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BIOLOGY, M8 2023 HSC 29a

Organisms use various mechanisms to maintain their internal environment within tolerance limits.

Outline a physiological adaptation in endotherms which assists in maintaining their internal environment.   (2 marks)

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→ Endotherms have developed the ability to change the diameter of their blood vessels to be able to maintain a stable internal temperature.

→ If their internal temperature increases the blood vessels will dilate (vasodilation) which will cause warm blood to flush through and heat will radiate from the skin.

→ If their internal temperature drops the blood vessels will constrict (vasoconstriction) which will reduce the heat radiating from the skin and reduce heat loss.
 

Other answers could include

→ Sweating to maintain temperature.

→ Shivering/goosebumps to maintain temperature.

Show Worked Solution

→ Endotherms have developed the ability to change the diameter of their blood vessels to be able to maintain a stable internal temperature.

→ If their internal temperature increases the blood vessels will dilate (vasodilation) which will cause warm blood to flush through and heat will radiate from the skin.

→ If their internal temperature drops the blood vessels will constrict (vasoconstriction) which will reduce the heat radiating from the skin and reduce heat loss.
 

Other answers could include

→ Sweating to maintain temperature.

→ Shivering/goosebumps to maintain temperature.

BIOLOGY, M8 2018 HSC 12 MC

The graph shows four possible relationships between ambient temperature and body temperature.
 

Which line on the graph represents the relationship between ambient temperature and body temperature for an endotherm in a terrestrial environment?

  1. `W`
  2. `X`
  3. `Y`
  4. `Z`
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`B`

Show Worked Solution

→ Endotherms are animals which perform complex processes to maintain a constant internal body temperature over a variety of external temperatures.

`=>B`


♦♦♦ Mean mark 25%.

BIOLOGY, M8 2020 HSC 1 MC

In maintaining homeostasis, which of the following is a behavioural adaptation?

  1. Sweating to cool down
  2. Curling up in a ball to keep warm
  3. Speeding up or slowing down cell metabolism
  4. Skin going red as more blood flows to surface
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`B`

Show Worked Solution

Curling into a ball to keep warm is a behavioural response of an organism that helps it maintain body temperature.

`=>B`

BIOLOGY, M8 2021 HSC 29

The koala is a mammal that maintains a stable body temperature of close to 36.6°C.

A study was conducted. Koalas were observed in natural forests in south-eastern Australia. Their posture in the tree and the ambient temperature were recorded. Ambient temperatures were divided into two categories, hot and mild.

The graph shows the posture of koalas observed.
 

Explain the adaptations used by the koalas in this study to maintain a stable body temperature. Make reference to the stimulus provided.   (4 marks)

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→ Posture is a behavioural adaptation that changes the surface area of skin exposed to the air or tree trunk. Posture is often seen associated with hot or mild air temperatures. 

→ In mild conditions, koalas were often seen curling up, minimising heat loss by reducing surface area exposed to air, a behaviour that was never observed during hot conditions.

→ In hotter conditions, the koalas were seen leaning against, and hugging trees much more often than during milder conditions. Since the trees were shown to have lower temperatures, this exposes their ventral surface to the cool trunk and acts as a heat sink.
 

Other answers could include:

→ Reference to the physiological adaptation of directing blood flow to the stomach region to increase cooling when this are is in contact with the tree.

Show Worked Solution

→ Posture is a behavioural adaptation that changes the surface area of skin exposed to the air or tree trunk. Posture is often seen associated with hot or mild air temperatures. 

→ In mild conditions, koalas were often seen curling up, minimising heat loss by reducing surface area exposed to air, a behaviour that was never observed during hot conditions.

→ In hotter conditions, the koalas were seen leaning against, and hugging trees much more often than during milder conditions. Since the trees were shown to have lower temperatures, this exposes their ventral surface to the cool trunk and acts as a heat sink.
 

Other answers could include:

→ Reference to the physiological adaptation of directing blood flow to the stomach region to increase cooling when this are is in contact with the tree.