P6 Photosynthesis Notes

1.1 Importance of Energy to Living Things

1. Energy is the ability to do work.

2. The life processes of all living things are nutrition, respiration, growth, excretion, movement, reproduction and sensitivity to stimuli. Living things need energy from food to carry out the life processes.

⚡ Where Does Energy Come From?

3. The Sun is the primary or main source of energy for all living things on Earth.

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DID YOU KNOW? All the food you eat — whether it's rice, meat, or fruit — originally got its energy from sunlight!

1.2 How Plants Obtain Energy

1. Plants make their own food using:

(a) light energy obtained from the Sun,
(b) carbon dioxide from the air and,
(c) water from the soil.

2. The process through which plants make their own food is called photosynthesis.

3. A green substance found in plant cells helps to trap light energy from the Sun. This substance is called chlorophyll.

4. Chlorophyll is mostly found in the leaves of plants.

🌿 How Plants Make Food — Photosynthesis

5. During photosynthesis, plants produce:

(a) food in the form of sugar, which will provide the plants with the energy needed for their life processes, and
(b) oxygen gas, which is used by living organisms.

6. Excess food in plants is converted to starch, which can be stored in plant parts such as roots, stems (tubers), seeds and fruits.

🌱 How Plants Transport Materials

1.3 How Animals Obtain Energy

1. Animals cannot make their own food unlike plants because they do not have chlorophyll that traps light energy needed for photosynthesis. Instead, animals obtain the energy needed for life processes by eating food.

2. Animals can be grouped according to the types of food they eat. The three groups are:

🔗 What Do Animals Eat?

(a) plant eaters (herbivores) — animals that eat only plants,
(b) animal eaters (carnivores) — animals that eat only animals, and
(c) plant-and-animal eaters (omnivores) — animals that eat both plants and animals.

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DID YOU KNOW? Humans are omnivores! We can eat both plants (fruits, vegetables) and animals (meat, fish). That's why we need to choose a balanced diet.

1.4 Rate of Photosynthesis

1. The rate of photosynthesis refers to the speed at which plants make food in the presence of light.

📊 What Affects How Fast Plants Make Food?

2. Factors that affect the rate of photosynthesis include:

(a) intensity and colour of light,
(b) amount of chlorophyll in the leaves, and
(c) amount of carbon dioxide in the air.

3. The greater the intensity of light, the amount of chlorophyll in leaves and the amount of carbon dioxide in the air, the faster the rate of photosynthesis.

📝 Photosynthesis Equation

Light Energy + Carbon Dioxide + Water
↓ (in the presence of chlorophyll)
Sugar (Food) + Oxygen

🌍

DID YOU KNOW? Without photosynthesis, there would be no oxygen for us to breathe and no food for us to eat! Plants are literally keeping us alive every day.

🌿 Photosynthesis