Grade Six Science

Hello Boys and Girls,

I trust you had a good week and that you will have an even better one. It’s time for Science once again and we’ll be looking at pollination for a bit. Do you remember the steps of pollination? Remind your friend of them.

For You to Do:

1. List the steps of pollination.

2. Name at least four agents of pollination.

3. Explain the two types/ways of pollination.

4. What is seed dispersal? Give two examples of how this can be done.

5. Where are the pollen grains found?

6. Where can the stigmas be found?

7. Name two types of pollination that you know of. Explain each of them. 8. Name at least three agents of cross pollination.

9. Which type of cross pollination seems to be the most common among flowers? 10. Describe flowers that are pollinated by a) insects b) the wind

11. Complete the following:

Check to ensure that your answers are correct.

Now let’s look at why pollination is important to the world.

Biological Importance

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Economic Importance

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Why is Pollination Important

Helps in the reproduction of flowering plants through the formation of seeds and then fruits

Produces food for humans and animals. More than half of the world’s fat and oils, such as oil palm, canola, and sunflowers, come from pollination. Almost all fruit and grain crop production in the U.S. depends on pollination.

Maintains genetic diversity within a plant population.

Helps water, oxygen, and carbon cycle to continue in nature.

Environmental Importance

Flowering plants produced through pollination helps in:

● Cleaning up the environment by producing oxygen and reducing the carbon dioxide level of the atmosphere.

Purifying the rainwater before reaching the water table.

Preventing soil erosion.

Helps in the production of food, medicines, fibers, oils, resins, latex, gums, tannins, soaps, waxes, and plant-based dyes.

What do you think would happen if no pollination takes place?

We looked at pollination and saw how important it was to the flower. (What are some of the animals that visit flowers in order to pollinate them?)

Yes, when the pollen grain falls on the stigma, it absorbs moisture and swells. As it swells, the covering bursts open and a tiny tube grows out of the pollen grain and into the ovary.

When the pollen tube reaches an ovule, a particle in the pollen grain passes down the tube in the ovule and unites with the particle in the ovule. This union of the two cells (male and female) is called fertilisation. Do remember that fertilisation comes after pollination.

So after pollination and fertilization, the fruit is ready to be formed. After successful pollination and fertilisation fruits may be formed. The ovules become the seeds and the ovary becomes the fruit. Of course, they become the fruits in accordance with the type of seeds. ● ● ●

A fruit is a ripe fertilised ovary of a flowering plant.

A seed is a fertilised ovule.

A seed is always found inside of a fruit. (except the strawberry)

You will see that the petals wither and drop off. (Their use is over – there is no need to attract agents of pollination.)

The ovules develop into seeds, and the other parts into the flesh and rest of the fruit. The fruit gets bigger and develops the specific features of that fruit.

The fruits can be utilised by man. They are sometimes picked by man; and of course this does not always occur. (Think of places where this will not happen.)

The fruit is used by the plant for spreading its species (kinds) far and wide. The spreading of fruits and seeds far and wide is called dispersal. Can you think of ways in which fruits and seeds can be dispersed (scattered)?

Chat about it with a friend. What did you come up with?

The dispersal of fruits and seeds can be by ● wind

● animals

● water

● explosive mechanism

Dispersal by Wind

The seeds dispersed by wind are small and light. Some of these seeds have wing-like structures, parachute- like structures, or are hairy. Can you suggest some examples? Did you mention silk-cotton, poppy, dandelion or thistle?

Dispersal by Animals

The fruits are often eaten and the seeds dropped, sometimes after passing through the body, e.g. guava, bird-vine. Some of these seeds have hooks or the seeds may be sticky and fasten to the bird’s beak so that they are wiped off on to a branch, e.g. bird-vine.

Dispersal by Water

Can you find any examples of seeds dispersed by water? The mangrove seed (we have been hearing a lot about mangroves recently) and the coconut are two examples. These seeds are dropped in the water and are carried away.

Dispersal by Explosive Mechanisms

Some fruits when ripe suddenly burst open and the seeds are then scattered near and far away from the parent plant. (Why is this an advantage for these seeds?) Many peas and beans do this.

Let's look at fruits for a short while. Of course they become the fruits in accordance with the type of seeds.

Let's look at fruits for a short while. Name as many fruits as you can in your Science scrap book and paste in some pictures of them. You can also draw and colour a few.

Complete the chart below.

A question for you- Do all fruits have seeds?

We will discuss more about this next week, DV. Until then goodbye, Boys and Girls, and be safe.