95. Which one of the following statements DOES NOT explain altruism?
(A) Altruism reduces the fitness of the individual that displays this behavior
(B) Altruism increases the fitness of other individuals in the population
(C) Altruism reduces the fitness of the individual that displays this behavior and at the same time
increases the fitness of other individuals in the population
(D) Altruistic behavior helps the individual escape from predators

Here’s a complete, SEO-friendly article on the topic, optimized for search engines with a focus on the key phrase “which statement does not explain altruism.” I’ve structured it for readability, included the correct answer upfront, and explained all options with evolutionary biology context tailored to your interests in genetics and population genetics.

In evolutionary biology, altruism refers to behaviors where an individual sacrifices its own reproductive success to benefit others. This MCQ tests your understanding of altruism’s core definition, especially in population genetics contexts like kin selection or inclusive fitness. Let’s dive straight into the answer and unpack every option.

Correct Answer: (D) Altruistic behavior helps the individual escape from predators

Option D does not explain altruism because true altruism, by definition, reduces the altruist’s fitness while benefiting others. Escaping predators boosts the altruist’s own survival and fitness, making it a selfish (or self-preserving) behavior, not altruistic.

Detailed Explanation of All Options

Option (A): Altruism reduces the fitness of the individual that displays this behavior

This accurately explains altruism. Fitness in evolutionary terms means reproductive success. Altruistic acts, like a bird warning its flock of danger at personal risk, lower the actor’s direct fitness. This aligns with foundational concepts from Hamilton’s rule ($rB>C$), where the cost (C) to the altruist is key.

Option (B): Altruism increases the fitness of other individuals in the population

This correctly describes altruism. The recipient gains a fitness boost—think sterile worker bees foraging for the queen. Even if spread across non-kin (group selection models), the benefit to others defines the behavior, resolving the paradox via mechanisms like reciprocity or kin selection.

Option (C): Altruism reduces the fitness of the individual that displays this behavior and at the same time increases the fitness of other individuals in the population

This fully explains altruism. It captures the dual essence: a net cost to the actor and a benefit to others. Classic examples include ground squirrels alarm-calling (reducing their own survival odds but aiding kin). This matches the precise definition in population genetics, emphasizing inclusive fitness.

Option (D): Altruistic behavior helps the individual escape from predators

This does NOT explain altruism—it’s the incorrect choice. If the behavior aids the individual’s own escape, it enhances that individual’s fitness, qualifying as selfish adaptation, not altruism. For instance, a deer fleeing predators prioritizes self-preservation, with no fitness cost or recipient benefit required for the label.

Why This Matters in Evolutionary Biology

Altruism challenges naive Darwinian selection, explained by theories like kin selection (favoring relatives sharing genes) or reciprocal altruism (tit-for-tat cooperation). Misidentifying selfish acts as altruistic muddles fitness analyses in genetic studies. For researchers in genetics or plant biology, analogous “altruistic” traits (e.g., sacrificial pollen donation) follow similar logic.

Mastering these distinctions sharpens exam prep for topics like enzyme kinetics in microbial cooperation or plant immune signaling.