Biology: Wrold of Plants
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Advantages of there being a wide variety of plants:
1. They vary in size - From microscopic alge to giant trees.
2. They can be found in different habitats - Eg, deserts, salt water, forests.
If man continues to destroy forests then:
1. Plants will become extinct.
2. Animals that depend on those plants for food or shelter will also be affected.
The main uses for plants are:
1. Medicine: Eg morphene from poppies.
2. Food: Eg flower from wheat
3. Building Materials: Eg wood for furniture
1. Land is prepared. (Trenches are dug to drain out water and add air.)
2. Young trees are planted.
3. Weeds are cleared and animals are kept away.
4. Trees are thinned. (Ie only the best ones are kept.)
5. Lower branches are removed.
6. After 50 years the trees are chopped down.
7. Wood is used (Eg furniture, telegraph poles or railway tracks.)
Potential uses for plants provide us with:
1. New medicines eg, anti-cancer drugs or antibiotics.
2. New food sources.
Provides starch for the embryo.
Grows and develops into the new plant.
Testa (Seed Coat)
Protects the embryo.
Germination will only take place if the avaliability of _______ and _________ are right.
Germination will only take place if the avaliability of water and temperature are right.
As temperature increases from 0oC to 20oC seed germination chances will ___________. At temperatures above 20oC, germination will ____________.
As temperature increases from 0oC to 20oC, seed germination chances will increase. As temperatures above 20oC, germination chances will decrease.
Protects the unopened flower.
Attracts insects and animals
Male reproductive organ.
Contains male gametes. (pollen)
Where pollen grains land.
Contains female gametes. (ovules)
Contains a sugary solution called nectar.
The transfer of pollen grains from the anther to the stigma.
Self Pollination is...
The transfer of pollen from the anther to the stigma of the same plant.
Cross pollination is...
The transfer of pollen from the anther to the stigma of a different plant.
Insect Pollinated plants have:
1. Large and brightly coloured flowers.
2. A nectary with nectar.
3. Anthers and stigmas are enclosed within the petals.
4. Fewer, but larger pollen grains.
Wind Pollinated plants have:
1. Small and dull flowers.
2. No nectary or nectar.
3. Anthers and stigmas hang outside the petals.
4. Many small, smooth and light pollen grains.
Stages of Fertilisation:
1. Pollen grain lands on the stigma.
2. Pollen grain grows a tube down the ovary.
3. The nucleus from the pollen grain travels forn the tube and enters the ovule.
4. Male and female nuclei fuse and a zygote is formed.
How fruit formation occurs:
The petals, stigma, style and anthers die, leaving the fertilised ovules inside. the ovules become seeds. The ovary wallswells into a fruit or a nut.
Methods of Seed Dispersal.
1. Animal internal: Strawberry, tomato.
2. Animal External: Burdock, cleavers.
3. Wind Pollination: Elm, ash.
4. Explosion: Sweet pea, violet.
Methods of growing plants artificially:
- 1. Grafting
- 2. Layering
- 3. Taking cuttings
Advantages of growing plants artificially:
2. Can produce large numbers of plants.
3. Quality of fruit is assured.
4. A way of conserving rare plants.
A clone is...
the offspring of a plant which are genetically identical to each other and their parent.
Underground Food Stores
A from of Asexual reproduction which could include:
1. Bulbs: Eg onions or dafodills.
2. Tubers: Eg potatoes.
Another from of Asexual reproduction. Eg spider plants and strawberries.
Advantages of Sexual Reproduction in plants:
1. Variation is created.
2. Wider habitats are exploited (Through seed dispersal.)
3. Less competition between offspring.
Advantages of Asexual Reproduction in plants:
1. Quick method of reproduction.
2. No vulnerable stages involved.
3. Since offspring are clumped, if enviroment suits the partent it will suit the offspring.
4. Reduced competition from other species.
All cells in a plant need supplied with:
Specialist cells exist to do this.
Carries water from the roots to the leaves.
Carries food from the leaves to the roots.
What cell do plants use to take in Carbon Dioxide?
External Leaf Structure:
Central Leaf Blade
Bundles of xylem and phloem transport water and sugar.
Very large surface area to absorb light.
Internal Leaf Structure:
Protects the inner layer of cells and is transparent to allow light through.
Top layer of cells arranged to have maximum exposure to sunlight. Responsible for the majority of photosynthesis.
They have moist air spaces between them which allow gases to dissolve and diffuse easily between cells.
Contains small holes called stomata, which allow gases in and out of the leaf.
What is lost through stomata?
What happens in Green plants if excess glucose is produced?
It is stored as starch.
How do green plants convert light energy into chemical energy?
Word Equation for Photosynthesis
- Carbon Dioxide + Water ---> Glucose + Oxygen
- * Carbon Dioxide and Water are the Raw materials.
* Glucose and Oxygen are the products.
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