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Ch 12 And 13 Notes

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Chapter 12- Ecosystem (a) define the term ecosystem; (b) state that ecosystems are dynamic systems; (c) define the terms biotic factor and abiotic factor, using named examples; (d) define the terms producer, consumer,decomposer and trophic level; (e) describe how energy is transferred though ecosystems; (f) outline how energy transfers between trophic levels can be measured; (g) discuss the efficiency of energy transfers between trophic levels; (h) explain how human activities can manipulate the flow of energy through ecosystems (HSW6b); (i) describe one example of primary succession resulting in a climax community; (j) describe how the distribution and abundance of organisms can be measured, using line transects, belt transects, quadrats and point quadrats (HSW3); (k) describe the role of decomposers in the decomposition of organic material; (l) describe how microorganisms recycle nitrogen within ecosystems. (Only Nitrosomonas, Nitrobacter and Rhizobium need to be identified by name). Ecology: study of interaction between organisms and their environment

Ecosystem: All the living organisms and all the non-living components in specific habitat, and their interactions.


Habitat: the place where an organisms lives Population: all of the organisms of one species, who live in the same place at the same time, and can breed together Community: all the population of different species who live in the same place at the same time, and can interact with each other

Role that each species play in an ecosystem- niche Ecosystem is a dynamic system: population sizes rise and fall e.g.

Predator's population size goes up, size of prey will go down

Living components of the environment that affect the distribution and abundance of a species- biotic factors



Parasitism: one organisms (parasite) lives in close association with an organisms of a different species (host) and causes it harm Predation: one organisms (predator) kills and eats another (prey) Competition: two organisms both require something that is in short supply Mutualism: two organisms of different species live in close association, both benefiting from the relationship

Non-living components of the environment that affect the distribution and abundance of a species- abiotic factors




Light intensity: affects the rate of photosynthesis in plants and the behaviour of animals CO2 concentration: affects photosynthesising plants Oxygen concentration: affects organisms that respire aerobically Temperature: affects the rate of metabolic reactions in both endothermic and ectothermic organisms Immediate source of energy is ATP








Initial entry of energy into most ecosystems takes place during photosynthesis Energy from the sunlight used to make carbohydrates, proteins and fatscarbohydrates and other organic substances serve as supplies of chemical energy to all of the other organisms Plants are producers-an organism that converts simple inorganic compounds or energy from light into complex organic compounds consumers- an organism that gains energy from complex organic matter, and convert complex organic molecules into simpler ones which can be digested Primary consumers : first consumer in the food chain, herbivore Carnivore: organisms feeds on meat only Herbivore: feeds on the producer Omnivore: feds on both animals and plant

Energy is transferred by organisms consuming each other Arrows in the food chain indicate the direction in which the energy flows Trophic level- each feeding stage in food chain Pyramids: represents the energy stored at each trophic level LIMITATIONS: pyramids of number- different species are different sizes

Pyramid of biomass: same mass of tissue in different species may store different amount of energy Pyramids of energy: only take snapchat of ecosystem at one time and pop. can change

The interrelationship between many food chains- drawn as food web Measuring energy transfers between trophic levels
Food chain is worked out- only give a partial picture- producer that is eaten by only one consumer, and that this consumer feeds entirely on that producer and nothing else- done in lab-outside world there are too many uncontrolled variables

1. Population size of each species is measured

2. Mean dry mass of single organism is measured- kill sample, then drying to constant mass by heating to drive off water

3. The energy content per gram of dry mass is calculated- burning a sample of dry material of known mass in a calorimeter and measuring the heat that is produced

4. The total energy content in the population is calculated Energy content= number of organisms x mean dry mass of one organisms x energy content of 1g of dry mass Whenever energy is transferred from one form to another some is always lost as heat Only about 3% of sunlight energy is converted to chemical energy. Reason for inefficiency:

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