IB Biology HL D4.3 Climate Change

[Maximum number: 3]

Average human internal (core) body temperature is $36.4^{\circ} \mathrm{C}$ , with slight variations between day and night. The average surface temperature of the Earth in the 20th century was $13.9^{\circ} \mathrm{C}$ . It has now risen to $14.8^{\circ} \mathrm{C}$ .

(a)

Explain how the burning of fossil fuels has contributed to the increase in the Earth's temperature.

[ 2 ]

a. $\quad \mathrm{CO}_{2}$ is released/is a greenhouse gas;

b. long wave radiation/heat/infrared (emitted by the Earth) trapped/absorbed by $\mathrm{CO}_{2}$ ;

c. (so) heat retained in atmosphere;

Marking guidance:

Do not award a mark for 'Earth's temperature is increased' as this is in the question.

b. Do not accept 'reflected back' instead of trapped or absorbed and do not accept absorption of any type of radiation from the sun.

The word 'heat' can be used for both marking points b. and c. but in b. the idea is heat retained by $\mathrm{CO}_{2}$ the whereas the idea in c. is heat retention in the atmosphere.

(b)

Melting polar ice due to global warming is reducing reflection of sunlight from the Earth. Identify with a reason whether this will result in positive or negative feedback.

[ 1 ]

[Maximum number: 4]

Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world's forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.

Boreal forest in winter, with a dense stand of tall pointed trees covered in snow beside an open snow-covered foreground.

(a)

In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to accumulate. Suggest reasons for this.

[ 2 ]

(b)

An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.

[ 2 ]

[Maximum number: 14]

Global warming has changed both the thickness and surface area of sea ice of the Arctic Ocean as well as the Southern Ocean that surrounds Antarctica. Sea ice is highly sensitive to changes in temperature.

Scientists have calculated a long-term mean for the surface area of sea ice in the Arctic and in the Southern Ocean around Antarctica. This mean value is used as a reference to examine changes in ice extent. The graph shows the variations from this mean (zero line) over a period of time.

(a)

State the trend in the surface area of sea ice in the Southern Ocean around Antarctica.

[ 1 ]

(b)

Distinguish between changes in the surface area of sea ice in the Arctic and Antarctica.

[ 2 ]

(c)

Discuss the data as evidence of global warming.

Adélie penguins (Pygoscelis adeliae) are only found in Antarctica and need sea ice for feeding and nesting. Biologists are able to deduce how these penguins have responded to changes in their environment for the last 35000 years, as the Antarctic conditions have preserved their bones and their nests. The image is a map of Antarctica and the surrounding Southern Ocean. It shows the trends in the length of the sea ice season (days of the year when sea ice is increasing) and the sites of nine Adélie penguin colonies.

[ 3 ]

(d)

Describe the trends in the length of the sea ice season around the Antarctic Peninsula and in the Ross Sea.

[ 2 ]

(e)

The graphs show the changes in penguin population in three of the colonies shown on the map.

Analyse the trends in colony size of the Adélie penguins in relation to the changes in the sea ice.

[ 3 ]

(f)

Discuss the use of Adélie penguins in studying the effects of global warming.

[ 3 ]

[Maximum number: 2]

Average human internal (core) body temperature is $36.4^{\circ} \mathrm{C}$ , with slight variations between day and night. The average surface temperature of the Earth in the 20th century was $13.9^{\circ} \mathrm{C}$ . It has now risen to $14.8^{\circ} \mathrm{C}$ .

Explain how the burning of fossil fuels has contributed to the increase in the Earth's temperature.

a. $\quad \mathrm{CO}_{2}$ is released/is a greenhouse gas;

b. long wave radiation/heat/infrared (emitted by the Earth) trapped/absorbed by $\mathrm{CO}_{2}$ ;

c. (so) heat retained in atmosphere;

Marking guidance:

Do not award a mark for 'Earth's temperature is increased' as this is in the question.

b. Do not accept 'reflected back' instead of trapped or absorbed and do not accept absorption of any type of radiation from the sun.

The word 'heat' can be used for both marking points b. and c. but in b. the idea is heat retained by $\mathrm{CO}_{2}$ the whereas the idea in c. is heat retention in the atmosphere.

[Maximum number: 1]

Average human internal (core) body temperature is $36.4^{\circ} \mathrm{C}$ , with slight variations between day and night. The average surface temperature of the Earth in the 20th century was $13.9^{\circ} \mathrm{C}$ . It has now risen to $14.8^{\circ} \mathrm{C}$ .

Melting polar ice due to global warming is reducing reflection of sunlight from the Earth. Identify with a reason whether this will result in positive or negative feedback.

[Maximum number: 2]

Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world's forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.

An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.

[Maximum number: 1]

What is a consequence of ocean water having a very high temperature?

A

Decreased bleaching of coral reefs

B

Increased production of oxygen

C

Increase in energy flow through food chains

D

Reduced nutrient upwelling to the surface

[Maximum number: 1]

Aedes japonicus and Aedes albopictus are invasive mosquito species that have recently become established in Western Europe. A. japonicus is more suited to the cooler regions in central Europe, while A. albopictus is adapted to warmer temperatures of the Mediterranean regions.

Photograph of an Aedes japonicus mosquito standing on skin, showing its proboscis, wings and long legs.

A. japonicus

Photograph of an Aedes albopictus mosquito standing on skin, with contrasting pale markings on its dark body and legs.

A. albopictus

Suggest a possible impact of increasing mean temperatures in Europe on the distribution of A. albopictus.

[Maximum number: 8]

Coral reefs are among the most spectacular ecosystems on Earth. They support a rich diversity of life and provide economic benefits to the people who use them. In Papua New Guinea in the Pacific Ocean north of Australia the following data were collected. Coral cover is the percentage of the reef surface covered by live hard coral.

Dual-axis line graph for 1994–2004: dashed line gives live coral cover on the left percentage axis, 0–80%; grey solid line gives mean annual ocean temperature on the right axis, 24.30–24.70°C.

(a)

Acidification of the world's oceans is an increasing threat to the health of oceanic life including coral reefs. Corals perform calcification to create their calcium carbonate exteriors. An experiment was conducted on Heron Island, Southern Great Barrier Reef, Australia. For the experiment the pH was altered by dissolving carbon dioxide in the water. Three different coral species were used, with each test group at two different temperature ranges and three different pH values. The white line in each photograph represents 5 cm .

Porolithon onkodes

[ 2 ]

(i)

Describe the trend in calcification when the pH is decreased at $25-26^{\circ} \mathrm{C}$ .

[ 1 ]

(ii)

Using all of the data, comment on the hypothesis that ocean acidification in warming seas will have the same effect on all species of coral.

[ 1 ]

a. greater reduction in calcification as pH drops at the higher temperature in P. onkodes than on the other two species (so hypothesis not supported)

b. net loss in calcification at lowest pH and highest temperature in P. onkodes whereas there is still calcification in the other two species (so hypothesis not supported)

c. warming reduces calcification at all pH levels in A. intermedia but not in the other two species (so hypothesis not supported)

d. combined effect of acidification and warming is a larger reduction in calcification in A. intermedia than in the other two species (so hypothesis not supported)

e. more calcification as temperature rises at lower pH / pH 7.9 and 7.6 in P. Iobata whereas there is less in the other two species (so hypothesis not supported)

f. more calcification as pH drops from 8.2 to 7.9 at higher temperature in P. Iobata whereas there is a drop/no rise in the other two species (so hypothesis not supported)

This answer is based on the larger drop in calcification between 8.2 and 7.6 at both temperatures in onkodes than the other two species.

This answer is based only on whether there are positive values for calcification or negative.

This answer is based on the drop in calcification at each pH when the temperature rises in intermedia, whereas in the other species there is a rise at one or more of the pHs.

This answer is based on the larger overall drop in calcification between pH 8.2 at $25 / 26^{\circ} \mathrm{C}$ and 7.6 at $28 / 29^{\circ} \mathrm{C}$ .

The answer must either state pHs 7.9 and 7.6 or specify lower pH or greater acidification.

The answer must state the two pH values and state higher temperature or $28-29^{\circ} \mathrm{C}$ .

(b)

Suggest another marine animal that has parts made of calcium carbonate and may therefore be damaged due to ocean acidification.

[ 1 ]

(c)

Outline causes of ocean acidification.

[ 2 ]

(d)

Discuss the need for international cooperation to solve the problems of declining coral populations.

[ 3 ]

[Maximum number: 1]

Explain how the following influence the enhanced greenhouse effect.

Explain how reforestation of desert influences the enhanced greenhouse effect.

decreases $\mathrm{CO}_{2}$ concentration lowering greenhouse effect as trees/plants act as a carbon sink/photosynthesis absorbs $\mathrm{CO}_{2}$

[Maximum number: 2]

The black-legged tick (Ixodes scapularis) is an arthropod which sucks blood from humans and other mammals. It is encountered mainly in wooded and semi-wooded areas.

Some ticks can be infected by the bacterium Borrelia burgdorferi. When a tick bites a human, the bacterium is often introduced, causing Lyme disease. Lyme disease is a public health problem in North America and, if left untreated, can cause important neurological impairment. The diagram represents the two-year life cycle of a tick.

Using the life cycle diagram and the graph for the year 2000, analyse the distribution of adult ticks throughout the different seasons.

a	higher temperatures so more transpiration/droughts/dehydration/water shortage
b	more forest fires
c	more/new pests/diseases because of the changed conditions
d	competition from trees/plants «that colonize/spread to boreal forests»
e	trees/«named» organisms «of boreal forests» not adapted to warmer conditions OR trees/«named» organisms migrate/change their distribution due to warmer conditions
f	trees die so loss of habitat for animals
g	faster decomposition/nutrient cycling «so conditions in the ecosystem change»
h	standing water/floods due to more snow/permafrost melting

a	higher temperatures so more transpiration/droughts/dehydration/water shortage
b	more forest fires
c	more/new pests/diseases because of the changed conditions
d	competition from trees/plants «that colonize/spread to boreal forests»
e	trees/«named» organisms «of boreal forests» not adapted to warmer conditions OR trees/«named» organisms migrate/change their distribution due to warmer conditions
f	trees die so loss of habitat for animals
g	faster decomposition/nutrient cycling «so conditions in the ecosystem change»
h	standing water/floods due to more snow/permafrost melting

a	international cooperation needed to reduce carbon dioxide emission/concentrations
b	carbon dioxide produced anywhere increases the greenhouse effect/global warming/ocean acidification/health of coral everywhere
c	ocean currents/tides/wind move carbon dioxide/acid/heat around the world / oceans of the world are interconnected/part of one overall system
d	(some) coral reefs are in international waters (or words to that effect) / coral reefs cannot be protected by single national governments alone
e	the more groups of people/nations/corporations that reduce their carbon emissions, the lower the impact on coral will become / not enough for one country/group/corporation to reduce carbon dioxide emissions
f	sharing of technology/research/information/resources
g	aid to poorer/developing countries (to help with coral conservation)
h	reference to an economic/ecological benefit of conserving coral reefs

IB Biology HL D4.3 Climate Change Questions

Exam points

Covered syllabus points

a	positive feedback because warming causes melting of polar ice;
b	positive feedback because less ice means less sunlight is reflected (lower albedo);
c	positive feedback because more heat is absorbed by the Earth's surface which becomes warmer;

Covered syllabus points

Question 1

Question (a)

Question (b)

Question 2

Question (a)

Question (b)

Question 3

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question (f)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question (a)

Question (i)

Question (ii)

Question (b)

Question (c)

Question (d)

Question 10

Question 11