13 Energy and Ecosystems

Question 1

What do we call the level at which an organism feeds?

Answer 1

The Trophic Level

Question 2

What does a food chain show?

Answer 2

How energy is transferred from one living organism to another.

Question 3

Why is energy not recycled?

Answer 3

It flows through an ecosystem.

Question 4

What happens at each trophic level in a food chain?

Answer 4

some energy is lost, and therefore unavailable to the organism at the next energy level. Some energy remains stored in dead organisms and waste material, which is then only available to decomposers.

Question 5

What are the advantages of drawing a pyramid of biomass?

Answer 5

Counting the number of organisms does not always provide an accurate picture about how much living tissue exists at each level. A better approach is to draw a pyramid of biomass, where the area of bars proportional to the dry mass of all the organisms at that trophic level.

Question 6

What is another word for a decomposer?

Answer 6

Saprobionts

Question 7

Define biomass

Answer 7

The total mass of living material in a specific area at a given time.

Question 8

What is net primary production and what is its equation?

Answer 8

Primary production= Plants
NPP= Gross primary production (total) - R (Respiratory losses)
The chemical energy store left over after respiratory losses.

Question 9

What is the secondary net production and its equation?

Answer 9

N= I - (F+R)
N represents the net production
I represents the chemical energy store of ingested food
F represents the energy lost in faeces and urine
R represents energy lost in respiration

Question 10

State three reasons for the small percentage of energy transferred at each trophic level.

Answer 10

1. Most food chains have only four or five trophic levels because insufficient energy is available to support a large enough breeding population at trophic levels higher than these.
2. The total mass of an organism in a particular place (biomass) is less at higher trophic levels.
3. The total amount of energy available is less at each level as one moves up a food chain.

Question 11

What is the formula for calculating the efficiency of energy transfers?

Answer 11

percentage effieciency= energy available after the transfer DIVIDED BY energy avilable before the transfer X 100

Question 12

Describe the one simple sequence at the heart of all nutrient cycles

Answer 12

1. The nutrient is taken up by producers (plants) as simple inorganic molecules.
2. The producer incorporates the nutrient into complex organic molecules.
3. When the producer is eaten, the nutrient passes into consumers.
4. It then passes along the food chain when these animals are eaten by other consumers.
5. When the producers and consumers die, their complex molecules are broken down by saprobiontic microorganisms that release the nutrient in its original simple form.