Unit 3: Control and Regulation
Environmental Influences on Growth
Name: __________________ Teacher: ________________
Effect of Chemicals on Growth Revision
a) Why do all living things need nitrogen?
b) From where do plants get a supply of nitrogen?
c) From where do animals get a supply of nitrogen?
d) What is meant by the term “diffusion”?
e) Which chemicals are extracted from the bloodstream to build up the hard
mineral part of bone?
f) What is a catalyst?
g) What is an enzyme?
h) Where does foetal development of a mammal take place?
i) How does the foetus obtain food?
j) Name two substances which are:
i) Removed from the mother’s blood supply by the foetus
ii) Added to the mother’s blood supply by the foetus
m) What are the tiny hair-like structures which line the trachea and bronchi
n) Explain how dust and germs are prevented from entering the lungs.
The importance of Macro-elements in plants.
Plants need large amounts of carbon, oxygen, and hydrogen for the manufacture of carbohydrates, fats and protein (nitrogen also needed).
Plants also need other elements in small, but appreciable, quantities - these are called macro-elements. A macro-element is an element that is required in small but significant quantities for healthy growth and development. Plants obtain the macro-elements they need from the soil through the root hairs either by diffusion or active transport.
Some of the macro-elements needed by a plant are Nitrogen(N), Phosphorus (P),
Potassium (K) and Magnesium (Mg).
Macro-elements are absorbed in solution by the root hairs and transported in the xylem.
Use Chapter 31 of your Torrance textbook to help you complete the
What are the 4 macro-elements needed by the plant used for?
Water culture experiment
The importance of the macro-elements to a plant can be shown by setting up a `water culture' experiment. This involves setting up a series of plants in mineral solutions each solution deficient in one element. This experiment is used to show element deficiency symptoms in plants.
Read Torrance page 264 (old), page 289 (new) on the 'Water Culture
Experiment' to answer the questions below related to this experiment.
Water culture experiment
1. Why was the solution aerated?
2. Why is it good experimental procedure to use several seedlings?
3. An opaque cover was put over the container, what could have happened if
this hadn’t been done?
4. Why do you think the seedlings were left for several weeks?
Now answer Torrance TYK questions 1-2 p270 (old), page 295 (new)
The importance of Iron and Calcium in mammals
Animals also require small amounts of minerals for healthy growth. This comes from the food they eat. Two examples of minerals needed for healthy growth are iron and calcium.
Iron is a beneficial element. It is essential for growth and development. It is the constituent of many enzymes e.g. catalase. It is needed to make cytochrome and haemoglobin.
Foodstuffs rich in iron are meat, eggs, fish, green vegetables and cereals. Iron is less well absorbed from vegetables so vegetarians have to be careful not to become anaemic. Babies have an iron store to keep them going whilst they are milk fed.
Summary of iron importance:
; Component of in red blood cells, so needed for oxygen
; Component of (H carrier system), so it is needed for
; Lack of iron results in .
; Food sources containing iron:
Calcium is found in dairy products. As with the macro-elements needed by plants we can deduce the role of calcium from deficiency symptoms.
Lack of calcium:
1. In children reduced calcification of bones results in stunted growth.
2. In adults it leads to a loss of calcium from bones resulting in height loss and
Calcium is needed for:
; Component of bones, teeth and shells.
; Needed for the .
; Needed for .
; Needed for cell membrane formation.
; Food rich in calcium:
The effect of Vitamin D deficiency in humans.
Vitamins are substances needed for a healthy diet. Vitamin D is made by the action of sunlight on the skin cells so deficiency is rare. The main dietary source
of vitamin D is fish oils.
It is needed to promote absorption of calcium and phosphate from the gut.
In children deficiency of Vitamin D leads to rickets. This is due to growth
of bones without the hardening due to low concentrations of calcium and potassium in the blood and the legs tend to bend under the weight of the body, making them bow-legged.
; Needed for the absorption of ___from the _____ into
the bloodstream and its subsequent uptake by .
; Lack of vitamin D in children results in soft bones resulting in bow legs.
Condition called .
; Food rich in vitamin D: .
; Vitamin D is also produced by the skin in the presence of sunlight (U.V.
Answer the following questions:
1. Vitamin doses are given as international units (IU). 1µg of vitamin activity
= 40 IU
a) If 100m1 of cow's milk contains 0.03µg of vitamin, how many IU
units would one litre of milk contain?
b) If the recommended daily intake of vitamin D for an infant is 10 µg
and its mother's milk contains 0.9µg per 100 ml, how much milk
would the infant have to drink per day?
2. a) What is Rickets and describe the symptoms in children?
b) Before 1900 the incidence of rickets in children of poorer classes in
the larger cities was 75%. Suggest 2 reasons why the incidence was
The inhibiting effect of Lead on enzyme activity
Lead is a heavy metal, which is a poison that inactivates enzymes. Like all heavy metals, it cannot be removed from the body, it is stored in bones and teeth. Lead irreversibly affects the functions of enzymes. Its action may be demonstrated on the enzyme catalase. If added to a test tube containing hydrogen peroxide and liver the action of the catalase in the liver is stopped.
In a living animal poisoned by lead the increased hydrogen peroxide produced in all living cells causes leakage to capillary walls. This results in a swelling in the brain which in the rigid skull causes brain damage. Other symptoms of lead poisoning
are anaemia, stomach pains, vomiting, clumsiness and kidney failure.
Chapter 31 of your Torrance textbook will help you answer the following questions:
1. Suggest 3 ways young children may ingest lead.
2. What are the 2 methods pursued to reduce lead levels in the environment?
3. Write out the equation for the action of catalase on hydrogen peroxide.
Complete the statements below using the following words: lead free, drinking water, weights, lead, exhaust fumes, copper pipes
Sources of lead:
; Lead water pipes therefore _____enters _________ _______.
_________ ________ now replace lead.
; Leaded petrol - ________ ________ from this petrol contains
__________. ________ _______ petrol has now replaced it.
; Paint - some old paints contain . Young children can eat flakes of
peeling paint. Most paint is now _______ _______.
; Fishing __________ - many were made of _________ . This was linked to a
fall in swan populations. The swans swallowed the and
became poisoned by the ___________.
The effect of drugs on foetal development.
Some drugs can adversely affect growth and development. This is especially true in the early stages of pregnancy when the foetal organs are developing. Many drugs taken by the mother can cross the placenta by diffusion and have a bad affect on foetal development.
In the 1960s Thalidomide was a drug prescribed for morning sickness but
resulted in severe deformities when passed from the mother's blood to the
foetus. Alcohol can also affect the foetus and nicotine can cause a high rate of foetal and infant mortality.
Complete the blanks below, Torrance chapter 31 will also help you.
This was a drug used to combat _________ _________in pregnancy. If taken at certain critical stages during early pregnancy the ______ of the foetus failed to develop. Hands were attached to shoulders, feet attached to hips. Malformation of eyes and ears also occurred in some cases. The drug is no longer used in the U.K.
This drug has a toxic effect on the liver. Excessive drinking by the mother can lead to spontaneous abortion. Alcohol causes the blood vessels in the umbilical cord to _________ temporarily starving the foetus of sufficient
for normal development. This retards , resulting in lower than
average birth weight and slower mental development. Extreme alcohol abuse may lead to _______ ________ _________– symptoms: growth and mental
retardation, facial abnormalities, abnormal limb and joint development and heart defects. Alcohol also has an adverse effect on sperm production.
Nicotine is a poisonous drug found in tobacco plants. Nicotine in the bloodstream prevents sufficient reaching foetal tissues including brain cells,
adversely affecting development.
________ __________ in tobacco smoke reduces the oxygen carried in the foetal bloodstream retarding growth and development.
Tar, also present in tobacco smoke, is known to contain 30 harmful substances, some which are carcinogens.
Now answer TYK questions 3-4 & AYK question 6 p270 (old), p295 (new).
Effect of Light on Growth
Germination of seeds generally happens underground in darkness. The young plant uses its starch store to grow. To ensure the plant reach the light quickly the shoots elongate in darkness and do not produce expanded leaves. The pale spindly plant which has small curled yellow leaves and long weak internodes (region
of stem that lacks leaves or branches), at this stage is said to be etoilated and any
plant deprived of light will take on this appearance.
Draw the etiolated plant from Torrance p273 (old), p299 (new).
Effect of Light on Flowering
Some plants stop producing vegetative buds and start producing flower buds in response to a change in the period of illumination (photoperiod), to which they are
exposed. Such a response is known as photoperiodism.
There are three distinct plant types.
Long Day (short night) Plants
Only flower when the number of hours of light is above a certain level, e.g.
spinach must receive at least 13 hours of light before it will flower. The length of the critical period of illumination varies with each species.
Short Day (long night) Plants
Only flower when the number of light hours is below a certain level, e.g.
strawberry plants must receive at least 14 hours of darkness before they flower.