Worksheet

From a Tick Bite to the Health Lab: Acorns, Mice and Ticks

Grade 7 life science: use a county health lab's acorn, mouse and tick surveys and a windstorm site comparison to argue how ecosystem changes affect populations.

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10 questions
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Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students use multi-year survey data to argue how a change in a living part of a forest affects other populations.
Students use a site comparison and a lab test to argue how a change in a physical part of a forest affects a population.
Students judge which evidence answers a competing explanation.

How to use

Read paragraphs 1–3 together and have students trace the tick's two-year life cycle with a finger before they read Table 1. Section 2 works well in pairs, followed by a short class discussion of the skeptic's question.

Curriculum

NGSS standard covered

MS-LS2-4

Argue from evidence that changes to physical or living parts of an ecosystem affect its populations.

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From a Tick Bite to the Health Lab: Acorns, Mice and Ticks

Use seven years of forest surveys and a windstorm comparison to argue how ecosystem changes affect a tick population.

Acorns, mice and ticks

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

What the Health Lab Counts

1Last July, after a hike in Hollow Creek Forest, seventh grader Mateus Oliveira found a tiny tick on his leg. His doctor, Dr. Seo-yeon Park, removed it, cleaned the spot and told him what signs to watch for. She explained that black-legged ticks can carry the bacteria that cause Lyme disease, and that the county health lab counts ticks in the forest every summer. In the fall, Mateus's class visited the lab, and a lab biologist, Ms. Adaeze Nwosu, shared the lab's records with them.

2A black-legged tick usually lives about two years and takes one blood meal at each of three stages: larva, nymph and adult. Larvae hatch in midsummer and feed in late summer, most often on a small mammal such as a white-footed mouse. After that meal, they drop into the leaf litter, wait through the winter and become nymphs. Nymphs look for their meal the following June and July. They are the stage most likely to bite people, because they are about the size of a poppy seed and easy to miss. Adults feed mostly on deer in the fall.

3White-footed mice eat many foods, but acorns are one of their favorites, and mice store them to eat through the winter. Oak trees in a forest tend to make a huge acorn crop in some years and very few acorns in others. Each fall, the lab counts acorns that fall into baskets on the forest floor. Each July, it traps mice, counts them and lets them go. Also each July, workers drag a white cloth along 100 m of trail and count the nymphs that cling to it (Table 1).

4In spring 2024, a windstorm blew down most of the trees on a 20-hectare patch at the edge of the forest. With the trees gone, sunlight now reaches the ground there. Ticks lose water quickly in dry air and spend most of their time in the leaf litter. In July 2025, the lab compared the blowdown patch with the closed forest nearby (Table 2). It also kept groups of nymphs in jars of air at three humidities for 10 days (Table 3).

Table 1. Hollow Creek Forest Surveys
Year	Acorns per m² (fall)	Mice per hectare (July)	Nymphs per 100 m (July)
2019	8	20	14
2020	95	18	12
2021	5	70	16
2022	10	15	48
2023	6	22	13
2024	70	19	15
2025	9	62	17

The nymph count in July 2022 was how many times the nymph count in July 2021? times

Which pattern does Table 1 show?

A. Mice were most common in the falls with the most acorns.
B. Nymph counts rose year by year from 2019 to 2025.
C. Nymphs peaked in the same year as each big acorn crop.
D. A big acorn crop led to a mouse peak, then a nymph peak.

Use paragraphs 2 and 3. Why did the nymphs peak in 2022, two summers after the big 2020 acorn crop, and not in 2021?

A. Ticks lay their eggs inside acorns, and the eggs take two years to hatch.
B. Deer ate the 2020 acorns, and the deer carried the nymphs into the forest in 2022.
C. The 2021 mice fed many larvae in late summer, and those larvae became nymphs in 2022.
D. Nymphs feed on acorns, and the 2020 acorns did not sprout until 2022.

Complete the chain of causes for the next peak. Use words from the bank. Two words are left over.

Word bank: acorns · mice · larvae · nymphs · deer · adults

In fall 2024, the oaks made a big crop of . In July 2025, there were many . Those animals fed many tick in late summer, so in July 2026 the lab expects many .

Which nymph count for the closed forest in July 2026 does Table 1 support best?

A. About 15 per 100 m, because the 2025 acorn crop was small
B. About 45 per 100 m, because the many mice of 2025 fed many larvae
C. About 5 per 100 m, because the mice will crash in 2026
D. About 90 per 100 m, because acorns and mice both rose in 2025

After the windstorm

Use paragraph 4 and Tables 2 and 3 to answer the questions.

Table 2. Two Sites in July 2025
Site	Tree cover (%)	Leaf litter humidity (%)	Mice per hectare	Nymphs per 100 m
Closed forest	90	92	62	17
Blowdown patch	15	70	60	4

Table 3. Jar Test (20 nymphs per jar, same temperature)
Air humidity (%)	Alive after 10 days (%)
95	90
85	55
75	15

In July 2025, how many fewer nymphs per 100 m were counted in the blowdown patch than in the closed forest? nymphs

A skeptic says, “There were fewer nymphs in the blowdown patch only because fewer mice live there.” Which evidence answers the skeptic best?

A. The mice per hectare were about the same at both sites, 62 and 60.
B. The closed forest had 17 nymphs per 100 m, as Table 1 shows.
C. The windstorm blew down trees on a patch of 20 hectares.
D. Tree cover was 90% in the closed forest and 15% in the blowdown.

Circle the two results that, together, best support this claim: “Drier leaf litter after the windstorm lowered the tick population in the blowdown patch.”

The leaf litter humidity was 70% in the blowdown and 92% in the closed forest.The blowdown patch had 60 mice per hectare.In the jar test, 90% of nymphs lived 10 days at 95% humidity, but 15% lived at 75%.The oaks made 70 acorns per m² in fall 2024.Workers counted nymphs by dragging a white cloth along 100 m of trail.

Young trees are starting to grow in the blowdown patch. Suppose that in about 20 years their leaves shade the ground as the closed forest does now. Which prediction does the evidence support best?

A. The litter will stay moister, so nymph counts will rise toward the closed forest's counts.
B. Nymph counts will fall further, since shade will make the leaf litter drier.
C. The shade will drive the mice away, so nymph counts will drop below 4 per 100 m.
D. The leaf litter will stay as dry as it was in 2025, so nymphs will stay near 4 per 100 m.

10.

Mateus's cousin says, “Tick numbers in the forest just go up and down by chance. Nothing else in the ecosystem changes them.” Write an argument against this claim. Use evidence from Table 1 and from Table 2 or Table 3, and explain how one change to a living part and one change to a physical part of the forest affected the tick population.