6.6 - Ecosystems

Question 1

Define Habitat

Answer 1

The place where an organism lives

Question 2

Define population

Answer 2

All the organisms of 1 species in a habitat

Question 3

Define Producer

Answer 3

An organism that produces organic molecules using sunlight energy

Question 4

Define Consumer

Answer 4

An organism that eats other organisms

Question 5

Define decomposer

Answer 5

An organism that breaks down dead or undigested organic material.

Question 6

Define Trophic level

Answer 6

A stage in the food chain occupied by a particular group of organisms.

Question 7

What is a biotic factor?

Answer 7

The living features of an ecosystem (Predators or food)

Question 8

What is an abiotic factor?

Answer 8

Non - living features of an ecosystem (Temperature, rainfall, topology and soil nutrient availability)

Question 9

What is Net productivity?

Answer 9

The amount of energy that available to the next tropic level.

Question 10

What is the net productivity equation?

Answer 10

Net productivity =
Gross productivity - respiratory loss

Question 11

What is the Energy Efficiency equation?

Answer 11

(Energy transferred / Energy intake) x 100

Question 12

How do we measure energy change through tropic levels?

Answer 12

Calculate the energy difference between each level.
This energy can be calculated by working out the biomass of the organism.

Question 13

How can humans increase the transfer of energy?

Answer 13

1. Herbicides to kill weeds which compete with crops.
2. Fungicides so crops use more energy for growth, not fighting infection.
3. Insecticides or natural predators so less biomass is lost from pests eating crops.
4. Intensive livestock rearing:
   - Animals kept in warm indoor pens, with restricted movement, so less energy is wasted keeping warm and moving.
   - Animals given feed which is higher in energy, so more energy for growth.

Question 14

What is nitrogen fixation, and what are the reactions and bacteria required?

Answer 14

Where Nitrogen gas is converted to Ammonia
Rhizobium - found in mutualistic plants
Azotobacter - found in living soil

Question 15

What is Ammonification?

Answer 15

Nitrogen in dead organisms are turned into ammonia by decomposers.

Question 16

What is Nitrification?

Answer 16

Ammonium ions in soil are changed into nitrites and nitrates.
Ammonia -> nitrites - Nitrosomonas
Nitrites -> Nitrates - Nitrobacter

Question 17

What is denitrification?

Answer 17

Nitrates in soil are converted into nitrogen gas by denitrifying bacteria
Only done in anaerobic conditions.

Question 18

What is primary succession?

Answer 18

Happens on land which has been newly formed or exposed. There is no soil or organic matter.

Question 19

What is secondary succession?

Answer 19

Happens on land that has been cleared of all the plants, but soil still remains.

Question 20

How does primary succession occur?

Answer 20

1. Abiotic conditions are very harsh, so only pioneer species grow, and these change the abiotic conditions, and eventually die and decompose
2. This makes conditions less hostile and other organisms grow. This process repeats until soil is more fertile and multiple habitats form.

Question 21

How can succession be prevented or Deflected?

Answer 21

Human activities can prevent succession. When it’s stopped artificially the climax community is called the phlagioclimax.

When succession is deflected the climax community is one that’s different to any natural stages of the ecosystem.