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26.10:

כושר כולל

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Biology
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JoVE Core Biology
Inclusive Fitness

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כשירות כוללת מתייחסת למידה שבה פרט מעביר את הגנים שלו הן ישירות באמצעות יצירת צאצאים, והן בעקיפין על-ידי סיוע לקרובי משפחה לשכפל את הגנים המשותפים שלהם. לדוגמה, דבורות פועלות, שהן נקבות, אינן מתרבות, אולם הן עוסקות בהתנהגויות זולתניות, כגון הבאת מזון, אשר עוזרות למלכה שלהן לשרוד ולהתרבות. מאחר שהפועלות הן קרובות משפחה של המלכה בדרך כלל בנותיה, רבים מהגנים שלהן מועברים דרך הצאצאים של המלכה מניחים שהתנהגות זולתנית זו כלפי קרובים התפתחה דרך ברירת שארים, הברירה הטבעית של התנהגויות המגבירות את הצלחת הרבייה של קרובי משפחה.במקרה של הדבורה הפועלת, הזולתנות שלהן מגבירה את כשירותן הכוללת, על אף שהן בעצמן אינן מתרבות.

26.10:

כושר כולל

Most altruistic behavior—in which one animal helps another at a cost to themselves—occurs between relatives. Scientists think these altruistic behaviors evolved because they increase the inclusive fitness of the animal providing help.

Inclusive fitness is an individual’s ability to pass down their genes—both through their offspring and the offspring of close relatives with shared genes. If an animal helps a close relative improve their reproductive success, this increases the animal’s inclusive fitness, preserving the behavior in the gene pool.

Eusocial Animals

For example, eusocial animals that live in colonies with only one reproductively capable female (a queen)—such as bees and naked mole rats—are all closely related to other members of the colony. The queen is usually the mother, sibling, or aunt of the other members of the colony, depending on the species. The non-reproductive members typically care for and protect the queen and her offspring, often risking their survival. By helping the queen pass down her genes, the inclusive fitness of the non-reproductive individuals increases since they share a similar genetic makeup.

Kin Selection

The natural selection of behaviors that increase the reproductive success of relatives is called kin selection, and it also acts on animals that are not as closely related as eusocial animals. It is theorized that the degree of relatedness affects whether an altruistic behavior will evolve. This is represented by Hamilton’s rule, which weighs the cost of altruism with the benefits, varying in proportion to relatedness. In other words, animals that are more closely related will be more likely to engage in altruistic behavior towards one another, because their inclusive fitness is increased to a greater extent when they share more genes.

Suggested Reading

Galbraith, David A., Sarah D. Kocher, Tom Glenn, Istvan Albert, Greg J. Hunt, Joan E. Strassmann, David C. Queller, and Christina M. Grozinger. “Testing the Kinship Theory of Intragenomic Conflict in Honey Bees (Apis Mellifera).” Proceedings of the National Academy of Sciences, January 7, 2016, 201516636. [Source]