Higher Biology Effects of Chemicals and Light on Growth in Animals

2 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.

3 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

4 Iron  Iron deficiency has the following symptoms: Headaches Fatigue Lack of energy Anaemia

5 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

6 Calcium  Lack of calcium can cause the following : Blood clots not forming properly Weak bones- osteoporosis

7 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

8 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?

9 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

10 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 B 6 and zinc.

11 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

12 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.

13 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 to have caused severe limb deformations in children whose mothers took thalidomide.

14 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.

15 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.

16 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.

17 Long day breeders  Increasing day length stimulates reproductive activity in these organisms, i.e. in the spring.  E.g. rabbits and birds

18 Short day breeders  Gonadal activity and reproductive behaviour are triggered by decreasing photoperiods which occur in autumn.  E.g. sheep and deer

19 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.

20 Practice Questions  Torrance 1. TYK page 277 Q1-4

21 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.