Which of the following is an example of stabilizing...

Which of the following is an example of stabilizing selection? a. Over time, Equus developed strength, intelligence, speed, and durable grinding teeth. b. British land snails mainly have two different phenotypes. c. Swiss starlings usually lay four or five eggs, thereby increasing their chances of more offspring. d. Drug resistance increases with each generation; the resistant bacteria survive, and the nonresistant bacteria get killed off. e. All of these are correct

Which of the following is an example of stabilizing selection?
a. Over time, Equus developed strength, intelligence, speed, and durable grinding teeth.
b. British land snails mainly have two different phenotypes.
c. Swiss starlings usually lay four or five eggs, thereby increasing their chances of more offspring.
d. Drug resistance increases with each generation; the resistant bacteria survive, and the nonresistant bacteria get killed off.
e. All of these are correct

Key Concepts

Natural Selection

Natural selection is the fundamental mechanism of evolution that drives changes in the traits of populations over time. It operates by favoring individuals whose traits provide a reproductive advantage in a given environment, leading to the differential survival and reproduction of those individuals.

Phenotypic Variation

Phenotypic variation refers to the differences in physical traits among individuals within a population. This variation is driven by genetic differences and environmental factors, and it is essential for natural selection to act upon, as it provides the raw material for evolutionary change.

Stabilizing Selection

Stabilizing selection is a form of natural selection in which intermediate variants are favored over extreme phenotypes. This process reduces phenotypic variability and maintains the status quo within a population by selecting against individuals with traits that deviate from the optimal average.

Transcript

00:01 Okay, so here we have a question that asks about stabilizing selection.

00:05 So, stabilizing selection is a form of selection that favors the intermediate phenotype, as opposed to the two extreme ends.

00:14 So we're going to look at each example presented by the question and see whether it fits the example of stabilizing selection.

00:21 So the first one says that over time, equus developed strength, intelligence, speed, and durable binding.

00:27 So this makes sense, but if we think about it, is it stabilizing selection? it wouldn't be.

00:34 It's actually favoring one extreme end of the, one extreme end of all these phenotypes in terms of greater amounts of strength, greater intelligence, faster speed, and durable grinding teeth.

00:47 It would all be heading in one direction in terms of selection for these specific traits.

00:53 And this is actually directional selection.

00:55 So a would be incorrect.

00:57 B says british land snails mainly have two different phenotypes.

01:01 So that is actually an example of disruptive selection where they're favoring two extreme ends of the phenotype and the intermediate phenotype is the least common.

01:13 Stabilizing selection would mean that there is mainly one phenotype which is the intermediate.

01:17 So b would be incorrect.

01:19 C says swiss starlings usually weigh four or five eggs, thereby increasing their chances of more offspring...

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