitrogen for plants ◦ Release extra nitrogen into the soil. Decomposers--make the nitrogen from decaying organisms and wastes available in the soil by turning it to ammonia (NH 3) which changes in the soil to ammonium (NH 4+) in a process called ammonification. Soil bacteria turns ammonium into nitrites (NO 2 -) and nitrates (NO 3 -) in a process called nitrification. Plants can use the nitrates and then animals can eat the plants. Anaerobic bacteria return nitrogen to the air by breaking down soil nitrates in the process of denitrification.
Phosphorus Cycle � � Phosphorus is necessary for healthy bones, teeth, and the formation of DNA and RNA. The erosion of rocks is important in adding phosphorus to the soil and water. Excreted wastes and decaying organisms also add phosphorus to soil and water. Plants absorb phosphorus. Animals get phosphorus from plants.