Seeds and seed dispersal, part 2 KS3

Learning Objective To understand the different ways in which plants disperse their seeds.

What does seed dispersal mean?

Seed dispersal is when seeds are transported from the plant to another area in order to grow.

What do you think plants decide to spread their seeds out over a wider area?

If a mother plant and a baby plant are in the same place they will compete for water, sunlight and carbon dioxide. The baby plant is much weaker and therefore will in most cases not receive enough and die.

With your talk partner can you think of any ways in which seeds might travel from one place to another?

We call these methods of seed dispersal.

Animal dispersal by hooked fruits Some species of plant use hooks on their fruits.

These attach themselves to the fur of mammals or feathers of birds and get carried from one place to another.

Acorns fall from the tree and sprout Acorns fall from trees and roll.

If they are not destroyed by animals, white oak acorns can sprout rapidly after falling from the tree.Â

Animal burial Hard nuts are usually destroyed if chewed or eaten. However, animals such as squirrels may store them to eat later and forget to go back to get them, giving them a chance to germinate. On rare occasions, birds such as blue jays can transport acorns long distances.

Soft fruit dispersal Fleshy fruits are eaten by animals.

The seeds are then dispersed after passing through the digestive system of animals that have eaten the fleshy fruits.Â

Wind dispersal Some plants, such as the dandelion, have seeds that act as parachutes, which are carried away by the wind.

Spinning dispersal Maple fruits are winged, two-seeded pods. They spin like helicopters as they fall from the tree, providing a longer time for dispersal by wind.

Plantlet reproduction Spider plants, amongst others, send out stems which produce plantlets, these baby plants then try to root themselves.

Carried by water Some plants grow near rivers, lakes, streams or oceans.

Their fruits/seeds fall from the plant and are carried away by the water.

Exploding Plants Spider plants, amongst others, send out stems which produce plantlets, these baby plants then try to root themselves.

Watch seed pods exploding http://www.youtube.com/wat ch?v=j2zlhQxoRZQ

Questions to ask about your seed?

1. Is the seed coated with edible flesh?

2. Is your seed heavy or light?

3. Is your seed sticky?

4. Does your seed have hooks?

5. Is your seed found by water?

6. Does your seed have wings?

7. Does your seed roll?

8. Have you ever seen animals holding your seed?

9. Has your plant have long stems which could root and form new plants?

10. Does your plant explode?

Lets finish by looking at this short video clip http://www.bbc.co.uk/learn ingzone/clips/seeddispersal/2258.html