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What evidence can you cite to support the claim that the timing of entry into hibernation by grizzly bears is regulated? Justify why this evidence supports the claim. a. Grizzly bears go into hibernation at the end of winters. This observation provides evidence that there is some environmental cue that triggers physiological changes in bears. b. Grizzly bears do not go into hibernation at the beginning of autumn. This observation provides evidence that there is some environmental cue that triggers physiological changes in bears. c. Grizzly bears go into hibernation at random times during the year. This observation provides evidence that there is some environmental cue that triggers physiological changes in bears. d. Grizzly bears do not go into hibernation at random times during the year. This observation provides evidence that there is some environmental cue that triggers physiological changes in bears.

Step by step solution

01

- Understand the Claim

The claim is that the timing of entry into hibernation by grizzly bears is regulated. We need to identify evidence that supports this regulation and justify why this evidence supports the claim.

02

- Analyze Option a

Option a states that grizzly bears go into hibernation at the end of winters. Evaluate whether this observation suggests that an environmental cue triggers physiological changes in bears.

03

- Analyze Option b

Option b states that grizzly bears do not go into hibernation at the beginning of autumn. Evaluate whether this observation suggests that an environmental cue triggers physiological changes in bears.

04

- Analyze Option c

Option c states that grizzly bears go into hibernation at random times during the year. Determine whether this observation supports or contradicts the idea that their hibernation is regulated by an environmental cue.

05

- Analyze Option d

Option d states that grizzly bears do not go into hibernation at random times during the year. Determine whether this observation supports the claim that an environmental cue triggers physiological changes.

06

- Justification of Evidence

Option A discusses hibernating at the end of winter, but bears typically hibernate during the winter. Option B shows bears do not hibernate at the start of autumn, indicating a controlled timing. Option C describes random hibernation timing, which opposes the regulation claim. Option D describes non-random hibernation times, supporting the existence of environmental cues. Options b and d provide the strongest evidence for regulated hibernation, but Option d specifically highlights it is not random, clearly showing regulation by environmental triggers.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Environmental Cues

Grizzly bears rely heavily on environmental cues to determine when to enter hibernation. These cues include changes in temperature, day length, and food availability. As winter approaches, the temperature drops and days become shorter. These changes signal to the bear's body that it's time to start preparing for hibernation. Food scarcity is another cue. As the food supply dwindles, bears instinctively know they need to conserve energy, leading them to enter hibernation. By responding to these environmental cues, grizzly bears can ensure they are in tune with the seasonal changes, allowing for a successful and timely entry into hibernation.

Physiological Changes

When grizzly bears receive the environmental signals to begin hibernation, they undergo significant physiological changes. One of the most notable changes is the reduction in metabolic rate. The bear's body temperature drops, and its heart rate slows down remarkably. These changes help conserve energy since the bear won't be eating during hibernation. Additionally, bears store large amounts of body fat in preparation for the hibernation period. This fat serves as the primary energy resource during their long sleep. The body also undergoes changes in hormone levels, such as an increase in melatonin, which supports the hibernation process.

Hibernation Timing

The timing of hibernation is crucial and strategically planned. Grizzly bears typically start their hibernation as winter approaches and environmental conditions become harsh. They do not enter hibernation at the beginning of autumn or random times throughout the year. Instead, their entry into hibernation is precisely regulated. This timing ensures that bears conserve energy when food is scarce and temperature conditions are severe. The regularity and predictability of hibernation timing demonstrate that bears respond to specific environmental triggers, making their survival more efficient and effective.

Regulation of Hibernation

The regulation of hibernation in grizzly bears is a complex process governed by both external and internal factors. Environmental cues like dwindling food resources, dropping temperatures, and decreasing daylight hours act as external signals. Internally, grizzly bears experience hormonal changes that prepare their bodies for hibernation. A key aspect of this regulation is the consistency in hibernation entry times across various bear populations, indicating a strong biological and environmental influence. The predictability in their behavior underscores how well these environmental and physiological triggers are synchronized, ensuring the bear's survival during winter months.