Topic 5: Homeostasis

Which statement best describes homeostasis?

Which sequence shows the stimulus-response model in the correct order?

In a negative feedback system, what does the response do to the change that was detected?

On a hot afternoon on Rottnest Island, the temperature of a quokka's blood rises. Thermoreceptors detect the rise, the hypothalamus sends nerve impulses, and blood vessels near the skin widen so more heat is lost. In this pathway, what is the effector?

A feedback loop for the water content of the blood is listed below. ADH is a hormone that makes the walls of the kidney's collecting ducts more permeable to water. Stage 1: sweating on a hot day raises the solute concentration of the blood. Stage 2: osmoreceptors in the hypothalamus detect the change. Stage 3: the pituitary gland releases more ADH into the blood. Stage 4: ? Stage 5: the solute concentration of the blood falls back towards normal. Which statement completes Stage 4?

Early on a cool morning, a bobtail lizard's body temperature is below its preferred range. It basks on a sunny rock until its body temperature reaches the preferred range, then moves into the shade of a shrub. Which statement about this behaviour is correct?

In a mammal, where are the receptors that monitor the temperature of the blood flowing through the brain?

After an injury, a man's hypothalamus no longer processes signals from his thermoreceptors, although his receptors, nerves, muscles and sweat glands all work normally. He sits for two hours in a room at 8 °C in light clothing. What is the most likely outcome?

Which statement correctly distinguishes endotherms from ectotherms?

Two animals, X and Y, were each kept for two hours in a chamber at eight air temperatures, with no shade or shelter to move to, and their body temperatures were measured (graph). Which conclusion is supported by the graph?

On a hot afternoon a red kangaroo licks its forearms, where a network of blood vessels lies close to the skin. How does this behaviour cool the kangaroo?

When a person's core temperature starts to fall, the arterioles supplying the skin constrict. What is the effect?

Two cubes model a small and a large animal: one has sides of 1 cm and the other sides of 3 cm. How does the surface area to volume ratio of the small cube compare with that of the large cube?

The honey possum is a tiny marsupial of the south-west heathlands. On cold nights when nectar is scarce it can enter torpor, letting its body temperature fall well below normal. Why does torpor help it survive?

In the flippers of little penguins, arteries carrying warm blood from the body run right beside veins carrying cool blood back from the flipper tips. What is the effect of this arrangement in cold water?

Which of these is a physiological response that helps an animal regulate its body temperature?

A student recorded the air temperature and the body temperature of a ring-tailed dragon in the Pilbara every hour one morning (table). Based on the table, by how many degrees more did the dragon's body temperature rise than the air temperature between 07:00 and 09:00?

A student recorded the air temperature, body temperature and behaviour of a ring-tailed dragon in the Pilbara every hour one morning (table). Which conclusion is best supported by the data in the table?

On a hot, humid day in Broome, a man working outside sweats heavily, yet his core temperature keeps rising. What is the best explanation?

Students filled three cube-shaped metal containers of different sizes with water at 60 °C, placed them side by side in a room at 20 °C and recorded the fall in temperature after 20 minutes (table). Which conclusion about animals is best supported by these results?

Most bony fish excrete their nitrogenous waste mainly as ammonia. Why is ammonia suited to life in water?

Birds and most reptiles lay shelled eggs on land, and their embryos excrete nitrogenous waste as uric acid. Why is uric acid suited to an embryo inside a shelled egg?

The table shows the percentage of nitrogen that four vertebrates, W to Z, excrete as each type of nitrogenous waste. Based on the table, which animal is most likely to live where water is scarcest?

Which list ranks the three nitrogenous wastes from the lowest to the highest energy cost to produce?

The tadpoles of the motorbike frog live in ponds and excrete mostly ammonia. The adult frogs spend much of their time on land and excrete mostly urea. What is the best explanation for this change?

The body fluids of a freshwater fish have a higher solute concentration than the river water around it. Which combination of responses keeps its water and salt balance?

A pink snapper lives in the sea off Perth. Its body fluids have a lower solute concentration than seawater. Which statement describes its water and salt balance?

Black bream live in the Swan River estuary. After heavy winter rain, a bream moves from salty water near the river mouth to almost fresh water upstream, and stays there. Its blood stays at a solute concentration between that of fresh water and seawater. What changes in the bream once it is upstream?

Sharks keep a high concentration of urea in their blood, which brings the solute concentration of their body fluids to slightly above that of seawater. How does this help a shark's water balance?

Wedge-tailed shearwaters that nest on Rottnest Island feed at sea and swallow seawater with their food. Glands above their eyes secrete a salt solution that drips from the nostrils. How do these glands help water balance?

The spinifex hopping mouse lives in sandy deserts and may never drink. Which of its adaptations for water balance is behavioural?

In a laboratory study, a hopping mouse ate only dry seeds and drank no water. Its daily water gains and losses are shown in the table; the evaporative loss was not measured. The mouse's body mass stayed constant, so its water gains equalled its losses. What was its evaporative water loss per day?

In the arid interior, the water-holding frog burrows underground in the dry season, stores dilute urine in its large bladder, and sheds layers of skin that form a cocoon around its body. How does the cocoon help?

The leaves of many banksias have their stomata in pits on the lower surface, and the pits are lined with hairs. How do the pits and hairs reduce water loss?

In dry weather, the leaves of a desert grass roll up into a tube, with almost all of the stomata on the inner surface. How does rolling reduce water loss?

Some succulent plants of arid areas open their stomata at night and close them by day. They store the carbon dioxide taken in at night and use it for photosynthesis the next day. What is the main advantage?

Old man saltbush grows in salty soils of the Wheatbelt. The surface of its leaves is covered in tiny bladder cells that fill with salt, then burst or are shed. How does this help the plant?

Grey mangroves in Shark Bay grow in waterlogged mud that holds very little oxygen. Many pencil-like roots grow up out of the mud. What is the main role of these roots?

On a hot, dry afternoon in the jarrah forest, a jarrah tree closes most of its stomata. Apart from saving water, what is the main effect on the leaves?

A student counted 25 stomata in one circular field of view on the lower surface of a saltbush leaf. The field of view was 0.40 mm in diameter. What was the stomatal density, to the nearest whole number? (Area of a circle = πr².)

Students coated the leaves of a garden plant with petroleum jelly, which stops water vapour passing through, on one surface, both surfaces or neither, and found each leaf's percentage loss in mass after 48 hours (table). What is the independent variable in this investigation?

Students coated the leaves of a garden plant with petroleum jelly, which stops water vapour passing through, on one surface, both surfaces or neither, and weighed each leaf before and after 48 hours (table). Which conclusion is best supported by the data?

An African lungfish normally lives in a pool and excretes most of its nitrogen as ammonia. When the pool dries, it burrows into the mud, seals itself in a cocoon of mucus and stays there for months without water. What change in its nitrogenous waste is most likely while it is buried?

In a pot trial, wheat and old man saltbush were watered with salt solutions of five concentrations (graph). Which explanation best accounts for the results at 15 g L⁻¹?

The table shows the mass of each nitrogenous waste stored inside chicken eggs at four stages of incubation. Nothing passes out through the shell except gases and water vapour. Which statement best explains the data?

The stages of a response during a long run are listed below. Stage 1: the runner's core temperature rises. Stage 2: thermoreceptors in the hypothalamus detect the rise. Stage 3: ? Stage 4: sweat glands secrete more sweat onto the skin. Stage 5: the sweat evaporates and core temperature falls towards normal. Which statement completes Stage 3?

In an investigation, a volunteer's skin was treated with a drug that stops the cold receptors in her skin from sending nerve impulses. The thermoreceptors in her hypothalamus, her nerves, her muscles and her blood vessels were unaffected. She then sat in water at 20 °C for 40 minutes. Compared with the same test without the drug, what is the most likely result?

During an infection, a chemical acts on the hypothalamus and raises the set point for core temperature from 37.0 °C to 39.0 °C. Hours later the chemical is cleared and the set point returns to 37.0 °C. Which responses are most likely (i) just after the set point rises, while the core is still at 37.0 °C, and (ii) just after it returns to 37.0 °C, while the core is still at 39.0 °C?

Animal P (body mass 20 g) and animal Q (body mass 80 g) were each kept at four air temperatures, and the total oxygen use of each animal was measured (table). One is an endotherm and the other is an ectotherm. Which statement is correct?

The table shows the daily water budget of a spinifex hopping mouse and a wedge-tailed shearwater, a seabird that drinks seawater and removes the extra salt through glands above its eyes. For each animal the daily water gains equalled the losses. Which statement is correct?

The table shows the nitrogenous waste made by three embryos, X, Y and Z, by the time they hatch. They are a motorbike frog (eggs in jelly in a pond), a flatback turtle (leathery eggs buried in damp beach sand, which take up water from the sand) and an emu (hard-shelled eggs that lose water vapour through the shell). Which embryo is most likely the flatback turtle, and why?

Leaves of plant P, a succulent from coastal dunes, and plant Q, a bean, were studied over 12 hours of daylight and the 12 hours of darkness that followed (table). Over the whole 24 hours, how many times as much carbon dioxide did P take up for each gram of water it lost, compared with Q?