Unit 1 " Matter & its construction "

Lesson 3Adaptation & continuity of life

* Mammoth & dinosaurs extincted because they couldn't adapt to environmental conditions .* Some forms of adaptation in living organisms :

1- Hibernation:Some reptiles & some insects hid in burrows also frogs bury themselves in the mud in winter . (GR ) To overcome low temperature.

2- Aestivation:Jeroboa , desert snail & some insects hide in humid burrows during summer . (GR ) To overcome high temp & shortage of water .

3- Birds migration:Some birds e.g. Quail migrate in winter from cold regions to warmer regions then they return back to their homes in spring . (GR ) To overcome low temperature .

4- Adaptation for hiding:Camouflage: It's the ability of some living organisms to hide from their enemies or capture the prey . examples:- Leaf insect , stick insect & chameleon .5- Adaptation in aquatic plants :

Aquatic plants ( totally submerged e.g. elodea ) .( Partially submerged e.g. Nile rose)

Aquatic plants face 3 problems :

1- Shortage of oxygen 2- Shortage of light 3- Water currents

Adaptation of elodea plant :

- Roots are weak ( GR ) * they don't need to fix the plant or absorb water- Leaves are small , thin , ribbon like & neck less (GR )* not to be cut by water currents .

- Stem is elastic .( GR )

* not to be cut by water currents .

- Stem has air vacuoles .( GR ) * to store oxygen that helps in respiration & keeps the floating .6- Adaptation in desert plants :

Desert plants face 3 problems :

1- Shortage of water 2- High temperature 3- Strong wind

Adaptation in desert plants :

- Roots may extend vertically for long distances in Calamagrostis plant ( GR ) To reach underground water.

- Roots may extend horizontally for long distances in Cactus & Opuntia ( GR ) To absorb rain water .

- Leaves are small , ribbon like spiraled around themselves & have few stomata ( GR ) To reduce loss of water by transpiration process .

- Leaves are modified into spines in Opuntia plants ( GR ) To reduce loss of water by transpiration .

- Leaves store water in cactus & they are covered with wax ( GR ) To reduce loss of water .- Stem are short in cactus & calamagrostis (GR ) . To avoid strong winds .

- Stem are rich in green plastids ( GR )

To perform photosynthesis .7- Adaptation in camel :

- Camel has large no. of lachrymal glands & long eyelashes ( GR )To protect its eye from sand.- Camel can close & open its nostril ( GR )To prevent sand from entering its nose.- Camel has forked upper lip & strong teeth. (GR )To eat spiny & dry desert plants without harming it.- Camel has small ear covered from inside with hair (GR )To prevent sand from entering them.- Camel has flat pads (GR ) To walk easily on sand not sinks.- Camel has thick skin in its pads ( GR )To walk on hot sand

- Camel don't sweat till its blood temperature reaches 40 C (GR)To decrease loss of water.- Camel stores fats in its hump to keep it for 3 4 months without eating any food.( GR ) Camel can stay without food for 3 months .Note:

- Camel stores fats in its humps & stores 100 liter of water in one of its stomach - Camel can lose 25 % of its body weight when water and food are not available. PAGE 5