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 Range Tolerance Range
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.
Response Stimulus Effector Receptor Modulator Negative Feedback Systems
Tolerance Response Optimum Negative Feedback Systems Time
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.
Response Stimulus Effector Receptor Modulator Question Set 1
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 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.
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 • 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 • 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 • 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.