Suppose you were studying several species of human. In one,...

Name: Problem 15, Chapter 26: Biological Science
Uploaded: 2020-06-05T23:06:12-08:00
Duration: 5 min 51 s
Channel: John Barone
Description: Suppose you were studying several species of human. In one, males never lifted a finger to help females raise children. In another, males provided just as much parental care as females except for actually carrying the baby during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?

Suppose you were studying several species of human. In one, males never lifted a finger to help females raise children. In another, males provided just as much parental care as females except for actually carrying the baby during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?

Key Concepts

Anisogamy

Anisogamy refers to the inherent difference between male and female gametes, with females typically producing large, nutrient-rich eggs and males producing small, mobile sperm. This fundamental asymmetry underpins many aspects of sexual reproduction and remains constant across species, regardless of differences in subsequent parental care behaviors.

Parental Investment Theory

Parental Investment Theory addresses the different amounts and types of care that each sex provides to offspring. It explains that when one sex contributes significantly more resources to offspring survival—such as through gestation or extended nurturing—the reproductive strategies and behaviors of that sex will diverge from the other. This theory helps predict variations in mating strategies and competition across species with different parental roles.

Sexual Dimorphism

Sexual Dimorphism describes the differences in size, morphology, or behavior between males and females of a species. These differences often result from varying sexual selection pressures and parental investment patterns, with species exhibiting high levels of male-male competition or low levels of paternal care typically showing greater dimorphism compared to species where parental roles are more balanced.

Sexual Selection

Sexual Selection is the evolutionary process by which traits become more or less common based on their impact on an individual’s ability to secure mates. This process is closely linked to parental investment, as the sex with lower investment tends to compete more intensely for mates, leading to the development of exaggerated traits. Shifts in parental investment patterns can alter the intensity of sexual selection and, consequently, the degree of sexual dimorphism observed in a species.

Transcript

00:01 This question is asking us about a situation in which we have two species, one in which the males invest nothing in their offspring, and another species where the males invest a lot in there.

00:13 So let's think about that.

00:15 We'll make them sort of categories here.

00:17 So males invest a lot.

00:32 And the other species were males invest nothing.

00:51 So the question really is interested in two different issues.

00:55 One is the fundamental asymmetry of sex.

01:04 And what we mean by that is that in most species, almost all species, where you have different gen two genders, males invest less in their gametes in their sperm and females invest in their eggs.

01:17 So there is this fundamental asymmetry that females invest more.

01:23 Within that context, though, there's a lot of range.

01:25 And so when you have a species where males invest a lot, the asymmetry is less.

01:33 They may not manage to invest as much as the females do, but they still manage to invest a lot.

01:40 So the asymmetry is lower.

01:49 Of course, if males are investing nothing, then the asymmetry is very high.

02:03 And since almost all the investment is coming from the females.

02:13 So the fundamental asymmetry is lower...

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