Energy In Ecosystems

Question 1

Define Producer

Answer 1

an organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water

Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions

Question 2

Define consumer

Answer 2

Obtains energy by feeding on other organisms

Question 3

Define saprobionts

Answer 3

(Decomposers)
Break down complex material in dead organisms into simple ones.
This releases valuable minerals and elements in a form that can be absorbed by plants- contributed to recycling

Question 4

Define food chain

Answer 4

Feeding relationship made up of tropic levels

Question 5

Define food web

Answer 5

In a single habitat food chains will be linked to form food webs

Question 6

Define biomass

Answer 6

Total mass of living material in a specific area, in a given time
Measures using dry mass per given area in a given time (gm-2) or volume (gm-3)

Question 7

Explain why most food chains have no more than 4/5 tropic levels

Answer 7

Energy loss from one tropic level to next becomes very large after several stages

Question 8

Define GPP

Answer 8

Gross primary production is the total quantity of the chemical energy store in plant biomass
Includes organic material used in respiration and stored as new plant tissue

Question 9

Equation with NPP GPP R

Answer 9

NPP= GPP-R

Net primary productivity = gross primary productivity - respiratory losses

Question 10

What is NPP

Answer 10

Net primary productivity is the energy available for plant growth and reproduction
NPP values are used to compare the productivity of different ecosystems

Question 11

In a food chain the low % of energy transfer is due to:

Answer 11

Some of the organism isn’t consumed
Some parts can’t be digested so when consumed=faeces
Loss due to excretory materials eg urine
Loss due to heat loss from respiration

Question 12

Most of the suns energy is not converted to organic matter by photosynthesis because:

Answer 12

Most of suns energy is reflected back into space
Not all wavelength of light can be absorbed
Light might not fall on a chlorophyll molecule
Low CO2 may limit rate of photosynthesis

Question 13

Net production of consumers equation

Answer 13

N = I - (F+R)

Net production= chemical energy store of ingested food - (energy lost respiring +energy lost in faeces and urine)

Question 14

Percentage efficiency equation

Answer 14

Energy available after transfer/energy available before transfer x 100

Question 15

Keeping animals in confined spaces increases energy conversion rate because:

Answer 15

Movement is restricted so less energy used in muscle contraction
Environment kept warm so reduced heat loss
Feeding controlled so animals receive optimum amount and type of food for max growth and no wastage
Predators excluded so no loss to other organisms in food web

Question 16

The inefficiency of energy transfer between trophic levels means that:

Answer 16

Most food chains only have 4/5 trophic levels
The total mass of organisms in a particular place is less at higher trophic levels
Total amount of energy available decreases moving up the food chain

Question 17

Why would keeping animals in the dark for longer periods improve the energy conversion rate

Answer 17

More time spent resting, less energy is expended and more energy is converted into body mass

Question 18

Pest control aim

Answer 18

Balance cost of pest control with the benefits it brings

Simplify the food web and so limit effect of pests on productivity to a commercially acceptable level

Question 19

Pesticides are used to increase productivity. Suggest how their use might sometimes reduce productivity

Answer 19

Pesticide might kill beneficial organism (eg ones that prey on organisms that are harmful to the farmed organism)

If the pesticide kills most of the pests then the population of organisms (predators) feeding on it will fall. With no predators controlling it, pest pop increases possibly to higher level

The crop will be even more affected by pest so decreases productivity