Night Flowers and Fish Gifts on a Barrier Island

Explain how a dune flower's structures and a seabird's behavior help each one reproduce.

Answer Key

Flowers that open at sunset

Read the passage and Table 1, then answer the questions.

A Week at the Field Station

1Sandpiper Island is a long, narrow barrier island of beaches and sand dunes. The island, its field station, the people and the numbers here are made up, but they are based on real studies. In June, sixth grader Idris Pemberton spent a week helping station biologist Dr. Celia Moreau with two studies of how living things on the island reproduce.

2The first study was about a low dune plant called evening primrose. Its pale yellow flowers open around sunset, give off a strong sweet scent after dark and wilt by the next afternoon, so each flower is open for about one night and one morning. Nectar sits at the bottom of a long, narrow tube. The pollen grains are linked by fine, sticky threads, so a whole string of grains can catch on a visitor at once. At night, large moths hover at the flowers and reach the nectar with long tongues. In the morning, a few bees visit the flowers that are still open.

3Dr. Moreau tagged 120 flower buds on plants growing close together and split them into four groups of 30. She used mesh bags to keep visitors away at certain times. Three weeks later, Idris counted how many flowers in each group had formed seed capsules.

4The second study was about common terns, seabirds that nest in a colony on open sand. Before the female lays her eggs, her mate flies out to sea again and again and brings her small fish. This is called courtship feeding. Later, when a gull flies low over the colony, many terns rise up and dive at it. A gull that lands can eat eggs or chicks. From a blind, the team counted how many fish each male brought in an hour before egg laying, then checked every nest until the chicks could fly.

Table 1. Evening Primrose Bagging Test
Group	Open to visitors	Flowers	Made seed capsules
A	Night and morning	30	24
B	Morning only	30	6
C	Night only	30	22
D	Never (bagged)	30	2

Use Table 1.

What percent of the Group A flowers made seed capsules? 80%

Which conclusion do Groups B and C together support best?

A. Visitors made little difference, since Groups B and C formed about the same number of capsules.
B. The mesh bags damaged the flowers, since both bagged groups formed few capsules.
C. Night visitors such as moths carried most of the pollen between flowers.
D. Morning visitors such as bees carried most of the pollen between flowers.

Why did Dr. Moreau keep the Group D flowers bagged the whole time?

A. To give the moths a group of flowers where they could rest during the day
B. To see how many flowers form capsules when no visitor can reach them
C. To make the four groups end up with equal numbers of capsules
D. To test whether a different kind of primrose grows better inside a bag

Use paragraph 2 and Table 1. How does opening at sunset and giving off a strong scent after dark most likely help the primrose reproduce?

A. It saves the nectar for the morning, so the bees will carry more pollen to other flowers.
B. It keeps the flower closed during the day, so the seeds can form inside it while it is cool.
C. It lets the scent soak into the sand, so the seeds that fall there sprout sooner.
D. It draws night-flying moths while the flower is fresh, so pollen gets carried between flowers.

How do the sticky threads that link the pollen grains most likely help the primrose?

A. They glue the moth to the flower, so it stays there until the next morning.
B. They let many grains catch on one moth and travel with it to the next flower.
C. They tie the flower shut, so less nectar washes away in the rain.
D. They hold the pollen in the flower, so it lands on that same flower's pistil.

Fish gifts in the tern colony

Use paragraph 4 and Table 2 to answer the questions.

Table 2. Tern Nests by Courtship Feeding (40 pairs)
Fish brought per hour	Pairs	Eggs per nest (avg.)	Egg mass (g, avg.)	Young that flew (avg.)
Less than 2	10	2	18	0.8
2 to less than 4	20	2.5	20	1.3
4 or more	10	2.9	21	1.8

"Young that flew" means the average number of chicks per nest that lived until they could fly.

On average, pairs whose males brought 4 or more fish per hour had 0.9 more eggs per nest than pairs whose males brought less than 2.

How many eggs in all did the 20 pairs in the middle row lay? 50 eggs

Which pattern does Table 2 show?

A. Pairs with more fish tended to have more eggs, heavier eggs and more chicks that flew.
B. Pairs with more fish had about 2.5 eggs per nest, the same as pairs with few fish.
C. Pairs with more fish laid more eggs, but fewer of their chicks lived until they could fly.
D. Pairs with more fish had more eggs, but their eggs were lighter, about 18 g each.

Use paragraph 4 and Table 2. How does courtship feeding most likely help the pair reproduce?

A. The fish give the female extra food energy and nutrients to build her eggs.
B. The fish make the eggs hatch a few days sooner, before the gulls arrive.
C. The fish lead other males out to sea, so fewer males crowd into the colony.
D. The fish are stored in the nest, where the chicks eat them weeks later when they hatch.

10.

Match each structure or behavior from the island to the way it most likely helps reproduction.

Flowers that open around sunsetE
Sticky threads linking pollen grainsC
A male tern bringing fish to his mateB
Terns diving at a gull over the colonyD
Nectar at the bottom of a long tubeA

A. Rewards a visitor that has a long tongue
B. Gives the female extra food for her eggs
C. Moves many grains on a single visit
D. Drives off a bird that eats eggs and chicks
E. Matches the hours when moths are flying

11.

A new parking lot keeps bright lights on all night beside one patch of dunes, and far fewer moths visit the primroses there. Which prediction for that patch fits Table 1 best?

A. More flowers would likely form capsules, since the lights keep them open longer.
B. More flowers would likely form capsules, since bees could see better at night.
C. Fewer flowers would likely form capsules, closer to the result for Group B.
D. About as many flowers would form capsules, since bees visit in the morning.

12.

Idris's friend says, "Bringing fish to his mate is just a habit. It does not change how many young terns a pair raises." Do the data support this? Write a claim, give evidence from Table 2 and paragraph 4, and explain your reasoning.

Claim: The data do not support this; courtship feeding most likely helps a pair raise more young. Evidence: Pairs whose males brought 4 or more fish per hour averaged 2.9 eggs per nest, each about 21 g, and 1.8 chicks per nest that lived until they could fly. Pairs whose males brought less than 2 fish per hour averaged only 2.0 eggs of about 18 g and 0.8 chicks that flew. Reasoning: The fish come before egg laying, so they give the female extra food to build more and heavier eggs. Larger, better-supplied eggs may give chicks a better start, and more eggs give the pair more chances to raise young. So the male's behavior raises the pair's chance of reproducing successfully.