Natural Sciences Grade 7 Term 1: Live and Living Sexual Reproduction in Angiosperms (PPT 2)

Topic 3 Sexual Reproduction Pollination Natural Sciences – Grade 7

Process of sexual production in Angiosperms 4 Steps in the life cycle of a plant: pollination fertilisation seeds and fruits form seeds germinate and new plants grow Flowers are reproductive organs of the Angiosperm plant. Most flowers contain male and female parts. Sperms form in the male parts of the flower and Ova (eggs) from in the female parts of the flower. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Pollination It is the transfer of pollen from the anther to the stigma. Pollen is spread by pollinators. Examples: insects, birds and mammals Flowers are adapted to the various methods of pollination. After the sperm and ova have formed in the reproductive organs of the flower, the sperm must get to the ovum. The sperm is in the pollen of the flower. Pollination is when ripe pollen goes from the anther, to the ripe female stigma of the same species. Seed can only form in a flower if it has been pollinated. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Wind pollination Grasses is an example of wind pollinated flowers: they sit at the tips of long stems they do NOT have bright petals, nectar or a scent. their pollen is very small and light. they have long stigmas and filaments that hang out of the flowers. The flowers of wind pollinated plants do NOT have to have brightly coloured and scented flowers as they do NOT have to attract insects, birds or bats. The pollen is light so that it can be carried by the wind and the long stigmas and filaments allow the pollen to be exposed to the wind. Grasses are typical examples of flowers that use wind pollination. Ask your learners if they know what a grass flower looks like. Chances are that not many will know, as this is because they are very small and are not colourful. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Wind pollination These flowers produce a large amount of pollen. This increases the chances of pollen landing on stigmas. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Pollination by Water Plants that live in water are usually pollinated by the movement of water. The pollen grains from the stamen of the one plant will be carried across the surface of the water to the pistal of another flower. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Pollination by water Natural Sciences - Grade 7

Pollination by insects and birds Insects, birds, bats and mice are important pollinators of plants. These insects and animals rely on pollen and nectar as food. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Insect pollinated flowers have a sweet scent are brightly coloured - usually blue, red, white or purple produce nectar produce sticky pollen to stick to the insect have stamens and a stigma inside the flower Insect pollinated flowers have a sweet scent to attract the insects as insects have a very good sense of smell. The colours mentioned on the slide are typically the colours that attract insects. The sticky pollen sticks to the insect’s body or legs and this rubs onto the body, because the insect has to enter the flower to access the stamens and stigma. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Pollination by insects Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Bird pollinated flowers have brightly coloured petals - usually red, yellow and orange have no scent produce large amounts of nectar flowers are tube shaped have long stamens and stigmas Bird pollinated flowers do not typically have a scent as birds do not have a good sense of smell. They produce larger amounts of nectar as food for the birds. They are tube shaped so that pollen sticks to the birds’ beaks when they visit the flowers. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Flowers are adapted for pollination Flowers have evolved over time and have adapted to the way in which they are pollinated. Adapted means: to be suited to the particular conditions; how the plant looks and behaves to survive where it lives. Animal pollinators have also evolved over time to pollinate a particular flower. Adapted = suited to the particular conditions. Explain that, over millions of years, the structure of the flower has changed in ways that make it more likely to be pollinated by one particular pollinator. The animal visits the flower for food and it has also become adapted over time to pollinate particular flowers. Therefore we say the flower and the animal pollinator have evolved together over time. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Flowers are adapted for pollination To pollinate a type of flower, the animal must – visit that type of flower regularly, e.g. for food prefer that type of flower so that it can carry the right kind of pollen as it moves from flower to flower The plant must - give a reward, e.g. food or something attract the animal, e.g. smell, colour or shape be shaped in such a way that it puts pollen on that particular size and shape of animal Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Adaptations for insect pollination Insect pollinated plants usually have – brightly coloured petals sugar-rich nectar honey-guides stigma and style in the correct position to dust pollen onto the insect or to pull it off the insect a landing platform for the insect Two-thirds of flowering plants are insect pollinated. Honey-guides = lines that direct the insect to the correct place on the flower. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Adaptation facts: moths moths fly mostly at night moth pollinated flowers are usually white or very pale with a strong night scent (smell) Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Adaptation facts: bees The shape and colour of the flower will depend on the type of insect that pollinates it, for example – bees cannot see red colours bee-pollinated flowers are usually yellow, blue or ultra-violet Humans cannot see ultra-violet Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

How do bees pollinate flowers? bees collect nectar from a young flower the hairs on the bees’ bodies get brushed with pollen from the ripe stamen the stamen shrivels up the stigma ripens and moves into position bees are attracted by nectar from the older flower some of the pollen on them will enter the flower and the sticky stigma brushes the pollen off. Further explain this process by means of the diagramme on the next slide Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Pollination by bees Natural Sciences - Grade 7

Adaptations for bird pollination Bird pollinated plants usually have – brightly coloured petals sugar-rich nectar large size with narrow tube wide enough for a bird’s beak, but too narrow for insects to eat the nectar stigma and style in the correct position to dust pollen onto the bird’s feather or to pull it off a strong stalk as a landing platform for the bird to perch on or flowers hang well out of the plant so the birds can feed by hovering in front of the flower Bird pollination is much less common than insect pollination. Birds need larger, stronger flowers and more nectar, because they are much larger than bees. Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Adaptation facts: birds birds are attracted to red colours birds have a weak sense of smell, so bird-pollinated flowers are often not scented Not scented = has no smell Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7

Pollination by birds Natural Sciences - Grade 7

Humans depend on pollinators We depend on seeds for our food crops. Without pollination, there will not be any seeds. Wind pollinated crops such as cereals are grown in large blocks close together e.g. maize, rice and wheat. Animal pollinated crops are mostly pollinated by bees. In fruit and vegetable growing areas, beekeepers move hives from one orchard to another in fruit and vegetable growing areas: fruits, e.g. apples, pears, citrus vegetables, e.g. peas, beans, marrows and tomatoes Citrus = oranges, naartjies, lemons Natural Sciences - Grade 7 Natural Sciences - Grade 7 Natural Sciences - Grade 7