• Cells are the basic unit that builds on all living things. It performs all life functions such as growth, respiration and excretion

• Cells are divided into two types :

1. Animal cells

2. Plant cells

• Unisel organisms are organisms that have only one cell.

• Examples: - Paramecium, Chlamydomonas, Euglena & Amoeba

• Multicellular organism is an organism consisting of more than one cell.

• Examples: - Hydra, Spirogyra, Mucor, cat & human

• Specific cells are cells that have been differentiate and customize to perform specific functions.

• Examples :

  1. Epithelium cells - Forms a layer that protects the organs of the body. These cells also secrete mucus.

  2. Muscle cells - Muscle cells that contract and relax can cause movement.

  3. Nerve cells - Have long fibers that play a role in transmitting information in the form of impulses throughout the body.

  4. White blood cells - Change their shape to surround foreign particles and destroy them.

  5. Epidermis Cells - It works to reduce water loss, enabling gas exchange and absorption of water and nutrients.

  6. Palisade cells - Contains chlorophyll to absorb light and to carry out photosynthesis process.

  7. Guard cells - Guard cells control the opening & closing of stoma. Stoma is a small pore between the guard cells.

• Cell Organisation starts with cells -> tissues -> organs -> systems -> Organisms

There are various systems that carry out the main functions of the human body. Among them are: -

1. Blood circulatory system - It transports oxygen, nutrients and hormones to all parts of the body.

2. Respiratory system - Carries oxygen and releases carbon dioxide from cells in the body.

3. Digestive system - Break down complex foods into simpler ones to allow absorption by the body.

4. Excretory system - Removes excretory waste from the body.

5. Integumentary system - Protects the body from dehydration and regulates body temperature.

6. Muscular system - Helps the movement of the body and internal organs.

7. Skeletal system - Supports the body and protects internal organs such as the lungs and heart.

8. Lymphatic system - Drains the lymphatic fluid into the blood vessels to protect the body from infections of bacteria, virus and more.

9. Nervous system - Carries information from the brain to the whole body in the form of impulse.

10. Endocrine system - Produces hormones to coordinate reactions in the body.

11. Reproductive system - Produces sperm and ovum to produce offspring.

• Respiration can be divided into external respiration (breathing) and internal respiration (cell respiration).

• Respiratory is the exchange of gas between the organism and its environment whereas cell respiration is the oxidation process and break down of glucose that occur inside living cells to release energy.

• Cell respiration requires oxygen and glucose to produce energy, carbon dioxide and water.

• Photosynthesis is a process that synthesizes its own food. It requires sunlight, carbon dioxide, water and chlorophyll to produce glucose & oxygen