Seed dispersal
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Seed Dispersal. flower pollinated by animals. Reproduction in plants — getting the flowers pollinated. Plants have adaptations to help them in pollination. Flowers that are pollinated by animals are usually large and colourful.

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Seed Dispersal

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Seed dispersal

Seed Dispersal


Reproduction in plants getting the flowers pollinated

flower pollinated by animals

Reproduction in plants — getting the flowers pollinated

  • Plants have adaptations to help them in pollination.

  • Flowers that are pollinated by animals are usually large and colourful.

  • They also have nectar and a fragrance so that the animals are attracted to them.


Reproduction in plants getting the flowers pollinated1

flower pollinated by wind

Reproduction in plants — getting the flowers pollinated

  • Plants have adaptations to help them in pollination.

  • Flowers that are pollinated by wind are usually small, plain and without fragrance because they do not need to attract animals.


From flower to fruit

From Flower to Fruit

  • When all the ovules in a flower have been fertilized, the petals, stamens, stigma and style are no longer needed.

  • They will usually wither and fall, leaving an ovary in which the ovules are developing into seeds.

  • The fruit protects the seeds.

  • What is so important about seeds such that they need protection?

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GE2009


Flower to fruit

Flower to Fruit

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GE2009


Pea fruit from flowers

Pea fruit from flowers

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


The fruit and the seeds

The Fruit and the Seeds

  • Seeds will grow into new plants and ensure the continual existence of that type of plant.

  • However, seeds cannot grow too close to their parent plant. Why?

    • OVERCROWDING

      • Overcrowding leads to competition for:

        • Water

        • Space

        • Nutrients

        • Light

    • Get to grow in new habitats where conditions may be even better.

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Before we look at dispersal

Before we look at dispersal…

  • Take note of the THREE points:

  • Dispersal method of the fruit and the dispersal agent.

  • Characteristics of the fruit that supports dispersal.

  • Dispersal pattern of the fruit.

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Agents of dispersal

AGENTS OF DISPERSAL

  • Seeds and fruits are modified in different ways to be dispersed using one or two of the agents of dispersal.

  • Which parts get modified?

The testa and pericarp are often modified to help in dispersal

Seed

An ovule which has been fertilised and become mature. Its wall is the testa.

A mature ovary which contains fertilised seeds. Its wall is the pericarp

Fruit

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Reproduction in plants getting the seeds dispersed

Reproduction in plants — getting the seeds dispersed

  • Flowering plants have different adaptations to enable their seeds to be dispersed as far away as possible.

  • The different methods of seed dispersal are…

    • by wind

    • by animals

    • by water

    • by splitting open forcefully


Reproduction in plants getting the seeds dispersed1

Reproduction in plants — getting the seeds dispersed

What are the adaptations that help thesefruits/seeds to be dispersed?

  • Dispersal by wind

  • small

  • light

  • dry

  • wing-like

shorea

angsana


Dispersal by wind

Dispersal by Wind

  • Plants which depend on the wind for the dispersal of seeds usually have

    • light seeds or

    • wings or

    • a parachute of fine hairs or

    • feathery hairs that act like many little parachutes

  • to help keep them floating in the air

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Dispersal pattern wind

Dispersal Pattern - Wind

Parent

Wind direction

Legend

Offspring


Reproduction in plants getting the seeds dispersed2

How about lovegrass? How does it disperse?

Reproduction in plants — getting the seeds dispersed

What are the adaptations that help thesefruits/seeds to be dispersed?

  • Dispersal by animals (eaten)

  • bright colours

  • sweet

  • juicy

  • Dispersal by animals (carried)

  • small

  • hooks stiff hairs

tomato


Dispersal by animals

Dispersal by Animals

  • Three ways

    • First way

      • The seeds or fruits have hooks or sticky hair that catch onto the fur of animals or clothing of human beings

    • Second way

      • Fruits get eaten by animals and seeds are thrown onto the ground as they are too big to be eaten by animals; or

      • Fruits and seeds get eaten by animals but the seeds are too hard to be digested by animals and are passed out in the droppings

    • Third way

      • Animals collect the fruits and seeds and take them to their burrows.

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Dispersal pattern animals

Dispersal Pattern - Animals

Parent

Wind direction

Legend

Offspring


Reproduction in plants getting the seeds dispersed3

Reproduction in plants ― getting the seeds dispersed

What are the adaptations that help thesefruits/seeds to be dispersed?

  • Dispersal by water

  • buoyant

  • waterproof

  • air spaces

  • Dispersal by splitting open

  • dry and hard fruit wall

coconut

saga


Dispersal by water

Dispersal by Water

  • Plants which depend on the water for the dispersal of seeds usually have

    • Some feature that will allow it to float

    • Some protective covering to protect it during its long water journey.

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Seed dispersal

Pong Pong

Coconut

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Seed dispersal

Nipah Fruit

Lotus Fruit Pod

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Dispersal pattern water

Dispersal Pattern - Water

Parent

Downstream

Wind direction

Legend

Offspring


Dispersal by explosive mechanism or splitting of the fruit

Dispersal by Explosive Mechanism or Splitting of the Fruit

The fruit wall suddenly breaks into several parts and the movement causes the seeds to be shot out. This is caused by the unequal drying up of the fruit wall. The wall may split in one, two or many places along the line/lines of dehiscence (lines of splitting).

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Seed dispersal

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Seed dispersal

Unripe

Ripe

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Seed dispersal

Ripe and unripe Kapok fruits

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Seed dispersal

Mrs Theresa Teo GE2003

Edited Mr Lin Lixun GEO2009


Dispersal pattern splitting action or explosive mechanism only

Dispersal Pattern – Splitting Action or Explosive Mechanism Only

Parent

Wind direction

Legend

Offspring


Dispersal pattern splitting action with wind

Dispersal Pattern – Splitting Action WITH Wind

Parent

Wind direction

Legend

Offspring


At a glance

seed dispersal

by wind

by water

by animals

by splitting open

  • Fruits/seeds

  • dry and hard fruit wall

  • Fruits/seeds

  • small

  • light

  • dry

  • wing-like

  • Fruits/seeds

  • buoyant

  • waterproof

  • air spaces

  • Fruits/seeds

  • brightly coloured

  • sweet

  • juicy

  • Fruits/seeds

  • small

  • hooks

  • stiff hairs

At a glance…

Adaptations for reproduction

plants


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