Classifying Plants PDF

Classifying plants We can easily compare plants based on their characteristics. For example: 1. their leaf size and shape 2. whether there are flowers or not 3. and how the petals look 4. the length and depth of the roots 5. the type of root system...

Classifying plants We can easily compare plants based on their characteristics. For example: 1. their leaf size and shape 2. whether there are flowers or not 3. and how the petals look 4. the length and depth of the roots 5. the type of root system 2 One particularly useful way is grouping plants according to how they reproduce sexually. If we group plants based on the way that they sexually reproduce we can quickly see two distinct groups: Plants with seeds Seedless plants Plants can also reproduce asexually by making a clone or copy of themselves. In this way new plants can grow from cuttings and tubers (like potatoes), from bulbs and rhizomes, or from shoots and side branches. Plants that do not produce seeds include ferns, mosses and algae. These plants produce spores. The spores often develop in structures found on the underside of the leaves or fronds. The spores grow into new plants. 3 Ferns have been around for about 400 million years. That is even older than dinosaurs, and they are still living on Earth today. The following photo shows a close-up of the underside of a fern leaf. Can you see the clusters of capsule-shaped structures that form the tiny spores? 4 The close-up photo on the right shows a moss sporophyte. This contains the spores of the moss plant. 5 Do you know what lichen is? You often see it growing on rocks and tree trunks. Do you think lichen is a plant? Lichen actually consist of two different organisms growing together! A fungus and a green alga grow together in a symbiotic relationship. The fungus absorbs water from the environment and provides the algae with an environment to grow in. The green algae photosynthesizes, providing food for the itself and the fungus. 6 The other group of plants produces seeds. These plants can either produce seeds in flowers or they can produce seeds in cones Plants that produce seeds in flowers are plants that produce seeds in cones are called angiosperms called gymnosperms. 7 8 Gymnosperms The word gymnosperm means 'naked seed'. Gymnosperms are considered to have naked seeds as the seeds are not covered in a fruit In South Africa we have plants called cycads that are often referred to as 'living fossils'. Cycads grew in great numbers during the Jurassic period. 9 10 Another gymnosperm which is native to South Africa, and grown a lot in the Cape is the Mountain Cypress. They grow especially well at high altitudes, such as in the Cederberg Mountains. 11 There are several species of gymnosperms which are not indigenous to South Africa. What does this mean? 12 Angiosperms Angiosperms are flowering plants. They produce flowers which develop into seeds that can grow into new flowering plants. We can group flowering plants into two major groups: monocotyledons dicotyledons All the angiosperm plants that we are studying have the following characteristics in common: roots stems leaves flowers fruits seeds 13 Monocotyledons: QUESTIONS: 1. Describe the leaves of the monocotyledons in the photos. How would you describe the veins in the leaves? Make a drawing to accompany your description. 2. Describe the stems. Are they woody stems or green (herbaceous) stems? 14 monocotyledonous flowers QUESTIONS: 1. Count how many petals are on each flower. 2. What can you generalize about the number of petals (and other flower parts) in monocotyledonous flowers? 15 Dicotyledons: QUESTIONS: 1. Describe the leaves of the dicotyledons in the photos. How would you describe the veins in the leaves. Make a drawing to accompany your description. 2 Describe the stems. Are they woody stems or green (herbaceous) stems? 16 dicotyledonous flowers QUESTIONS: 1. Count how many petals are on each flower. 2. What can you generalize about the number of petals (and other flower parts) in monocotyledonous flowers? 17 Look at the following image which shows the difference between monocotyledonous seeds and dicotyledonous seeds. Monocotyledons have one cotyledon dicotyledons have two cotyledons. 18