Energy and Ecosystems

Question 1

Ecosystem definition

Answer 1

The community and non-living components of its environment

Question 2

How is light energy stored?

Answer 2

Within the bonds of organic molecules

Question 3

What are organic compounds produced by photosynthesis used for?

Answer 3

Respiration and biomass

Question 4

What are 3 examples of organic molecules formed and what are they used for?

Answer 4

1. Amino acids: enzymes for photosynthesis/respiration
2. Phospholipids: phospholipid bilayers
3. Glucose: respiration/storage

Question 5

Biomass definition

Answer 5

The mass of organic molecules

Question 6

What can biomass be represented as?

Answer 6

1. Dry biomass
2. Mass of carbon

Question 7

Why is fresh biomass not used?

Answer 7

The amount of water can vary

Question 8

How do you measure the dry biomass of grass?

Answer 8

1. Heat the grass in an oven to evaporate water
2. Weigh the mass of grass
3. Reheat and reweigh
4. Repeat until a constant mass is reached to ensure all water has been removed

Question 9

What are the units of biomass?

Answer 9

kg m-2 year-1

Question 10

What is the equation for energy released from biomass?

Answer 10

Energy released = volume of water (cm3) x temperature increase x specific heat capacity of water

Question 11

What are the inaccuracies with calorimetry?

Answer 11

1. Heat lost to the surroundings
2. Heat can escape from the water due to the calorimeter not being insulated

Question 12

What are the 3 ways an enclosed calorimeter allows you to accurately measure energy released?

Answer 12

1. Insulated, preventing loss of heat by conduction
2. Stirrer ensures heat is evenly distributed
3. Water has a high specific heat capacity

Question 13

Why can’t food webs exceed a high number of trophic levels?

Answer 13

Energy lost at each trophic level so there isn’t enough energy to sustain a population

Question 14

GPP definition

Answer 14

Chemical energy store in plant biomass in a given area in a given time

Question 15

What does GPP directly relate to?

Answer 15

Rate of photosynthesis

Question 16

Why is a low amount of energy converted to biomass in PLANTS?

Answer 16

1. Some light is reflected off the leaf
2. Some light misses the chlorophyll
3. Some light is the wrong wavelength for photosynthesis

Question 17

NPP definition

Answer 17

Chemical energy store in plant biomass AFTER respiratory losses

Question 18

NPP equation

Answer 18

NPP = GPP - R

Question 19

What are the units of NPP?

Answer 19

kJ m-2 year-1

Question 20

How can energy be lost between trophic levels?

Answer 20

1. Excretion
2. Egestion
3. Heat energy lost due to respiration

Question 21

Why is less energy transferred between producer and primary consumer than primary and secondary consumer?

Answer 21

Producers contain lots of cellulose which is difficult to digest so less energy is absorbed and more energy is lost through egestion

Question 22

N definition

Answer 22

Chemical energy stored as biomass in a consumer which is available to the next trophic level

Question 23

N equation

Answer 23

N = I - (F + R)

Question 24

What 3 strategies are used to increase productivity in livestock?

Answer 24

1. Movement is restricted so less respiration occurs for muscle contraction
2. Animals kept indoors or in heated rooms so less respiration occurs to generate heat to maintain body temperature
3. Animals fed a high calorie diet designed for maximum absorption and minimum faeces production

Question 25

How can food webs be simplified to increase the proportion of energy transferred to humans?

Answer 25

1. Chemical pesticides
2. Biological control