5 Energy transfers- Energy & Ecosystems

Question 1

Why are plants central to all ecosystems?

Answer 1

They produce biomass through photosynthesis

Question 2

What are producers?

Answer 2

Green plants that use light energy to produce organic molecules (like carbs)

Question 3

In what ways are organic molecules produced by plants used?

Answer 3

-As respiratory substances
-To make other biological molecules (eg carbs, proteins,lipids) These form new biomass

Question 4

What is biomass?

Answer 4

The chemical energy store for an organism

Question 5

What is the role of biomass in a food chain?

Answer 5

Can be passed along food chain to different tropic levels

Question 6

What do food chains show?

Answer 6

How energy flows within a biological community

Question 7

What is the role of producers and consumers in food chains?

Answer 7

-Producers (plants, algae) make biomass and are at the base of all food chains

-Consumers rely on producers as their energy source , when they eat plants + algae, chemical energy stored in biomass is transferred

Question 8

How can you measure biomass?

Answer 8

-Dry mass of tissue per unit of area/mass of carbon in an organism
-Calorimeters

Question 9

What is the dry mass of tissue per unit area and how can this be obtained?

Answer 9

-Mass of an organism after its water has been removed
-To remove the water, the organism is dried in an oven for several days
-Dry mass of a sample can be used to estimate the total dry mass of a population or a given area

Question 10

How is dry mass usually measured?

Answer 10

Grams/kilograms per meter (gm-², kg m-²)

Question 11

What is the mass of carbon of an organism, how does it differ from dry mass?

Answer 11

-Measure of mass of carbon an organism has
-Water content not taken into account
-Usually about half dry mass amount

Question 12

What does calorimetry do?

Answer 12

-Energy contained within dry biomass can be measured using a calorimeter
-This burns biomass, calculates chemical energy released per gram (by measuring change in temp of know volume of water as a result of sample being burnt)

Question 13

What is gross primary production (GPP)?

Answer 13

The chemical energy stored in plant biomass, in given area/volume

Question 14

What is respiratory loss (R)?

Answer 14

During respiration nearly half of GPP is lost as heat

Question 15

What is net primary production (NPP) and how is it calculated?

Answer 15

The chemical energy stored in biomass after respiratory losses (R) to the environment have been taken into account
NPP= GPP-R

Question 16

What is secondary/consumer production?

Answer 16

The production of new biomass by consumer

Question 17

Why can consumers not convert all the energy available from the previous trophic level into new biomass?

Answer 17

Energy is lost, primarily to-
Respiration
Excretion (faeces, urine)

Question 18

How is net consumer production calculated and what do the letters in the equation represent?

Answer 18

N= I - (F + R)
N= net production of new biomass by consumers
I= chemical energy stored in ingested food
F= chemical energy lost to environment in faeces + urine
R= chemical energy used in respiration

Question 19

What is productivity?

Answer 19

The rate of production of new biomass

Question 20

What is primary productivity?

Answer 20

The rate of primary production of green plants

Question 21

What is secondary productivity?

Answer 21

The rate of secondary production by consumers (herbivores, with a lower secondary production than carnivores as they eat plant material high in cellulose, which is hard to digest so more energy is lost in excretion)

Question 22

How is productivity measured?

Answer 22

Biomass in a given area in a given time
Example of unit= kJ ha-^1 year-^1

Question 23

How do farming practices attempt to maximise primary productivity?

Answer 23

Increasing efficiency of energy transfer, by:
Simplifying food webs;
Reducing respiratory losses

Question 24

How can limiting factors be overcome to maximise primary productivity?

Answer 24

-Maximising plant exposure to light
-Using warmer temp in greenhouses
-Irrigation to maximise water supply

Question 25

How do fertilisers maximise primary productivity?

Answer 25

-Can be sprayed on fields to maintain nutrient levels in soil, which help plants convert energy to biomass efficiently

Question 26

How do pesticides maximise primary productivity?

Answer 26

-Remove any pests that might spoil crop & cause loss of biomass
-Herbicides kill weeds, reduce competition for resources like sunlight/soil nutrients
-Fungicides prevent fungal diseases

Question 27

What methods of reducing energy loss to maximise secondary productivity are used?

Answer 27

Limiting movements of animals- reduce respiration
Using heating in barns
Antibiotics- prevent energy lost to pathogens

Question 28

How does increasing growth rate maximise secondary productivity?

Answer 28

Helps maximise rate of production of biomass, eg-
-Selective breeding to make breeds w/ higher growth rates
-Steroids to increase growth rates & accumulation of biomass
-Harvest when young; most of animals’s energy is used for growth when young so accumulation of biomass is maximised