biology paper 2- ecology and environment

Question 1

define habitat

Answer 1

the place where an organism lives

Question 2

define population

Answer 2

all the organisms of one species in a habitat

Question 3

define community

Answer 3

all the different species in a habitat

Question 4

define an ecosytem

Answer 4

all the organisms living in a particular area and all the non-living conditions

Question 5

what are quadrats used for?

Answer 5

used to sample the distribution of organisms in their habitats
-used to estimate the population of an organism in different areas

Question 6

how do you complete a quadrat?

Answer 6

• measure area of filed
• place a 1m^2 quadrat on the ground at a random point
• count all the organisms int he area
• place results in table
• multiply the number of organisms by the total area

Question 7

how does the sample size affect the accuracy of the estimate?

Answer 7

the bigger the sample, the more accurate the estimate of the population
- better to use the quadrat at several points to get an average value for the number of organisms in 1m^2, then multiply by the total area

Question 8

how can quadrats be used to investigate the distribution of organisms?

Answer 8

• laid out along a line called a transect
• make out the area you want to study
• collect data along the line using quadrats placed next to each other

Question 9

producer?

Answer 9

makes its own food through photosynthesis

Question 10

consumer?

Answer 10

eats producers- primary, secondary, tertiary

Question 11

decomposer?

Answer 11

organisms that eat and breakdown dead and dying material and waste

Question 12

what are pyramids of biomass?

Answer 12

shows the mass of living materials at that stage in the food chain

Question 13

what are pyramids of numbers?

Answer 13

shows the number of organisms at that stage of the food chain

Question 14

what are pyramids or energy transfer?

Answer 14

shows the amount of energy transferred to each trophic level in a food chain

Question 15

how much energy is transferred to each trophic level?

Answer 15

10% because some parts of food are eaten and energy is taken in
some parts of food are indigestible so come out as waste
some is used for respiration
energy is lost as heat

Question 16

what is the carbon cycle?

Answer 16

shows how carbon is recycled

• respiration use sugars that react with oxygen to produce CO2
• photosynthesis - produces carbohydrates, fats, proteins and O2 from CO2
• combustion- fuels that react with oxygen to release CO2, water and energy
• Decomposition- bacteria and fungi break down waste and dead remains. this releases energy, water and CO2

Question 17

what are the effects of carbon monoxide?

Answer 17

1- when fossil fuels are burnt without enough oxygen they produce carbon monoxide
2- it’s poisonous as it combines with red blood cells and prevents them from carrying oxygen
3- mostly released in car emissions. most modern cars are fitted with catalytic converters that turn CO into CO2

Question 18

what are the effects of sulfur dioxide?

Answer 18

• caused by burning fossil fuels come from sulfur impurities in the fossil fuels
• SO2 mixes with rain clouds to form dilute sulfuric acid which falls as acid rain
• internal combustion engines in cars and power stations are the main causes of acid rain

Question 19

what does acid rain do?

Answer 19

1- causes lakes to become acidic. Severe effect on the lake’s ecosystem. Many organisms are sensitive to change sin pH and can’t survive in more acidic conditions=plants and animals die
2- acid rain can kill trees. the acid damages leaves and releases toxic substances from the soil, making it hard for the trees to take up nutrients

Question 20

what are the green house gases and how are they produced?

Answer 20

1- CO2= released by humans into atmosphere from industrial processes, car exhausts, fossil fuels, deforestation
2- METHANE- produced naturally-rotting plants in marshland, rice growing and cattle rearing
3- NITROUS OXIDE- released naturally by bacteria in soils and the ocean, more after fertiliser is used, vehicle engines
4- CFCs- man-made chemicals that were once used in aerosol sprays and fridges, they damage the ozone layer and prevent UV radiation reaching Earth

Question 21

what’s the greenhouse effect?

Answer 21

greenhouse gases make a layer around the Earth
the layer traps some of the energy and reflects it back to Earth
this causes an increases in temperature known as global warming
CONSEQUENCES- Global warming (type of climate change), drought, melting ice caps, water levels rise, plant and animal death

Question 22

what is eutrophication?

Answer 22

the build-up of nutrients in a waterway including nitrates and phoshates

Question 23

where do these nutrients come from?

Answer 23

sewage
insecticide spraying
excess fertiliser use

Question 24

how does eutrophication do damage to rivers and lakes?

Answer 24

1- fertilisers enter the water adding extra nutrients
2- these cause algae to grow fast and block out the light
3- plant’s can’t photosynthesise due to lack of light and start to die
4- with more food available, microorganisms that feed on dead plants increase in number and deplete all the oxygen in the water
5- organisms that need oxygen, like fish, die

Question 25

how does deforestation affect soil?

Answer 25

1- leaching- trees take up nutrients from the soil before they can be washed away by rain, but return them to the soil when leaves die
- so when trees are removed nutrients get leached away but don’t get replaced, leaving infertile soil
2- soil erosion- tree roots hold the soil together
- when trees are removed, soil can be washed away by the rain leaving infertile ground

Question 26

how does deforestation affect the water cycle?

Answer 26

• trees stop rainwater reaching rivers too quickly
• when they’re removed, rainwater can run straight into rivers- lead to flooding
• transpiration from trees releases some of the rainwater back into the atmosphere so when cut down can make the local climate drier

Question 27

how does deforestation affect the balance of carbon dioxide and oxygen?

Answer 27

• forest take up CO2 by photosynthesis, store it in wood, and slowly release it when they decompose
• when trees are cut down and burnt, the stored carbon is released at once as CO2 contributing to global warming
• fewer trees means less photosynthesis so less oxygen released. this causes oxygen level in the atmosphere to drop

Question 28

describe the water cycle

Answer 28

water on earth is constantly recycled:

1- heat from the Sun makes water evaporate from the land and sea, turning it into water vapour. Water also evaporates from plants- transpiration

2- the warm water vapour is carried upwards (as warm air rises). When it gets higher up it cools and condenses to form clouds

3- water falls from the clouds as precipitation: rain, snow or hail, and is returned to the land and the sea

Question 29

describe the nitrogen cycle

Answer 29

1- the atmosphere contains about 78% nitrogen gas, N2. This is very unreactive and so it can’t be used directly by plants or animals

2- nitrogen is needed for making proteins for growth, so living organisms need to get it:

3- plants get their nitrogen from the soil, so nitrogen in the air has to be turned into nitrogen compounds (nitrates) before plants can use it. Animals can only get proteins by eating plants or each other

4-Nitrogen fixation is the process of turning nitrogen gas from the air into nitrogen compounds in the soil which plants can use:

• > LIGHTNING- there’s so much energy in a bolt of lightning that it’s enough to make nitrogen react with oxygen in the air to give nitrates
• > NITROGEN-FIXING BACTERIA in roots and soil

5- 4 different types of bacteria involved in the nitrogen cycle

a) DECOMPOSERS: break down proteins- in rotting plants and animals, and urea (in animal waste) and turn them into ammonia- nitrogen compound
b) NITRIFYING BACTERIA: turn ammonia in decaying matter into nitrates
c) NITROGEN-FIXING BACTERIA: Turn atmospheric N2 into nitrogen compounds that plants can use
d) DENITRIFYING BACTERIA: turn nitrates back into N2 gas- no benefit to living organims

some live in the soil and some live in NODULES on plant roots

Question 30

what are the two ways of nitrogen fixation?

Answer 30

• > LIGHTNING- there’s so much energy in a bolt of lightning that it’s enough to make nitrogen react with oxygen in the air to give nitrates
• > NITROGEN-FIXING BACTERIA in roots and soil

Question 31

what are the 4 different types of bacteria involved in the nitrogen cycle?

Answer 31

a) DECOMPOSERS: break down proteins- in rotting plants and animals, and urea (in animal waste) and turn them into ammonia- nitrogen compound
b) NITRIFYING BACTERIA: turn ammonia in decaying matter into nitrates
c) NITROGEN-FIXING BACTERIA: Turn atmospheric N2 into nitrogen compounds that plants can use
d) DENITRIFYING BACTERIA: turn nitrates back into N2 gas- no benefit to living organims

Question 32

where do the bacteria live in the nitrogen cycle?

Answer 32

some of these bacteria live in the soil and some of them live in NODULES on plant

Question 33

what are other causes of eutrophication?

Answer 33

1-pollution by sewage- it contains lots of phosphates from detergents, e.g. washing powder. It also contains nitrates from urine and faeces.
2- these extra nutrients cause eutrophication in the same way fertilisers do