form 1 chap 2

CHAPTER 2

CELL AS A UNIT OF LIFE

• Cells are basic units of all living things.

• All living things including animals, plants, and humans are made up of cells.

• Like bricks that make up a house, cells are the building block of life.

• Robert Hooke (1635-1703) was the first person to name the cell.

• A ‘cell’ means a small room. he came across cells when he was examining pieces of cork under the microscope he had invented.

• A cell is the smallest unit of living things. It can be function and survive on its own.

• Cell are responsible to carrying out life processes.

MICROSCOPE

• A microscope makes an object look bigger than it actually is. It magnifies the object.

• It is used to observe very tiny objects which are not visible to the naked eye.

• Cells of living things can be observed with a microscope.

• Organism can be divided into 2 groups namely unicellular organisms and multicellular organisms.

UNICELLULAR ORGANISMS• Unicellular organisms are organisms that consist

of only 1 cell only.(‘uni’ means one).

• Also known as unicellular microorganisms because their tiny size.

• These organisms usually live in the sea, rivers, and lakes.

• Unicellular organisms carry out all the life processes such as movement, response, respiration, digestion, excretion, reproduction, and growth.

• Examples of unicellular organisms are euglena, amoeba, paramecium, yeast, and chlamydomonas.

MULTICELLULAR ORGANISMS

• Multicellular organisms are organisms that consist of many cell (‘multi’ means many).

• Like unicellular organisms, multicellular organisms carry out all the processes of life.

• Multicellular organisms are made up of many types of cells.

• Each type of cell has a different structure and carries out only specific function.

• Man is the most complex multicellular organisms.

Cell organisation in the human body

• Human being are the most complex multicellular organisms(has billions of cells).

• In multicellular organisms, different function are carried out by different types of cells.

• This is known as cell specialisation.

From cell to tissue

• In multicellular organisms, the same type of cells form groups.

• These group are called tissue.

• Each cell in a tissue carries out the same function.

From tissue to organ

• A few different types of tissues group together to form an organ.

• An organ carries out a specific function.

• Eg. Heart(organ) is made up of muscular tissue, nervous tissue and connecting tissue. The heart pump blood to all parts of the body.

BRAIN

EAR

SKIN

HEART

STOMACH

EYE

NOSE

LUNG

LIVER

INTESTINEAPPENDIX

From organ to system• A few group of organ which work together to

perform a specific function forms a system.

• A system carries out a function.

• System ensure that our bodies function normally.

• The kidneys, the lungs, the liver, the skin are excretory organ. Together they make up the excretory system.

From system to organism.

• There are many systems in our bodies.

• All systems in the body work together to produce an independent organisms.

• These systems do not work independently. They all cooperate with one another so that the human body function as a whole.

• Cells are organised in the following way.

• The end