B13. Energy and Ecosystems (FINSIHED)

Question 1

What are producers?

Answer 1

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

Question 2

What are consumers?

Answer 2

Organisms that obtain their energy by consuming other organisms rather than energy of sunlight directly

Question 3

What are the types of consumers and what do they indicate?

Answer 3

Primary consumers, first in chain of consumers, feed off producers; Secondary consumers, consume primary consumers; tertiary consumers - consume secondary consumers, top of the chain

Question 4

What are saprobionts?

Answer 4

Decomposers, group of organisms that break down the complex material in dead organisms into simple ones.

Question 5

What is a food chain?

Answer 5

Describes a feeding relationship in which organisms are consumed in this order; Producers > primary consumers > secondary consumers > tertiary consumers

Question 6

What is a torphic level?

Answer 6

Stage of the food chain eg. producer, primary consume

Question 7

How is direction of energy flow represented in a food chain?

Answer 7

Arrow shows directional energy flow

Question 8

What are food webs and why are they produced?

Answer 8

Food chains will be linked together forming a food web due to animals not relying on a single food source within a single habitat

Question 9

What is biomass?

Answer 9

Total mass of living material in a specific area at a given time

Question 10

What procedure is necessary to produce reliable biomass results and why?

Answer 10

Biomass is measured using dry mass per given area due to presence of varying amounts of water

Question 11

How is energy of biomass estimated?

Answer 11

Calorimetry; Bomb calorimetry, sample of dry material is weighed and is then burnt in pure oxygen within a bomb; Bomb surrounded by water bath and the heat of combustion causes a temp rise in water

Question 12

What is the source of energy for ecosystems?

Answer 12

The Sun

Question 13

How efficient is energy absorption of the Sun’s energy?

Answer 13

1% - 3%;

Question 14

What happens to the majority of the Sun’s energy?

Answer 14

Over 90% is reflected back by clouds and dust or absorbed by atmosphere; Not all wavelengths of light can be absorbed by photosynthesis; Limiting factors ie. low CO2 levels limit photosynthesis

Question 15

What is gross primary production?

Answer 15

Total quantity of chemical energy stored in plant biomass in a given area or volume

Question 16

What is net primary productivity?

Answer 16

Energy store from gross primary production left after factoring plants 20% - 50% net losses to respiration

Question 17

What’s the equation for net primary production?

Answer 17

Net primary production = Gross primary production - respiratory losses

Question 18

Why is less energy available in the upper trophic levels?

Answer 18

Some organisms aren’t consumed; Some parts are consumed but cannot be digested and are lost in faeces; Some of the energy is lost in excretory materials; Some energy lost as heat from respiration

Question 19

Why is less energy available in mammals and birds?

Answer 19

High energy use due to high body temperature; More energy needed to maintain their body temperature when heat is constantly being lost to the environment

Question 20

What is the equation for net production of consumers?

Answer 20

Net production = Chemical energy store of ingested food - ( Energy lost in faeces and urine + Energy lost in respiration)

Question 21

What observations can be made while climbing the trophic levels?

Answer 21

Only 4 - 5 trophic levels due to insufficient energy to support; Total biomass decreases; Total amount of energy available decreases

Question 22

How is energy conserved of livestock in farming?

Answer 22

Movement restricted, less energy used in muscle contractions; Environment kept warmer, less heat loss; Feeding controlled to optimum amount; Predators are excluded

Question 23

How does energy flow in an ecosystem and is this a problem?

Answer 23

Energy enters ecosystem as sunlight is lost as heat; Heat cannot be recycled; Linear unidirectional flow; Not a problem as the Sun supplies the energy

Question 24

What is the simple sequence all nutrient cycles follow?

Answer 24

Nutrient taken up by producers as simple inorganic molecules; Producer incorporates nutrients into complex organic molecules; Producer eaten, nutrient pases into consumer; Passes along food chain; When producers and consumers die their complex molecules are broken down by saprobiontic microorganisms that release the nutrient in its original simple form.

Question 25

What are the main stages of the nitrogen cycle?

Answer 25

Ammonification, nitrification, nitrogen fixation, denitrification

Question 26

What occurs in ammonification?

Answer 26

Production of ammonia from organic nitrogenous compounds, urea, proteins, nucleic acids, vitamins. Saprobiotic microorganisms, fungi, bacteria, feed on faeces & dead organisms materials releasing ammonia; Forms ammonia ions in soil

Question 27

What occurs in nitrification?

Answer 27

Nitrifying bacteria oxidises ammonium ions to nitrite ions; nitrite ions oxidised to nitrate ions

Question 28

What conditions needed for nitrification?

Answer 28

Nitrifying bacteria require oxygen - Soil with many air spaces

Question 29

What occurs in nitrogen fixation and when does it occur naturally?

Answer 29

Nitrogen gas is converted into nitrogenous compounds; Naturally when lightning passes through the atmosphere

Question 30

What are the two main microorganisms that carry out nitrogen fixation?

Answer 30

Free living nitrogen fixing bacteria; Mutualistic nitrogen fixing bacteria, found in nodules on the roots of plants such as peas and beans

Question 31

What do free living nitrogen fixing bacteria do?

Answer 31

Bacteria reduce gaseous nitrogen to ammonia, using it to produce amino acids; Nitrogen rich compounds are released when they die and decay

Question 32

What occurs in denitrification?

Answer 32

Anaerobic denitrifying bacteria use nitrates in soil during respiration; Producing nitrogen gas

Question 33

What are the conditions for denitrification?

Answer 33

Soils that has low oxygen concentration ie. become waterlogged;

Question 34

Why does denitrification negatively affect crop productivity and how is it counteracted?

Answer 34

Reduces availability of nitrogenous compounds for plants; Soil must be well aerated to prevent build up of denitrifying bacteria, plough field

Question 35

Explain the phosphorus cycle.

Answer 35

Phosphorus exists as phosphate ions in the form of sedimentary rock deposits; Weather and erosion dissolves phosphate ions; Absorbed by plants into biomass; Consumed by consumers, excess phosphate excreted; On death of plants and animals decomposers and fungi break down releasing phosphate ions into water and soil; Phosphate ions in excreta released by decomposition and dissolved out of rocks; Transported by streams and rivers into lakes and oceans where they form sedimentary rocks;

Question 36

What is the role of mycorrhiza in nutrient cycle?

Answer 36

Improving the uptake of relatively scarce ions such as phosphate ions

Question 37

What type of relation does mycorrhizal and plants , fungi have?

Answer 37

Mutualistic; Plant benefits from improved water and inorganic ion uptake and fungus receives organic compounds ie sugars and amino acids from plant

Question 38

What does natural organic fertiliser contain?

Answer 38

Dead and decaying remains of plants and animals, animal wastes ie. manure, slurry and bone meal

Question 39

What does artificial inorganic fertiliser contain?

Answer 39

Mined from rocks and deposits, then converted into different forms and blended together to give appropriate balance of minerals; Always contains Nitrogen, Phosphorus and Potassium

Question 40

What fertiliser causes the greatest long term increase in productivity?

Answer 40

Combination of natural and artificial fertilisers. Vital that minerals are added in appropriate quantities

Question 41

What are the effects of nitrogen containing fertilisers?

Answer 41

Increases growth, area of leaves, rate of photosynthesis, improves crop productivity; Reduced species diversity, Nitrogen rich soils favours growth; Leaching; Eutrophication

Question 42

What occurs in leaching?

Answer 42

Nutrients are removed from the soil; Rainwater dissolves soluble nutrients ie. Nitrate ions, carrying them deep into soil, eventually beyond the reach of plant roots

Question 43

What are the negative effects of leaching?

Answer 43

Leached nitrate ions find their way into watercourses ie. streams and rivers; Harmful effect on humans if its drinking water source; Causes eutrophication

Question 44

What is eutrophication?

Answer 44

Process by which nutrient concentrations increase in bodies of water

Question 45

What happens during eutrophication?

Answer 45

Lakes and rivers have low conc of nitrate ions, nitrate ions are limiting factor for plant and algal growth; Nitrate ion conc increases due to leaching; Algae grow at surface, upper layer of water becomes densely populated with algae, algal bloom; Algal bloom absorbs light; Light becomes limiting factor for plants at lower depths, plants die; Lack of dead plants and algae is no longer limiting factor for saprobiontic bacteria; Increased oxygen demand due to saprobiontic bacteria; O2 conc in H2O reduced and nitrates are released from decaying organism; O2 becomes limiting factor for aerobic organisms, death; Less competition for anaerobic organism; Anaerobic organism decompose dead material releasing more nitrates and toxic waste ie hydrogen sulphide, water is putrid