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Ecology Y8

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Alex Van Dijk

on 24 September 2014

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Transcript of Ecology Y8

Pyramids of number show the number of individuals in a population for a particular species in a food chain.
Example 1:
Oak tree -> Insect -> Woodpecker
Example 2
Clover -> Snail -> Thrush -> Sparrowhawk
Energy moves from producers to primary consumers and then from primary consumers to secondary consumers.
We say that the energy moves up trophic levels.
The biomass of a population is the dry mass (without water) of the population (in kg or tonnes).
A pyramid of biomass shows the biomass at each trophic level.
Pyramids of biomass always go from wide to narrow. Why?
Food chains are not an accurate representation of a community in a particular habitat.
There will be many food chains occurring in a habitat. A food web shows them all.
Name a producer, a primary consumer, secondary consumer and a tertiary consumer in this food web.
Name animals that compete for the same food.
A habitat will contain many interactions between animals.
Some will be predator-prey interactions.
Some will be competitors.
Some animals will have a mutualistic relationship.
Predator Prey
Energy is used at each trophic level because:
Not everything that is eaten is fully absorbed, some is excreted.
Energy is used for movement, respiration, reproduction and maintaining body temperature (in warm-blooded animals)
Some parts of an organism will not be eaten (bones, shells etc.)
Key terms
Flow of energy in ecosystems
A producer is an organism that produces its own food.
Plants are producers because they photosynthesise.
Consumers are organisms that rely on other organisms for their food.
All animals and fungi are consumers.
An animal that eats only plants is known as a herbivore. They are also a primary consumer.
An animal that only eats other animals is known as a carnivore. They cannot be a primary consumer, but can be secondary or tertiary consumer depending on which animals they eat.
An animal that eats both plants and animals is known as an omnivore. They can be primary or higher consumers.
Food chains
A food chain can be used to represent the feeding relationships in an ecosystem.
It shows the flow of energy from organism to the next, starting with a producer.
Organisms that only eat dead material are known as decomposers.
Predator-prey relationships
The number of organisms of a particular species in a particular ecosystem is known as its population.
The population of a predator and its prey are tightly linked.

Why is this the case?
Explain the pattern in this graph.
Answer the following questions:
When is the hare population at its highest?
What happens to the lynx population after this peak?
What other reasons, aside from predator-prey interactions, might there be to explain the fluctuation in numbers seen on the graph?
Our work on pyramids of biomass allows us to explain a particular observation.
Often the top predator is the species that is worst affected by the presence of toxins in an ecosystem.
A common example is the drop in birds of prey as a result of the use of an insecticide known as DDT.
In areas where DDT was used these birds of prey were far less able to produce viable offspring as their egg shells were too thin.
DDT is a persistent chemical. Persistent means that it does not get cleared out of the body and that it stays there.
A bird of prey such as a an osprey eats many large fish, who eat many small fish, who eat a lot of zooplankton which absorbed DDT in its water from run off from a field.
As you move up the food chain the concentration of the DDT in the organisms increases.
This process is known as biomagnification.
Research what happened in Minamata, Japan in the 1950s, when mercury built up in the food chain.
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