Topic 5: Climate change

Question 1

Explain how reforestation of tropical rainforests can be used to minimise climate change (3)

Answer 1

-Growing trees
-Means net uptake of CO2 by photosynthesis > respiration
-Reduces CO2 in atmosphere
-Slows rate of global warming

Question 2

Explain why burning wood chips does not increase carbon dioxide in the long term (4)

Answer 2

-Plants photosynthesise and take in the carbon dioxide from the atmosphere
-Overall, even if burning wood chips released carbon dioxide into the atmosphere, the other live plants would cancel that out as they are also taking in the carbon dioxide
-New trees are built in order to replace those that are cut down
-No net increase in carbon dioxide (carbon neutral)

Question 3

Golden snub-nosed monkeys live in areas with very cold winters.

The seeds in their diets contain lipids and carbohydrates.

Climate change is reducing seed production by plants in their habitat.
Discuss the impact of climate change on the monkey population (4)

Answer 3

-Fewer seeds = decrease in plant population
-Fewer seeds = less food/energy
-Lipids + carbohydrates contain lots of stored energy
-Monkeys will not generate enough heat to survive winter
-Monkey population will decrease in size

Question 4

An oakwood woodland studied. Pollen analysis showed that pine trees grew there in the past

Describe how pollen analysis could have been carried out in the oak woodland (3)

Answer 4

-Take a peat/soil core from the oak woodland

-There is analysis of peat/soil layers. E.g. the deeper the layer the older the pollen/dating of peat using carbon 14

• Identify different pollen using a microscope

Question 5

Other abiotic factors can affect the growth rate of trees

Explain why a decrease in temperature could affect the growth rate of a tree (3)

Answer 5

-Reduced rate of enzyme catalysed reactions
-Reduced rate of photosynthesis
-Reduced rate of carbohydrate/new cell/cell wall production

Question 6

Explain how studying pollen grains in peat bogs can provide evidence of climate change (4)

Answer 6

-Pollen preserved in peat bogs
-A plant species can be identified from its pollen
-Climate affects the type of plants growing
-Depth of peat correlates with period of time since pollen was produced
-Changes in pollen over time indicate changes in climate

Question 7

State how the age of layers in a peat bog can be determined (1)

Answer 7

Carbon -14 dating

Question 8

Explain why the conditions in peat bogs prevent decomposition (3)

Answer 8

-Conditions are anaerobic
-Therefore less aerobic respiration by decomposers
-Acidic conditions inhibit/denature enzymes
-Therefore enzymes cannot digest/break down organic material

Question 9

Suggest why pollen in peat bogs is preserved for many years (4)

Answer 9

-Lack of /very slow decomposition
-Due to lack of microorganisms involved in decomposition
-As a result there are fewer enzymes
-Lower PH reduces enzyme activity/kills microorganisms
-Low oxygen affects respiration of microorganisms

Question 10

Describe the structure of cellulose in cells walls (4)

Answer 10

-Cellulose is a polysaccharide of Beta glucose
-It has 1-4 glycosidic bonds
-Cellulose molecules arranged as microfibrils
-Joined by hydrogen bonds

Question 11

State what is meant by the term global warming

Answer 11

Increase in average temperature of the earth’s surface

Question 12

Explain why rainfall could affect the tree ring width (3)

Answer 12

-Use of water in light-dependent reaction
-Glucose is used for energy and cellulose is used for new cells
-Use of water in transport
-Increase in tree ring growth results from an increase in number/size of xylem

Question 13

Explain why the increase in greenhouse gases is leading to a decrease in the growth of seagrass (3)

Answer 13

-Carbon dioxide dissolves in to the water
-This increases acidity of water
-Increased global warming could increase water temperature
-Therefore change in temperature/PH will denature the enzymes so less seagrass survive

Question 14

Discuss the possible effects of a reduction in seagrass on animals living in the Mediterranean sea (4)

Answer 14

-The number of aquatic animals would decrease
-Less seagrass means there is less food for primary consumers
-Less oxygen or food due to an decrease in photosynthesis
-Less oxygen for respiration by animals

Question 15

Seagrass is long-living and more resistant to breakdown by microorganisms than plants surviving in the rainforest

Explain why maintaining a healthy population of seagrass reduces the release of carbon dioxide into the atmosphere (3)

Answer 15

-Seagrass takes up carbon dioxide by photosynthesis
-Less decomposition/decay by decomposers keeps them healthy
-Therefore the carbon remains locked in the plant/sea grass is a carbon sink

Question 16

Explain why an increase in environmental temperature may lead to a shorter life cycle (2)

Answer 16

-Life cycle depends on metabolic reactions
-Increase in temperature increases the kinetic energy of enzymes
-Therefore there will be more frequent collisions between enzyme and substrates

Question 17

Devise a laboratory investigation to study the effect of temperature on the duration of the larval stage in a specialist butterfly species (6)

Answer 17

-Independent variable - range of temperatures between 5-35 C - cant be controlled with water baths
-Dependent variable - measure time from hatching to pupating
-Variables to be controlled - age of eggs, same species, same source…
-Use a buffer solution to control PH
-Monitor eggs/larvae at regular intervals of time e.g. 24-72 hours max
-Record length of time since eggs hatched
-Calculate mean length of temperature for each temperature
-Statistical tests: Standard deviation

Question 18

Explain why temperature affects the growth of plants (4)

Answer 18

-Light independent stage of photosynthesis is catalysed by enzymes/RUBISCO

-Activity of RUBISCO increases as the temperature increases

-More carbon is fixed in the Calvin cycle

-Greater rate of production of GP/GALP/Glucose

-Leading to increase in growth of plants

Question 19

Describe and explain how global warming could affect plant species (4)

Answer 19

-Increased temperatures increase the activity of enzymes e.g. RUBISCO
-More glucose is produced as a result, leading to more growth for plants
-Change in the distribution of species
-Could lead to extinction of species

Question 20

Explain why a diet based on plant protein produces lower greenhouse gas emissions than a diet based on animal protein (3)

Answer 20

-Plants photosynthesise, absorbing CO2
-Respiration happens more in animals than in plants, hence more CO2 is released from animals
-Animals release methane

Question 21

Explain why the farming of beef cattle on deforested land produces more greenhouse gas emissions than from those reared on natural pastures (3)

Answer 21

-Deforestation removes a carbon sink
-This reduces the amount of carbon fixation as less photosynthesis is happening
-Burning trees releases CO2 into the atmosphere

Question 22

Explain the impact of cutting down trees on climate change (4)

Answer 22

-Less photosynthesis
-Less carbon dioxide will be fixed / more CO2 remains in the atmosphere
-Because CO2 is a greenhouse gas
-More heat energy trapped in the atmosphere
-Increasing surface temperature of earth