Sunday, 22 May 2011

4.7 Energy efficiency

Explain why only about 10% of energy is transferred from one trophic level to the next

Pyramid of Energy

(Measured in Kj)
As you can see 100% producer, only 10% makes it into the primary consumer and only 1% of the 100% makes it into the secondary consumers.
This is because energy will be lost from respiration, not all of the 100% is actually available to the  primary consumer, for example a mice cannot digest cellulose from plants which contains energy, and it will be lost in the form of faeces.

4.6 Energy and substances in food chains

Understand the transfer of substances and of energy along a food chain

Energy and substances transfer along the food chain from producer to the tertiary consumer.
Organic Molecules - Carbohydrates, Proteins, Lipids
Consist of
CHON are all substances which we call matter

4.5 Food Chains and Food Webs

Understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer.
Food chain links together the Producer to the Primary Consumer to the Secondary Consumer and then to the Tertiary Consumer.
  • One organism per trophic level.
  • In a food chain you cannot show an animal being an omnivore (eating plants and meat) or having 2 or more trophic levels.
  • It shows the flow of matter and flow of energy.
Allows us to provide a better description of the ecosystem
Ecosystem is composed of community of organisms which are interactive in this case the interaction the food web describes is feeding
It shows organisms feeding at different trophic levels.
Organisms can have multiple predators, multiple prey results in food chain becoming linked.
Example of a food Web:
(P=Producer, 1=Primary Consumers, 2=Secondary Consumers, 3=Tertiary Consumers)

4.4 Trophic Levels

Recall the names given to different trophic levels to include producers, primary, secondary and tertiary consumers and decomposers

Trophic = Feed
Photosynthesis (Light energy to Chemical Energy)=> Herbivores => Carnivore => Top Carnivore
{Producer => Primary Consumers => Secondary Consumers => Tertiary consumers }=> Decomposers
These are all broken down to nitrates and phosphates by the decomposers


4.3 Quadrates Samples

Describe the use of quadrates as a technique for sampling the distribution of organisms in their habitats
We can sample the population in an area using Quadrates Sampling. Sample has to be random (so no bias introduce), and has to be representative, so we have to take a sample large enough that the estimate of the population is closer the the true population of the area.
How to make a quadrate sample?
1.Set up a grid across the area you want to sample
2.Select random numbers that gives the x,y coordinate to know where to place your quadrates
3.Calculate the area of your quadrate and then count the number of organisms in it
We need a representative sample - the bigger the better, we should be looking at 10 quadrates/ 10% of the actual area
Recording Data:
Then, make a table with Quadrate and Number of Organism
Add up the organism/the Number of Quadrates = Number of Orgaisms per meter^2

We can use this data to compare the number of populations between two different areas.

Tuesday, 10 May 2011

4.2 Quadrates

4.2 Recall the uses of quadrats to estimate the population size of an organism in two different area.
Quadrating is a method of sampling in locations to find out the population at a location and to compare to the population at different locations. Quadrats are based on squares that can be made of any material such as wood, metal, strings etc. Quadrats are used to count the population in a particular area, and is used to sample the area and the number of individuals in an area. This method would be repeated several times for an approximate estimate of the population size.
Picture of a person using Quadrats to sample:

4.1 Ecosystems