4.7

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

Causes of the losses

ü  100 kJ of grass energy eaten by the mouse, but only 10 kJ is to become part of the mouse because the mice use the energy for respiration.

ü  Not all 100 kJ is available to the mouse to start with. Mice cannot digest cellulose so plant cell wall cannot be digested. The energy is lost as faeces, undigested material.

4.6

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

ü  Chemical energy takes the form of organic molecules: Carbohydrates, Proteins & Lipids.

ü  The same CHON molecules are food for all animals in the food chain.

ü  C – C, C – O, C – H, O – H, C – N all represent energy (in the bonds) used for growth and respiration.

ü  CHON are the substances / matter.

4.5

4.5 Understand the concepts of food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer

Food Chain

ü  Food chain links the producer to the primary consumer and so on.

ü  One organism is shown at each trophic level.

ü  In a food chain, you cannot show an omnivore or feeding at more than 2 trophic levels.

ü  Food chains show the flow of matter and energy.

Food Web

1) Organisms can have multiple predators

2) Organisms may feed on multiple preys.

3) They are linked.

4.4

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

Trophic: feed

Photosynthesis (Producer: turns light energy into chemical energy) à Herbivore (Primary consumer: chemical energy of plant into chemical energy of the fly) à Carnivore (Secondary consumer: chemical energy from one form to another)à Top Carnivore (Tertiary consumer: chemical energy from one form to another)

At some stage, they die. They are broken down by decomposers (fungi & bacteria). They break down complex molecules into nitrates and phosphates.

4.3

4.3 Describe the use of quadrates as a technique for sampling the distribution of organisms in their habitats

Sand Dune to sample the population of daisies in the area

Sample needs to be random, no bias introduced. Sample needs to be representative. It has to be large enough that the estimate is as close to the true population as possible.

From a bird’s eye view, you set up a grid system with equal sizes.

Random numbers are generated for the x and the y coordinates. For example, (1, 1)

Count the number of daisies in the shaded square.

We need a representative sample: the bigger the better. 10 quadrates or the 10% of the actual area

Quadrate	Number of Daisies per m2
1	4
2	6
3	2

Add up the right column and divided by the number of quadrates: Average number of daisies per m²

You can use this to compare the difference in number of daisies between quadrates.

4.2

4.2 Recall the use of quadrats to estimate the population size of an organism in two different areas

Sand Dune Ecosystem made of population that forms the community and the habitat

Area divided into two: Grazed by cattle, Ungrazed areas

1)     Count the number of individuals in the population

2)     Technique used: Quadratting

Quadrates: Method of sampling different locations within an ecosystem, to compare respective population sizes. Quadrate squares are made out of wood / string / metal into grid e.g. (0.5 m x 0.5 m OR 1 m x 1 m)

The quadrate is used to sample the area. Count the number of individuals. This will be repeated a number of times to get an estimate of the population size.

4.1

4.1 Understand the terms: population, community, habitat and ecosystem

Ecosystem (e.g. forest with waterfall and life etc): Community of Organisms & Habitat

Community of Organisms: Made up of population of different species interacting

- Population: Number of individuals of a particular species

- Species: Organisms that reproduce fertile offspring

- Interaction: A common example would be feeding

Habitat: Includes all the abiotic factors – non-biological factors e.g. cycle of daylight and dark, temperature, photo period, rainfall, humidity, slope of the land, geology