Fox Factor

Year 1

120

12

Year 2

180

15

Year 3

60

22

Year 4

20

8

Year 5

90

5

Plot Population Over Time

Population

Time (Years)

Yr 1 Yr 2 Yr 3 Yr 4 Yr 5

*Hint: Use a solid line for Arctic Foxes and a dashed line for Lemmings.

Post-Graphing Analysis

1. Why does the Arctic Fox population peak *after* (lag behind) the lemming population? Use trophic energy rules to explain this delay.

2. Predict what would happen to the tundra ecosystem's plant biomass (producers) in Year 4, based on the consumer population sizes recorded. Why?

Grade 6-8 Life Science • Fox Factor Lab Journal Page 2 of 2

Fox Factor Lab Journal

Answer Key & Grading Rubric

Part 1: Scientific Analysis Answer Key

Q1: Physiological connection between ear size and heat regulation.

[Sample Answer] Ears contain blood vessels. Fennec foxes have a high surface-area-to-volume ratio in their massive, thin ears, allowing hot blood to radiate heat into the cooler air, cooling their core temperature. Arctic foxes have a low surface-area-to-volume ratio in their small, rounded ears, preventing heat from escaping and maintaining a stable core temperature in subzero climates.

Q2: Why seasonal variation selected for coat changes in the tundra but not the desert.

[Sample Answer] The tundra habitat changes drastically. In winter, everything is white snow/ice. In summer, the snow melts, exposing brown rocks and grass. Natural selection favored camouflage that adapted to both backdrops. The desert background remains sandy-gold year-round, meaning seasonal variation was not a selective pressure for color-changing genes.

Q3: How climate change and forest encroachment shift selective pressures.

[Sample Answer] If the tundra warms and the boreal forest moves north, pure white coats will become a disadvantage in winter due to lack of snow. Natural selection would favor foxes that stay brown-gray longer. Additionally, competition with the larger Red Fox would select for larger body sizes or altered hunting behaviors in the Arctic Fox.

Part 2: Food Web & Graphing Answers

Food Web Species Layout:

• Producer: Tundra Lichens/Mosses
• Primary Consumer: Lemmings
• Secondary Consumer: Arctic Fox
• Arrows flow from: Mosses → Lemmings → Arctic Fox

Q4 Key Point (Lag Phase):

Predators can only reproduce successfully after a massive energy influx (prey population surge). This gestation and development period creates a natural lag.

Q5: Plant biomass in Year 4.

[Sample Answer] Plant biomass would increase/explode. In Year 4, the lemming population crashed to its lowest point (20). Since lemmings are the primary herbivore consuming the producers, their low numbers would relieve grazing pressure, allowing plants/mosses to recover and increase their biomass.

Criteria

Exceeds Standards (4)

Meets Standards (3)

Developing (1-2)

Adaptation Table

Accurately details physical traits with environmental connection.

Completes table with correct characteristics.

Table is incomplete or confuses traits of the two species.

Population Graph

Perfectly graphs both populations with scales and identifies lag.

Plots points correctly for both populations.

Plots points incorrectly or fails to differentiate species.

Grade 6-8 Life Science • Fox Factor Teacher Resource Page 2 of 2