Question 1: Describe Achieved

Kauri snails, or pūpū-rangi (Paryphanta spp.), are northern giant land snails that evolved in New Zealand before two nocturnal predators, possums and hedgehogs, were introduced. They live in fertile soil full of earthworms and can live 20 years or more. They are most active at night and spend the day under leaf litter or plants. Their droppings show they eat mainly earthworms and some small snails, whose shells supply calcium. They mate mostly from April to July, apparently set off by weather such as rain, and lay about six eggs three times a year, in a hole they dig or under leaf litter at the foot of a tree. Hedgehogs (Erinaceus europaeus) are also out at night and eat kauri snails; where it is cold they may hibernate for some months of the year, once the ground falls below 11 °C. Brushtail possums (Trichosurus vulpecula), also nocturnal, eat kauri snails too, spotting the slow snails from up in the trees.

Describe the relationship between the kauri snail and the possum and between the possum and the hedgehog, an advantage and a disadvantage for the snail of being active at night, and the snail’s egg laying, the hedgehog’s hibernation and the possum’s nocturnal behaviour.

The 2024 paper, page 2 ↗ Marking schedule, page 2 ↗

Work it out

Try it on paper first. Stuck? Take one hint at a time.

1 What is the relationship between the possum and the kauri snail?
Predation: the possum hunts, kills and eats the snail. The possum benefits and the snail is harmed.
2 And between the possum and the hedgehog?
Interspecific competition: two species after the same limited food, since both are out at night and both eat kauri snails.
3 What does “nocturnal” mean, and what does the snail gain by it?
A nocturnal animal is active at night and rests by day. The snail gains because earthworms, its main food, come to the surface at night, and the cool, damp night stops it drying out.
4 What does the snail lose by it?
Its introduced predators, possums and hedgehogs, are nocturnal too, so it is out when they are hunting.
5 What is hibernation?
A long, deep dormancy through the cold months: body temperature and metabolic rate fall right down, and the animal lives on stored fat.
6 What do the snail’s egg laying and the possum’s night activity each do for it?
Laying three times a year gives the snail more than one chance to breed each year. Being nocturnal puts the possum out at the same time as its snail prey.

Answer The possum and the kauri snail are predator and prey: the possum hunts and eats the snail, benefiting while the snail is harmed. The possum and the hedgehog are in interspecific competition, both nocturnal and both eating kauri snails. Nocturnal means active at night and resting by day. For the snail it is an advantage because earthworms come to the surface at night and the damp night stops it drying out; it is a disadvantage because possums and hedgehogs hunt at night too. Hibernation is a deep dormancy through the cold months, with body temperature and metabolism lowered and stored fat used for energy. Laying three times a year gives the snail several chances to breed, and being nocturnal puts the possum out when its prey is.

What the marker wanted

Achieved Describes, one point each: predation between possum and snail; competition between the possum and the hedgehog for the same food; an advantage for the snail of being nocturnal; a disadvantage; hibernation; why laying several clutches a year helps; what nocturnal means; an advantage for the possum of being nocturnal. Four make A4.

The schedule marks the question as one answer from N0 to E8. Achieved points count first: one or two give N1 or N2, three A3, four A4. Above that, two Merit points give M5 and three M6. In 2024 Excellence needs more than usual: TWO Excellence points give E7, three or more E8.

In our words, from NZQA’s 2024 marking schedule.

Common mistake

Leaving out what “nocturnal” and “hibernation” mean. NZQA’s 2024 report says Not Achieved answers to Question One often missed these definitions.

How did it go?

Got it moves it further out. Review brings it back tomorrow.