5. Los niveles de organización

BIOGEOSPHERE Bilingual Biology and Geology I.E.S. "J.S.Elcano (Sanlúcar Bda.)

Unit 5: Living beings 1 2 3 4 5

5. Levels of organisation

Living beings can be classified into two different groups:

unicellular and multicellular.

- Unicellular living things have only one cell. E.g. paramecia, bacteria, etc.

In unicellular (or single-celled) organisms, the single cell performs all life

functions.

Sometimes they form colonies, groups of cells in which everyone

functions independently although they live together.

- Multicellular living things have many cells. E.g. plants and animals.

All cells work together to carry out the vital functions.

They are dependent on one another and they are organised in

levels of organisation.

- Cells are the basic units of living beings.

They are specialised. Each type has a unique shape and structure

and has a specific function.

Example: muscle cells are long and can contract.

- Tissues are groups of cells with the same function.

Example: muscle cells form muscle tissue.

- Organs are groups of various tissues which act together.

Example: a muscle is an organ made up of muscle tissue,

nerve tissue and connective tissue.

- Systems are made up of several organs.

Example: the digestive system includes the stomach,

the intestines, etc.

READING ACTIVITIES

After reading the text, copy and answer the following questions into your notebook:

Remember: you must make complete sentences.

5.1. Fill in blanks with the following words and complete the text:

shape number relationship reproduction size

multicellular alone organisms work specialized

nutrition unicellular small functions complex

“We can classify the ............................... according to the .............................of cells that make them up, in two groups, that are: .....................................organisms, formed for a single cell and ................................ organisms formed for many cells.

Unicellular organisms live without other cells to help them. So the cell does all things that it needs to live: ………………… , ……………………..and ………………………….

Multicellular organisms are ………….…..organisms. They can have a …………….number of cells, or millions of cells. These cells are not all the same. They have different ……………….. and ………………, and do only a kind of ………………in the organism. The cells are……………………….. by themselves, they cannot do all the vital ……………………. They need other cells to do other work. They live together, but cannot live……………”

5.2. Classify the following elements into its organisation level: