Download Homeostasis revision

Energy requirements of plants
and animals
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Plants and animals require energy for:
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Growth
Activity
Maintenance
Tolerance Range
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All organisms have tolerance ranges within
which various internal conditions must be
maintained.
The maintenance of internal conditions is
known as homeostasis.
Organisms have an optimum level for
internal conditions
Tolerance Range
Temperature (degrees
celcius)
Temperature Tolerance range
30
Optimum
25
20
15
10
5
Tolerance Range
0
5 10 15 20 25 26 27 28 29 30 31 32 33 34 35 40 45 50 55
Time
Feedback systems
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In order for organisms to maintain stable
internal conditions, they have a range of
regulatory mechanisms known as
homoeostatic responses.
Homeostasis ensures that internal
conditions remain within the normal
tolerance range for individual organisms.
Negative Feedback Systems
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Negative feedback systems regulate internal
conditions by constantly monitoring changes in
the internal environment and then making
adjustments based on these changes.
Negative Feedback Systems use changes in
internal conditions as a stimulus. The organs
responsible for detecting changes in the
environment are known as receptors.
Negative Feedback Systems

Messages detected by the receptors, about
changes in the internal conditions, are
normally received by a coordinating centre
known as a modulator. These modulators
are often found in the central nervous
systems of organisms.
Negative Feedback Systems

Once the stimulus information is
coordinated in the modulating centre, then
an appropriate response from an effector is
normally solicited. The effector initiates
changes in the physiology of an organism
which result in a change in internal
conditions towards the optimum.
Negative Feedback Systems
Response
Stimulus
Effector
Receptor
Modulator
Negative Feedback Systems
Negative Feedback Systems
Response
Tolerance
Optimum
Time
Question Set 1
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Explain the difference between an optimum
level and tolerance range in living things.
The optimum level for any internal factor is
that level at which the performance of an
organism is optimised.
The tolerance range is the range for an
internal factor in which an organism can
function without adverse effects.
Question Set 1

Draw a diagram to show the system by
which an organism maintains its internal
environment.
Question Set 1
Response
Stimulus
Effector
Receptor
Modulator
Question Set 1
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What is the difference between homeostasis and a
negative feedback system?
Homeostasis is the maintenance of a constant
internal environment, mediated by feedback
systems.
A system in which a change in the internal
environment results in a homeostatic response
which brings the internal factor back towards the
optimum level.
Carbon Dioxide
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It is important to keep carbon dioxide levels
within the tolerance range of animals because:
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In large quantities carbon dioxide can change the pH
of an organism’s internal environment. This can
have an adverse effect on the functioning of
enzymes.
Very low levels of carbon dioxide can also cause
problems because the regulation of breathing rates in
many organisms are often governed by levels of
carbon dioxide.
Carbon Dioxide
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The relationship between controlling the levels of
carbon dioxide and oxygen in the body is very close.
If carbon dioxide levels increase, then generally
speaking, the levels of oxygen in the body will be
depleted.
In order to decrease the levels of carbon dioxide, the
body will increase ventilation rates (breathing).
This will, in turn, increase the levels of oxygen in the
body.
Glucose Control
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Glucose is a fundamental substance necessary for
cellular respiration. It is used to provide the
energy necessary for converting ADP and P into
ATP, which is then used to drive other metabolic
reactions.
Levels of glucose in the body fluctuate based on
food intake and activity levels. These
fluctuations are monitored and adjusted by the
pancreas.
Glucose Control
Glucose Control
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Glucose is the ‘ready’ form of energy in
the body, while glycogen is a complex
carbohydrate which is used to store glucose
energy in the body. Glycogen is
predominantly stored in the liver and the
skeletal muscles of the human body.
Glycogenesis
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This is the formation of glycogen from
glucose. This glycogen would be stored in
the liver and skeletal muscle.
Glycogenesis would occur when there are
excess amounts of glucose in the blood.
Insulin, a hormone produced by the Beta
cells in the pancreas, will cause the body to
convert excess glucose into glycogen.
Glycogenolysis
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This is the process which converts glycogen into
glucose for use in cellular respiration.
Glycogenolysis occurs predominantly when there
are low glucose levels in the blood.
Glucagon, a hormone produced by Alpha cells in
the pancreas, results in glycogen being converted
into glucose.
Gluconeogenesis
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This process occurs predominantly when
both the levels of glucose and glycogen are
low in the blood system.
In this process, substances other than
glycogen are converted into glucose. The
substances converted into glucose might
include fats and proteins.
Water Balance
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The amount and concentration of water
within an organism, and the relative
concentration compared to the environment
is extremely important.
Water is required because all of the
metabolic activities of living things take
place within a water soluble environment.
Water Balance
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The concentration of dissolved substances is also
very important since the concentration of various
substance can affect the rate at which essential
metabolic reactions take place.
Finally, the relative concentration of an organism
compared to an environment will affect the rates
at which passive forms of transport take place.
An organism can be adversely affected, via the
osmotic loss or gain of water, if the concentration
of its body does not suit its environment and its
internal tolerance limits.
Water Balance
Temperature
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It is important for temperature to be
maintained within the tolerance range of an
organism.
Ectothermic organisms are those for which
body temperature is largely controlled by
the ambient temperature.
Endothermic organisms are those for which
body temperature is internally regulated.
Temperature
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The advantage of ectothermy is that minimum
energy is invested by the organism into regulating
body temperature.
The disadvantage of ectothermy is that these
organisms rely on the ambient temperature to
provide the energy required for activity.
Therefore, activity levels often coincide with high
levels of ambient temperature.
Temperature
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The advantage of endothermy is that the activities of the
organism can be undertaken independently of ambient
temperature.
The disadvantage of endothermy is that considerable
amounts of metabolic energy are often required to
maintain body temperature within tolerance ranges.
Those organisms which are small and endothermic need
to generate more heat via metabolic activity because they
lose more heat to the environment through their relatively
larger surface in relation to volume.
Temperature
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It is important to note that the control of
body temperature is largely a case of
‘balancing’ heat loss to the environment
and heat gained from the environment and
other means.
The nett gain or loss of heat energy will
determine the body temperature of an
organism.
Temperature
Temperature
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If the temperature of an organism falls
below its tolerance range then the normal
chemical reactions which occur within cells
gradually slow and ultimately stop. This is
because the rate of any chemical reaction is
greatly affected by temperature. Generally,
we call a fall in an organism’s temperature
to below its tolerance range, hypothermia.
Temperature
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If the temperature of an organism rises
above its tolerance range then the organism
runs the risk of doing permanent damage to
essential proteins in the body, such as
enzymes.
All proteins are denatured (their shape is
changed) by extremes of temperature.
Temperature
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The shape of enzymes is essential for their
normal functioning. If an enzyme is
denatured by temperature then it ceases to
be able to undertake its role as a chemical
catalyst for essential metabolic reactions.
Generally, if the temperature of an
organism rises above its tolerance range,
we call it hyperthermia.
Temperature
Temperature
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It is important to note that there are
physical, physiological and behavioural
mechanisms for controlling temperature.
Organisms use different combinations of
these as a means of maintaining normal
body temperature within their tolerance
range.
Temperature
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Physical adaptations for regulating body
temperature include:
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Piloerection – body hair stands on end to reduce heat
loss by convection over the surface of the body.
(mammals)
Adaptive increases or decreases in surface area –
Organisms may have increased or decreased surface
area which allows for more efficient control and
transfer of heat energy, as required. The large ears of
many Australian marsupials are an example of using
large surface areas to conduct/convect excess heat to
the environment.
Temperature

Physiological adaptations for regulating
body temperature include:
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Vasoconstriction and Vasodilation – the
control of blood flow to the extremities by
reducing or increasing the diameter of blood
vessels near the surface. This increases or
decreases the rate of heat loss via conduction
and convection.
Temperature

Physiological adaptations for regulating
body temperature include:

Evaporative Cooling – including panting and
sweating. Both means of losing excess heat
to the environment via the energy needed to
cause water to evaporate. As the water
evaporates it carries excess heat energy with
it into the atmosphere.
Temperature
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Physiological adaptations for regulating body
temperature include:
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Shivering – increased, and spasmodic muscle
movement, requires increased metabolic energy.
Along with the energy needed for muscle
contraction, heat is produced which helps to increase
the temperature of the body.
Changes in metabolic rate – similar to above.
Changes in metabolic rate will produce more or less
heat as required to maintain body temperature within
normal tolerance range.
Temperature
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Behavioural adaptations for regulating body
temperature include:
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Exposure control – All of those behaviours which
aim to increase or decrease exposure to extremes in
ambient temperature. These include:
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Basking in sun to increase temperature
Hibernating or torpor during extremes of temperature
Nocturnal habit which reduces exposure to extremely high
temperatures.
Burrowing to reduce exposure to extremes of temperature.
Temperature

Behavioural adaptations for regulating body
temperature include:
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Increasing or Decreasing surface area available for
heat exchange. This includes such things as huddling
in groups and rolling into a ball to reduce heat loss to
the environment. Similarly, organisms attempting to
increase heat loss to the environment will ‘spread
out’ parts of their body to increase surface area.
Question Set 2

Give the word equation for cellular
respiration.
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C6H12O6 + O2 +ADP + P  CO2 + H2O + ATP
Question Set 2
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Which part of the human body is the
effector for glucose control and explain
how this occurs?
Pancreas
Question Set 2
Question Set 2
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Why is it important to keep the temperature of an
organism within its tolerance limits?
If temperature rise above tolerance limits then
there is a risk of denaturing the proteins of the
body. Specifically, enzymes can be damaged so
that they do not function thus blocking essential
chemical reactions.
If temperatures drop below tolerance limits then
there is a risk of essential chemical reactions
slowing and possibly stopping.
Question Set 2
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
Give four means by which organisms
adapted to regulate temperature.
Refer to slides 26 to 41 for answers.
Wastes
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As a result of normal activity, living
organisms produce waste materials.
These waste materials can become toxic to
the organism if they rise above normal
tolerance limits.
Organisms will expend energy to actively
eliminate wastes from their body.
Nitrogenous Waste
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One of the most toxic wastes are those which
result from the breakdown of nitrogen based
compounds, such as proteins.
The nitrogen based wastes produced are known
as nitrogenous wastes. The main form of
nitrogenous waste is ammonia (NH3). This can
then be converted into urea or uric acid.
Nitrogenous Waste
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Ammonia is the simplest form of
nitrogenous waste. It is:
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Water soluble and requires large amounts of
water to be removed from the body.
Highly toxic so it must be eliminated from
the body as quickly as possible.
Low in energy cost to produce.
Produced by fish and juvenile amphibians.
Nitrogenous Waste
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Urea is a more complex form of nitrogenous
waste. It is:
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Water soluble but requires less water to be eliminated
from the organism. Normally leaves organism in a
solution known as urine. Organisms that produce
urea can normally control the concentration of their
urine, thus allowing for the control of water loss.
Toxic but not as toxic as ammonia.
Produced using some energy.
Produced by mammals.
Nitrogenous Waste
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Uric acid is a very complex form of waste. It is:
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Water Insoluble and can be stored as a paste for
extended periods of time.
Non-toxic which also allows it to be stored for
extended periods of time.
Extremely energy ‘hungry’ so requires large amounts
of energy to be produced from ammonia.
Produced by birds and reptiles.
Nitrogenous Waste
Osmosis
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Osmosis is the passive (does not use
energy) movement of water, through a
semi-permeable membrane, from an area of
relatively low concentration of solution to
an area of relatively high concentration of
solution.
Osmosis
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If the concentration inside an organism is lower than the
surrounding environment, then the organism is said to be
hypotonic in relation to its environment.
If the concentration inside an organism is higher than the
surrounding environment, then the organism is said to be
hypertonic in relation to its environment.
If the concentration inside an organism is the same as the
surrounding environment, then the organism is said to be
isotonic in relation to its environment.
Osmosis
Osmotic Pressure in Animals
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Organisms can deal with the movement of water
into or out of their body in a couple of ways:
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They can maintain their body concentration at the
same as their environment (isotonic). These
organisms are known as osmoconformers.
They can maintain body concentration within their
normal tolerance limits which is either above
(hypertonic) or below (hypotonic) their environment.
These organisms are known as osmoregulators.
Osmotic Pressure in Animals
Osmoconformers
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Osmoconformers do not need to deal with a
nett gain or loss of water because there is
no osmotic pressure for water to enter or
leave their cells.
This group of organisms includes the sea
anenome and jellyfish.
Fish in Salt water
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Fish which live in a salt water environment
generally have a body concentration which is
lower than their environment. They are
hypotonic.
This means that there will be a nett movement of
water out of their body via osmosis.
This also means that there will be a nett
movement of salts into the body via diffusion.
Fish in Salt Water
Fish in Fresh Water
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Fish which live in a fresh water environment
generally have a body concentration which is
high than their environment. They are
hypertonic.
This means that there will be a nett movement of
water into their body via osmosis.
This also means that there will be a nett
movement of salts out of their body via diffusion.
Fish in Fresh Water
Question Set 3
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What are the three forms of nitrogenous
waste?
Ammonia, Urea, Uric Acid
Question Set 3
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Why is nitrogenous waste produced by
organisms?
Nitrogenous waste is produced as a result
of the breakdown of nitrogen based
compounds, such as proteins.
Question Set 3
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Give a definition of osmosis.
Osmosis is the passive (does not use
energy) movement of water, through a
semi-permeable membrane, from an area of
relatively low concentration of solution to
an area of relatively high concentration of
solution.
Question Set 3
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Describe the movement of solutes and solvents in
a fish which is living in salt water.
Fish which live in a salt water environment
generally have a body concentration which is
lower than their environment. They are
hypotonic.
This means that there will be a nett movement of
water out of their body via osmosis.
This also means that there will be a nett
movement of salts into the body via diffusion.
Question Set 3
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Describe the movement of solutes and solvents in
a fish which is living in fresh water.
Fish which live in a fresh water environment
generally have a body concentration which is
high than their environment. They are
hypertonic.
This means that there will be a nett movement of
water into their body via osmosis.
This also means that there will be a nett
movement of salts out of their body via diffusion.
Plants dealing with water
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Plants must also maintain water balance.
More complex, terrestrial plants must have
mechanisms for maintaining a level of
water within their tolerance range.
They must also be able to move water
around their body to meet the requirements
of the various parts of the plant.
Angiosperms –A vascular plant
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The angiosperms (flowering plants) have adapted
to become vascular plants. They have specialised
tissue for conducting water and nutrients around
the plant.
Angiosperms are generally terrestrial plants with
a wide range of sizes, shapes and niches.
The angiosperms live in a wide range of
environments with varied water supplies.
Vascular Tissue
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Vascular plants have two types of vascular
tissue.
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Xylem is responsible for carrying water
which flows from the roots, up through the
stems and out into the atmosphere through the
stomata on the leaves.
This flow of water is known as transpiration.
Xylem Vessels
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Xylem forms a network of
continuous tubes throughout
the plant
Water moves through xylem
by a combination of processes
including capillary action,
adhesion and cohesion of
water molecules and osmotic
pressure
Vascular Tissue
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Phloem is responsible for transporting
water and nutrients from one location to
another in a plant.
This relocation of water and nutrients in
known as translocation.
Phloem Vessels
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Phloem is shown here in
cross section (top &
bottom) and longitudinal
section (middle)
It differs from xylem in
that it is living tissue. It
has to be living because it
relies on active transport to
move sugars around the
plant
Transpiration
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This is the movement of water from the ground
through a plant and out into the atmosphere
Water travels in the xylem of roots, stems and
leaves and exits the plant via the stomata
This process also provides soil minerals to the
plant, because they are dissolved in the water
Excess water loss leads to the collapse of the
plant (wilting)
Transpiration continued
Plant Adaptation

In order to be successful in the wide range of
environments, plants adapt various features to better suit
them to their environment. These include:
 Leaf size and colour
 Stomatal Rhythm
 Stomatal structure and distribution
 Cuticle presence
 Growth habit
 Root shape and structure
 Reproductive strategy
 Photosynthetic rhythm
 Leaf hairs
Leaf Size and Colour
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In high light intensity environments, plants
reduce both the amount of chlorophyll in leaves
and the surface area of the leaves.
In low light intensity environments, plants will
have more chlorophyll in the leaves and the
leaves will have a larger surface area.
Plants may also take on a silver or grey colour to
reflect more of the excess available light
Plants may also vary the surface area of leaves
exposed to intense light and heat by leaf rolling or
hanging leaves vertically.
Stomatal Rhythm
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In order to reduce water loss through
transpiration during the hottest parts of the
day, plants will reduce the amount of time
that stomata are open in daylight.
Reversed or reduced stomatal rhythms
mean that plants need to modify their
photosynthetic processes.
Photosynthesis – light dependent
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Plants with reversed stomatal rhythms will
undertake light dependent phase photosynthesis
during the day. This does not require the stomata
to be open since light dependent phase
photosynthesis only fixes light energy as
chemical energy in the form of electron transfer
molecules.
This occurs in the stroma of choloplasts.
Photosynthesis – light
independent
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At night, when the loss of water through transpiration is
less, plants with reverse stomatal rhythms will open their
stomata. This allows essential gases to be exchanged with
the environment. It is at this point that light independent
phase photosynthesis can occur. This occurs in the
stroma of choloplasts. Carbon dioxide enters the leaf
through the stomata and oxygen exits.
This gas exchange occurs in the spongy mesophyll of the
leaf. This tissue has a large number of air spaces between
the mesophyll cells to allow maximum gas exchange.
Stomatal Structure
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Another plant adaptation, used in arid environments,
involves changes in the structure of stomata to reduce
water loss gas exchange.
The stomata may be sunken to provide a humid cavity
above the opening and therefore reduce water loss.
The stomata may be covered with ‘flap-like’ cells which
again promotes a humid environment above the stomatal
opening.
Stomata may also be found only on the underside of
leaves which reduces their direct exposure to the direct
heat of the sun.
Stomatal function
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Stomata open and close based on the turgidity of the guard cells.
When they are turgid (ie full of fluid), the stomata are open. When
they are flaccid, the stomata are closed.
Guard cells contain more chloroplasts than the surrounding epidermal
cells, so when they photosynthesise and accumulate sugars, they set
up a concentration gradient so that water moves in by osmosis, and
the stomata open
This can create problems if water is scarce, because the plant may
lose water faster than it can replace it from the soil. If this happens,
the plant will wilt, and water will move out of the guard cells, closing
the stomata.
This solves the problem of water loss, but also prevents the uptake of
CO2, and thus limits photosynthesis
Leaf adaptations
Leaf adaptations continued


In the sections on the previous slide, can
you see the structural adaptations of the
leaves?
Rank them in order of least adapted to a
dry environment to most adapted.
Leaf Covering
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Some plants have developed a waxy cuticle
which is impermeable to water. This
reduces the loss of water through the
surface of the leaf in arid environments.
Leaves may also have leaf hairs which
promote a humid region around the leaves.
This in turn reduces water loss through
transpiration.
Growth Habit
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Plants show varied growth habits in relation to
their environment.
Plants living in high rainfall areas tend to be
larger with more branching and leaves. They
tend towards tallness to allow them to compete
with other plants for available light.
Plants living in arid areas tend to be smaller and
closer to ground with smaller leaves.
Some plants, like Acacias, have reduced or absent
leaves to reduce water loss. Instead they have
modified stems known as phyllodes.
Root Structure
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Plants will also vary their root structure in
different environmental conditions.
They may grow long tap roots in extremely dry
conditions. These plants are known as
Phreatophytes.
Other plants will use roots which range over a
wide area, just below the ground, to increase the
surface area over which water is collected.
Question Set 4
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
Give four adaptations of plants for
conserving water and explain how each of
these works.
Refer to slides 68-82 for answers.