Mr Exham IGCSE - Cell Differentiation and Organisation

MAKING SENSE OFCELL DIFFERENTIATION AND ORGANISATION

IGCSE Biology1.1 Life Processes

Cell differentiation and organisation

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Learning Objectives• Can you explain the organisation of an

organism using the following terms: organelles, cells, tissues, organs and organ systems?


Cell Division• Multicellular organisms begin life as a single

fertilised egg cell called a ZYGOTE.• It then divides over and over again by MITOSIS

Zygote


Embryo

Differentiation• As the developing embryo grows, cells

become specialised to carry out particular roles.

• This is called differentiation and is controlled by genes.

• As all cells have the same genes, some must be switched on and some switched off for this to work. This is discussed further in the IGCSE course.


Specialised cells• Here are a few examples of specialised cells

that you will meet throughout the IGCSE Biology course.

• They will be mentioned briefly here as they will be explained fully in each relevant section.


Nerve cell (Neurone)

• Very long cell for carrying impulses around the body along its axon.

• Insulated by a myelin sheath to make the signal travel quicker.


Dendron

Cell body

Axon

Myelin sheath

Dendrites

Muscle

Sperm cell• Sperm cells have a tail for swimming.• The head contains the genes from the father

in the nucleus.• The acrosome digests its way into the egg for

fertilisation.


TailNucleus

Acrosome

Palisade cell• This cell is found in the leaves of plants.• It is packed full of chloroplasts for

photosynthesis. • It is a regular shape in order to pack many into

the leaf.


Xylem Vessel• This carries the water up the stem of a plant.• It is dead, hollow and strengthened in order

to do this.


Cells tissues and organs• Each cell has many organelles inside it’s

cytoplasm to help it carry out its function.• Cells with a similar function are grouped

together in TISSUES.• A collection of similar tissues carrying out a

particular function is called an ORGAN.• In animals, jobs are usually carried out by

several different organs working together. This is called an ORGAN SYSTEM.


Organelles

Cells

Tissues

Organs

Organ Systems


Some of the key major human organs


The 7 main organ systems• Digestive• Respiratory• Circulatory• Excretory• Nervous• Endocrine• Reproductive


These will all be covered in detail

in the rest of IGCSE

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