4.7

• A pyramid of energy is used
• Reasons for loss of energy:
- respiration
- excretion (energy which has not been able to be digested)
- heat loss
• Since the mouse can only use 10% of the energy from the producer, this would suggest that the owl can only use 1% of the energy it gets from eating the mouse
• When the organisms eventually die, when they will be broken down by micro organisms, which are called decomposers

4.6 : Energy and substances in food chains

producer = Bush grass
primary consumer = Impala
secondary consumer = Leopard
tertiary consumer = Lion

• producer converts light energy into chemical energy
• CE takes the form of different organic molecules such as:
- carbohydrates
- proteins
- lipids

These molecules (called food) consist of
C-H
C-O
C-C
O-H
C-N
bonds
• These bonds represent energy and carbon, hydrogen, oxygen and nitrogen are the matter(substances)

• The substance (the energy in the bonds) is passed down at each stage in the food chain

4.5a: Food chain & 4.5b: Food webs

• Producer -> Primary Consumer -> Secondary Consumer -> Tertiary Consumer

• Only one organism per trophic level
• In a food chain you cannot show an animal as an omnivore (eating at more than one level)
• food chains show the flow of matter and energy

• provides us with a better description of the ecosystem (in this case, feeding)
• Can show feeding at different trophic levels. This can have consequences:
- multiple predators
- feeding on multiple prey
-results in food chains being linked

4.4 Trophic levels

• Trophic = feed


For example: 
A carrot plant (producer) is doing photosynthesis, turning light energy into chemical energy


The carrot fly (a herbivore) is eating the carrot plant, which is called a primary consumer. It takes in the CE of the plant and turn it into CE of the fly


The fly catcher eats the carrot fly (a carnivore), a secondary consumer. It changes the CE once again from one form to another


The sparrow-hawk (top carnivore) eats the fly catcher, a tertiary consumer. It changes the CE again to suit itself


• All these die at some point, where decomposers break the molecules into nitrates and phosphates
• examples of decomposers: fungi, bacteria

4.3: Quadrates samples

Describe the use of quadrats as a technique for sampling the distribution of organisms in their habitat



• The quadrat sample that you take has to be random so there is no bias, and has to be representative (large enough) so that the estimate is as close to the true population as possible
• A grid system would be set up across the field. There would be an x and y axis, as well as numbers running across the sides of the graph
• Then random numbers would be generated for the x and y coordinate so we know where we want to place our quadrat
• Then we would count the number of whatever species we are counting.
• Your representative sample would be ideally around 10 quadrats or 10% of the whole area.
• The number of that species would be recorded into a table, then


   total of species        = number of species/m²
number of quadrats 

4.2: quadrates

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



• The sand dune ecosystem: it is made up of a number of different species of population which form the community of the ecosystem (and the habitat).
• There is a fence that splits the area in two: an ungrazed area and a grazed area (grazed by cattle and agriculture).
• quadrating: counting the size of a population.
• The quadrat is a square (0.5mx0.5m) and used to sample different areas of the land, and gain an estimate of the populations size.
• This way populations between two different areas can be compared.

4.1: Ecosystems

Understand the terms: population, community and ecosystem.




Ecosystem
An ecosystem is a community of organisms in a certain habitat

Habitat
(abiotic factors)
eg sunlight, temperature, rainfall, humidity, slope of the land, geology
note they are all non-biological

Community of organisms
made up of a population of varying species which interact with each other

Population
Number of individuals of a specific species

Species
Organisms that reproduce and make offspring