Fruit and Seed Dispersal (Leaving Cert Biology): Revision Notes

Fruit and Seed Dispersal

• Dispersal is the carrying of the seed as far as possible from the parent plant.
• Dispersal is necessary to:
  • Avoid large numbers of seeds competing with one other and with the parent plant.
  • Increase the chance of survival for the plant.
  • Find new areas for growth.
  • Increase the numbers of the species.
• The main methods of seed dispersal are wind, water, animal, and self-dispersal.

1. Wind Dispersal

• Some seeds are very small and are carried long distances by the wind.
• Dandelions, thistles, and clematis produce parachute devices that help to disperse the seeds.
• Sycamore and ash produce fruit with wings that increase the distance over which the seeds can be dispersed.

2. Water Dispersal

• Seeds or fruits are light, buoyant, and adapted to float.
• Common in plants near water.
• Plants like the water lily and coconuts have light, air-filled fruits that can float and are dispersed by water.

3. Animal Dispersal

• There are two methods of animal dispersal:

1. External Transport

• Sticky or hooked seeds attach to the fur, feathers, or skin of animals and are carried away.
• Examples: Burdock, goose grass.

2. Internal Transport

• Edible fruits are eaten by animals, and the seeds pass through their digestive system unharmed.
• Examples: Blackberries, strawberries.

4. Self Dispersal

• Some plants have mechanisms to eject seeds forcefully from the fruit.
• Peas and beans: Have dry fruits (pods) that shrivel and burst open, scattering seeds.