Topic 5 - Energy Transfer in Ecosystems

Question 1

What is an ecosystem ?

Answer 1

all the living organisms in an area and all the non living conditions.

Question 2

What are producers ?

Answer 2

Organisms that make their own food, e.g. plants and algae produce their own food through photosynthesis.

Question 3

what is the function of photosynthesis in plants?

Answer 3

to release energy for growth and to make useful organic compounds.

Question 4

what is the biomass of a plant ?

Answer 4

the biological molecules in a plant it can be measures in terms of mass of carbon, or dry mass of tissue per given area.

Question 5

How is energy transferred through an ecosystem ?

Answer 5

when living organisms eat other organisms.

Question 6

what is dry mass ?

Answer 6

the mass of the organism with the water removed.

Question 7

how would you measure dry mass ?

Answer 7

• a sample of an organism is dried in an oven set to a low temperature.
• the mass is weighted at regular intervals until the weight is constant so you know that all water is removed.
• typical unit is km m^-2

Question 8

how can you estimate the amount of chemical energy in biomass ?

Answer 8

• in a calorimeter.
• a sample of dry biomass is burnt and the energy released is used to heat a known volume of water.
• the chnage in temperature of the water is used to calculate the chemical energy of the dry biomass.

Question 9

what is the calculation for efficiency of energy transfer ?

Answer 9

(energy out / energy in) x 100

Question 10

What is the calculation for net primary consumption ?

Answer 10

net primary production = gross primary production - respiratory loss.
NPP = GPP-R

Question 11

what is net primary production

Answer 11

the energy available to the plant for growth and reproduction

Question 12

what is the equation for net production of consumers

Answer 12

net production of consumers = chemical energy store - (energy loss by faeces/urine - respiratory loss).
N=I - (F +R )

Question 13

what is the function of decomposers

Answer 13

they breakdown dead or undigested material, allowing nutrients to be recycled.

Question 14

how do farmers reduce energy loss in plants

Answer 14

• simplifying food webs by eliminating organisms that compete with the organisms being farmed.
• weeds- compete with plants for resources (herbicides)
• insects - damage leaved, eat crops, cause disease (insecticides)

Question 15

how can farmers reduce respiratory loss

Answer 15

restricting movement - small pens
heating - indoors and heated

Question 16

what is a natural ecosystem

Answer 16

one that has not been chnaged by human activity.
Nutrients ar recycled through food webs, but human activity often disturbs the cycle of nutrients

Question 17

what are saprobionts

Answer 17

decomposer bacteria

Question 18

what do saprobionts do ?

Answer 18

feed on the remains of dead plabts and animals and on their waste producs, breaking them down. This allows for chemical elements in their remains to be recycled.

Question 19

How do saprobioints digest waste

Answer 19

Saprobiotic nutrition through Extracelular digestion - they secrete enxymes and digest food externally, then absorb the nutrients they need. Organic molecules are broken down into inorganic ions.

Question 20

what is mycorrhizae

Answer 20

• fungi forming a symbiotic relationship with the roots of plants.
• The fungi are made of long thin strands called hyphae which connects to the plants roots.
• The hyphae increase the surface area of the plants roots, helping the plant absorb ions from the soil (e.g. phosphorous).
• Hyphae also increases the uptake of water.
• In turn, the fungi obtain organic compounds such as glucose from the plant.

Question 21

what do plants and animals need nitrogen for

Answer 21

to make proteins and nucleic acid (DNA and RNA)

Question 22

why do plants and animals need bacteria to convert nitrogen gas to nitrogen containing compounds

Answer 22

They cannot use nitrogen in the form of gas

Question 23

what is the nitrogen cycle

Answer 23

the process of converting nitrogen to a usable form and then passing it between different living organisms and the non living environment

Question 24

what are the 4 processes in the nitrogen cycle

Answer 24

nitrogen fixing, ammonification, nitrification and denitrification

Question 25

Explain the process of nitrogen fixing

Answer 25

**reduction** * nitrogen gas in the atmosphere is turned into nitrogen containing compounds by combining nirogen with hydrogen. * They have ezymes called nitrogenase. * Biological nitrogen fixing is carried out by bacteria in the root nodules of legummes, which convert nitrogen into ammonia which forms ammonium ions in solutions that can be used by plants. * They form a mutualistic relationship with the plant as they provide the plant with nitrogen compounds and the plant provides them with carbohydrates.

Question 26

What happens during ammonification

Answer 26

Nitrogen compounds from dead organisms or animal waste are turned into ammonia by saprobionts which goes onto form ammonium ions.

Question 27

What is nitrification

Answer 27

**oxidation** * ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates). * Nitrifying bacteria chnage ammonium ions into nitrites. * Other nitrifying bacteria changed nitrites into nitrates.

Question 28

What is denitrification

Answer 28

**reduction** * nitrates in the soil are converted into nitogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas. * This makes soil less fertile. * This happens under anaerobic conditions where there is no oxygen, e.g. waterlogged soils.

Question 29

what is the phosphorous cycle

Answer 29

shows how phosporus is passed through an ecosystem

Question 30

What do plants and animals need phosporus for

Answer 30

to male biological molecules like phospholipids, DNA and RNA.

Question 31

What is the process of the phosphorus cycle

Answer 31

* Phosphate ions in rocks are released into the soil by weathering. * Phosphate ions are taken into the plants through the roots. Mycorrhizae increases the rate at which phosphorus can be assimilated (absorbed and used). * Phosphate ions are transferred through the food chains as animals eat the plants and in turn are eaten by other animals. * Phosphate ions are lost from the animals in waste products. * When plants and animals die, saprobionts are involved in breaking down the organic compounds, releasing phosphate ions into the soil for assimilation by plants. Microoganisms also release phosphate ions into soil by urine and facease. * Weathering of roks also releases phosphate ions into seas, lakes and rivers. This is taken up by aquatic producers such as algae and passed along in food chains to birds. * The waste produced by birds contains lots of phosphate ions into the soil and is used as a natural fertiliser.

Question 32

How are nutrients lost by harvestation

Answer 32

when crops are harvested, they're removed from the field, decreasing the mineral ions of the soil in the nitrogen or phosphorous cycle.

Question 33

What are artificial fertilisers

Answer 33

inorganic fertilisers - contain pure chemicals as powders or pellets

Question 34

what are natural fertilisers

Answer 34

organic matter - manure, composted vegetables, crop residues and sewage sludge.

Question 35

what do fertilisers do

Answer 35

replace the lost miners ions and nutrients from farming, so more energy can be used for growth, increasing efficiency of energy transfer.

Question 36

what eutrophication

Answer 36

* mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers. * Large amounds of algae block light from reaching plants. * Eventually the plants die as they cannot photosynthesise enought, * Saprobiots feed on the dead plant matter, increasing the number of bacteria and reucing the oxygen concentration available in the water due to aerobic respiration. * Fish and other aquatic organisms die because there is not enough dissolved oxygen.

Question 37

give an example of saprobiotic feeders

Answer 37

fungus

Question 38

why is farming cattle for eating less efficent than farming crops due to energy transfer

Answer 38

* energy lost via respiration/excretion * energy lost between feeding levels