Science A Bio


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  • Created by: leena
  • Created on: 05-06-12 15:12

controlling conditions

The body carefully controls its internal enviroment

internal conditions are controlled:

water content

ion contenet


blood sugar levels

must keep them contast^

water leaves the body as we breathe and sweat

we lose excess water in urine (produced by kidneys)

also we lose ions in our sweat and urine

tempreture must be kept constant otherwise the enzymes in our body will not work properly 

sugar in the bood is the energy source for cells. the level of in sugar in our bood is controlled by the pancreas

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Hormones and the control of plant growth

Plants are sensitive to light,gravity and moisture

plants shoots grow towards light this response is called PHOTOTROPISM

roots grow down towards gravity. this is called GRAVITROPISM

roots aso grow towards water

AUXIN is the horomone which controls phototropism and gravitropism

unequal distribution of auxin causes unequal growth 

RESULTS bending of the shoot or root.

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Using hormones


use contraceptive pill to prevent unwanted pregnancies

plan when they want a baby

other women use horomones to help them become pregnant

older women to have babies (egg donor who is given hormones to produced extra eggs)


plants hormoromes can be used by farmers and gardeners

weedkillers are used to kill unwanted plants on lawns

encourage fruite ripen 

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