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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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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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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.