Hot deserts 1

Question 1

What are the conditions of a hot desert?

Answer 1

-Hot, dry ecosystems

-Little rainfall

-Extreme temps (huge diurnal range)

-Harsh environments

Question 2

How much rainfall does a hot desert receive per year?

Answer 2

under 250mm

Question 3

What is the diurnal range of hot deserts?

Answer 3

-Up to 45°C during the day

-Can drop below 0°C at night

Question 4

The harsh environment means that…

Answer 4

…plants and animals have lots of adaptations to suit the difficult conditions.

Question 5

What is interdependence?

Answer 5

How two or more species depend on each other.

Question 6

Describe the interdependence of plants and animals in hot deserts.

Answer 6

-Plants take up nutrients from the soil and provide water and nutrients to the animals that eat them.

-In turn, animals spread seeds through their dung, helping plants to reproduce.

Question 7

Describe the interdependence of climate and soils in hot deserts.

Answer 7

-The hot and dry climate affects soils

-High evaporation rates mean soils are salty

-Soils are relatively low in nutrients as there is little decomposition of dead material by fungi and bacteria

Question 8

Describe the interdependence of soils and plants/animals/people in hot deserts.

Answer 8

-Little decomposition means infertile soils

-This means that plants struggle to grow

-Sparse vegetation limits the amount of food available

-Which means that deserts can only support low density populations of animals and people

Question 9

Biodiversity

Answer 9

The variety of organisms living in an area (plants + animals)

Question 10

Why is biodiversity in hot deserts low?

Answer 10

-Little rainfall and extreme temps make it hard for plants and animals to survive

-Soils are infertile so nutrient cycling is very slow

Question 11

How will climate change impact biodiversity in hot deserts?

Answer 11

It will lower biodiversity as it will lead to more extreme temps which makes survival even harder.

Question 12

Camel adaptations

Answer 12

-Thick insulating fur

-Hump (stored fat) that can be broken down for nutrients

-large, thick, wide feet preventing the camel sinking into the sand, or getting burnt by it

-2 sets of interlocking eyelashes (see in sandstorms)

Question 13

How is thick insulating fur an advantage for animals in hot deserts?

Answer 13

-Protects them from the sun by day

-Keeps warmth in by night

-(so insulates both from cold and heat)

Question 14

Fennec fox adaptations

Answer 14

-Thick insulating fur

-They live in underground burrows (where the heat is less extreme)

-Small to shed heat faster

-Large ears give them a large surface area to lose heat from

-Camouflage coat (protects from predators)

-Furry pads on feat (maximum traction across sand)

Question 15

Hot Desert animals are adapted to…

Answer 15

…cope with the harsh (hot and dry) physical conditions.

Question 16

Hot desert plants are adapted to…

Answer 16

…help them cope with the high temperatures and limited supply of water

Question 17

Cacti adaptations

Answer 17

-Are succulents (store water in stems)

-Have thick, waxy skins (to hold water and reduce the rate of transpiration)

-Spines

Question 18

How are spines on cacti an advantage?

Answer 18

-Having spines rather than leaves reduces the surface area through which water can be lost by transpiration

-Contain toxins to protect from predators (such as Jackrabbits)

Question 19

Mesquite tree adaptations

Answer 19

-Taproots which are long to reach deep water supplies (up to 50m underground)

-Fibrous roots

Question 20

Fibrous roots

Answer 20

Laterally spreading roots widely dispersed around the tree, near the surface of the ground, to absorb as much water as possible when it rains.

Question 21

Where is biodiversity the highest in hot deserts?

Answer 21

Around water sources, such as oasis.

Question 22

Why is biodiversity in hot desert environments particularly vulnerable to human activity?

Answer 22

-Most species (a + p) live near water sources

-This is also where human pops. are the highest

-Human activity in these areas is therefore likely to have a negative impact on biodiversity

-If water sources are used up (e.g. for irrigation) or contaminated (e.g. by livestock) there is no water available for p+a so they might die

-Also, human activities are thought to be contributing to climate change

-CC may make some desert environments hotter and drier

-So species that are adapted to particular conditions may move or die out

Question 23

What is desertification?

Answer 23

The process by which semi-arid land becomes desert.

Question 24

How does population growth cause desertification?

Answer 24

-There is a clear link between migration and desertification

-More people in an area puts more pressure on the land as this increases the likelihood of overcultivation and animals overgrazing

Question 24

How does climate change cause desertification? (rainfall)

Answer 24

-It will reduce rainfall in areas that are already dry

-This means less rainfall is available for plant growth, so more plants will die, which reduces biodiversity

Question 25

How does climate change cause desertification? (temps)

Answer 25

-As global temperatures are increasing, more water will be evaporating from the land

-This makes the soil drier, so plants will struggle to grow, and soil erosion is more likely

Question 26

How does desertification in one area lead to the risk desertification in another?

Answer 26

Desertification often causes people to migrate which puts pressure on the land they’ve moved to, increasing the risk of desertification there too.

Question 27

How does overgrazing cause desertification?

Answer 27

-Allowing cattle to overgraze can lead to soil erosion as the vegetation is eaten away faster than it can regrow.

-Fewer plants stabilising the soil increases the risk of desertification in that area.

-The trampling of the soil by animals also erodes it.

Question 28

How does over-cultivation cause desertification?

Answer 28

-Crops are grown to provide food or to sell as produce for profit

-Too many crops in an area can lead to soil degradation, whereby the soil loses its nutrients before it has time to replace and recharge them.

-This leads to desertification.

Question 29

How does soil erosion cause desertification?

Answer 29

-Once the top-soil layer is removed from an area by either wind or water, this makes it harder for vegetation to grow.

Question 30

Each time land is used for grazing or crops…

Answer 30

…the soil loses fertility.

Question 31

How does the removal of fuel wood cause desertification?

Answer 31

-Indigenous people who live in the desert rely on wood for fuel to heat their homes and cook as these communities aren’t often developed.

-Cutting down the few trees there are in the desert leaves the soil exposed, and the area at risk of desertification.

Question 32

Name the activities which can lead to desertification.

Answer 32

-Climate change
-Population growth
-Overgrazing
-Over-cultivation
-Soil erosion
-Removal of fuel wood

Question 33

What is soil erosion?

Answer 33

The removal of top-soil (containing the most nutrients) from an area by either wind or water.

Question 34

What strategies can be used to combat desertification?

Answer 34

-Water and soil management

-Tree planting

-The use of appropriate technology

Question 35

Why it it the areas on the fringes of hot deserts that are at risk of desertification?

Answer 35

These areas are most vulnerable to human activity as most people who live in deserts live on the fringes (or around water sources).

Activities such as over-cultivation and allowing animals to overgraze can lead to an increased risk of desertification.

Question 36

How does water management combat desertification?

Answer 36

-Growing crops that need little water reduces water use

-Techniques can be used to make sure that the little water available is being used efficiently

-For example, farmers could use drip irrigation techniques instead of surface irrigation to water crops, which ensures that the soil isn’t eroded by lots of water being added at once.

Question 37

How does soil management combat desertification?

Answer 37

-Leaving areas of land to rest (fallow) between planting crops, or letting animals graze, lets the soil recover its nutrients

-Rotating crops that take different nutrients from the soil prevents the same nutrients being continually removed

-Compost can be used to add extra nutrients to the soil

Question 38

How does tree planting combat desertification?

Answer 38

-Trees act as windbreaks, reducing soil erosion by wind.

-Trees can stabilise the sand, preventing the desert from encroaching on farmland (by increasing soil fertility and water retention).

-If grown in amongst crops, the trees provide shade which reduces temperatures and evaporation rates.

Question 39

How does the use of appropriate technology combat desertification?

Answer 39

-Appropriate technology is technology suited to the needs, wealth, and knowledge of people who live in a local area

-This means that it is cheap and easily available to them.

-It often provides sustainable solutions that help to combat desertification

-For example, sand fences can be constructed to stabilise the soil, reducing erosion

-Solar cookers reduce the rate of deforestation as they use the sun’s energy to heat food.

Question 40

Native

Answer 40

An animal/plant that lives in an area.

Question 41

Indigenous

Answer 41

An animal/plant that has always lived in an area.

Question 42

Endemic

Answer 42

An animal/plant that only lives in one area and cannot be found anywhere else.

Question 43

What are temperature like in hot deserts? Why?

Answer 43

Extreme due to a lack of cloud cover. (temps can reach 45 degrees during the day and 0 degrees at night). We would call this an extreme diurnal range.

Question 44

Pressure is …

Answer 44

…permanently high.

Question 45

Describe the location of hot deserts.

Answer 45

Hot deserts are mainly found on or around the tropics of Cancer and Capricorn (30 degrees N and S of the equator).

They are found in every continent bar Antarctica.

The largest hot deserts are found in Africa and Australia, the largest in the world being the Sahara in Northern Africa.

Question 46

For an area to classify as a desert, it needs…

Answer 46

…less than 250mm of rainfall per year.

Question 47

Is soil fertile in hot deserts? Why?

Answer 47

No.

There are few plants and animals in hot deserts.

This means that very little decomposition occurs, which means that the soil cannot gain many nutrients from the dying plant and animal material.

Hence, it is infertile.

Question 48

Semi- arid land

Answer 48

An area on the fringe of a desert with semi- fertile soil. These areas are vulnerable to soil erosion and desertification.

Question 49

Overgrazing

Answer 49

Farmers have more livestock in an area than the environment can sustain. This can damage the whole ecosystem.

Question 50

How many seasons do hot deserts have?

Answer 50

2 (The summer being the part of the year where it is significantly warmer).
(or the wet and dry season).

Question 51

How many people live in hot deserts?

Answer 51

Over 1 billion.

Question 52

Biodiversity in hot deserts.

Answer 52

Hot deserts have a relatively low biodiversity.

Small areas around ephemeral (temporary) ponds and rivers or along the desert margins have the highest levels of biodiversity, and contain a high proportion of species that are endemic (unique) to the desert.

Areas with water also have the highest density of human populations.

Question 53

How can people threaten biodiversity in hot deserts?

Answer 53

People can threaten biodiversity by increasing desertification and by over contaminating water supplies.

Question 54

Give an example of how changing one part of the ecosystem will have a knock on effect.

Answer 54

Allowing cattle to overgraze can cause soil erosion.

With fewer plants stabilising the soil, the wind can blow fine sand particles into the atmosphere, forming dust clouds.

This reduces rainfall, making deserts even drier.

Without rainfall, water supplies can dry up and people, plants, and livestock may die.

Question 55

The nutrient cycle is …. than that of tropical rainforests, and involves …

Answer 55

much slower

fewer nutrients

Question 56

Why are hot deserts sterile environments?

Answer 56

Bacteria cannot function without water/moisture.

Question 57

What human factors might affect the nutrient cycle?

Answer 57

Overgrazing
Burning firewood

Question 58

What physical factors may affect the nutrient cycle?

Answer 58

Dry climate
Low rainfall

Question 59

Tree planting example

Answer 59

In the Sahara desert there is a project called the ‘Great green wall’ - a wall of trees is being planted that aims to span 8000km across the Sahara.