Name: natural selection and adaptive evolution
Uploaded: 2026-06-01T06:27:51.341Z
Duration: 1 min 32 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

Biological Evolution- Unity and Diversity

LS.Bio.9.1

What is Natural Selection?

One of the most remarkable aspects of the natural world is the fit between organisms and their environments.Coyotes, for example, have teeth and other traits that allow them to eat birds with ease. And the wings of birds, in turn, give them the chance to escape predators like coyotes.Natural selection is the evolutionary process that generates such matches between organisms and their environments. Evolution by natural selection or adaptive evolution occurs if three conditions are met.First, there must be variation in traits among individuals, such as the difference in color among these beetles. These trait variations stem from random genetic mutations, which occur regardless of whether they are good or bad for the organism.Second, these trait differences must be heritable, meaning that they can be passed down from parent to offspring.Third, some forms of the trait must provide an advantage in survival and reproduction.Here, green beetles are better camouflaged on green grass than yellow beetles, so more yellow beetles are seen and eaten by birds.Because of this advantage, green beetles represent a greater and greater proportion of the population over the course of generations. In this case, green color is an adaptation for beetles living in a green grassy environment.

what is natural selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become more common within a population or species. Naturally selected traits initially arise via random genetic mutations. In order for selection to occur, there must be variation within a population, the trait controlling the variation must be heritable, and there must be an evolutionary advantage for variation in the trait.<h4>The Theory of Natural Selection</h4>Natural selection is a phenomenon that favors individuals that are better adapted to their environment. Charles Darwin described the process in his 1859 publication, On the Origin of Species:&#x201C;Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection, in order to mark its relation to man&#x27;s power of selection&#x201D;.It is also worth noting that the phrase &#x201C;survival of the fittest,&#x201D; commonly used when referring to natural selection and often misattributed to Darwin, was coined by his contemporary, Herbert Spencer. Darwin later adopted this phrasing in his works.At the time of the inception of his theory of evolution by natural selection, Darwin did not know that the heritable traits acted upon by selection were genes. This knowledge would come soon after, when Gregor Mendel published his &#x201C;Experiments in Plant Hybridization&#x201D; in 1865, introducing the world to genetics.<h4>Conditions of Natural Selection</h4>For natural selection to occur, there needs to be trait variation. Snowshoe hares, for example, are brown in the spring and summer months, but during the winter, their coat changes to white. There also needs to be an evolutionary advantage to the trait; any hares that do not change color and remain brown are more easily visible to predators in the snow and are therefore less likely to survive and reproduce. The third condition is that the trait needs to be heritable. For the snowshoe hares, it is variation at a single location on the Agouti gene that natural selection acts upon.Interestingly, there is some evidence that the effects of climate change on snow seasons are shifting selection pressures; individuals in some hare populations are reverting back to keeping their brown coat year-round. This process, typically occurring over many generations within a population, is referred to as adaptive evolution.

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Education

JoVE Core

Evolution

Natural Selection

KEY TERMS AND CONCEPTS

natural selection and adaptive evolution

Natural selection is an evolutionary process that changes populations over time. Individuals with traits that help them survive and reproduce tend to leave more offspring. As those favorable traits are passed on, they become more common in the population or species.

These helpful traits usually begin with random genetic mutations. Natural selection can act only when a population shows variation, the trait is heritable, and the variation gives an evolutionary advantage. In other words, the trait must differ among individuals, be inherited, and improve survival or reproduction in that environment.

Charles Darwin described this process in his 1859 book, On the Origin of Species. He explained that even small useful variations can be preserved because individuals with those traits are more likely to survive and pass them on. The phrase “survival of the fittest” is often linked to Darwin, but it was coined by Herbert Spencer. Darwin later used it in his own writing.

Darwin did not yet know that genes carry the heritable traits acted on by natural selection. That connection came later, after Gregor Mendel published Experiments in Plant Hybridization in 1865 and introduced genetics. This helped explain how traits are inherited from one generation to the next.

A clear example is the snowshoe hare. These hares are brown in spring and summer, but their coat turns white in winter. Hares that stay brown in snowy conditions are easier for predators to see, so they are less likely to survive and reproduce. In this case, variation at a single location on the Agouti gene is one target of natural selection.

Natural selection usually works over many generations within a population. This long-term change is called adaptive evolution. In snowshoe hares, climate change and shorter snow seasons may be shifting selection pressures, and some populations may be returning to brown coats year-round.

Natural Selection and Adaptive Evolution

natural-selection-and-adaptive-evolution-in-populations

Natural selection is an evolutionary process that changes populations over time. Individuals with traits that help them survive and reproduce tend to leave more offspring. As those favorable traits are passed on, they become more common in the population or species. These helpful traits usually begin with random genetic mutations. Natural selection can act only when a population shows variation, the trait is heritable, and the variation gives an evolutionary advantage. In other words, the...

types of selection

Natural Selection Patterns in Populations

Natural selection can change how alleles and traits appear in a population. The main patterns are directional selection, stabilizing selection, and disruptive selection. Each pattern favors a different range of phenotypes, or observable traits. Directional selection favors one extreme of a trait. In sockeye salmon, selection appears to favor earlier migration in the season. Later in the migration season, fishing pressure is higher. Fish that arrive and spawn earlier may have a better chance to...

frequency-dependent selection

Common vs Rare Trait Selection

Common vs rare trait selection describes how a trait’s fitness can change based on how often it appears in a population. This process is called frequency-dependent selection. It can happen between species or within a single species. The effect may be positive, where common phenotypes do better, or negative, where rare phenotypes do better. Positive frequency-dependent selection gives an advantage to the most common phenotype. This is often seen in mimicry systems. In Central America,...

limits to natural selection

Why Natural Selection Has Limits

Natural selection has limits, even when a trait would seem helpful. Organisms that fit their environment better are more likely to survive and reproduce. But evolution does not always produce perfectly adapted organisms. One limit is that natural selection can only work with genetic variation that already exists. For example, red tusks might help elephants by discouraging ivory-seeking poachers. If no allele, or gene variant, for red tusks is present, natural selection cannot raise its...

key terms and concepts

Explore how natural selection changes populations, why heritable variation matters, and how snowshoe hares show adaptive evolution in changing environments.

Natural Selection and Adaptive Evolution | JoVE K12

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biology

LS.Bio.9.3

LS.Bio.9.4

Pennsylvania State Academic Standards

Life Science

Natural Selection and Evolution

3.1.9-12.T

3.1.9-12.U

3.1.9-12.W

Louisiana Student Standards for Science

High School

Life Sciences

Biological Evolution: Unity And Diversity

HS-LS4-2

HS-LS4-3

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Mechanisms

Virginia  Standards of Learning

HIgh School

BIO.7

BIO.7.c

LS.11

LS.11.a

LS.11.c

Minnesota Academic Standards in Science

3.2.1 9L.3.2.1.3

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Biological Evolution: Unity and Diversity

HS-LS4-4

Arizona Science Standards

HS.L4

HS.L4U1.27

HS+B.L4

HS+B.L4U1.14

Alabama Course of Study Science

Unity and Diversity

9-12.B.4.14

Next Generation Science Standards

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-3

Florida Department of Education

SC.912.L.15

SC.912.L.15.13

Texas Essential Knowledge and Skills

BIO.10

BIO.10.A

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

B-LS4-2.

B-LS4-3.

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-3.

HS-LS4-1.

HS-LS4-3.

HS-LS4-4.

Georgia Standards of Excellence

Ecology

SEC2.

SEC2.c

SB6.d

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Hybrid Zones

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Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become ...

Types of Selection

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Frequency-dependent Selection

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Limits to Natural Selection

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Convergent Evolution

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LS.Bio.9.2

Use models to illustrate the conditions required for natural selection, including the overproduction of offspring, inherited variation, and the struggle to survive.

Construct an explanation to explain how natural selection leads to adaptations within populations.

Extinction

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LS.Bio.10.1

Synteny and Evolution

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Taxonomy

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LS.Bio.10.2

Understand natural selection as a mechanism for biological evolution.

Natural Selection and Adaptive Evolution

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