Question 2: Discuss Excellence

The honey bee (Apis mellifera) is active by day, and its pollen foraging is tied to its circadian rhythm. Bees find their way around and back to the hive by cues from their surroundings, including the Sun’s position as a compass, and can forage 5 km out and still get home when cloud hides the Sun. In a total solar eclipse the Moon covers the Sun completely, so bees meet darkness at a time they normally would not. Biologists compared foraging on an ordinary day with the day of a total eclipse. Their graph (Figure 4) is greyed out in NZQA’s public copy; as the schedule reads it, ordinary-day foraging climbs through the morning to a peak near 1:30 pm and eases off slowly in the late afternoon, while on the eclipse day it is normal until the eclipse, falls to a handful of bees in totality, comes back only slowly, and stays under the ordinary day until after 3 pm, when it rises above it.

Discuss the behaviour of honey bees on a normal day and on the day of a total solar eclipse, including why some bees kept foraging in the eclipse’s darkness.

The 2025 paper, page 6 ↗ Marking schedule, page 4 ↗

Work it out

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

1 Start from the explain answer: how do the clock and the cues work together to get a bee home, whatever the weather?
The circadian clock lets the bee read the Sun as a compass at any hour on a sunny day; polarised light, landmarks, scent and possibly the magnetic field cover overcast days. Because no single cue has to be available, a forager almost always gets back.
2 Why does reliable homing matter to the colony?
A forager that gets home survives to forage again, and the nectar and pollen it carries feed the colony and its brood. More food reaching the hive means more young reared and a stronger colony, which increases its reproductive success.
3 Compare the two days in Figure 4. Where do they match and where do they differ?
They match before the eclipse. During totality the eclipse day drops to a few bees, where a normal day is heading for its 1:30 pm peak; it recovers slowly, stays low until about 3 pm, then overtakes the normal day.
4 Why did most bees stop?
Darkness is the cue that ends the foraging day, and without the Sun the compass fails, so most bees acted as at dusk: they stayed in or came home, which keeps them from getting lost.
5 Why did some bees keep foraging?
The circadian clock is entrained by light but does not reset in minutes, so for some bees it still read midday and the darkness did not register as night. Bees also vary: some respond less to a drop in light and may treat it like passing cloud, and some can lean on other cues, such as the magnetic field, which the eclipse does not change.
6 What does that variation do for the colony?
Most foragers are kept safe while the compass is out, and the few that continue keep some food coming in during an event that lasts only minutes. Either way the colony loses little foraging, which protects its survival and reproductive success.

Answer On a normal day the circadian clock lets honey bees read the Sun as a compass at any hour, and polarised light, landmarks, scent and possibly the magnetic field cover overcast days, so foragers almost always get home. That keeps foragers alive and brings nectar and pollen to the hive, so more brood is reared and the colony’s reproductive success increases. Figure 4 shows the two days matching until the eclipse. During totality foraging fell to a few bees, where a normal day was building to its 1:30 pm peak; it recovered slowly, stayed low until about 3 pm, then rose above the normal day. Most bees stopped because darkness is the cue that ends foraging and the sun compass fails without the Sun, so they acted as at dusk and avoided getting lost. Some kept foraging because the clock, though entrained by light, does not reset in minutes: for them it was still midday, and the darkness did not register as night. Individual bees also differ: some react less to falling light and may treat it as passing cloud, and some can use cues the eclipse leaves untouched, such as the magnetic field. So most foragers are kept safe and a few keep food coming in, and the colony loses little.

What the marker wanted

Achieved The describe points: diurnal, circadian rhythm, the homing cues, and foraging on each day.
Merit Those explained: why the clock and the sun compass go together, which cues work on sunny and on overcast days, both foraging patterns, and why some bees forage in the dark.
Excellence A detailed discussion of two things. First, the circadian rhythm, and how bees get home by environmental cues both on sunny days AND on overcast ones, linked to survival or reproductive success. Second, foraging on the eclipse day compared with a normal day, using Figure 4, and why some bees still forage. One gives E7, both E8.

One answer, N0 to E8. Excellence points come last: one gives E7, both give E8.

In our words, from NZQA’s 2025 marking schedule.

Common mistake

Explaining the foraging at each time of day separately without relating the times to each other or to the colony’s survival. NZQA’s 2025 report says this is where many Merit answers stopped.

How did it go?

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