Life Science. Structure of a plant; Plants are living organisms just like. animals and humans. Like all living. things they need key things to live;

Transcription

1 6.6.3 Life Science Structure of a plant; Plants are living organisms just like animals and humans. Like all living things they need key things to live; water, sunlight, oxygen and food. Plants are different from animals because they can make their own food, they are known as producers. They also need to reproduce to ensure the species survives. Most plants are made of five basic parts each with specific jobs; 1. Roots 2. Stem 3. Leaf 4. Buds 5. Flower 51

2 Each part of the plant has important functions: Anchorage Gas exchange Structure/ strength Circulation Food production Waste removal Reproduction 1. Anchorage Just like a ships anchor a plants roots also hold the plant firmly in place. The roots anchor the plant in the soil so that it doesn t get removed by wind or animals. The part of the plant responsible for anchorage in plants are called the roots. 52

3 The larger and taller plants are, the bigger the root system is they needed for anchorage. The pictures show the different types of roots some plants have. Plant roots also take in water and dissolved nutrients from the soil. The root hairs absorb the water and nutrients from the soil to feed the plant and keep it alive. Main root Root hair 53

4 2. Circulation Water and nutrients are transported from the root to the plant through special tubes. The plant s circulation system is made of two types of tubes: Xylem: strong and thick tubes that transport the water and nutrients from the roots to the leaves. Phloem: thin tubes that transport dissolved sugars around the plant. In order to see the tiny tubes Xylem inside the plants scientists carefully slice open the root and stem and use a microscope to observe the small detail. 54 Phloem

5 Activity 1: You will need; Celery stick, beaker, water food colouring or dye, knife. Steps: Cut 2.5 cm from the bottom of the celery stick. Draw a picture of what you see across the celery cut Half fill the beaker with water and place a few drops of colouring to change the water colour. Place the celery into the beaker (the cut side in the water). Predict (P): What do you think will happen to the celery after it is placed in the coloured water?.. Leave overnight and observe the next day. Draw your observations in the box. Explain (E) What has happened?.. 55

6 3. Structure and strength The stem and roots provide the plant with structure and strength like a skeleton does for vertebrates. It supports the plants leaves and the tubes of the xylem and phloem so that water and minerals can be transported through the cells. 4. Gas exchange (Respiration) Leaves come in a range of shapes, sizes and colours. The top layer on the outside of the leaf is called the epidermis. It is usually waxy to help prevent the plant from losing too much water. The underside of the leaf also has an epidermis layer but this layer contains many tiny pores, breathing holes called stomata. Stomata CO2 entering H20 and O2 exiting 56

7 Activity 2: You will need; Hand lens, leaf, wax crayons. Steps; 1. Choose a leaf from outside - one that has already fallen on the ground don t pull one off a plant! 2. Examine both sides with the hand lens and draw in the boxes what you see on the top layer and the underneath layer. Top Layer Underneath Layer Make an impression of your leaf in the box using a wax crayon. Using another colour crayon trace the empty spaces where the veins are to show where the water and food travels through the leaf. 57

8 Activity 3: Teacher Demonstration You will need: One leaf from a tree (fresh), beaker, hot water. Steps: 1. Pour hot water into a beaker and place the leaf into the water. 2. Observe (O) the bubbles that form around the leaf. These are the leaf s stomata, tiny holes for breathing. Function of stomata; When the stomata are open carbon dioxide (CO2) from the atmosphere enters through the stomata. At the same time oxygen and water (H2O) is put back out into the atmosphere. Getting rid of the water is part of the waste process and helps to keep the plant cool. The stomata usually open in the daytime and close again at night. Stomata is the part of plant responsible for gas exchange and waste removal. 58

9 5. Food production Plants are known as producers, they use sunlight to make their own food. The process by which green plants make their food is called photosynthesis. Photosynthesis is carried out in all the green parts of plants, leaves and stem. Chloroplasts The leaves and stem are green because their cells contain a green pigment called chlorophyll. The chlorophyll is stored in the cells chloroplasts. The chlorophyll traps the light energy from the sun and converts it to food for the plant to use. Plants also use water and carbon dioxide to make food. Water + CO 2 + Sunlight (Chlorophyll) Sugar + Oxygen Food that is produced in the plant is usually stored in the plant itself. Some plants store the food in the stem and others store it in the roots. 59

10 The main function of the leaf involves three processes for food production: The stomata on the underside of the leaf allow the CO2 and sunlight to get inside the leaf. The chlorophyll absorbs light energy from the sun. The xylem and phloem transport the water and nutrients, and the phloem takes the food produced food around the plant. 60

11 Activity 4: You will need: Microscope, slide, cover slip, tiny leaf sample, drop of water, teat pipette. Steps: 1. Place the leaf sample on the slide and a small drop of water to wet the leaf, place a cover slip on top. 2. Place the slide sample on the microscope. 3. Experiment with different magnifications, adjusting the focus at each stage as needed. Look for the chloroplasts in the leaf. Can you see the cell wall or the leaf s stomata? 4. Draw what you observe under the microscope in the box. 61

12 6. Reproduction There are many different types of flowers; size, colour and shape. Like any living organisms plants need to reproduce to make new plants. Flowering plants grow from seeds, seeds are produced by the flower. Flowers also have male and female parts, which can be in the same flower or sometimes in different flowers. The following pictures show the main parts of a flower with male and female parts: Inside the flower are the parts of plant used for reproduction. 62

13 Activity 5: Teacher Assistance required You will need: One flower, scalpel Steps: 1. Teacher to dis-sect the flower using the scalpel down the middle (cross section) 2. Draw and label the cross section including the inside and outside parts of the flower in the space below; 63

14 Pollination is when pollen grains travel from the anther to the stigma. To make seeds, pollen grains must travel from the anther to the stigma. Some plants rely on insects to carry the pollen, other plants use wind or water. Once the pollen reaches the stigma, the pollen will meet the egg (ovule). The two cells will join together to form the seed inside the ovary. Fertilisation is the fusion of the pollen and the egg to form a new seed. 64

15 Key ideas: Plants are living things that have many functions. Different parts of the plant do different jobs, the main functions of the parts of a flowering plant are: o Anchorage Roots o Gas Exchange Stomata o Waste removal Stomata o Food production Leaf o Circulation Xylem and Phloem o Reproduction Flower Key words: Anchorage, Stomata, Xylem, Phloem, Chlorophyll, Anther Chloroplasts, Circulation, Pollination, Fertilisation, Stigma Project: Grow your own plant. You will need: Cotton wool, egg carton, seed (beans are good), water, warm spot (window-sill is good). Steps: 1. Place the seed inside the cotton wool and put in an egg carton. Wet the cotton wool down and place in a warm place. 2. Observe: 3. Record in a diary the growth and changes in the seed over 4 weeks. 65

16 Key Questions: Q1. List 4 things a plant needs to survive:..,..,..,... Q2. The plants parts have different functions. Complete the missing areas in the table: Plant Part Function in the plant Circulation of water and nutrients Flower Anchors and holds plant firmly in the soil Stomata Produces food for the plant Gets rid of waste 66