Natural Sciences Grade 7 Term 1: Life and Living Biodiversity (PPT 5)

Diversity of Plants (Part 1) Topic 2 Biodiversity Diversity of Plants (Part 1) Natural Sciences – Grade 7

Natural Sciences - Grade 7 Diversity of Plants There are over 290 000 species of plants all over the world. Their specific characteristics depend on the environment in which they live. The plant kingdom is divided into 2 main groups: 1. seed producing plants 2. spore producing plants Seeds = reproductive structures produced by flowering plants. Spores = small, single celled structures used for reproduction in some plants. Natural Sciences - Grade 7 3

Natural Sciences - Grade 7 Diversity of Plants Natural Sciences - Grade 7 4

Natural Sciences - Grade 7 Diversity of Plants Natural Sciences - Grade 7 5

Spore producing plants Some plants do not produce flowers or seeds. Examples: Mosses Ferns Natural Sciences - Grade 7 6

Spore producing plants They produce spores which are used for reproduction. In ferns, the spores develop in sori on the lower surface of the leaves. These spores are spread by the wind when they are ripe. Sori = spore producing structures that grow on the lower surface of fern leaves. Natural Sciences - Grade 7 7

Natural Sciences - Grade 7 Seed producing plants Plants that reproduce using seeds can be classified into two groups: Angiosperms and Gymnosperms Natural Sciences - Grade 7 8

Natural Sciences - Grade 7 Angiosperms The word “Angiosperm” comes from – Latin word angi = enclosed Greek word sperma = seed Therefore, Angiosperms are flowering plants that have closed seeds. Natural Sciences - Grade 7 9

Natural Sciences - Grade 7 Angiosperms It is the most diverse of plant groups. It is the largest group in the plant kingdom. All angiosperms reproduce using flowers. Seeds grow inside the flower after fertilisation. Please explain that to be diverse and large are two different things: Diverse = a large variety Large = a very big group (in numbers) You can see the pip or seed inside the fruit. We say that angiosperms produce “covered seeds” because the seeds are enclosed inside the fruit. Note: fertilisation will be discussed in topic 3. Natural Sciences - Grade 7 10

Natural Sciences - Grade 7 Gymnosperms These plants also produce seeds. But they are not surrounded by a fruit. The seeds form in cones instead of in flowers. Examples of gymnosperms include cycads and pine trees. Gymnosperms have male and female cones. With Angiosperms, the ovules are inside an ovary. With Gymnosperms, the ovules form on the scales of the female cone (e.g. The large cones on pine trees). The smaller male cone produces pollen, which is carried by the wind. Pollination occurs when the pollen lands on the female cones. Fertilisation occurs, then seeds form of which some will grow into new plants. Natural Sciences - Grade 7 11

Natural Sciences - Grade 7 Difference between Gymnosperms and Angiosperms during their seed formation This illustrates the difference between gymnosperms and angiosperms during their seed formation. It is not necessary to know detail, but it is important to show that gymnosperm seeds are made in a cone (hence they are also called conifers) and the seeds are exposed to the air. This is why they are called naked seeded plants. Angiosperms develop seeds within a fruit. They can produce many seeds like a tomato or fewer like an apple or even one, like the pip of an avocado or peach. The fruits or nuts develop from a flower which gymnosperms do not have. So if you see a plant that has flowers on it, it is an angiosperm. Natural Sciences - Grade 7 12