Page 15 - The World About Us

Joshua Tree
2.1.2
1.1.1

What is life like in the hot deserts?

The key feature of all life in hot
deserts is its ability to survive with very
li le water. This known as a xerophy c
adap on. Plants have adapted in many
similar ways across different deserts.
Many, like the cac of North
America, have dispensed with leaves
altogether. They have their chlorophyll
stored under a waxy skin. Thorns, sharp
spines and fine hairs help deter plant
eaters. They also act as surfaces on
which dew condenses. A concer na skin
allows cac to expand a er rainfall to
store moisture in their bodies.
Many desert trees have become
deciduous in between rainy spells. This
prevents moisture loss from the fig.36 Saguaro cac in the Sonoran Desert, southern USA.
stomata on the leaves.
which also act to radiate excess heat.
The paloverde bush has also evolved
a green bark packed with chlorophyll, so Fennec foxes have evolved to spend
when leaves are shed the bark takes most of their lives ac ve at night.
over as the site for photosynthesis. The
Joshua tree has roots up to 11m, to
search for water deep underground.
Trees such as the oco llo quickly
grow numerous, ny leaves when the
rain falls. It may grow leaves several
mes a year. In the deserts of North
America, ephemerals such as desert
mallow and chuparosa grow flowers in
just a few days a er rains fall.
Insects and animals also need to
survive with a lack of water. In the
Namib Desert, darkling beetles climb to
the top of sand dunes to collect fig.37 The Fennec fox, desert-adapted. fig.38 Joshua tree, a desert specialist.
morning fog on their bodies. In the
same desert, elephants will walk many
miles to find grasses and grass roots. compare the climates of Manaus and
These sparse plants grow in the beds of 1. Outline the Medan. (5)
ephemeral rivers, which may only flow distribu on of tropical rainforests
for a few days a year. 7. With reference to examples,
across the globe. (2) explain why hot deserts receive such
In the Sonoran Desert, in the United 2. Outline the distribu on of shallow low rainfall across the year. (6)
States, the great saguaro cac rely on water coral reefs across the world. (2)
migra ng bats to pollinate their night- 8. Outline reasons why rainforests
blooming flowers. The bats are 3. Outline the distribu on of the receive large amounts of rainfall. (4)
provided with an energy-rich drink of world’s hot deserts. (2) 9. Explain the reasons why tropical
nectar enabling them to fly across the 4. What is meant by the Sub-Tropical coral reefs are considered to be a fragile
desert. High Pressure (STHP) zone? (2) environment. (6).
Many animals have become 5. What is the Inter-Tropical 10. Describe and explain how some
nocturnal to avoid the intense heat of Convergence Zone (ITCZ)? (2) desert plants and animals have evolved
the day. The Sahara’s Fennec fox has adapta ons to be able to live in hot
excellent night vision and large ears, 6. Using fig.22 (p10) and fig.25 (p11), deserts. (8)

15

Ecosystems have distinct distributions and characteristics.