Energy requirements of plants and animals Plants and animals require energy for:

Growth Activity Maintenance

Tolerance Range 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 RangeTemperature Tolerance range

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Feedback systems 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 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 SystemsStimulus

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Negative Feedback Systems

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Question Set 1 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

Stimulus

Receptor

Modulator

Effector

Response

Question Set 1 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 It is important to keep carbon dioxide levels

within the tolerance range of animals because: 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 Physical adaptations for regulating body

temperature include: 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: 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 Physiological adaptations for regulating body

temperature include: 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 Behavioural adaptations for regulating body

temperature include: Exposure control – All of those behaviours which

aim to increase or decrease exposure to extremes in ambient temperature. These include: 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: 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. C6H12O6 + O2 +ADP + P CO2 + H2O + ATP

Question Set 2 Which part of the human body is the

effector for glucose control and explain how this occurs?

Pancreas

Question Set 2

Question Set 2 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 Give four means by which organisms

adapted to regulate temperature. Refer to slides 26 to 41 for answers.

Wastes 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 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 Ammonia is the simplest form of

nitrogenous waste. It is: 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 Urea is a more complex form of nitrogenous

waste. It is: 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 Uric acid is a very complex form of waste. It is:

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 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 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 Organisms can deal with the movement of water

into or out of their body in a couple of ways: 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 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 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 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 What are the three forms of nitrogenous

waste? Ammonia, Urea, Uric Acid

Question Set 3 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 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 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 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 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 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 Vascular plants have two types of vascular

tissue. 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 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 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 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 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 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 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 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 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 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 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 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 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 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 Give four adaptations of plants for

conserving water and explain how each of these works.

Refer to slides 68-82 for answers.