NCEA Level 3 Biology 91603 Plant and Animal Responses: past papers, practice and marking
- NCEA Level 3
- Biology
- AS91603
- 5 credits
- External exam
About 91603
AS91603, Demonstrate understanding of the responses of plants and animals to their external environment. Responses in space and time, and relationships within and between species. An extended-writing external where the marks come from the LINK to selective advantage, not the list.
What 91603 covers
- Plant responsesTropisms and auxin, nastic responses (turgor), comparing the two
- Biological timingBiological clocks, circadian, circannual, lunar and tidal rhythms, entrainment, actograms, photoperiodism and phytochrome
- Orientation behaviourTaxes, kineses, homing, navigation, migration
- Interspecific relationshipsCompetition (including allelopathy), mutualism, predation, parasitism, herbivory
- Intraspecific relationshipsTerritory and home range, hierarchy and agonistic behaviour, cooperative breeding, altruism and kin selection
- Reproductive behaviourCourtship, species recognition, mate choice, parental care, broadcast spawning
- Answer structureLinking responses to survival and reproductive success; costs and benefits; command words and bullet points
91603 past papers
Open a 91603 past paper beside your own Ako page, then get it marked, part by part.
Work through a past paper All NCEA Level 3 Biology past papers
Practice questions
Question 1: Plant responses
A tendril of kōhia, a native climbing vine, touches a branch on one side and then coils around it. The coiling is a growth response controlled by the plant hormone auxin.
- Explain how auxin causes the kōhia tendril to coil around the branch.(up to Merit)
- Predict what would happen to the kōhia tendril if the cells on the side away from the branch could not respond to auxin, and give a reason.(up to Merit)
Check your answer
Part a: what gets the marks
- Auxin is a plant hormone, made in growing tips, that makes plant cells elongate (grow longer).
- When the tendril touches the branch, auxin moves to the side of the tendril away from the contact, so that side has the higher auxin concentration.
- Cells on the side away from the branch elongate more than cells on the touching side, so this unequal (differential) growth curves the tendril around the branch, and continued curving forms the coil.
A full answer: Auxin is a plant hormone that causes cells to elongate. When the kōhia tendril touches a branch, auxin moves to the side away from the contact. Cells on that outer side elongate more than cells on the touching side, so the tendril grows unequally and curves around the branch. As it keeps growing this way, the curve becomes a coil.
Part b: what gets the marks
- Auxin is what makes cells elongate, so cells that cannot respond would not grow longer than the cells on the touching side.
- Without unequal growth on the two sides the tendril would keep growing straight and would not curve around the branch, so the kōhia could not hold on and climb.
A full answer: Auxin makes cells elongate, so cells that cannot respond would not grow longer than the cells on the touching side. With no unequal growth the tendril would keep growing straight and would not coil around the branch, so the kōhia could not hold on and climb.
What gets each grade
Question 2: Plant responses
Horokaka (*Disphyma australe*) is a native ice plant of coastal cliffs and sand. Its pink flowers open in bright sunshine, close in the late afternoon, and stay closed on cold, cloudy or wet days. The flowers are visited by bees, flies and butterflies, which fly most in warm, sunny weather.
- Name the response of the horokaka flowers, and describe it.(up to Achieved)
- State how this response differs from a tropism, and explain why the difference matters for a flower that opens and closes every day.(up to Merit)
Check your answer
Part a: what gets the marks
- The flowers show a nastic response to light intensity (photonasty).
- It is a non-directional, reversible movement: the petals open and close whatever direction the light comes from, and can do so again each day.
A full answer: The flowers show a nastic response to light (photonasty). It is a non-directional, reversible movement: the petals open in bright light and close in dim light, whatever direction the light comes from.
Part b: what gets the marks
- A tropism is a directional growth response, while a nastic response is a non-directional movement that is not growth.
- Because the nastic movement is caused by changes in cell turgor rather than growth, it is quick and can be reversed, so the horokaka flower can open and close many times during its life.
A full answer: A tropism is directional growth; a nastic response is a non-directional movement that is not growth. Because the horokaka petals move by changes in turgor, not by growth, the movement is fast and reversible, so the same flower can open and close every day for as long as it lasts.
What gets each grade
Question 3: Plant responses
The flowers of horokaka, a native coastal ice plant, open in bright sunshine and close in the late afternoon and on dull days. The opening and closing is caused by changes in the cells at the base of each petal.
- Explain how the petals of the horokaka flower open in bright sunshine and close again.(up to Merit)
- Explain why a horokaka flower is able to open and close again several times in one day when the sun keeps coming and going.(up to Merit)
Check your answer
Part a: what gets the marks
- Opening and closing are caused by changes in turgor (water pressure) in the cells at the base of the petals.
- In bright light, solutes (ions) are moved into these cells, raising their solute concentration, so water enters them by osmosis.
- The cells swell and their turgor pressure rises, pushing the petals outward so the flower opens; when the light fades, solutes and then water leave the cells, they lose turgor and the petals close.
A full answer: The movement is caused by turgor changes in cells at the base of the petals. In bright light, solutes are moved into these cells, so water enters by osmosis. The cells swell, turgor pressure rises, and they push the petals open. In dim light the solutes and water leave, the cells become less turgid and the petals close. Because no growth is involved, the movement is fast and reversible.
Part b: what gets the marks
- The petals move because of changes in turgor in the cells at their base, not because new cells are made, so nothing is used up by a movement.
- When the sun returns, solutes and then water move back into the cells by osmosis and the petals open again, and when it fades water leaves, so the movement is reversible and can be repeated.
A full answer: The petals move by changes in turgor in the cells at their base, not by growth, so nothing is used up. When the sun returns, solutes and then water move back into the cells by osmosis and the petals open; when it fades, water leaves and they close. The movement is reversible, so it can be repeated as often as the sun comes and goes.