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Is permanent and non-reversible

Involves:

Increase in the number of cells, size, complexity, and

organ functions in the organisms body.

Growth is necessary for the development of

body systems and the perpetuation of the life

cycle.Occurs in three stages namely, cell division,cell

elongation and cell differetiation.

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a) (an increase

number of cells)

Takes place by mitosis

Each cells divides to become two cells which areidentical to the original cell.

These two cells divide again to produce fourcells and the undergo another division toproduce eight cells .

This process repeats itself until a mass of cellsconsisting of many identical cells are formed.

After division, the cells enlarge.

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b) (an increase in

the volume of the cells)

Result of the taking in of water and nutrients

into the cell and diffusion .Water accumulates in the vacuoles of plant

cells causing the primary wall to stretch.

The nutrients are used in the building up ofprotoplasm leading to an increase in cell size.

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c) (cell change in

form and perform specialised functions)

Takes place after elongation

Cells begin to differ from each other to form groups ofspecialised cells

This enable cells to perform new and specialisedfunctions.

Example,cell differentiation in the epidermis of rootswhere the cells develop hair-like outgrowths to

enable the cell to have a large total surface area forabsorption of water from the soil.

Transformations of certain epidermal cells in theleaves into guard cells enable the plant to regulateloss of water from the leaves.

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We can measure growth by measuring any of

the following parameters:

Length or height

Volume

Fresh mass

Dry mass

The parameter used must

be appropriate to the

organism whose growth

is to be measured.

Example :increase in

height over human being

and plants.

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Refers to the length or height of an organisms that

is measured over a period of time.

- It is easy and quick

to carry out- There is no need to

kill the organisms

- It measures growth

in one dimensions

only and does not

take into accountgrowth in other

dimensions such as

growth in diameter

and weight.

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Refers to the mass of an organisms after all the

water has been removed from its body

- It is an accurate

measurement of the

amount of organic

matter present andtherefore an accurate

measurement of

growth

- Organisms have to be

killed

- Large numbers of

organisms are needed tomeasure growth change.

- Growth of the same

organisms cannot be taken.

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Refers to the mass of living organisms that is

measured without removing water from the body.

- Easy and convenient

method

- There is no need to

kill the organisms.

- Growth of organism

can be measured

continuously

- Not very accurate

because

measurement ofgrowth is affected by

the amount of water

present in the body