A living thing is called an organism, e.g. a dog is an organism, so is a daffodil. The characteristics of living things are:
- Feeding -living things need food to get energy.
- Movement – living things move either their whole body (animals) or parts of the body (plants).
- Respiration – process by which organisms obtain their energy.
- Sensitivity – organisms are able to respond to changes in their surroundings.
- Excretion – living things get rid of wastes they have made in their bodies which would be harmful.
- Reproduction – living things are able to make more of their own kind.
- Growth – living things get bigger.
There are many types of animals. They are important in agriculture as food; in medicine because they cause disease; in the fishing industry and as a source of pleasure and recreation. There are many types of plants. Plants form the first link in all food chains and are in important source of oxygen. A food chain is a feeding relationship between organisms. Plants are important in agriculture, industry, medicine and as a source of pleasure, e.g. gardening. Plants differ from animals in a number of ways, e.g. feeding and movement.
- Eyepiece – allows you to view the object to be magnified.
- Objective lens – magnifies the specimen.
- Course focus – lowers and raises the microscope to focus the object.
- Fine focus – allows accurate focusing at high power.
- Stage – holds the glass slide in position.
- Light source – bulb or mirror allow the object to be illuminated.
Exp: Preparing a slide involves the following steps.
- A drop of water is placed in the centre of a clean dry slide.
- A small piece of onion skin is peeled off and placed flat on the slide in the water using a forceps.
- A drop of Iodine is put on the specimen.
- A coverslip is lowered carefully at angle to cover the specimen and avoid air bubbles getting trapped.
- The onion is examined first at low power and then at higher powers.
All cells consist of the following parts:
- Cytoplasm contains dissolved substances, jelly-like
- Cell Membrane controls the entry and exit of substances in/out of the cell
- Nucleus controls the activities of the cell
- Vacuoles store food, large in plants small in animals
- Cell Wall give strength to the cell, plants only.
- Chloroplasts help plants make their food, plants only
Plant cells differ from animal cells in the following ways: large vacuoles, cell walls and chloroplasts. . Groups of similar cells with a special function form a tissue. e.g. muscle. Several tissues grouped together form organs, e.g. heart. When a group of organs work together to perform a function they make up a system, e.g. the circulatory system
Growth results from cells dividing.