Control and Regulation

1
Control and Regulation

• Higher Biology Unit 3

2
Growth and development

• Growth patterns in plants and animals
• Growth is the irreversible increase in the dry
  mass of an organism.
• To avoid killing the organism other factors, such
  as height or fresh weight, may be used to measure.

3

• Growth patterns
• A graph of growth measurements taken during the
  life of an organism often shows an s-shaped
  curve.

4
(No Transcript)
5

• Some different organisms show slightly different
  growth curves.

6

• Human

7

• Insect

8

• Annual plant growth curve

9

• Perennial plant growth curve (Tree)

10

• (b) Meristems
• A meristem is a group of undifferentiated plant
  cells which are capable of dividing repeatedly.
• Animals do not have meristems, growth takes place
  all over the organisms.

11
Apical meristems

• These increase the length of stems and roots.
• They are found at the tips of stems and roots.
• Cell division here produces primary tissues.

12
ROOT TIP
ROOT HAIRS
Elongation Vacuolation zone
Cell division zone
Differentiation zone
13
Cell division zone Following mitosis the
resulting cells are small cubes with a dense
cytoplasm. Elongation and vacuolation zone The
cells absorb water by osmosis causing them to
elongate. Many small vacuoles appear in the
cytoplasm. They eventually merge to form a large
sap vacuole. Differentiation zone Here,
unspecialised cells become altered to perform a
special function in a permanent tissue. e.g.
Xylem vessels or phloem tubes.
14
2. Lateral meristems

• These produce an increase in the thickness of
  stems and roots.
• The tissues produced by lateral meristems are
  called secondary tissues and they cause secondary
  thickening.

15
Development of tissues in the stem

• When primary tissues are fully formed, the stem
  (in cross section) looks like this

16

• Inside each vascular bundle a narrow meristem
  called cambium arises.
• Cambium is a lateral meristem which produces
  secondary xylem and secondary phloem.

17

• In time, the cambium extends between the vascular
  bundles where it continues to divide and produce
  a complete ring of secondary xylem and phloem.

18
(No Transcript)
19

• Each year a new ring of secondary xylem is
  formed. After 4 years the stem will look like
  this

20

• The xylem vessels (cells) produced in the cambium
  in the spring are larger then those produced in
  late summer and autumn.
• This difference shows up as an annual ring.
• The inner core of xylem is called wood.

21
(No Transcript)
22
Regeneration

• Regeneration is the process by which an organism
  replaces lost or damaged parts.
• The ability to regenerate depends on the presence
  of relatively undifferentiated cells.

23
1. Angiosperms (flowering plants)

• These have extensive powers of regeneration.
• Cuttings
• Sections of plant are cut off and then planted in
  the soil.
• The cutting is able to produce shoots and roots
  by regeneration.

24

• (b) Tissue culture
• Growers can mass produce identical clones of
  plants which show desirable features.

25
2. Mammals

• Mammals have only limited regenerative powers.
• Regeneration is restricted to the healing of
  wounds
• Mending broken bones
• The replacement of blood
• The regeneration of damaged liver

26
Genetic control of growth and development

• Jacob-Monod hypothesis of gene action in bacteria
• e.g. Lactose digestion by the bacterium E. coli.
• Lactose sugar is digested by E. coli into glucose
  and galactose.

27

• The reaction is controlled by the enzyme
  ß-galactosidase.
• ß-galactosidase
• lactose glucose galactose
• The enzyme is only produced by the bacteria when
  the substrate (lactose) is present.

28

• The substrate therefore acts as an inducer in the
  following way
• On the bacterial chromosome, three genes control
  the production of the ß-galactosidase enzyme.

29

• Structural gene codes for the manufacture of
  ß-galactosidase.
• Operator gene switches on the structural gene.
• Regulator gene produces repressor molecules
  which stop the operator switching on the
  structural gene.

30

• Operon structural gene operator gene
• If lactose is absent
• Repressor molecules prevent the operator gene
  from switching on the structural gene.
• No ß-galactosidase enzyme is produced.

31
(No Transcript)
32

• If lactose is present
• Repressor molecules are mopped up by some of
  the lactose.
• The operator gene is now free to switch on the
  structural gene.
• ß-galactosidase is produced.

33
(No Transcript)
34

• 2. Genetic control of metabolic pathways
• A metabolic pathway consists of several stages,
  each of which involves the conversion of one
  molecule to another during a break-down or
  synthesis process.

35

• Each stage in a metabolic pathway is controlled
  by an enzyme, as shown in the imaginary example
  below.

GENE 1
GENE 2
GENE 3
ENZYME 1
ENZYME 2
ENZYME 3
Metabolite D
Metabolite A
Metabolite B
Metabolite C
36

• If any one of the 3 genes is faulty then the
  enzyme is not made and the pathway is blocked.
• This happens with the illness phenylketonuria
  (PKU).

37

• In an unaffected person, surplus amounts of an
  amino acid phenylalanine are converted to
  harmless substances by a the following pathway

38
ENZYME 1
ENZYME 2
Phenylalanine
Tyrosine
Melanin

• In a PKU sufferer, a gene mutation means that
  ENZYME 1 cannot be made.
• Phenylalanine is then broken down into toxic
  wastes which can cause brain damage.

39
Essay practice

• Write an essay on
• The control of lactose metabolim in E. coli.
• (6 marks)
• Phenylketonuria in humans.
• (4 marks)

40
3. Genetic control of cell differentiation

• Gene Activation
• Every cell contains every gene but some genes are
  switched on (activated) in all cells while other
  genes are switched off in cells where they are
  not required (e.g insulin formation genes only
  remain switched on in pancreas cells).

41

• Genetic control of blood cell formation
• Differentiated red blood cells, phagocytes and
  lymphocytes are formed from undifferentiated
  cells by switching on of relevant genes (to make
  haemoglobin, antibodies etc) and the switching
  off of irrelevant genes.

42
Hormonal influences on growth

• Hormones are chemical messengers secreted into
  the blood by endocrine glands.
• They travel in the blood to target sites where
  they have their effect.

43
(a) Pituitary hormones

• The pituitary gland produces 2 hormones which
  affect growth and development

44

• Growth hormone
• Promotes growth by increasing amino acid
  transport into growing tissues, which stimulates
  protein production.
• 2) Thyroid-stimulating hormone
• Stimulates the thyroid gland to produce thyroxin.
• Thyroxin controls the rate of ATP synthesis in
  the cytochrome system and therefore the rate of
  metabolism and growth

45
Too much HGH
46
Too much TSH
47
(b) Plant growth substances (Plant hormones)

• Plant growth substances (hormones) which affect
  the growth and development of plants.
• Two important growth substances are
• Indole acetic acid (IAA)
• Gibberellic acid (GA)

48
(a) Auxins

• The commonest auxin is indole acetic acid (IAA).
• IAA is produced in apical meristems.

49

• It moves back from the meristems in two ways
• Diffusion, over short distances, from cell to
  cell.
• Translocation, over longer distances, in the
  phloem.

50

• IAA affects plant growth in the following ways
• At cell level (in meristems)
• Increases cell division
• Causes cell elongation by making cell walls more
  stretchy
• Causes phototropism (shoots growing towards the
  light) by stimulating growth on the shaded side.

51

• At organ level
• Elongation of roots and shoots is affected by IAA
  in the following way

Concentration of IAA (ppm) Effect on root Effect on shoot
Low (10-4) Stimulates elongation No effect
Medium (1) Inhibits elongation Stimulates elongation
High (500) Inhibits elongation Inhibits elongation
52
(No Transcript)
53
At the organ level IAA has these effects

• Apical dominance
• IAA from the apical bud at the shoot tip inhibits
  development of side branches further down the
  stem.

54

• (2) Fruit formation
• Following fertilisation, IAA stimulates the
  formation of the fruit around the seeds

55

• (3) Leaf abscission
• In autumn, IAA concentration drops and an
  abcission layer of cells forms at the base of the
  leaf or fruit stalk.
• The stalk snaps at this point and the leaf or
  fruit falls.

56
Commercial applications of auxins

• Make notes on the following (pg 255 256)
• Delaying fruit abscission
• Rooting powder
• Herbicides

57
(b) Gibberellins

• The commonest gibberellin is gibberellic acid
  (GA).
• GA plays a role in 3 aspects of plant life

58

• Dwarf plant varieties
• GA affects the height of a plant be elongating
  the internodes (sections of stem between the
  leaves).
• GA is deficient (for genetic reasons) in some
  dwarf varieties

59

• (2) Effect on bud dormancy
• Buds of deciduous (leaf-dropping) trees remain
  dormant during winter to protect delicate tissues
  from frost.
• In spring, GA is produced by the plant which
  breaks the dormancy and the buds open.

60

• (3) Role in germination of barley grains

61
(No Transcript)
62

• This is the sequence of events
• Embryo absorbs water
• Gibberellin is produced by the embryo.
• Gibberellin diffuses out to the aleurone layer.
• Aleurone layer produces a- amylase
• a- amylase converts starch in endosperm to
  maltose sugar.
• Sugar used in respiration to release energy,
  which is used for growth.

63
Environmental influences on growth

• Importance on macro-elements
• Plants
• All plants need carbon, hydrogen and oxygen. They
  also need a variety of other elements of which
  the most important are called macro-elements.

64

• The macro-element requirements of plants can be
  investigated by means of water-culture
  experiments

65

• Need for
• Air supply gives roots oxygen for respiration
• Blackened glass excludes light. This stops
  algae from growing and using up all the nutrients.

66
ELEMENT WHY IT IS NEEDED DEFICIENCY SYMPTOMS
NITROGEN To make amino acids and proteins Reduced growth and yellowish (chlorotic) leaves
PHOSPHOROUS To make ATP and DNA Reduced growth, leaf bases turn reddish
MAGNESIUM To make chlorophyll Reduced growth and leaves chlorotic between veins
POTASSIUM For transport of molecules across membranes Reduced growth, leaves die and fall off prematurely
67
PHOSPHORUS
NITROGEN
POTASSIUM
MAGNESIUM
68
(b) Animals
Element Why it is needed
Iron To make cytochrome Constituent of many enzymes Forms part of haemoglobin
Calcium Form bones and teeth Clotting of blood Contraction of muscle
69
(c) Inhibiting effect of lead on enzyme activity

• Lead can inhibit the activity of many of the
  enzymes which control metabolic pathways in the
  human body.
• This disrupts respiration and growth. It may also
  cause learning difficulties.

70
2. Effect of vitamin D deficiency in humans

• Role of vitamin D
• Essential to promote the absorption of calcium
  and phosphate from the intestine and their uptake
  by bones.
• Symptoms of deficiency
• Causes formation of soft abnormal bone. This is
  called Rickets.

71
(No Transcript)
72
3. Effects of drugs on foetal development

• Thalidomide

73
Thalidomide

• Taken during pregnancy to reduce morning
  sickness.
• Caused foetal limb deformity such as hands
  attached to shoulders, and feet to hips.

74
Alcohol and nicotine

• Drinking alcohol and smoking cigarettes
  containing nicotine during pregnancy can affect
  the foetus in these ways
• Retarded growth
• Reduced birth weight
• Slower mental development

75

• Foetal alcohol syndrome

76
4. Light

• Effects of light on vegetative shoot growth
• (i) Etiolation
• Etiolation (a tall, yellow stem) results from
  increased cell elongation produced by high auxin
  levels.

77

• The advantage of etiolation is to raise some of
  the plants leaves quickly above the soil or
  competing plants, so that photosynthesis can
  begin.

78

• (ii) Phototropism
• This is the directional growth by part of a plant
  in response to light from one direction.
• Positive phototropism
• (growth towards light)

79

• This is caused by greater elongation of cells on
  the shaded side of the plant.
• This is due to higher IAA levels on the shaded
  side.
• Positive phototropism exposes the shoot to
  maximum light energy needed for photosynthesis.

80

• (b) Effect of light on flowering
• For many plants this depends on the photoperiod.
• The photoperiod is the number of hours of
  daylight in a 24 hour period.

81

• (i) Long day plants flower when the photoperiod
  is above a certain length (e.g. Clover needs 12
  hours or more of light).
• (ii) Short day plants flower when the photoperiod
  is below a certain length (e.g. Chrysanthemum
  needs 4 hours or more of light).
• (iii) Day neutral plants flower at any time of
  the year, regardless of photoperiod.

82

• Note
• Other factors (temperature, nutrient
  availability) also affect flowering.
• Photoperiod works by triggering production of
  plant hormones.
• Synchronised flowering (controlled by
  photoperiod) increases pollination chances.

83

• (c) Effect of light on timing of breeding seasons
• Birds
• Birds are long day breeders. Increasing daylength
  (light reaches the brain through the skull)
  stimulates sex hormone production.
• Territorial behaviour and sexual activity follow.

84

• (ii) Mammals
• Mammals have varying gestation period (pregnancy)
  and show two main breeding strategies

85
Gestat-ion Strategy Stimulus Mating season Young born Example
Short (few weeks) Long day breeder Increasing photo-period Spring Early summer Hare
Long (several months) Short day breeder Decreasing photo-period Autumn Early summer Red Deer
86

• Each strategy results in the birth of young at a
  time when weather and food supply are likely to
  be favourable.

87
Physiological homeostasis

• This is the ability of an animal to keep the
  internal conditions of its body within tolerable
  limits.
• Some factors (e.g. water and glucose
  concentration of the blood) are controlled by
  negative feedback.

88
(No Transcript)
89

• Negative feedback means that the action of an
  effector organ brings about the opposite action a
  short while later.

90
1. Water content of the blood

• This needs to be keep constant to avoid
• Osmotic problems any increase in water content
  causes blood cells to swell and block
  capillaries.
• Changes in concentration of salts dissolved in
  blood.

91

• The blood water control is monitored by the
  hypothalamus in the brain.
• This causes the nearby pituitary gland to vary
  the level of ADH it produces.

92
Negative feedback control of water content of the
blood
93

• ADH (anti-diuretic hormone) travels in the blood
  to the kidney nephrons, where it affects the rate
  of water reabsorption from the glomerular
  filtrate into the blood capillaries.

94
Revision Sheet

• On one side of A4 make small revision poster
  explaining homeostasis and control of water
  content of the blood.
• Why controlling water content is important?
• What is the receptor?
• What message is sent to the kidneys?
• What happens at the effector (the nephron)?
• Try to think of a mnemonic or a rhyme to help you
  remember it!
• Make it colourful as colour helps you remember
  things.

95
2. Control of blood sugar level

• Glucose is continuously consumed from the blood
  during respiration by the bodys cells.
• Fresh glucose is only obtained when we eat, but a
  homeostatic mechanism ensures an adequate level
  in the blood at all times.

96

• A raised blood sugar level is detected by the
  pancreas which increases insulin production.
• Insulin (a hormone) travels in the blood to the
  liver where it causes the conversion of glucose
  to glycogen.

97

• When blood glucose falls the pancreas increases
  production of another hormone, glucagon.
• This travels to the liver and causes glycogen to
  turn back to glucose.

98
Negative feedback control of blood glucose level
99
Diabetes mellitus

• Make own notes from Higher Biology textbook.

100
Adrenaline

• Adrenaline is a hormone released by the adrenal
  glands in cases of stress and danger.
• Adrenaline promotes the rapid breakdown of
  glycogen to glucose so that more energy can be
  provided quickly.

101
3. Control of body temperature

• This is controlled to provide optimum conditions
  for our enzyme-controlled metabolism.

102

• Endotherm An animal which produces its body heat
  internally. It possesses homeostatic mechanisms
  to maintain a constant body temperature. e.g.
  Mammals and birds
• Ectotherm An animal which receives most of its
  heat from the environment. e.g. Snakes or lizards.

103

• The temperature monitoring centre is in the
  hypothalamus in the brain.
• This controls homeostatic mechanisms to regulate
  the bodys core temperature at 37 ºC.

104
(No Transcript)
105

• The hypothalamus receives information about body
  temperature from two sources
• Skin thermoreceptors
• Communicate with hypothalamus by nerve impulses
• Give information to on body surface temperatures.

106

• (ii) Central thermoreceptors
• In hypothalamus itself
• Detect body temperature (body core) changes

107

• Necessary action to adjust body temperature is
  sent by nerve impulses to effector organs.

108
(No Transcript)
109
Role of the skin

• Correction of overheating
• (a) Vasodilation

110
(No Transcript)
111

• (b) Increase in rate of sweating
• As sweat evaporates from the skin surface, heat
  energy is taken away from the body, cooling the
  skin.

112

• 2. Correction of overcooling
• (a) Vasoconstriction

113
(No Transcript)
114

• (b) Decreased rate of sweating
• Sweating is reduced to a minimum to conserve heat.

115

• (c) Contraction of hair erector muscles

116
Body response to heat loss

• The subjects arm was stuck in a basin of ice
  cold water. One temperature sensor was placed
  between the thumb and forefinger, the other was
  placed under the arm to monitor core temperature.

117
(No Transcript)
118

• The finger temperature reading decreased as the
  body redirects the blood to the more vital
  organs.
• The core temperature increases as the metabolic
  rate of the body increases hence producing more
  heat.

119
Regulations of populations

• Population is a group of individuals of the same
  species which makes up part of an ecosystem.
• Population density is the number of individuals
  of the same type present per unit area of a
  habitat.

120

• Population dynamics is the study of population
  changes (growth, maintenance and decline) and the
  factors which cause these.
• Birth rate of a population is a measure of the
  number of new individuals produced by a
  population over a certain time period.
• Death rate is a measure of the number of
  individuals that died during the same time
  interval.

121
(No Transcript)
122

• At points A and B the birth rate is higher
  than the death rate and the population grows.
• At point C the birth and death rates are equal.
  At this time the population size will remain
  relatively stable this is the carrying capacity
  of the ecosystem.

123
Population stability

• Animal populations usually fluctuate around a
  certain level which the available environmental
  resources can maintain.
• This is the carrying capacity of the environment.

124

• Despite short-term fluctuations the birth rate
  equals the death rate and, in the longer term,
  number remain fairly stable.

125

• Very stable populations can be maintained in the
  laboratory where the conditions can be carefully
  maintained

126

• Wild populations fluctuate more than this due to
  environmental factors

127
Factors affecting population change

• Density-independent factors
• These factors affect the death rate of a
  population equally, regardless of the size of a
  population.
• Abiotic factors
• operate in this
• way.

128
(No Transcript)
129

• The loss is the same, regardless of the size of
  the original population.

130

• Density-dependent factors
• These factors have a greater or lesser effect,
  depending on the population density.

131

• A higher proportion of the population will die
  when the population density is high.
• Density dependent factors include food supply,
  disease, predators and competition.

132

• Food supply
• When there is not enough food for a population
  some individuals (probably the weakest) will
  starve. The denser the population the more
  individuals will suffer.

133

• (b) Disease
• If a population of animal is living at high
  density then disease transmission is more likely
  and the death rate will increase.
• e.g. Myxomatosis rabbits

134
(No Transcript)
135

• (c) Competition
• This may involve competition for food, living
  space etc.
• When the number of animals present outstrips the
  available food supply, competition occurs between
  individuals.

136
(No Transcript)
137

• (d) Predation
• A dense prey population is more likely to attract
  predators than a small population.

138
Predator-prey interactions

• A balance exists between populations of predators
  and their prey.
• An increase in prey leads to an increase in
  predators.
• The increased predator population reduces the
  prey numbers
• The predators have less prey and their numbers
  fall.

139

• A classic example of this is the interaction
  between snowshoe hares and lynxes in Canada.

140
(No Transcript)
141
Monitoring populations

• Monitoring populations of certain species is
  important for the following reasons
• Food species
• Fish
• Stocks of edible species need to be monitored to
  ensure catches do not exceed the rate of
  reproduction.

142

• (b) Red deer
• Deer populations have grown in Scotland as a
  result of lack of predators. To prevent
  environmental damage many deer are culled and the
  meat sold as venison.

143

• 2. Control of pest species
• Monitoring populations of pest species provides
  information needed for their control.

144

• Greenfly
• Greenfly reproduce when environmental conditions
  are favourable and wingless individuals are
  produced.
• When conditions deteriorate, winged greenfly are
  produced allowing them to be dispersed.
• Gardeners can spray plants with pesticide or
  introduce ladybirds when it will have the maximum
  effect.

145
(No Transcript)
146

• (b) Mosquitoes
• Blood sucking female mosquitoes are vectors for
  several diseases such as malaria that affects
  humans.

147

• Monitoring populations of mosquitoes enables
  scientists to find out
• Where the eggs are laid
• What time of day the females feed on blood
• How often the females feed
• Where the insect rests when its not feeding
• Such information is vital when planning a
  programme of control measures.

148

• 3. Endangered species
• Any successful conservation programme depends on
  accurate knowledge of population changes of the
  organism concerned.
• e.g. Black rhino, dolphin, albatross, panda

149

• 4. Indicator species
• Some wildlife species act as an indicator of the
  health of the environment by their presence or
  absence.

150

• Freshwater invertebrates
• Presence of mayfly or stonefly nymphs shows high
  oxygen levels in the water.

151

• Many sludgeworms or rat-tailed maggots shows low
  oxygen levels in the water.

152

• (b) Lichens
• The presence or absence of lichens on tree trunks
  and walls indicates a low level of sulphur
  dioxide air pollution.

153
(No Transcript)
154
Plant succession

• Plant succession is the natural change in a
  habitat from an initial simple pioneer community
  to a final, relatively stable, climax community.

155
(No Transcript)
156

• The change at each stage may modify the habitat
  in one or more ways
• Addition of humus (dead organic matter)
• Increase in fertility (e.g. Clover family)
• Change in soil moisture

157

• Each change makes the habitat less suitable for
  the current community and more favourable for a
  different community which succeeds it.
• (e.g. Reeds lower the water level of a marsh,
  drying it enough for willow trees to grow).

158

• Primary succession
• Takes place during colonisation of a barren area
  which has not been previously inhabited (e.g.
  Bare rock).
• Secondary succession
• Occurs during the colonisation of an area which
  has previously been occupied by a well-developed
  community but has become barren (e.g. A felled
  forest).

159

• During succession the following changes take
  place
• Increase in biomass of the community
• Increase in the species diversity (especially
  plants and invertebrates)
• Increase in the food web complexity.

160
Effect of environment on climax plant communities

• A climax community is
• The final product of long-term unidirectional
  change with in a community.
• Self-perpetuating and, under natural conditions,
  not replaced by another community.
• A mature community is in dynamic equilibrium with
  its environment.

161
(No Transcript)
162
(No Transcript)
163
(No Transcript)
164
(No Transcript)
165
(No Transcript)
166

• Climate
• Temperature and rainfall vary widely round the
  world, resulting in different climax communities,
  e.g.
• very hot, very dry desert
• Very hot, always wet rainforest
• Very hot, seasonal rain savannah
• Warm, regular rain broadleaf forest
• Very cold, dry Tundra

167

• 2. Soil type
• The chemical composition of the underlying rock
  affects the pH and the mineral content of the
  soil.
• In North East Scotland
• Acid soils (common) Heather is dominant
• Basic soils (alkali, over limestone) Support a
  rich variety of flowering plants.

168
THE END!!!