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Ch. 35 Behavioral Adaptations to the Environment
Taylor - Campbell Biology: Concepts & Connections 10th Edition
Taylor, Simon, Dickey, Hogan10th EditionCampbell Biology: Concepts & ConnectionsISBN: 9780136538783Not the one you use?Change textbook
Chapter 35, Problem 10

Scientists studying scrub jays found that it is common for 'helpers' to assist mated pairs of birds in raising their young. The helpers lack territories and mates of their own. Instead, they help the territory owners gather food for their offspring. Propose a hypothesis to explain what advantage there might be for the helpers to engage in this behavior instead of seeking their own territories and mates. How would you test your hypothesis? If your hypothesis is correct, what kind of results would you expect your tests to yield?

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Step 1: Formulate a hypothesis based on kin selection theory. Suggest that helpers assist relatives in raising their young to increase the survival rate of their shared genes. This behavior could be advantageous because it helps ensure the propagation of genes they share with the offspring, even if the helpers do not reproduce themselves.
Step 2: Design an experiment to test the hypothesis. Collect genetic samples from the helpers, the mated pairs, and the offspring in multiple scrub jay populations. Use genetic markers to determine the relatedness between the helpers and the offspring they assist.
Step 3: Observe and record the behavior of the helpers. Note how much time they spend gathering food for the offspring, defending the territory, and performing other supportive tasks. Compare this with the behavior of non-helper scrub jays in similar environments.
Step 4: Analyze the data to see if there is a significant correlation between the genetic relatedness of the helpers to the offspring and the amount of assistance they provide. Use statistical methods to determine if helpers are more likely to assist closely related offspring.
Step 5: Interpret the results. If the hypothesis is correct, you would expect to find that helpers are more genetically related to the offspring they assist than to offspring in other territories. Additionally, you might find that territories with helpers have higher offspring survival rates compared to those without helpers.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cooperative Breeding

Cooperative breeding is a social system where individuals, known as helpers, assist in the rearing of offspring that are not their own. This behavior is often observed in species like scrub jays, where helpers contribute to the care and feeding of young birds. The advantages for helpers may include increased survival rates for their kin, as well as potential future reproductive opportunities within the group.
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Inclusive Fitness

Inclusive fitness is a concept in evolutionary biology that explains how an organism's genetic success is derived not only from its own reproduction but also from the support of relatives' reproduction. By helping relatives raise their young, helpers can enhance the survival of shared genes, thereby increasing their overall genetic contribution to future generations, even if they do not reproduce directly.
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Hypothesis Testing

Hypothesis testing is a scientific method used to determine the validity of a proposed explanation for a phenomenon. In this context, one might hypothesize that helpers gain indirect benefits, such as increased future mating opportunities or enhanced survival skills. Testing this hypothesis could involve observing helper behavior, measuring reproductive success of helpers versus non-helpers, and analyzing genetic relatedness to assess the benefits of cooperative behavior.
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Related Practice
Textbook Question
In Module 35.3, you learned that Norway rat offspring whose mothers don't interact much with them grow up to be fearful and anxious in new situations. Suggest a possible ultimate cause for this link between maternal behavior and stress response of offspring. (Hint: Under what circumstances might high reactivity to stress be more adaptive than being relaxed?)
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Textbook Question

A chorus of frogs fills the air on a spring evening. The frog calls are courtship signals.

What are the functions of courtship behaviors?

How might a behavioral ecologist explain the proximate cause of this behavior?

The ultimate cause?

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Textbook Question

Crows break the shells of certain molluscs before eating them by dropping them onto rocks. Hypothesizing that crows drop the molluscs from a height that gives the most food for the least effort (optimal foraging), a researcher dropped shells from different heights and counted the drops it took to break them. a. The researcher measured the average drop height for crows and found that it was 5.23 m. Does this support the researcher's hypothesis? Explain. b. Describe an experiment to determine whether dropping molluscs from an optimal height is learned or innate.

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Textbook Question

Researchers are very interested in studying identical twins who were raised apart. Among other things, they hope to answer questions about the roles of inheritance and upbringing in human behavior.

Why do identical twins make such good subjects for this kind of research?

What do the results of such studies suggest to you? What are the potential pitfalls of this research?

What abuses might occur in the use of these data if the studies are not evaluated critically?

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Textbook Question
SCIENTIFIC THINKING Jane Goodall's work revealed that in areas of abundant food, chimpanzees may live in groups of several dozen individuals. State a hypothesis about the chimpanzee mating system that could be tested by observing one of these groups. What data would you collect to test your hypothesis? How would you interpret the results? (Note: A sexually mature female chimpanzee undergoes a hormonal cycle about 36 days long that is reflected in easily observed changes in the appearance of her genital area. Females are most sexually receptive, and males are most attracted to them, for about a week during the middle of the cycle.)
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