Plants The equation for photosynthesis can be completed as follows: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2 In this equation, carbon dioxide (CO2) and water (H2O), in the presence of light energy, are transformed by chloroplasts into glucose (C6H12O6) and oxygen gas (O2). This process occurs during photosynthesis, a vital metabolic process in plants that enables them to convert sunlight into chemical energy, stored in the form of glucose, while releasing oxygen as a byproduct. 2 Add labels to the diagram below to show how energy absorbed by plants keeps animals alive. Sun: The Sun provides energy in the form of sunlight. Plants: Plants absorb sunlight through their leaves and convert it into food. Food: The food plants make (glucose) contains energy. Herbivores: Animals like rabbits and cows eat plants to get energy from the food stored in them. Carnivores/Omnivores: Animals like lions and humans eat herbivores to obtain the energy stored in their bodies. Energy Transfer: The energy from plants passes on to herbivores, and then to carnivores/omnivores as they eat each other. In this simplified explanation, sunlight is converted into food by plants, and animals obtain energy by consuming plants or other animals. This energy transfer sustains animal life. 3 Add labels to the diagram below to show how water and carbon dioxide enter a leaf, where photosynthesis takes place, and what happens to the products made. Label: Leaf Explanation: The leaf is where plants make food. Label: Carbon Dioxide (CO2) Explanation: Plants take in carbon dioxide from the air through tiny openings on the leaf. Label: Water (H2O) Explanation: Plants get water from the ground through their roots, and it travels up to the leaf through tubes. Label: Photosynthesis Explanation: Inside the leaf, plants use sunlight to combine carbon dioxide and water to make food. Label: Food (Sugar) Explanation: The food made by plants is a type of sugar called glucose. It gives plants energy to grow. Label: Oxygen (O2) Explanation: As a byproduct of photosynthesis, plants release oxygen back into the air. In this simplified description, plants take in carbon dioxide and water, use sunlight to make food (glucose), and release oxygen. 4 Abiola placed cress seeds on damp cotton wool in two dishes. He placed one dish in a dark cupboard and one in bright light. Draw the seedlings in the diagrams below. Scenario 1: Seedlings Grown in Sunlight and Kept in Darkness After 2 days: Seedlings grown in sunlight: They will have started growing with green stems and leaves. Seedlings kept in darkness: They will have pale, elongated stems as they stretch towards light (which is not present). The seedlings in darkness may have underdeveloped or no leaves. After 7 days: Seedlings grown in sunlight: They will continue growing, with more developed stems and leaves. They will have a healthy green color. Seedlings kept in darkness: They will still have pale, elongated stems as they try to find light. Leaf growth will be limited or absent, and they will remain weak and underdeveloped. In summary, after 2 days, seedlings grown in sunlight will have green stems and leaves, while those kept in darkness will have pale, elongated stems with underdeveloped leaves. After 7 days, the seedlings grown in sunlight will continue growing with healthy green stems and leaves, while the seedlings kept in darkness will remain weak and underdeveloped, with limited or no leaf growth. Aphids feed by pushing pointed mouthparts into the phloem tubes in a plant's veins. a Explain what phloem tubes are and why plants need them. b Suggest how the aphids affect the plants they feed on. a) Phloem tubes are like tiny pipes inside plants that carry food and nutrients to different parts of the plant. Plants need them to distribute sugars produced during photosynthesis to where they are needed for growth, energy, and other important processes. b) Aphids, small insects that feed on plants, can harm the plants they feed on in a few ways: They damage the phloem tubes, disrupting the plant's ability to transport nutrients effectively. By sucking the sugary sap from the phloem, they take away the plant's food source, leading to weakened growth and development. Aphids can also spread diseases from one plant to another, causing further damage and reducing the plant's health. In response to aphid feeding, plants may undergo changes in their growth and defense mechanisms, which can affect their overall well-being. In summary, phloem tubes are important for transporting food in plants, and aphids harm plants by damaging the tubes, taking away nutrients, spreading diseases, and triggering changes in plant growth and defense. 13.2 Preliminary tests 1. The four sentences below describe how Salma investigated photosynthesis. Write the letter at the start of each sentence in the correct box on the diagram. a Salma measured the rate of photosynthesis under red, blue and green light. b Salma wondered whether the colour of light affected photosynthesis. The results showed that photosynthesis was faster under red and blue light. d Salma thought that plants could not use green light because they look green. This suggests that they reflect green light and absorb red and blue. In the diagram, you would place the letters corresponding to the sentences in the appropriate boxes based on their role in the investigation. For example: Sentence a: "Salma measured the rate of photosynthesis under red, blue, and green light." This would go under "Test the explanation." Sentence b: "Salma wondered whether the color of light affected photosynthesis." This would go under "Ask a question." Sentence c: "The results showed that photosynthesis was faster under red and blue light." This would go under "Check the evidence." Sentence d: "Salma thought that plants could not use green light because they look green. This suggests that they reflect green light and absorb red and blue." This would go under "Suggest an explanation." Place the corresponding letters (a, b, c, d) in the respective boxes on the diagram. 2 . Link each piece of equipment Salma used to the job it does. Ans; Question 2: Lamp: Produces white light. Filter: Removes every color from light except one. Syringe: Removes air from leaf discs. Timer: Measures how long leaf discs take to rise. Water: Provides dissolved carbon dioxide for photosynthesis. Marc plans to repeat Salma's experiment with a different plant. He checks his method. a. Leaf discs 50 cm from a lamp (in white light) take 47 minutes to rise. How should he change his method? b. Explain why this will improve his investigation. c. Marc tests his filter with a light meter. The reading under the green and blue ones is 100 lux but under the red one it is 200 lux. How should he change his method? d. Explain why this will improve his investigation. Ans: a. Marc should move the leaf discs closer to the lamp. b. This will improve his investigation because placing the leaf discs closer to the lamp will provide them with more light, which can increase the rate of photosynthesis. It will make the process faster and allow for more accurate measurements. c. Marc should find a filter that blocks green and blue light but allows red light to pass through. d. This will improve his investigation by ensuring that the filter effectively isolates the different colors of light being tested. It will provide clearer results by removing unwanted light and allowing Marc to specifically study the effects of red light on photosynthesis. 13.3 Plant growth 1. Color the leaves below to show how mineral deficiencies affect maize leaves. a. phosphorous deficiency b. Potassium deficiency c. Nitrogen deficiency a. Phosphorus deficiency: Color the leaves light green or bluish-green. Add purple discoloration along the veins. b. Potassium deficiency: Color the leaves yellow or pale. Create necrotic spots or yellowing along the edges of the leaves. c. Nitrogen deficiency: Color the leaves pale or yellowish-green, starting from the base and spreading towards the tips. Make the color uniform throughout the leaf. 2. Draw lines to link each statement on the left to one of the stages in developing a scientific explanation Ans: To link each statement on the left to the stages in developing a scientific explanation on the right: a. What scientists did to learn more about a mineral deficiency Stage: Collect evidence to test the possible explanation (i) b. Compared the control and test batches of maize. The leaves only turn yellow in the test batch. Stage: Check the evidence to see if it supports the suggested explanation (k) c. Suggested that the plants might be short of magnesium because the green chlorophyll in chloroplasts contains magnesium. Stage: Use creative thought to suggest a possible explanation (h) d. Wondered what makes maize leaves turn yellow in some parts of the country. Stage: Ask a question about something that has been observed (g) e. Grew two lots of maize. Gave the control batch every mineral and the test batch every mineral except magnesium. Stage: Collect evidence to test the possible explanation (i) f. Stage in developing a scientific explanation This is not linked to any specific statement. It represents the overall process of developing a scientific explanation. g. Ask a question about something that has been observed. This is not linked to any specific statement. It represents the stage of asking a question based on observation. h. Use creative thought to suggest a possible explanation. This is linked to statement c. i. Collect evidence to test the possible explanation. This is linked to statements a and e. k. Check the evidence to see if it supports the suggested explanation. This is linked to statement b. 3 Complete the sentences below to describe why each mineral is needed. Nitrogen is used to make ……………… Magnesium is used to make……………………. Photosynthesis and respiration rely on……………..and…………………………….. Ans: Nitrogen is used to make proteins, enzymes, and nucleic acids. It is an essential component of these molecules and is required for growth, development, and various metabolic processes in plants. Magnesium is used to make chlorophyll, the pigment responsible for capturing light energy during photosynthesis. It is an integral part of the chlorophyll molecule and plays a crucial role in the absorption of light and the conversion of light energy into chemical energy. Photosynthesis relies on sunlight and carbon dioxide. Sunlight provides the energy needed for the photosynthetic process, while carbon dioxide serves as the carbon source for building organic compounds. Respiration relies on oxygen and glucose. Oxygen is required for the breakdown of glucose during cellular respiration, where energy is released and utilized by the plant for various metabolic activities. Glucose, derived from photosynthesis, serves as the primary energy source for respiration. Scientists compared maize grown using hydroponics with maize plants grown using aeroponics. They measured how quickly they could take in minerals. The graph shows their results. a Describe the results in the graph. b Describe the main difference between hydroponics and aeroponics. d. How would the differences shown in the graph affect the growth of the plants? Ans: a. Results in the graph: The graph shows the mineral uptake (in units) over time (in minutes) for maize plants grown using hydroponics and aeroponics. The hydroponics line starts at 2 units and gradually increases to 6 units over time. On the other hand, the aeroponics line starts at 0 units and quickly rises to 4 units within a short period of time, then remains relatively stable. b. Main difference between hydroponics and aeroponics: The main difference between hydroponics and aeroponics is the way the plants receive water and nutrients. In hydroponics, plants are grown in a nutrient-rich water solution, while in aeroponics, plants are grown in a mist or air environment with the nutrient solution sprayed directly onto the roots. d. How the differences shown in the graph affect plant growth: The graph indicates that aeroponics allows for faster mineral uptake compared to hydroponics. This suggests that plants grown using aeroponics may have an advantage in terms of nutrient absorption and availability. This faster uptake of minerals can potentially promote faster growth, healthier development, and higher yields in plants grown using aeroponics compared to those grown using hydroponics. Additionally, the increased oxygen availability in aeroponics may also contribute to improved root development and overall plant health. 1 Makeup six sentences about plants and metals. Each sentence must use one word or phrase from each column of the table. You may need to use some words or phrases more than once. Ans: Plants can absorb a lot of metal, including many metals that are toxic in large quantities. Only small amounts of metals are needed for plant growth, as they are used to build their cells. Hyperaccumulators are plants that can absorb high metal concentrations, which can be used to clean soil. Plants need metals in trace amounts for various physiological processes. Some metals, when present in high concentrations, can be toxic to plant growth. Plants have the ability to prevent the toxic effects of metals by regulating the absorption and accumulation of metals in their tissues. 2. Colour and label the diagram below to explain how a hyperaccumulator can remove toxic metals from soil. Ans: Imagine a diagram of a plant in soil: Roots: Draw roots going into the soil. Toxic metals: Color some parts of the soil red to represent the presence of toxic metals. Hyperaccumulator plant: Color the plant green to represent a hyperaccumulator plant. Metal absorption: Draw arrows from the roots to the plant, indicating the plant's ability to absorb toxic metals from the soil. Metal storage: Inside the plant, draw circles or compartments to represent the storage of the absorbed toxic metals. Detoxification: Add symbols or arrows to show the plant's ability to detoxify or reduce the harmful effects of the toxic metals. Clean soil: Color the remaining soil area without toxic metals in a lighter color to represent the removal or reduction of toxic metals from the soil. In summary, a hyperaccumulator plant absorbs toxic metals from the soil through its roots. It stores these metals within its tissues and has mechanisms to detoxify or minimize their harmful effects. As a result, the soil surrounding the hyperaccumulator plant becomes cleaner as the plant removes or reduces the presence of toxic metals. 3 Scientists planted Chinese brake ferns in pots of contaminated soil. The graph shows how the amount of arsenic in these plants changed. a Where was most of the arsenic accumulated? b. When did the ferns take in most arsenic? c. Scientists plan to burn the ferns. The arsenic will be left in a small quantity of ash. Suggest one thing they could do with the ash. As: a. Most of the arsenic was accumulated in the roots of the Chinese brake ferns. b. The ferns took in the most arsenic at around 8 weeks. Regarding the use of ash containing arsenic, scientists could consider the following option: They could properly dispose of the ash in a controlled and contained environment, such as a hazardous waste facility, to prevent the release of arsenic back into the environment. This ensures the safe management of the toxic material and minimizes the risk of contamination.
