Higher Biology

Effects of Chemicals and Light on Growth in Animals

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Effects of chemicals and light on animals

By the end of this lesson you should be able to:

Know the importance of iron and calcium in animals. Explain how lead inhibits the activity of enzymes. Describe the effect of vitamin D deficiency in humans. Describe the effects of alcohol, thalidomide and

nicotine on the developing foetus. Explain the term photoperiodism. Describe the effect of light on the timing of

breeding in birds and animals.

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Iron Iron is needed by animals for:

Haemoglobin Hydrogen carriers e.g. in the cytochrome

system Enzymes e.g. catalase

Food rich in iron are: Meat Fish Green veg Cereals beans

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Iron Iron deficiency has the following

symptoms: Headaches Fatigue Lack of energy Anaemia

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Calcium Calcium is needed by animals for:

Strong bones Strong teeth Muscle contraction Blood clotting Shells (in invertebrates)

Food rich in calcium are: Dairy products Leafy green veg Nuts

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Calcium Lack of calcium can

cause the following : Blood clots not

forming properly Weak bones-

osteoporosis

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Vitamin D

Vitamin D is needed by humans to: Develop and maintain healthy teeth and

bones Regulate the absorption and metabolism of

calcium in the intestine.

Food rich in Vitamin D are: Cod liver oil Egg yolk Full cream milk

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Vitamin D- deficiency

A deficiency causes bow-shaped legs because the bones do not harden.

This is called rickets. Exposure to U.V. light (the

sun) enables the body to make it’s own Vitamin D.

Rickets can be a problem for people in northern latitudes.

Why?

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Effects of drugs on foetal development

A developing baby is totally dependent on its mother for the nutrients it needs to grow.

However, since the mother “shares” its blood supply with the baby- any substances in the mother’s blood will also affect the developing baby.

Drugs or chemicals can pass across the placenta and through the umbilical cord to the baby.

We will look at: Alcohol Nicotine Thalidomide

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Effect of Alcohol Higher chance of spontaneous abortion The blood vessels in the umbilical cord

can collapse temporarily. This means that the foetus is deprived

of oxygen- which can affect the brain development.

effects of alcohol on the foetus Alcohol interferes with the normal

absorption of e.g. vitamin B6 and zinc.

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Effect of Alcohol In severe cases causes foetal alcohol

syndrome. Symptoms:

Pre- and post-natal growth retardation Facial abnormalities Heart defects Development of abnormal joints and limbs Mental retardation

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Effect of Nicotine Smoking increases the risk of:

Having a miscarriage (twice as likely) Premature birth Still birth Cot death

effects of nicotine

Carbon monoxide (CO) reduces the concentration of oxygen that can be carried in the blood.

Heavy smokers tend to have smaller and lighter babies.

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Effect of Thalidomide This is a drug which was used in the

1950s to treat morning sickness. It was banned from use

in the 1960s after it was shown tohave caused severe limbdeformationsin childrenwhosemothers tookthalidomide.

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Effect of Lead Lead inhibits enzyme activity in

metabolic pathways. Early symptoms of lead poisoning are:

Vomiting Clumsiness Irritability Headaches

Certain brain cells become injured by lead, which can lead to: Subtle learning difficulties Profound mental retardation.

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How does lead get into the body? Inhaled from exhaust fumes from

vehicles using leaded petrol. (removed in UK)

Drinking water carried in old lead pipes.

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Photoperiodism A response to a change in the period of

light is called photoperiodism. The photoperiod is the change in period

of illumination. Activity of the sex organs in birds and

animals is controlled by changes in the photoperiod.

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Long day breeders Increasing day length stimulates

reproductive activity in these organisms, i.e. in the spring.

E.g. rabbits and birds

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Short day breeders Gonadal activity and reproductive

behaviour are triggered by decreasing photoperiods which occur in autumn.

E.g. sheep and deer

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What’s the advantage?For both short day and long day breeders: Breeding is timed so that the young are

born when conditions are favourable. i.e warmer weather and plenty of food.

As larger mammals, like sheep, have longer gestation periods then these animals are reproductively active in autumn.

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Practice Questions

Torrance1. TYK page 277 Q1-4

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Effects of chemicals and light on animals

Can you do it?

Know the importance of iron and calcium in animals. Explain how lead inhibits the activity of enzymes. Describe the effect of vitamin D deficiency in humans. Describe the effects of alcohol, thalidomide and

nicotine on the developing foetus. Explain the term photoperiodism. Describe the effect of light on the timing of

breeding in birds and animals.