Reproduction of cells    Using a microscope

A cell is the basic structure of all life. Every living organism is made up of at least one cell..

Some organisms (eg amoeba) have only one cell (these are called single cellular organisms) but most have many cells (eg human) and these are called multicellular organisms.

[remember an organism is the name given to ANY living thing, animal or plant, whatever it's size]

ANIMAL CELL (Amoeba x1000)

PLANT CELL (Leaf cell x 750)

Definitions:

Cell membrane: The living outer layer to the cell. The membrane is selective about which substances enter and leave the cell.

Nucleus: Controls the function and behaviour of the cell. Contains the genetic information (genes). The genes are grouped into packages called chromosomes.

Cytoplasm: The liquid contents of the cel (excluding the nucleus). Contains structures for carrying out respiration (these are called mitochondria).

Chloroplasts: Where photosynthesis is carried out. Chlorosplasts contain a green chemical called chlorophyll which is needed for photosynthesis to take place.

Large vacuole: A cavity in the cytoplasm of a plant cell. It contains cell sap. It helps keep the cell rigid. Some cells ( animal and plant) also contain a smaller vacuole that helps regulate the water content of the cell.

Cell wall: A structure made odf cellulose that surrounds a plant cell and helps it keep its shape.

TISSUE: A group of cells that have a single use is called tissue

ORGAN: A group of tissues that have a single use is called an organ. Each organ has a particular job to do

ORGANISM: An organism is any complete living thing.
In the case of a mammal an organism is made of many organs

The human body is made up of ORGANS.

In order of size:  CELLS  ------>   TISSUE  ----->  ORGAN  -------->  ORGANISM

[Of course some organisms, like the amoeba, do not have organs as they are only a single cell to start with]

Examples of some cells in a human A: Sperm cell B: Nerve cell C: Muscle cells

How a single cell multiplies   

 A single cell multiplies by dividing in two 
This is called binary fission and is a type of asexual reproduction.

This page is part of a site that uses frames.
If you cannot see navigation links to the left or top then click here to return to the start.