Trophic Levels:

in an ecosystem, there must be a flow of energy occurring. the sun is the ultimate source of energy but at each level energy is stored, used and lost.
these levels are called trophic levels (from the greek triphos meaning 'food).
all feeding relationships in an ecosystem show a one-way flow of energy. the energy is not recycled.
the sun supplies the energy to the plants. the process of photosynthesis captures the energy contained in sunlight and produces carbohydrates. the plant gains the energy that it requires to power its metabolism through the production of sugars. starches are formed which make up plant tissue. when an animal eats a plant, it use the energy stored in the plant to form its own body cells. at this level most energy is lost in the conversion from plant tissue to animal tissue. only 10 percent moves up to the next trophic level. this means that at each levels most of the energy is lost.
Feeding Relationships:
autotrophs or producers are organisms that amke their won food. example green plants and algae. heterotrophs or consumers must consum other organisms in order to gain the supply of energy they need for life.
primary consumers - herbivores.
- secondary or tertiary consumers.
- carnivores.
- omnivores.
heterotrophs.
scavengers: animals that eat dead organism.
detritivores: animals that ingest organic litter and detritus.
decomposers: fungi and bacteria that causes chemical decay of organic matter and absorb the broken down material.
primary consumers are eaten by secondary consumers, and secondary consumers are eaten by tertiary consumers. all herbivores, carnivores and omnivores are predators as well.
Herbivores:
these animals maybe small (snail) or large (kangaroo). it takes a large amount of plant material to supply the energy to keep a herbivore alive.
because of this herbivores spend most of the day eating, they are more numerous than carnivores and it takes more herbivores to keep the carnivore alive.
producers -> consumers.
plant -> caterpillar -> bird.
the plant is a producer. caterpillar is a first order consumer or primary consumer. and the bird is a second order consumer or secondary consumer.
food chains:
a simple food chain can show the interactions of organisms in an ecosystem.
a food chain illustrates what eats what.
the arrow means eaten by.
producer -> herbivore -> carnivore.
a food chain always begins with a producer.
why must a food chain always begin with a producer? because sun is the ultimate source of energy and supplies plants, in which herbivores eat, and need to eat a lot of this to remain alive. it need it for photosynthesis. plants can make their own food, anything after plants, is dependent on other animals.
each step in the food chain is called a trophic level.
food webs: food chains are useful for identifying direct relationships. however, in ecosystems, the relationships may not be so straightforward. you can get a more detailed picture of th einteractions in an ecosystem if the food chains are combined to form a food web. a food web is a series of food chains combined together.

Food pyramids:
pyramids of numbers.
show the number of organisms at each trophic level. the pyramid has a base much greater than its top. this shows the normal ecosystem with more producers than herbivores and more herbivores than carnivores. why are there usually more producers than consumers in an ecosystem? it is because there is a loss of energy at every trophic level. at each level only one tenth of the matter consumed is used to make body cells. the rest is used to keep warm, to move, and to power all the living processes (metabolism) in the animals. some of the materials passes through undigested.
this means that you need more plants to support a number of herbivores and more herbivores than carnivores (because energy is lost at every trophic level).
Food Pyramid:
top carnivore
carnivores
herbivores
autotrophs.
pyramid of biomass.
is the amount of organic/living matter in an organism. there are more plants than animals. the animals that eat plants (herbivores) are more abundant than the next level of consumers. the top consumers are usually the least abundant of any group in the ecosystem. in some circumstances, it is better to weigh the organisms instead of counting them. a gum tree obviously has more effect on the ecosystem than a tussock of grass.
in this case organisms are weighed to calculate the biomass (the biologically mass) to measure biomass the organism is usually dehydrated. this means that water is drained before weighing.
biomass in grass:
2g: teritary consumers.
10g: secondary consumers.
40g: consumers.
820g: producers.
Pyramid of biomass: from the diagram, it can be seen that it takes 820 g of a producer to support 40 g of first order consumer, 10 grams of secondary consumer which in turn supports 2g of teritary consumer. why does this happen?
if you think of a herbivore eating a plant it does not convert all of the matter contained in the plant into the herbivore. some of the material is indigestable and passes out of the animal as faeces. a lot of the material is consumed during respiration. this fuels the activities of the herbivore. only a small amount of biomass on one level becomes biomass on the next. much is lost through heat released during respiration. at each level there is a loss of up to 90 percent of biomass.
Pyramids of energy:
energy pyramids represent the flow of energy through the ecosystem. at each trophic level there is only 10 percent efficiency. that means that 90 percent of the energy is lost at each level. a plant uses 10 percent of the light energy available. when a herbivore consumes a plant there is only 10 percent of the energy stored in the plant tissue as sugar that is converted into energy in the herbivore and so on up the food chain. if humans were the top consumers and only ate plants, there would be energy loss in the food chain.
pyramid of energy (ks/m swuare year).

COMPETITION BETWEEN SPECIES:
populations will continue to expand until the numbers are limited by one of the resources they require. examples of resources that organisms need are:
water
food
shelter
nesting sites
mates
light
soil and weather.
COMPETITION:
where there is more than one species contending for the same limited resource, we say that the organisms are 'competing'.
usually one species has an advantage over the other and may limit the growth of that population.
on rock platforms in NSW there are 2 species of mollusc that feed on algae. one is the limpet cellena sp and the other melanerita sp melanertia moves faster than cellena if the algae are in short supply than melanerita has an advantage over the competitor. it can remove the algae form the rock before cellana.
Competitive exclusive principal:
proposes that 2 different species cannot coexist in the same place. if they are competing for the same limited resource.

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