Component 1.5 - Energy And Ecosystems

Question 1

What is an ecosystem?

Answer 1

A characteristic community of interdependent species interacting with the abiotic components of their habitat

Question 2

Where does the energy come from to support ecosystems?

Answer 2

• Mainly from the sun incorporated by photosynthesis

- Chemical reactions incorporated in chemosynthesis e.g in hydrothermal vents

Question 3

What is a meant by a community?

Answer 3

Interacting populations of two or more species in the same habitat at the time

Question 4

What is a trophic level?

Answer 4

Feeding level - the number of times that energy has been transferred between the sun and successive organisms along a food chain

Question 5

What are saprobiants?

Answer 5

A micro-organism that obtains its food from the dead or decaying remains of other organisms

Question 6

What are decomposers and detrivores?

Answer 6

Detrivores- organisms which feed on small fragments of organic debris (detritus) e.g fallen leaves and remains of dead organisms

Decomposers - microbes such as bacteria that obtain nutrients from dead organisms and animal waste (complete process of decomposition started by detrivores)

Question 7

Why is a food chain limited to 4 or 5 trophic levels?

Answer 7

After 4 or 5 trophic levels, there is not enough energy energy to support another one

Question 8

Why are tropical food chains usually longer than arctic ones?

Answer 8

In tropical environments more energy is fixed in photosynthesis, so more energy can be passed on to the next trophic level.

Question 9

What is the formula for photosynthetic efficiency?

Answer 9

PE = Quantity of light energy incorporated into product/Quantity of energy falling on the plant x100

Question 10

Why may the light that falls on the plant not be absorbed?

Answer 10

1) Wrong wavelength
2) Reflected
3) Transmitted straight through the leaf

Question 11

What is Gross Primary Productivity and Production?

Answer 11

The rate of production of chemical energy in organic chemicals by photosynthesis measured in kJ m^-2 y^-1

Gross primary production which is the total energy incorporated in photosynthesis is 0.2% of global sunlight energy

Question 12

What is net primary productivity and production?

Answer 12

The rate at which energy is incorporated into a plants biomass and made available to heterotrophs measured in kJ m^-2 y^-1

Net primary production which is the total chemical energy made available to heterotrophs is 0.1% of global sunlight energy

Question 13

How do you work out Net primary production from Gross primary production?

Answer 13

GPP - respiration = NPP

Question 14

Why do crop plants have a higher GPP and NPP?

Answer 14

Because they have been selectively bred for high productivity (PE)

Question 15

What is Primary productivity?

Answer 15

The rate at which energy is converted by producers to biomass

Question 16

What is secondary productivity?

Answer 16

The rate at which consumers convert the chemical energy of their food into biomass

Question 17

How is energy lost from the food chain?

Answer 17

1) Excretion or egestion
2) Respiration and muscle contraction (heat)
3) Energy remains in molecules in parts of animal that have not been eaten e.g fur and bones

Question 18

What are limitations of the pyramid of number?

Answer 18

• It does not take into account size of organisms
• Does not recognise the difference between juvenile and adult forms
• May be difficult to draw to scale
• Pyramid may be inverted

Question 19

What are the limitations of the pyramids of biomass?

Answer 19

• Difficult to accurately measure (e.g plants roots)
• May be inverted
• May seem to contribute more to the next trophic level e.g bones and beaks

Question 20

What is a pyramid of energy?

Answer 20

• As energy is passed from one level to the next, some is lost and the bars decrease in size - never inverted

Question 21

Why is a pyramid of energy the most accurate way of representing feeding relationships?

Answer 21

• Make it easy to compare efficiency of energy transfer between trophic levels in different communities
• Shows energy transferred from one level to the next, per unit area of volume, per unit time.

Question 22

Define habitat

Answer 22

The place in which an organism lives

Question 23

Why are farm animals often kept in smaller spaces?

Answer 23

1) Factory farms more efficient as less energy is lost
2) Reduces energy losses via respiration by controlling the temperature as less energy needed to maintain body temperature
3) Animals are stocked at high densities which restricts movement so reduces energy loss via respiration for muscle contraction
4) Herbivores are lower down the food chain than carnivores so less energy is lost via respiration or being expelled