Revision session 4

Multiple choice questions 1Select the best explanation of how some bacteria are metabolically

active in hot springs. (a) At high temperatures enzymes are not needed to catalyse

chemical reactions. (b) Their enzymes have high optimal temperatures. (c) Their enzymes are insensitive to temperature. (d) They use molecules other than proteins to catalyse chemical

reactions.

An endotherm moves from a cool place to a hotter one. Which of the following changes is most likely to occur?

(a) Skin muscles will contract to hold hairs erect. (b) Blood vessels near the body surface will dilate (expand). (c) Urine production will increase. (d) Body temperature will fall, to compensate

Multiple choice questions 1Select the best explanation of how some bacteria are metabolically

active in hot springs. (a) At high temperatures enzymes are not needed to catalyse

chemical reactions. (b) Their enzymes have high optimal temperatures. (c) Their enzymes are insensitive to temperature. (d) They use molecules other than proteins to catalyse chemical

reactions.

An endotherm moves from a cool place to a hotter one. Which of the following changes is most likely to occur?

(a) Skin muscles will contract to hold hairs erect. (b) Blood vessels near the body surface will dilate (expand). (c) Urine production will increase. (d) Body temperature will fall, to compensate

Multiple choice questions 2Eastern coral snakes are brightly coloured, with red, yellow and black rings

along their bodies. The snakes are poisonous and their bite kills many animals quickly. Predators rarely attack these snakes and those that do are usually killed. Which of the following is the most likely explanation of why the snakes are rarely attacked?

(a) Only predators that avoid the snakes survive to breed. (b) Predators are bitten and learn to avoid the snakes. (c) The colourings camouflage the snakes. (d) The predators that survive the snake's bite pass on resistance to their

offspring.

A non-poisonous snake called the scarlet king snake lives in the same habitat as the eastern coral snake. The two species have similar colours. A biologist reasoned that predators would not attack scarlet king snakes because they looked so much like the dangerous eastern coral snakes. Which of the following best defines this suggestion?

(a) It is an observation. (b) It is an hypothesis. (c) It is a theory. (d) It is a conclusion.

Multiple choice questions 2Eastern coral snakes are brightly coloured, with red, yellow and black rings

along their bodies. The snakes are poisonous and their bite kills many animals quickly. Predators rarely attack these snakes and those that do are usually killed. Which of the following is the most likely explanation of why the snakes are rarely attacked?

(a) Only predators that avoid the snakes survive to breed. (b) Predators are bitten and learn to avoid the snakes. (c) The colourings camouflage the snakes. (d) The predators that survive the snake's bite pass on resistance to their

offspring.

A non-poisonous snake called the scarlet king snake lives in the same habitat as the eastern coral snake. The two species have similar colours. A biologist reasoned that predators would not attack scarlet king snakes because they looked so much like the dangerous eastern coral snakes. Which of the following best defines this suggestion?

(a) It is an observation. (b) It is an hypothesis. (c) It is a theory. (d) It is a conclusion.

Multiple choice questions 3

What is the most likely environment for this plant? (a) a swampy environment (b) a tropical rainforest environment (c) an arid environment (d) a moist woodland environment

Multiple choice questions 3

What is the most likely environment for this plant? (a) a swampy environment (b) a tropical rainforest environment (c) an arid environment (d) a moist woodland environment

Short answer 2004 32a& bPopulations of snakes can be found on small, offshore islands. Studies have

shown that their only source of food is the eggs and chicks of birds nesting on the island. The birds' nesting season lasts for two months of the year and the snakes starve for the rest of the year, completing their reproductive cycle. Only during the coldest months are they inactive.

a) Explain why the snakes are able to survive without food for such a long period when a mammal would usually die.

b) A diet of eggs and birds leads to a high level of nitrogenous wastes in the body of the snake.

i) Which component of the snakes' diet leads to the high levels of nitrogenous wastes?

ii) Name the three types of nitrogenous wastes produced by animals, in order from the most toxic to the least toxic.

1. Most toxic2.3. Least toxic

Short answer 2004 32a& bPopulations of snakes can be found on small, offshore islands. Studies have shown

that their only source of food is the eggs and chicks of birds nesting on the island. The birds' nesting season lasts for two months of the year and the snakes starve for the rest of the year, completing their reproductive cycle. Only during the coldest months are they inactive.

a) Explain why the snakes are able to survive without food for such a long period when a mammal would usually die.

Ectotherms - Lower energy requirements than endotherms; Ectotherms don’t need to maintain high body temperature in cold weather; Endotherms use large amounts of energy to maintain temperature

b) A diet of eggs and birds leads to a high level of nitrogenous wastes in the body of the snake.

Which component of the snakes' diet leads to the high levels of nitrogenous wastes?

Proteins/amino acids in preyii) Name the three types of nitrogenous wastes produced by animals, in order from

the most toxic to the least toxic. Ammonia (most toxic), urea, uric acid (Least toxic) (all named but with error in order, 1 mark. All named in right order 3 marks)

Short answer 2004 32c& d

c) i) Which type of nitrogenous waste would snakes excrete?ii) List three ways in which this would help with the snakes’

survival

d) The snakes have never been observed to drink seawater, however the birds on which they feed are able to drink seawater without any ill effects

(i) Explain the likely osmotic effect of seawater on the body cells of animals which drink it.

(ii) In general terms, what would a bird's body need to do to successfully gain body water from sea water?

Short answer 2004 32c& dc) i) Which type of nitrogenous waste would snakes excrete? Uric acidii) List three ways in which this would help with the snakes’ survivalLittle water required to excrete it/can be highly concentratedLow toxicity/can be stored in bodyCan be stored in eggsd) The snakes have never been observed to drink seawater, however the birds

on which they feed are able to drink seawater without any ill effectsi) Explain the likely osmotic effect of seawater on the body cells of animals

which drink it. Higher salt concentration than body cellsDehydrate/Body cells lose water by osmosis (the word osmosis is notessential in the answer)ii) In general terms, what would a bird's body need to do to successfully gain

body water from sea water? Need to excrete large amounts of saltUse active transport to remove excess salt from the bodyExcrete salt via tear gland/Kidneys excrete excess salt

Short answer 2004 32e

The study of these snakes also has found that they are significantly larger than mainland snakes of the same species.

e) Provide one reason why this could help the snakes with water shortages, and one reason why this could help the snakes with food shortages.

i) Water shortage

ii) Food shortage

Short answer 2004 32e

The study of these snakes also has found that they are significantly larger than mainland snakes of the same species.

e) Provide one reason why this could help the snakes with water shortages, and one reason why this could help the snakes with food shortages.

i) Water shortage Larger snakes have lower SA:V ratiosLess water will be lost

ii) Food shortage Lower SA:V ratio of large snakes means slower heat loss 2 marksCan eat bigger chicks, hence can feed for longer periods 2 marksBeing larger they can store more food in their gut or as fat 2 marks

Extended answer 2004 36(d)

Describe the processes by which terrestrial animals and terrestrial plants maintain water balance.

Extended answer 2004 36(d)Describe the processes by which terrestrial animals and terrestrial plants maintain water

balance. Plants• water uptake via roots by osmosis• active transport of minerals into root hairs (1 mark) AND this increases water uptake (1

additional mark)• water loss via stomates by diffusion/transpiration/evaporation • definition/description of transpiration stream• description of stomate structure • description of stomate function (up to 2 marks)• labelled diagram/explanation of leaf including processes (up to 3 marks)• adaptations to regulate/reduce water loss, except stomata (up to 3 marks)Maximum 6 marks for plants

Animals• water uptake via drinking • use of metabolic water• water extraction from food • water loss in breathing • production of urine/faeces/metabolic waste/nitrogenous waste• water loss in temperature regulation/sweating/panting/licking• adaptations to regulate water loss, eg urea excretion in mammals (urine), uric acid excretion

in birds and reptiles, production of concentrated urine, feedback mechanisms using hormones/ADH, behavioural adaptations to reduce water loss, shape for optimal SA:V ratio to minimize water loss (up to 3 marks)

Maximum 6 marks for animals

Extended answer 2004 37(b)

Describe with the aid of diagrams i) the structures and processes by which water is absorbed

by root hairs, travels through the plant and exits the plant via the stomates.

ii) how the leaves of a desert-dwelling plant might be expected to differ from those of a plant growing in a moister environment.

Extended answer 2004 37(b - i)water uptake is via osmosis into root hairs• root hairs provide a large SA for water

absorption• root pressure• active uptake of minerals enhances osmosis• diagram/description of effect on water transport

by stomatal opening/closing• the transpiration stream draws water up via

xylem• capillarity is the result of cohesion and

adhesion• water adheres to xylem walls• the diameter of xylem vessels is small,

facilitating adhesion• water molecules cohere• solar energy drives the transpiration stream• whole plant drawing with labelled roots, xylem

and leaves• xylem drawing showing cohesion/adhesion• leaf drawing showing stomate, xylem and air

spaceMaximum 6 marks

Extended answer 2004 37(b - ii)Xerophytes have:• thicker cuticle• stomates recessed/in crypts• stomates surrounded by hairs• stomatal density is lower to reduce water loss/higher so photosynthesis is

effective during short time each day the stomata are opened• stomata concentrated on underside/shady side of leaf• tolerance to dehydration/wilting• leaves narrowed• leaves rolled/tomatose• leaves absent• leaves are shed during driest months• decrease in surface area of leaves• shiny, reflective leaves• leaves hang downwards• labelled diagram showing any of above (maximum 2)Maximum 6 marks

Extended answer 2005 37(b)

Examine the apparatus drawn below.

i) What is its purpose and how does it work?

ii) Name four (4) physical, environmental factors (other than plant structures) that would influence the independent variable being measured. Explain the effect of each factor.

Extended answer 2005 37(b)Examine the apparatus drawn below. i) What is its purpose and how does it

work? Measures transpiration• Water transpires from stomata in the

leaves• Xylem draws water up from the

reservoir to the leaves• The amount of water transpired over a

given time is measured by noting the movement of an air bubble against the scale

• Bubble can be moved back to start of scale

Note: maximum of 4 marks for the above.

Extended answer 2005 37(b)

ii) Name four (4) physical, environmental factors (other than plant structures) that would influence the independent variable being measured. Explain the effect of each factor. Temperature: increase increased evaporation rate• (due to greater kinetic energy of water particles)Wind: removes humid air from leaf surface increased evaporation rate• (due to greater concentration gradient inside/outside leaf)Light: stomata open only in light• Water loss is through stomata, so increased evaporation rate in lightHumidity of surrounding air: determines concentration gradient across leaf surface • drier air greater evaporation rateNote: maximum of 8 marks for the above with a maximum of two marks foreach named variable.Maximum 10 marks total