1. Miss Heretakis iheretakis@steuphemia.nsw.edu.au
YEAR 12 BIOLOGY!!
Miss Heretakis

2. End here 27/10
You need to read your notes, and add any information that you feel is necessary to satisfy the dot point.

3. MODEL OF A FEEDBACK SYSTEM
To keep the internal environment constant, the body operates under a feedback system. In a feedback system the response alters the stimulus.
There are 2 types of feedback mechanisms:
Negative feedback system means that the change to the stimuli is opposite to the initial situation. For example is a human increases in body temperatures so perspiration is produced to decrease the temperature.
Positive feedback system occurs when there is a change in the environment and the stimuli reinforces for the initial stimuli. For example during contractions in childbirth (stimuli) hormones are released (response).
MODEL OF A FEEDBACK SYSTEM
gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism
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Not as common!

4. Lets use a non living example for modeling homeostasis
The heater will perform set tasks in order to maintain a constant temperature of 200C
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5. MODEL OF A FEEDBACK SYSTEM
This is to be completed by next lesson.
(page 20-21)
gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism
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6. Temperature regulation
MODEL OF A FEEDBACK SYSTEM
gather, process and analyse information from secondary sources and use available evidence to develop a model of a feedback mechanism

7. Temperature limits of living organisms
Temperature Tolerance
Temperature is one of the many limiting factors that can determine the presence of life on Earth.
E.g. tissue temperatures greater than 42̊C are lethal to most organisms as important enzymes begin to denature.
Temperature limits of living organisms
identify the broad range of temperatures over which life is found compared with the narrow limits for individual species
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8. Temperature limits of living organisms
Chemical reactions that occur in cells take place only within a relatively narrow range of temperatures, due to the temperature sensitivity of enzymes. Extreme temperatures (above 100C ) denature not only proteins, but also nucleic acids. This destruction of DNA results in cell death. Its therefore not surprising that habitats that offer temperature conditions that are fairly stable are highly sought after and result in much competition.
identify the broad range of temperatures over which life is found compared with the narrow limits for individual species
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9. Temperature limits of living organisms
Range of Temperatures
Most living things live at temperatures between 10 and 35̊C.
The diverse array of living organisms on Earth are found across a broad range of temperatures—there are living creatures that can survive in temperatures as low as –70°C (at the poles) or as high as 56°C in deserts and 350°C (in hot vents in the sea).
Temperature limits of living organisms
identify the broad range of temperatures over which life is found compared with the narrow limits for individual species
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10. Temperature limits of living organisms
There is an enormous variation in temperature over the Earth. The average variation in environmental temperature is more prominent on land (-89 to 60̊C).
Species that occupy habitats with extreme conditions are referred to as extremophiles.
Temperature limits of living organisms
identify the broad range of temperatures over which life is found compared with the narrow limits for individual species
8/11

11. Temperature limits of living organisms
The range of temperatures over which life is found is BROAD compared to the narrow limits for individual species.
Much like enzymes, species have an optimal range of temperatures at which they can function. The temperature range in which a species can survive is called its tolerance range.
Temperature limits of living organisms
identify the broad range of temperatures over which life is found compared with the narrow limits for individual species
8/11

12. Temperature regulation in ectothermic and endothermic organisms
The terms ectotherms and endotherms relate to the ability of an animal to regulate its body temperature. ‘Therm’ relates to temperature, ‘ecto’ means outside and ‘endo’ means inside.
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
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13. Temperature regulation in ectothermic and endothermic organisms
ECTOTHERMS
Ectothermic organisms depend on an external source—the environment—for heat energy. E.g. Fish, amphibians, reptiles and most invertebrates
The body temperature of ectotherms is influenced by the ambient temperature (temperature of the environment).
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
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14. Temperature regulation in ectothermic and endothermic organisms
Ectotherms only have a limited ability to control their body temperature. In lab conditions, their body temperature fluctuates over a wide range of temperatures.
In nature, ectotherms adapt their behaviour to regulate their body temperature.
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

15. Temperature regulation in ectothermic and endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
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16. Temperature regulation in ectothermic and endothermic organisms
Example: Ectotherms
Temperature regulation in ectothermic and
endothermic organisms
Brown snakes are found across most of Australia, inhabiting a range of habitats from open grasslands to desert scrub, but not in rainforest areas.
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
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17. Temperature regulation in ectothermic and endothermic organisms
Brown snakes are usually diurnal (awake during the day). If the temperature rises beyond the snake’s tolerance level, it will seek shelter in the shade during the day and become active in the later part of the day (or night) when it is cooler. If the ambient temperature drops below the optimum range, brown snakes bask in the sunlight to gain additional heat. In very cool weather, the snake becomes less active, slowing down its metabolism and uses fat reserves. If the cold period is prolonged, the snake will hibernate in a sheltered spot.
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

18. Temperature regulation in ectothermic and endothermic organisms
ENDOTHERMS
Endotherms rely on internal sources such as metabolic activity for heat energy. E.g. Birds and mammals
Under lab conditions and in nature, the body temperature of an endothermic organism tends to remain stable despite variation in temperature.
Endotherms have the ability to control and maintain their body temperature at a stable level within a very narrow range (e.g. body temperature in humans is approx. 37̊̊C).
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
Body temp may fluctuate by about 1.5C.
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19. Temperature regulation in ectothermic and endothermic organisms
In low temperatures, the main source of heat in the body of endotherms is that generated as a result of the metabolic activity of their cells, particularly the muscle and liver cells.
The size of the animals body also plays a significant role in temperature regulation– a small body loses heat much more quickly and so small mammals often have a high metabolic rate.
Some endotherms have special heat-producing tissue called brown fat, which can be quickly metabolised in cold conditions. E.g. bentwing bat
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

20. Temperature regulation in ectothermic and endothermic organisms
If the ambient temperature is high, endotherms have a physiological cooling mechanism. The rate of heat loss from the body can be adjusted by altering the flow of blood near the surface. Evaporative cooling such as sweating, panting or licking saliva onto the body surface is a common cooling mechanism.
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

21. Temperature regulation in ectothermic and endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

22. Example: Fairy penguin
Temperature regulation in ectothermic and
endothermic organisms
Is found along the southern Australian coastline and in Tasmania and New Zealand. It is the smallest of all penguins and lives in burrows in coastal sand dunes, not in the ice and snow like most penguins.
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
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23. Temperature regulation in ectothermic and endothermic organisms
Fairy penguins have feathers that provide an insulating layer. These feathers trap a layer of air close to the skin which reduces the amount of heat lost. This layer of air can be altered depending on the ambient temperature. In cold conditions the feathers are lifted away from the skin, increasing the air layer and providing a greater degree of insulation.
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

24. Temperature regulation in ectothermic and endothermic organisms
Penguins also have behavioural mechanisms to regulate body temperature, moving into the water to cool down in hot conditions or huddling close together in cold conditions to reduce the surface area of each penguin exposed to the cold. They may also retreat to their burrows.
Temperature regulation in ectothermic and
endothermic organisms
compare responses of named Australian ectothermic and endothermic organisms to changes in the ambient temperature and explain how these responses assist temperature regulation
9/11

25. Adaptations and responses of Australian organisms
See handout given in class.
Adaptations and responses of Australian organisms
for temperature regulation
analyse information from secondary sources to describe adaptations and responses that have occurred in Australian organisms to assist temperature regulation
My year 12 assignment - printout

26. Temperature changes and responses in plants
Maintenance of a relatively stable internal environment is just as important for plant metabolism as it is for animals.
Plants respond to changes in light, water availability and temperature, all of which are linked, since heat is often associated with light and hot areas are often dry, compromising evaporative cooling
Temperature changes and responses in plants
identify some responses of plants to temperature change

27. Temperature changes and responses in plants
Plant responses to high temperatures
Australia is recognised as a country that is relatively warm and dry.
Temperatures above 40°C may cause damage to proteins and those above 75°C to chlorophyll pigment within the plant. Since plants cannot move into the shade the way animals can, plant responses to excessive temperature are mostly structural and physiological.
Temperature changes and responses in plants
identify some responses of plants to temperature change

28. Temperature changes and responses in plants
Evaporative cooling (transpiration)
Exposure to heat (and light) causes the stomata in plants to open, leading to a loss of water by transpiration (evaporation of water from the stomata of leaves).
The advantage of transpiration is that it cools the internal temperature of the plant.
A disadvantage of this is that it can lead the plant to dehydration due to excess water loss. Plants close their stomata in excessive heat to reduce water loss.
Temperature changes and responses in plants
identify some responses of plants to temperature change

29. Temperature changes and responses in plants
Turgor response – wilting
In extreme heat and dry conditions, plants transpire and lose turgor. As a result the leaves wilt, reducing the surface area exposed to the sun (and heat and light)
Wilting can be detrimental if permanent as it can lead to plant death.
E.g. hydrangeas, roses
identify some responses of plants to temperature change

30. Temperature changes and responses in plants
Leaf fall
Some trees (e.g. eucalypts) are evergreen trees that drop some of their leaves during the dry season in hot climates to reduce the surface area exposed to heat.
Temperature changes and responses in plants
identify some responses of plants to temperature change

31. Temperature changes and responses in plants
Reseeding and resprouting in response to fire
These responses ensure the plants survival after a fire.
Resprouters (e.g. bottle brush, eucalypts) have epicormic buds underneath the bark that are protected from damage by a fire and then resprout; or may have lignotubers, which are underground and sprout new growth after the fire.
Seeders (e.g. banksias, eucalypts) release seeds into the environment after the plant is exposed to extreme heat.
Temperature changes and responses in plants
identify some responses of plants to temperature change

32. Temperature changes and responses in plants
Plant responses to cold temperatures Organic anti-freeze Decreases in temperature causes some plants that live in areas such as the alpine to produce antifreeze proteins. The protein protects the cells of the plants by reducing the temperature at which the cytoplasm of the cell freezes.
Temperature changes and responses in plants
identify some responses of plants to temperature change

33. Temperature changes and responses in plants
Dormancy During cooler months, deciduous trees lose their and undergo a period of dormancy (a period of time where metabolic function comes to a standstill). e.g. The deciduous beech Northofagus tree is an Australian species which is found in Tasmania. The benefits of shedding leaves is that it enables the plants to slow down metabolic function.
Temperature changes and responses in plants
identify some responses of plants to temperature change

34. Temperature changes and responses in plants
Vernalisation
In order for some plants to develop flowers, they must have undergone a period of intense cold (e.g. tulips).
This is an adaptation as it ensures that budding only occurs in the warmer spring months and not during autumn or winter.
Temperature changes and responses in plants
identify some responses of plants to temperature change

35. Temperature regulation
Revision questions to be completed by next lesson.
(page 33)
Temperature regulation