Transcript unit-3-prep-1

Unit three
Lesson three
Adaptation and continuity
of life
Adaptation of desert plants:
Roots
They may:
Extends vertically in the soil
for great depth to reach the
humid layers of soil (to
absorb ground water), or:
Spread horizontally to absorb
a large amount of rain water
and store it:
(as in cactus plant)
Leaves
-They are small-sized, may be ribbon-like.
-They are used in storing water as in cactus.
-They are surrounded with a waxy layer to
A waxy layer to prevent
water loss by
transpiration.
-They are modified into
spines to reduce the
the loss of water during
transpiration.
Stems
-They are short to avoid the strong winds
as in cactus plant.
-They may be rich in chloroplasts to
perform photosynthesis.
Aestivation
In summer, when the temperature rises up,
the living organisms face:
1- An extreme rise in temperature.
2- A shortage in water and rain.
So, they become dormant and hide in
humid burrows avoiding the effects of high
temperature to keep the constancy of their
body temperature. As, jerboa, desert snail
and some insects
Adaptation for hiding:
Some animals can hide from their enemies
or to capture their preys and this is known
by camouflage.
Examples:
1- Leaf Insect. ( Looks exactly like the
plant leaves)
2- Stick Insect. ( Looks like the plant
branches)
3- Chameleons. ( Color themselves the
color of the environment )
Structural adaptations to the
environment
The camel is called The desert ship.
* It is an example of the most adapted animal
to live in desert.
* It is an example of the structural,
functional and behavioral adaptation which
helped it to live in the hard condition of
deserts.
Some adaptation features of camels
1- Eye lashes.
* The eye contains plenty of glands and two
rows of long eye lashes to protect it from
sand storms.
2- Nostrils.
* It controls opening and
closing to protect it from
sand storms.
3- Ears.
* It has small ears and covered by plenty
of hair from inside to prevent sand from
entering .
4- Upper lip.
* The upper lip is forked and the teeth has
strong enamel to enable it to eat spiny and
dry desert plants without any harm .
5- Body fur.
* Fur is more dense at some parts of body to
protect the camel from cold and less dense
over other body regions to allow loss of heat
during the day.
6- Legs.
* The legs are thick skinned to protect it
from the high temperature.
They end by broad pads to prevent diving in
smooth sand.
7- Blood temperature.
* Its blood temperature is not constant and
Changes from 34°c in the morning to 41ºc
during daylight hours so camel has no need
for sweating.
8- Sweat glands.
* They don´t start sweating unless the blood
temperature reaches 40ºc.
9- Storing fats.
* A camel can store fat in its hump to keep
it alive for 3 – 4 months without eating.
10- Drinking water.
* Camel drinks about 100 liters of water in
in 10 minutes without affecting in the blood
composition.
This can keep it for one week without drinking .
11- Losing of weight.
* The camel loses about 25 % of their body
weight if there is no food or water.
That doesn´t affect its blood composition .