Ecosystem

ECOSYSTEMS

1. Interaction of organisms with their physical environment through a flow of energy and a cycling of nutrients. All ecosystems run on energy captured by:

   • Detritivores: Dine on detritus (small particles of organic matter
   • Consumers: Heterotrophs, they feed of tissues, wastes and remains of producers. They are clasified by their diets:
     • Herbivores: Feed from plants
     • Carnivores: eat the flesh from animals
     • Parasites: Feed of the tissues of their living hosts
     • Omnivores: devour animal and plant materials
   • Decomposers: feed on organic wastes and remains
   • Primary producers: Autotrophs or self-feeders, they capture energy from the sun and use it in photosynthesi
   • Trophic levels: Positions of every organisms in a food chain. Graphically represented as ecological pyramids.
     • 1st level: Primary producers
     • 2nd level: Hervobores
     • 3rd level: Carnivores
     • 4th level: Detritivores and consumers
     • Food chain: Description of who eats whom in one path of energy flow in an ecosystem.
   • Flow of energy through ecosystems:
     • Biomass pyramid: depicts dry weight of orgnisms at each trophic level of an ecosystem.
     • Primary production: Primary producers capture energy and convert it into biomass.
     • Ecological efficiency: Tends to be greatest in aquatic systems, where primary producers usually lack lignin and consumers tend to be ectotherms.
     • Energy pyramid: Diagram that depicts the energy that enters each trophic level.

2. BIOGEOCHEMICAL CYCLES:: Slow movement of a nutrient among environmental reservoirs and into and out of food webs.

   • Water cycle: Movement of water among Earth’s atmosphere. Sunlight causes evaporation, forming clouds and they fall as precipitation (rain, snow or hail) going back to the primary source.
     • Watershed: Land area that drains into a particular stream or river.
     • Soilwater: Water between soil particles.
     • Aquifier: Porous rock layer that holds groundwater, drained through soil layers.
     • Groundwater: Water in soil and aquifiers.
     • Runoff: Water that flows over soil into streams.
     • Fresh water makes up a tiny portion of the global water supply. Excessive water withdrawals threaten many sources of drinking water, irrigation methods for example.
     • Eutrophication: Nutrient enrichment of an aquatic system.
   • Carbon cycle: Movement of carbon, mainly between the oceans, atmosphere and living organisms.
     • 1. Plants take up carbon dioxide from the air for use in photosyntesis.
     • 2. Carbon returns to air by aerobic respiration.
     • 3. Carbon diffuses between the atmosphere and the ocean. (Bicarbonate forms when carbon dioxide dissolves in seawater)
     • 4. Marine produces use bicarbonate in photosynthesis and marine organisms release carbon dioxide from aerobic respiration.
     • Atmospheric cycle: Biogeochemical cycle in which a gaseous form of an element plays a significant role.
     • 5. Some marine organisms incorporate carbon into their shells; when they die become part of sediments and over-time turn in limestone and chalik.
     • 6. Burning of fossil fuels derived from the ancient remains of plants puts additional carbon dioxide into the atmosphere.

3. GREENHOUSE GASES AND CLIMATE CHANGE

   • Greenhouse effect: Caused by excess of carbon dioxide.
   • Greenhouse gas: Atmospheric gas that absorbs heat emitted by Earth’s surface and remits it, thus keeping the planet warm.
   • 2. More light energy reaches and warms Earth’s surface.
   • 3. Earth’s warmed surface emits heat energy, some of it goes to space and the rest is absorbed and emitted in all direction by greenhouse gases.
   • 1. Earth’s atmosphere reflects some sunlight energy back into space.
   • Global climate change: Long-term alteration of Earth’s climate.

4. NITROGEN CYCLE: Atmosphere is 80% nitrogen. Movement of nitrogen among the atmosphere, soil, water and food webs.

   • Nitrogen fixation: Incorporation of nitrogen from gas into ammonia.
   • Ammonification: Breakdown of nitrogen-containing organic material resulting in the release of ammonia an ammonium ions.
   • Nitrification: Conversion of amonium to nitrates.
   • Denitrification: Conversion of nitrates or nitrites to gaseous form of nitrogen.
   • Human activities disrupted the nitrogen cycle:
     • Burning fossil fuels releases nitrous oxide, which is a greenhouse gas, into the air and destroys the ozone layer.
     • Wastewater that escapes from septic systems is another source of nitrate pollution.
     • Use of synthetic fertilizer encourages the production of nitrous oxide by bacteria. It is also a source of nitrates, which pollute drinking water.

5. PHOSPHORUS CYCLE: Movement of phosphorus among Earth’s rocks and waters, and into and out of food webs.

   • Sedimentary cycle: Biochemical cycle in which the atmosphere plays little role and rocks are the major reservoir. Weathering puts phosphates into water and producers take up dissolved phosphates.
   • Phosphate-rich wastes are a natural fertilizer, and phosphate from rocks can be used to produce fertilizer on an industrial scale.

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