Biology is a natural science. It is the science of the life. Its job is the investigation of the living beings. Plants, animals and people belong to the living beings. Biology examines the structure of living beings, life processes, environment and the connections between them.

Biology also helps to improve the environment of the people and useful living beings.

Biology increases the scientific knowledge of people about life. It also has great importance for other sciences and branches of economy, e.g., medicine and agriculture.

Its results are necessary to increase the number of useful living beings and improve their qualities. We receive resources from useful living beings, e.g., meat, milk and eggs. With the help of the biological investigation results the food production can be increased.

Biology is also necessary to fight against injurious living beings. They often cause illnesses among people, animals and plants or make the living conditions worse. With the help of biology one can fight against the illnesses academically.

Metabolism is the most important life process. Metabolism is the set of chemical reactions which takes place in every cell; metabolism takes place during the whole life. Without it no life is possible. Metabolism is connected with all other life processes, e.g., with growth and development. Every living being can grow and develop. If it grows, it becomes bigger. If it develops, it changes. In a certain segment of the development every living being can increase. The increase results in appearing the new living beings.

All living beings can react to processes in their environment. They react, for example, to changes of light and temperature. Such changes are irritants for the living beings. The reactions can be caused by irritants. Also, the movement is a common sign of the living beings. During metabolism the movement of materials takes place. Many animals can also move, move to another place. They can run, fly, swim or jump. One recognises the living beings by these signs. Dead living beings and objects do not have these signs.

1. Answer the questions using the information from the text. Underline first the important words of the answers in the text:

1. What is the job of Biology?

2. Which groups of the living beings does Biology distinguish?

3. What does Biology examine?

4. Where are the investigations of Biology necessary?

5. Which common signs can we find in all living beings?

2. Name the main concepts of the words, and use them in sentences.

3. Speak about the following subjects without looking at the text

The tasks and the importance of Biology

The characteristic features of the living beings

4. Is biological knowledge important for you personally?

5. How can production of food be increased with the help of biological knowledge?

The cells of a multicellular living being have different forms, all living beings consist of cells. Most cells can be seen only with the microscope. They have on an average a size from 10 to 100 µ (1 µ = 0,001 mm). The bacteria consist only of one cell. They are unicellular. An organ is a part of a living being which consists of different tissues. Every organ has a certain form and performs a certain function. Organs of humans and many animals are eyes, nose, ears, heart, lungs, stomach and bowel. Humans, many animals and plants belong to the multicellular living beings.

The cells of a multicellular living being have different forms, different construction and different functions.

1. Forms of cells

If cells have the same structure, they also have the same functions. Cells with the same structure and functions often join together and form groups. A group of cells with the same structure and functions is called tissue.

1.2 Tissue with intercellular substance (a) and without intercellular substance (b)

Tissues have different functions. There are tissues which serve for movement. Other tissues take up materials or react to irritants of the environment.

Tissue originates from the increase and development of cells. The cells of some tissue form materials (substances) which they deliver between the cells. These intercellular substances have great importance for the function of tissue.

An organ is a part of a living being which consists of different tissues. Every organ has a certain form and performs a certain function. Organs of humans and many animals are eyes, nose, ears, heart, lungs, stomach and bowel.

1.3 Body parts and organs of a human

The organ system is made up of several organs which have a common function. Lungs belong to the organ system which is responsible for respiration. Bowel and stomach belong to the organ system which takes up materials from the firm and liquid dishes and processes them.

All cells, tissues, organs and organ systems of a multicellular living being work together and form the organism, the body of the living being. Body parts of humans and some animals are head, neck, breast, belly, arms and legs.

1.4 Structure of a plant

1. Answer the questions using the information from the text:

1. What is the difference between the structure of unicellular living beings and multicellular living beings?

2. What are tissues, organs, organ systems?

3. What does organism consist of?

4. Where is tissue originated from?

5. Which organs do humans and many animals have?

6. Which human body parts do you know?

7. Which organs do plants have?

2. Practise the names of the plants organs and the names of the body parts organs of humans and some animals, e.g., of the cow. Show these parts and name them.