Section 8 - Ecology and the Environment

Question 1

How do you estimate population sizes using a quadrat (4)

Answer 1

• Place a 1m^2 quadrant at a random point within the area you’re investigating
• Count all organisms within the quadrat
• Multiply no. organisms by the total area of the habitat
• Do it in another area and compare population sizes

Question 2

Define ecosystem (2)

Answer 2

• All the living organisms living in a particular area
• And all the abiotic conditions, e.g climate, soil type

Question 3

Disadvantages of random sampling (2)

Answer 3

• May not be representative of the population
• Use a quadrat at several points and get an average value

Question 4

When fertilisers leach into water what effect does it cause (1)

Answer 4

• Eutrophication

Question 5

What happens when fertilisers leach into water (7)

Answer 5

• Eutrophication
• Fertiliser leach into water, adding extra nutrients (nitrates and phosphates)
• Extra nutrients cause algae to grow at a faster rate and block out the light
• Plants can’t photosynthesise due to lack of light and start to die
• Microorganisms that feed on dead plants increase in number
• deplete all the oxygen in the water
• organisms that need oxygen e.g fish, die

Question 6

Define habitat (1)

Answer 6

• The place where an organism lives, e.g a field

Question 7

Define population (1)

Answer 7

• All the organisms of one species in a habitat

Question 8

Define community (1)

Answer 8

• All the different species in a habitat

Question 9

Define ecosystem (2)

Answer 9

• All the organisms living in a particular area
• And all the abiotic conditions, e.g temperature

Question 10

How can you use quadrats to investigate the distribution of organisms (4)

Answer 10

• Lay quadrats along a line called a transect
• Mark out a line in the area you want to study
• Collect data along the line using quadrats
• Placed next to each other

Question 11

What would happen if lots of spiders died (3)

Answer 11

• Less food for the frogs, numbers might decrease
• Water spiders wouldn’t be eating Mayfly larvae, so numbers might increase
• Diving beatles wouldn’t be competing with water spiders for food, numbers might increase

Question 12

Describe the water cycle (5)

Answer 12

• Heat from the Sun makes water evaporate from the land and sea, turning it into water vapour
• Water also evaporates from plants, transpiration
• Warm water vapour is carried upwards as warm air rises
• When it gets higher it cools and condenses to form clouds
• Water falls from clouds as precipitation, returning to land and sea

Question 13

How is the carbon cycle affected by photosyenthesis (2)

Answer 13

• Process ‘powered’ by photosyenthesis.
• Green plants use carbon from carbon dioxide in the air to make carbohydrates, proteins and fats

Question 14

How does eating affect the carbon cycle (1)

Answer 14

• Eating passes the carbon compounds in the plant along to animals in a food chain or web

Question 15

How does respiration affect the carbon cycle (2)

Answer 15

• Plant and animal respiration while the organisms are alive
• Releases carbon dioxide back into the air

Question 16

When plants or animals die/are killed, how does this affect the carbon cycle (2)

Answer 16

• Die : they decompose and are broken down by bacteria and fungi
• Killed : turned into useful products

Question 17

How do plants and animals decomposing/being killed affect the carbon cycle (4)

Answer 17

• Plants/animals decompose, broken down by bacteria and fungi
• These decomposers release carbon dioxide back into the air by respiration, as they break down the material
• Some useful plants/animal products, e.g wood, are combusted
• This releases carbon dioxide back into the air

Question 18

Two main examples of nitrogen fixation (3)

Answer 18

• Lightning
• So much energy in one bolt of lightning, it’s enough to make nitrogen react with oxygen in the air to give nitrates
• Nitrogen fixing bacteria in roots and soil

Question 19

What is the process by which nitrogen from the air is turned into nitrogen compounds in the soill which plants can use (1)

Answer 19

Nitrogen fixation

Question 20

Four types of bacteria involved in the nitrogen cycle (8)

Answer 20

• Decomposers (break down proteins in rotting plants/animals and urea in animal waste to form ammonia, a nitrogen compound)
• Nitrifying bacteria (turn ammonia in decaying matter into nitrates)
• Nitrogen fixing bacteria (turn atmopsheric nitrogen into nitrogen compounds plants can use)
• Denitrifying bacteria (turn nitrates back into nitogen gas, no benefits)

Question 21

How is carbon monoxide produced and how is it harmful (2)

Answer 21

• When fossil fuels are burnt without enough air supply, produces carbon monoxide
• If it combines with red blood cells, it prevents them from carrying oxygen

Question 22

How is CO most commonly released and how are humans trying to stop this (2)

Answer 22

• CO mostly released in car emissions
• Modern cars are fitted with catalytic converters, that turn carbon monoxide into carbon dioxide

Question 23

How does acid rain fall (4)

Answer 23

• Burning fossil fuels releases sulfur dioxide
• Sulfur dioxide comes from sulfur impurities in fossil fuels
• Mixes with rain clouds to form sulfuric acid
• Falls as acid rain

Question 24

What is bad about acid rain (2)

Answer 24

• Causes lakes to become more acidic : many organisms can’t survive in acidic conditions so die
• Kills trees : acid releases toxic substances from the soil, making it hard for the trees to take up nutrients

Question 25

What are the main causes of acid rain (2)

Answer 25

• Internal combustion engines in cars
• Power stations

Question 27

Describe the greenhouse effect (9)

Answer 27

• Temp of the earth is a balance between heat it gets from the Sun, and heat it radiates back into space
• Gases in the atmosphere absorb most of the heat that would normally be radiated into space
• Re-radiate it in all directions (inc back towards the Earth)
• Greenhouse gases are the ones that keep the heat in
• E.g water vapour, carbon dioxide and methane
• Humans increasing amount of carbon dioxide
• Increasing levels of CFC’s and nitrou oxide
• Enhances greenhouse effect
• Causing global warming

Question 28

What things could climate change lead to (2)

Answer 28

• Changing crop growth patterns
• Flooding due to polar ice caps melting

Question 30

How do humans release carbon dioxide into the atmosphere (3)

Answer 30

• Car exhausts
• Industrial processes (burning fossil fuels)
• Deforestation (less trees to take in carbon dioxide for photosyenthesis)

Question 31

How do humans release methane into the atmosphere (3)

Answer 31

• Produced naturally e.g rotting plants in marshland
• Man made sources on the increase
• Rice growing and cattle rearing

Question 32

How do humans release nitrous oxide into the atmosphere (3)

Answer 32

• Released naturally by bacteria in soils and the ocean
• A lot more is released from soils after fertiliser is used
• It’s also released from vehicle engines and industry

Question 33

What are CFC’s and how are they releasing carbon dioxide into the atmosphere (3)

Answer 33

• Man mae chemicals in aerosol sprays and fridges
• Powerful greenhouse gases
• Most countries stopped producing them as they are damaging the ozone layer
• Some CFC’s still remain and get releases, e.g by leaks in old fridges

Question 34

How does deforestation cause leaching (3)

Answer 34

• Trees take up nutrients from the soil before they can be leached by rain
• and return them to soil when leaves die
• When trees are removed nutrients get leached, and don’t get replaced, leaving infertile soil

Question 35

How does deforestation disturb the water cycle (4)

Answer 35

• Trees stop rainwater reaching rivers too quickly
• When cut down, rainwater runs straight into rivers, leading to flooding
• Transpiration from trees releases some rainwater back into the atmosphere
• Can make the local climate drier

Question 36

How does deforestation cause soil erosion (3)

Answer 36

• Tree roots hold the soil together
• When trees are removed, soil can be eroded by rain
• Leaving infertile ground

Question 37

How does deforestation disturb the balance of carbon dioxide and oxygen (5)

Answer 37

• Forests take up carbon dioxide by photosyenthesis, store it in wood
• Slowly release it when they decompose (micro organisms respiring)
• When trees are cut down and burnt, stored carbon is released as carbon dioxide
• Contributing to global warming
• Fewer trees : fewer photosyenthesis : releases less oxygen : oxygen level in atmosphere drops