3.1.2.3 Hot deserts

Question 1

Describe the climate - name 3 general things

Answer 1

• Diurnal temperature → range from very hot in day (e.g. 45°C) to very cold at night (e.g 5°C)
• Very little rainfall → less than 250 mm per year
• When it rains also varies a lot → might only rain once
  every 2 or 3 years

Question 2

What is meant by a diurnal temperature range?

Answer 2

It means it experiences extreme range of temperatures in a single day

Question 3

Why does the desert have a diurnal temperature range?

Answer 3

Cloudless skies allow high levels of insulation in daytime + rapid heat loss at night

Question 4

What is the soil like?

Answer 4

• Shallow with coarse, gravelly texture

- Hardly any leaf fall = soil isn’t very fertile

Question 5

Describe how the plants are like (name 4 things)

Answer 5

• Plant growth is sparse due to lack of rainfall
• Plants have a short life cycle, only appearing when it rains
• Plants usually short (though cacti grow fairly tall) - low shrubs & short woody trees
• e.g. includes cacti & thornbushes

Question 6

Describe how the animals are like (name 2 things)

Answer 6

• Mammals tend to be small and nocturnal

- Most birds leave desert during harshest conditions

Question 7

Describe how the people are like (name 2 things)

Answer 7

• Many people living desert grow few crops where there are natural springs or wells to supply water (usually in desert fringes)
• Indigenous people are often nomadic: They travel all the time in search of food and water for their herds (mostly goats and sheep)

Question 8

What are desert fringes?

Answer 8

Areas at borders of hot deserts where there’s greater

biodiversity and large plants (a.k.a. Semi-desert, semiarid areas, inappropriate agriculture)

Question 9

Why are hot deserts are fragile, interdependent ecosystems?

Answer 9

Biotic (living) components of deserts + abiotic (non-living) components are closely related → if one of them changes, the others are affected

Question 10

Give an example how animals and plants are interdependent (nutrients)

Answer 10

1. Plants gain their nutrients from soil & provide nutrients and water to animals that eat them
2. In turn, animals spread seeds through their dung - helping plants reproduce

Question 11

Explain how the hot and dry climate affects soil & this affects plants

Answer 11

Soils are salty due to high evaporation and relatively low in nutrients because there’s little decomposition of dead plant material by fungi and bacteria ∴ plants struggle to grow

Question 12

Explain how the amount of vegetation affects animal populations

Answer 12

Sparse vegetation limits amount of food available → so desert can only support low-density populations of animals

Question 13

Explain why the water supplies in deserts can be extremely scare

Answer 13

Water supplies in deserts can be extremely scare ← rainfall is very low and coarse desert soil means rain that falls quickly drains away

Question 14

How does these scare water supplies affect animals and people?

Answer 14

Animals and people find ways of coping e.g. By constantly moving to new places or digging deep wells

Question 15

What do people ‘have’ to do to grow crops?

Answer 15

People have to irrigate (artificially water) land in order

to be able to grow crops

Question 16

Why is irrigation bad for animals and plants?

Answer 16

Drawing unsustainable amounts of water from wells lowers level of water underground - reducing amount available to other plants
∴ Plant species and animals that depend on them can struggle to survive as a result

Question 17

Explain how changes to components of ecosystem (e.g.
cattle overgrazing vegetation) can have knock-on effects
on whole ecosystem

Answer 17

• Without plant roots to stabilise the soil, wind can blow fine sand/soil particles away = soil erosion
• Soil erosion can lead to clouds of dust in atmosphere = can change climate of deserts - reducing rainfall, making it even drier

Question 18

How are plants’ roots adapted to help them cope with hot, dry conditions?

Answer 18

1. Roots are either extremely long to reach very deep water supplies
2. OR spread out very wide near surface to catch as much water as possible when it rains

Question 19

How are succulents adapted to cope with hot, dry conditions?

Answer 19

Have large, fleshy stems for storing water and thick waxy skin to reduce water loss (transpiration)

Question 20

Name 4 common plant adaptations to cope with hot, dry conditions

Answer 20

1. Roots are either extremely long or wide
2. Many plants (e.g. cacti) are succulents
3. Some plants have small leaves or spines
4. Seeds of some plants only germinate when it rains

Question 21

How does having small leaves or spines help plants to cope with hot, dry conditions?

Answer 21

Gives them a low surface area = reducing transpiration

Question 22

Why do some plants have sharp spines and toxins?

Answer 22

To stop animals from stealing water from stems

Question 23

Why do seeds of some plants only germinate when it rains?

Answer 23

Plants grow, flower and release seeds in just a few weeks = ensuring they only grow when there’s enough water to survive

Question 24

Name 6 animal adaptations to cope with high temperatures and limited supply of water

Answer 24

1. Nocturnal
2. Able to tolerate high body temperatures
3. Can store large amounts of fat
4. Get all water they need from what they eat
5. Have long limbs or ears
6. Minimise water loss from sweat and urine

Question 25

Name 2 animals that are able to tolerate high body temperatures

Answer 25

Lizards and snakes

Question 26

Explain how being nocturnal helps to cope with high temperatures

Answer 26

Being nocturnal means animals can stay cool in burrows during day or sit still in shade whist it’s hottest (e.g. Fennec foxes)

Question 27

Why do animals have long limbs or ears

Answer 27

Gives large surface area to lose heat from

Question 28

Explain how being able to store large amounts of fat helps to cope with limited supply of water

Answer 28

Some bigger animals store large amounts of fat which they can break down into water when needed (E.g. Camels’ humps)

Question 29

Give an example of animals that get all water they need from what they eat

Answer 29

Cactus mice get water from cactus fruits and insects

Question 30

Explain how camels are adapted to cope with sand

Answer 30

Camels keep sand out their eyes and nose during
sandstorms by having triple eyelids, long eyelashes and
being able to close their nostrils. Also have large, flat feet so they don’t sink into the sand.

Question 31

What is desertification?

Answer 31

The degradation of land so that it becomes more desert-like - it becomes drier and less productive

Question 32

How much of world’s surface is in risk of desertification?

Answer 32

1/3 of world’s land surface is at risk of desertification (especially margins of deserts)

Question 33

What is a key part of desertification?

Answer 33

Soil erosion

Question 34

How soil erosion leads to desertification?

Answer 34

1. Soil that is exposed (not covered by plants) is easily removed by wind or water
2. Nutrients in soil (e.g. Fallen leaves, dead plants) are lost making soil unproductive
3. Eventually ground becomes sandy, dusty, stony or just bare rock

Question 35

Name the main physical causes of desertification (due to climate change)

Answer 35

1. Rainfall - climate change is expected to reduce rainfall in areas that are quite dry
2. Temperatures - global temperatures are expected to increase

Question 36

Explain how reduced rainfall (due to climate change) can lead to desertification

Answer 36

• Less rain means less water available for plant growth so plants die
• Plant roots hold soil together, if plant dies soil easily eroded

Question 37

Explain how higher temperatures (due to climate change) can lead to desertification

Answer 37

• Higher temperatures mean more water evaporates from land and plants
• Makes soils drier and means plant die (so roots no longer hold soil together)

Question 38

Name 4 human activities that lead to desertification

Answer 38

• Removal of Fuel Wood
• Overgrazing
• Over-Cultivation
• Population Growth

Question 39

How does the removal of fuel wood lead to desertification?

Answer 39

• Many people in arid (dry) areas rely on wood for fuel for cooking
• Removal of trees leaves soil exposed so it’s more easily eroded

Question 40

How does overgrazing lead to desertification?

Answer 40

• Too many cattle or sheep eat plants faster than they can regrow ∴ leads to more soil erosion because plants
  no longer hold soil together
• Trampling by animals also erodes soil

Question 41

How does over-cultiavtion lead to desertification?

Answer 41

• If crops are planted in same area continually, all nutrients in soil get used up
• This means plants can no longer be grown in those soils and without plants soil erosion increases

Question 42

How does population growth lead to desertification?

Answer 42

This puts pressure on land leading to more deforestation (firewood), more overgrazing and more over-cultivation

Question 43

Name 4 ways how the risk of desertification can be reduced

Answer 43

• Water Management
• Tree Planting
• Soil Management
• Appropriate Technology

Question 44

Explain how water management can reduce the risk of desertification

Answer 44

1. Growing crops don’t need much water (e.g. Olives) can reduce water use
2. Using drip irrigation on crops instead of surface irrigation means soil isn’t eroded by lots of water added in one go

Question 45

Explain 3 ways how planting trees can reduce the risk of desertification

Answer 45

• Growing trees amongst crops protects crops (and soil) by providing shade ∴ reducing temperatures and evaporation rates
• Trees can be planted to act as windbreaks to protect soil from wind erosion
• Trees can stabilise sand to prevent desert from encroaching on farm land

Question 46

Explain 3 ways how soil management can reduce the risk of desertification

Answer 46

• Leaving areas of land to rest in between grazing or planting lets them recover their nutrients
• Rotating crops that use different nutrients from soil means that same nutrients don’t keep being removed
• Compost can be used to add extra nutrients to soil

Question 47

What is meant by using appropriate technology?

Answer 47

Means using cheap, sustainable and easily available materials that are easy for local people to maintain

Question 48

Give an example how technology can be used appropriately to reduce the risk of desertification

Answer 48

Sand fences (barriers to trap windblown sand) or terraces can be constructed to stabilise soil and reduce soil erosion

Question 49

Give an example how technology can be used appropriately to reduce the rate of deforestation (which leads to desertification)

Answer 49

By using solar cookers which use sun’s energy to heat food → they’re cheap and easy to make and don’t require wood as fuel to work