GRADE SIX SCIENCE

Hello Boys and Girls, Have you had a good week? Did you do lots of work during the week? Did you enjoy learning about flowers?

Great! Last week we looked at flowers. We will continue this week; but first let us answer a few questions on flowers to get you going.

1. Draw a flower and label it. 2. Name at least ten flowers found in Guyana. 3. What is the function of : the petals, the sepals and the epi-sepals?

Now let us continue by looking at how the parts of the flower function. Do remember that living things must reproduce to survive. Mature plants produce offspring (baby plants) that grow to be like their parents. Different kinds of plants reproduce in different ways. Flowering plants reproduce by growing flowers that make seeds.

Flowers are the sex organs of the plants. The male parts of the flower are the stamen and they make pollen. The pollen fertilises the female part (the pistil). Fertilisation results in seeds.

Pollination is the first step towards the formation of seeds. It is simply the transfer of pollen from the anther of a stamen to the stigma of a pistil.

Pollen grains are produced within pollen sacs inside the anther. These pollen sacs (usually four) open when the anther becomes mature and exposes the pollen grains. Pollination occurs when pollen grains fall on to the stigma of a flower.

Self – pollination takes place when pollen from the anther falls on the stigma of the same flower. Cross – pollination occurs when pollen grains fall on to the stigma of a flower on a separate plant. This is a more common method of pollination. Can you name any agents of cross – pollination? Share with a friend. Did your list include bees, other insects, man, other animals, water or wind?

Pollination by water is the least common. Pollination by wind is the simplest method. It is common among many plants. Plants that are only wind pollinated do not need to be sweet smelling or colourful. If the flowers do not have petals, they may be small and inconspicuous, often whitish.

The anthers of wind pollinated flowers hang outside of the flower. They release clouds of pollen grains into the air. The stigma and styles also hang outside these flowers. They are usually feathery so as to catch many pollen grains. Grasses and cereals are pollinated by wind.

Look at the table (at right) to compare flowers pollinated by the different agents.

For you to do: 1. Name four main parts of the flower.

2.

Describe and give the function of each of the following: leaf root stem flower

Insect pollinated flowers are usually large and bright. They may also have a scent and make sweet fluid called nectar. A bee visits a flower to collect nectar to make honey. Pollen from the anthers sticks to the bee. As the bee visits another flower, some pollen on its body bruises onto the stigma. Sometimes small birds pollinate flowers in this way.

Fertilisation and Fruiting Following pollination, the male pollen fertilises the female part of the flower and the ovules develop into seeds. The ovary becomes the fruit. It protects the seeds inside. Fruits take many forms. Some are soft and juicy. Others are hard and tough.

Until next week observe the visitors to the different flowers and name them. You can do so if you can. Goodbye!