1. Natural Sciences Grade 7
Term 1: Life and Living
Sexual Reproduction in Angiosperms
(PPT 4)

2. Topic 3 Sexual Reproduction
Seed Dispersal
Natural Sciences – Grade 7

3. Dispersal of Seeds and Fruits
Seeds need light, air, water, warmth and nutrients in order to grow.
Young plants will compete for the same resources as the parent plant.
It is an advantage for the seeds to be dispersed far away from the parent plant.
This dispersal can occur in a number of ways: wind, water, plant adaptations, animals and humans.
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

4. Wind
The seeds of the dandelion have hair-like extensions that help them drift away in the wind.
Some seeds, like the forest bush willow seeds, have wings to help them to be carried by the wind.
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

5. Fruits and seeds dispersed by the wind
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

6. Water
Some seeds are waterproof and can float, for example, the coconut.
Reed plants have a covering that traps air and allows the seed to float on water.
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

7. Water dispersal of seeds
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

8. Plant adaptations
The seeds of some plants dry out and then burst open. The “explosion” forces the seeds to disperse away from the parent plant.
Some seeds split when they fall to the ground. This causes the fruit to roll away from the parent plant.
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

9. Animals and Humans
Some seeds develop fruit to attract animals to eat them. The seeds are not digested, but pass through the animal and is released in the droppings.
Certain seeds have thorns, hooks and barbs. This allows the seed to stick to the fur of animals and shoes of people. The seeds later fall off in other places.
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

10. Seed germination
Seeds are able to survive bad conditions (extreme heat or cold) by going into a dormant state.
The seed will begin to grow when conditions become suitable.
Suitable conditions for seeds to grow are: water, oxygen, light and the right temperature.
When seeds begin to grow, we call it germination.
Dormant – not growing
Natural Sciences - Grade 7
Natural Sciences - Grade 7
Natural Sciences - Grade 7

11. Seed germination Natural Sciences - Grade 7 Natural Sciences - Grade 7