Communities and Ecosystems (2.2)
Sections |
Notes & ReviewNotes: Topics 2.2, 2.3, 1.2, 1.3jeopardy Review (2.2, 2.3, 1.2, 1.3) |
Respiration and Photosynthesis
Respiration = the conversion of organic matter into carbon dioxide and water in all living organisms releasing energy (heat)
|
Respiration is necessary for life. Without it, no processes in any living organisms (plant, animal, or bacteria) would be possible. It provides the energy (ATP) necessary to grow, breath, move, reproduce, excrete, eat, etc.
Photosynthesis is necessary for life due to providing the base for the energy in the ecosystem, plus producing and recycling oxygen. Note that plants do BOTH respiration and photosynthesis. When all carbon dioxide that plants produce in respiration is used up in photosynthesis, the rates of the two processes are equal. There is not net release of oxygen or carbon dioxide, usually occurs around dusk and dawn. Called a compensation point where the plants is neither adding biomass nor using it up to stay alive. |
Predation and Food Webs
Food chains and food webs allow us to see consumer interaction within an ecosystem. A food chain, at its most basic, is a series of who eats who. A chain always begins with an autotroph or producer.
Producers: make their own food
Food webs and food chains |
Heterotroph: an organism that must gain its food from another organism
|
Food Chains help us identify tropic levels: Trophic mean energy.
Note that the arrows in a food web (or food chain) represent the direction of energy movement, so the arrows go towards what is gaining the energy.
|
Food Webs allow us to the see the complexity of the interactions of an ecosystem. Few organisms only fall into a single trophic level.
Always start with the producers and work from there to determine each level. The following food web has been color coordinated with trophic levels as an example.
|
Lost energy in a Food web
Energy Efficiency:
|
Why does the loss of energy up a food chain limit the length of the chain (or biomass) an ecosystem can contain?
The amount of energy available to an entire ecosystem is found in its autotrophs. The less energy you begin with the less energy available at the higher trophic levels because it is lost as it moves up the food chain. The less energy available at the higher levels, the more organisms the higher trophic levels must eat in order to gain the energy needed for survival. At some point the amount of energy needed to survive and the amount of energy available are no longer compatible. It becomes more advantageous for an organism to occupy lower trophic levels, or in some cases multiple trophic levels, to ensure their energy requirements are met. The Energy Flow: Primary productivity at high trophic levels |
Ecological Pyramids
Ecological pyramids are quantitative representations of energy transfer and losses. They are dependent upon what feeds on what and what organisms exist at different trophic levels. They are attempt to demonstrate the ecosystem balance in various methods.
3 types of pyramids:
|
Productivity Pyramids are the most accurate. Why?
|
Drawing an Ecological Pyramid
Numbers and biomass pyramids can simply be drawn with the numbers given. Set a specific length for a certain number.
Energy pyramids are the hardest to draw as they require some calculations and scaling. Units are measured in kilojoules per meter squared per year. (KJm-2yr-1). See diagram below of completed energy pyramid from the problem with steps and calculations seen below that. You must be able to explain and draw an energy pyramid.
- ex. 1cm = 1 organism
Energy pyramids are the hardest to draw as they require some calculations and scaling. Units are measured in kilojoules per meter squared per year. (KJm-2yr-1). See diagram below of completed energy pyramid from the problem with steps and calculations seen below that. You must be able to explain and draw an energy pyramid.
BIOMAGNIFICATION/ BIOACCUMULATION
Bioaccumulation = the gradual increase of a toxin with a specific population overtime.
Virtual lab: Biomagnification with DDT |
|