4 Ecology and the environment

Question 1

What is a population?

Answer 1

the total number of individuals of one species in a particular habitat at a particular time

Question 2

What is a habitat?

Answer 2

places where specific organisms live

Question 3

What is an ecosystem?

Answer 3

area where organisms interact with their physicals environment

Question 4

What is a community?

Answer 4

formed of the populations of all the species present in an ecosystem at a particular time

Question 5

Investigating population using quadrats

Answer 5

calculate area of habitat
measure number of individuals in one quadrat and repeat many times to check result is reliable (10 quadrats)
calculate average number of individuals in a quadrat
calculate how many quadrats fit into area
multiply average number by number of quadrats
use random sampling
two tape measure at right angles to make 10m by 10m set of axes

Question 6

What are abiotic factors?

Answer 6

non-living
e.g. temperature, carbon dioxide and oxygen concentrations, minerals in the soil

Question 7

what are biotic factors?

Answer 7

living
e.g. competition between two species, predators, disease

Question 8

How do abiotic/biotic factors affect population size and distribution of organisms?

Answer 8

light: less photosynthesis
temperature: warm conditions needed for growth
moisture levels: water needed for growth
competition

Question 9

What are producers?

Answer 9

organisms which make their own food (e.g. photosynthesising plants)

Question 10

What are consumers?

Answer 10

organisms which eat other living things (e.g. animals)

Question 11

What are decomposers?

Answer 11

organisms which secrete digestive enzymes to decay dead organic matter to obtain their food; help recycle nutrients

Question 12

What do the arrows show in food chains/webs?

Answer 12

direction energy and biomass moves

Question 13

What do food chains/ food webs show?

Answer 13

feeding relationships in an ecosystem
food webs show links
e.g. one animal removed, look at web to predict what might happen, other populations increase/decrease

Question 14

What are pyramids of number?

Answer 14

show number of each organism counted in ecosystem

Question 15

What are pyramids of biomass?

Answer 15

show total mass of organisms in each trophic level (mass of one individual x number of individuals)

Question 16

What are pyramids of energy?

Answer 16

show total energy available in each trophic level per square metre per year

Question 17

Where can energy be lost?

Answer 17

evaporation, movement, heat loss, egestion of waste

Question 18

How much energy is transferred from one trophic level to next?

Answer 18

around 10%

Question 19

What are the stages of the carbon cycle?

Answer 19

plants:
CO₂ used by plants in photosynthesis/ release CO₂ to atmosphere in respiration
Release CO₂ to dead remains/ excretory products by death

animals:
release CO₂ to atmosphere by respiration
release CO₂ to dead remains/ excretory products by death and excretion

decomposers:
release CO₂ to atmosphere by respiration
take in CO₂ from remains/ excretory products by decay and absorption

fossil fuels:
release CO₂ to atmosphere by combustion

Question 20

PAPER 2 Describe the nitrogen cycle

Answer 20

bacteria to nitrate ions = nitrification using nitrifying bacteria
bacteria in soil to ammonium ions/ nitrogen in air to bacteria = nitrogen fixation using nitrogen-fixing bacteria found in soil and root nodules
nitrate ions to nitrogen in atmosphere = denitrification using denitrifying bacteria
decomposers to ammonium ions = decomposition

Question 21

What are the greenhouse gases?

Answer 21

water vapour, carbon dioxide, methane, nitrous oxide and CFCs

Question 22

How do greenhouse gasses result in a greenhouse gas effect?

Answer 22

sun emits solar radiation, some reflected by earth’s atmosphere, some pass through and absorbed by earths surface. Warms earth surface which emits infrared
some infrared passes through atmosphere, but some gases absorb the infrared, preventing it from escaping back into space, and re-emit to earths surface, surface gains more heat and infrared emitted again

Question 23

What is an enhanced greenhouse gas effect?

Answer 23

extra greenhouse effect cause by human activity

Question 24

What human activities contribute to greenhouse gases?

Answer 24

CO₂: burning fossil fuels, slash and burn forest clearance

Methane: cattle produce large volumes from anaerobic activity of bacteria in their gut, bacteria in waterlogged paddy fields for rice cultivation give off methane

Nitrous oxides: burning fossil fuels

CFCs: until 1990s used as solvent for aerosols such as deodorants. Used in fridges and freezers

Question 25

What are the potential effects of global warming?

Answer 25

melting of polar ice caps leading to sea levels rise, causing flooding in coastal regions worldwide

drought and desertification leading to crop failure and food shortage and famines

increased extreme weather events such as hurricanes as more energy present in weather systems

increase in heat related illness

Question 26

What is biodiversity?

Answer 26

The measure of how many different species live in an ecosystem

Question 27

How do you measure biodiversity using quadrats?

Answer 27

Use quadrats and random sampling (random coordinates to place multiple quadrats in same area)
for each quadrat, use an identification key and record the number of each different species
To find effect of abiotic/biotic factors:
select at least two different areas where variable is different,
estimate biodiversity is each area

Question 28

PAPER 2 What does deforestation destroy/cause?

Answer 28

destroys habitats
causing extinction and reducing biodiversity

Question 29

PAPER 2 How does deforestation effect the carbon cycle?

Answer 29

During photosynthesis CO₂ taken into plants. Plant becomes a ‘carbon sink’
Less plants to store carbon and CO₂ levels in atmosphere increase, O₂ levels decrease as less photosynthesis
Burning trees for energy also releases CO₂ back into atmosphere, further increase in atmospheric CO₂

Question 30

PAPER 2 What are the effects of deforestation?

Answer 30

leaching
soil erosion
disturbance of evapotranspiration and carbon cycle

Question 31

PAPER 2 What is leaching?

Answer 31

Loss of nutrients from soil due to run off/washing out of soil

Question 32

PAPER 2 Describe leaching

Answer 32

Normally, water absorbed by soil and taken up by roots of plants. Deforestation means water begins to ‘run off’ from soil into rivers and lakes

Mineral ions (Nitrates, phosphates, potassium) in soil are dissolved in soils water. Deforestation causes dissolved mineral ions (meant to be used for plant growth)to be removed from soil which runs off to rivers/lakes

Can lead to eutrophication

Question 33

PAPER 2 What is soil erosion?

Answer 33

Water run off in deforested areas may carry away some topsoil causing erosion
No roots to hold soil in place
Top soil contains most fertile, mineral ion rich materials: when lost to erosion, minerals are also lost, making land very difficult to use for crop growth and reducing chance of plants re-growing

Question 34

PAPER 2 What is evapotranspiration?

Answer 34

Water transferred from land to atmosphere by evaporation from soil and other surfaces and by transpiration from plants

Question 35

PAPER 2 How does deforestation cause disturbance of evapotranspiration?

Answer 35

evaporated water moves in atmosphere and eventually makes rain in rain clouds
Rain onto plants and cycle continue

Cycle broken due to deforestation: Transpiration stops, so water not put into atmosphere, and rain does not occur. Can lead to droughts

Question 36

How can sulphur dioxide be released into atmosphere?

Answer 36

Sulphur dioxide, nitrogen monoxide, nitrogen dioxide released into atmosphere from cars and factories

Question 37

Consequences of air pollution by sulphur dioxide

Answer 37

Gases react with atmospheric water vapour to form dilute acids (sulphuric and nitric acids)

Dilute acid can dissolve limestone buildings and statues

When rain falls, can decrease pH of rivers and lakes. Effects enzymes of organisms in rivers and lakes, resulting in death of fish and other animals

Acid rain can also kill trees and other plants.

Question 38

How had increased human population led to increase pollution?

Answer 38

more fossil fuels burnt for heat and power
more movement and use of transport
higher levels of industry for houses and goods

Question 39

How is carbon monoxide formed?

Answer 39

when substances containing carbon are burned in a limited supply of oxygen
e.g. vehicle exhaust gases contain significant amounts of carbon monoxide

Question 40

What is carbon monoxide a dangerous pollutant?

Answer 40

binds more strongly with haemoglobin than oxygen
person can lose consciousness, and die due to reduced aerobic respiration

Question 41

How do fertilisers cause leaching?

Answer 41

farmers add fertilisers to soil to increase yield of crops. Usually contain nitrates and phosphates. Very soluble in water
When lots present on farmland surrounding river it is washed out of soil when rains into river

Question 42

What are the effects of leached nitrates?

Answer 42

EUTROPHICATION:
nitrates absorbed by green algae in water
Multiply rapidly, growth called algae bloom
Blocks out sunlight for other plants
Unable to photosynthesise and die
algae on top eventually die
dead remains provide food for bacteria
bacteria multiply rapidly
large pop of bacteria respire, increasing BOD, using up oxygen in water
Decreases level of oxygen and results in death of other organisms in water e.g. fish, cannot respire

Question 43

How can sewage enter water supplies? What does it contain?

Answer 43

due to leaking pipes, or run off from farm land
Undigested food material - lots of biological molecules, including carbs, proteins, nucleic acids, fats

Question 44

What are the consequences of pollution of water by sewage?

Answer 44

sewage provide food source for bacteria
bacteria multiply rapidly
large pop of bacteria respire, increasing BOD, using up oxygen in water
decreases level of oxygen and results in death of other organism in water e.g. fish as cannot respire aerobically
NOT EUTROPHICATION AS NO ALGAE BLOOM