Name: two paths to new species
Uploaded: 2026-06-01T06:28:10.075Z
Duration: 1 min 7 s
Channel: JoVE

K12 Standards

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

NC K-12 Science Standard Course of Study

9-12

Biology

Biological Evolution- Unity and Diversity

LS.Bio.9.1

Speciation Rates

Speciation does not always happen at the same speed. Scientists describe two patterns of how evolutionary change happens during speciation: gradualism and punctuated equilibrium.Imagine a bird species living on an island with varied food sources.As natural selection favors birds with beak shapes better suited to available food sources, beak shapes change slightly over time.After many thousands, or even millions, of years, these tiny changes add up, and a new species forms.This process describes gradualism, in which populations change in small steps over many generations.Now consider a sudden event, such as a storm, that carries a small group of these birds to a new island.The available food is limited and different from before, which makes survival more difficult.Birds with beaks that are better suited to the new food survive and reproduce more, so the population&#x2019;s beak shape changes.A new species forms over a relatively short period and then remains stable for a long time, sometimes for thousands or even millions of years, until another rapid change is triggered.This pattern describes punctuated equilibrium, with brief bursts of speciation followed by long periods of stability.

speciation rates

Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.GradualismGradualism describes speciation as a slow, continuous process in which small changes accumulate over many generations. In a bird population living on an island with diverse food sources, individuals with beak shapes better matched to available foods are more likely to survive and reproduce. Over time, these slight adaptive differences become more common in the population. As divergence continues, reproductive isolation may eventually arise, preventing gene flow between populations. If this process persists for thousands or millions of years, the accumulation of many small modifications can ultimately produce a new species. Gradualism emphasizes incremental evolutionary change, where divergence occurs step by step rather than through abrupt transformation.Punctuated EquilibriumPunctuated equilibrium proposes that species often remain relatively unchanged for long periods, interrupted by comparatively brief episodes of rapid speciation. For example, a storm may carry a small group of birds to a new island, where food sources differ, and survival conditions are more demanding. Geographic isolation reduces gene flow with the original population, and under new selective pressures, individuals with advantageous traits leave more offspring. As a result, the population may change more quickly, and a new species can form over a relatively short evolutionary interval. This &#x201C;rapid&#x201D; change occurs over short geological timescales rather than instantaneously. The newly formed species may then persist in a relatively stable form for thousands or millions of years until another major environmental shift occurs. This model highlights the roles of isolation, environmental change, and rapid adaptation in producing evolutionary bursts.Comparing the Two ModelsBoth models describe valid patterns of evolutionary change. Gradualism emphasizes steady divergence over time, whereas punctuated equilibrium emphasizes long periods of stability followed by shorter episodes of speciation. Together, they demonstrate that the formation of new species does not occur according to a single universal rate.

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Education

JoVE Core

Evolution

Speciation and Diversity

KEY TERMS AND CONCEPTS

two paths to new species

Speciation can happen at different speeds, and evolutionary biologists describe those patterns with gradualism and punctuated equilibrium. Both models explain how new species arise. They also show that evolutionary change comes from heritable variation in a population, with natural selection often favoring traits that help survival and reproduction in a given environment.

Gradualism is the slow, steady path to speciation. Small changes build up over many generations. In one example, birds on an island may have different food sources, so birds with beak shapes that fit certain foods survive and reproduce more often. Over time, those slight advantages become more common, and reproductive isolation may eventually develop. When gene flow between populations stops, the two groups can keep diverging until a new species forms after thousands or millions of years.

Punctuated equilibrium describes a different pattern. Species may stay mostly unchanged for long periods, then experience short bursts of rapid speciation. A storm may carry a small group of birds to a new island with different food sources and harsher conditions. Geographic isolation cuts off gene flow with the original population, and natural selection can favor traits that improve reproduction in the new setting. The population may change quickly on a geological timescale, although not instantly.

After that burst of change, the new species may remain stable for thousands or millions of years. Another major environmental shift can later trigger more change. Gradualism and punctuated equilibrium both describe real evolutionary patterns. The main difference is timing. Gradualism emphasizes continuous, step-by-step divergence, while punctuated equilibrium emphasizes long stability broken by shorter episodes of speciation.

Two Paths to New Species

understanding species and reproductive barriers

How Species Stay Genetically Separate

Species stay genetically separate through reproductive barriers that limit mating, fertilization, or the survival of offspring. A species is a group of organisms that can interbreed and produce fertile offspring. Members of the same species often look alike because they share very similar genomes. Even so, some organisms that look similar are not the same species. Variation within a species is common. The common wall lizard, Podarcis muralis, has six morphs that differ in throat and underbelly...

formation of species

How New Species Form

Speciation is the process that creates new species from one original species or from multiple original species. The new species become separate from the parent species, and barriers to reproduction usually develop. The main routes are allopatric speciation, which happens with geographic isolation, and sympatric speciation, which happens without it. In allopatric speciation, gene flow between two populations is blocked by a geographic barrier such as a mountain range or habitat fragmentation.

genetics of speciation

Reproductive Barriers in Speciation

Reproductive barriers drive speciation by stopping gene flow between populations. Speciation is the evolutionary process that forms new, distinct species, which are groups that cannot freely reproduce with one another. The genetics behind this process focuses on traits and isolating mechanisms that keep populations reproductively isolated. Some barriers act before a zygote forms, and these are called pre-zygotic mechanisms. They prevent fertilization and create the strongest block to gene flow...

Speciation can happen at different speeds, and evolutionary biologists describe those patterns with gradualism and punctuated equilibrium. Both models explain how new species arise. They also show that evolutionary change comes from heritable variation in a population, with natural selection often favoring traits that help survival and reproduction in a given environment. Gradualism is the slow, steady path to speciation. Small changes build up over many generations. In one example, birds on...

hybrid zones

How Hybrid Zones Shape Species Change

Hybrid zones are narrow regions where two closely related species meet, mate, and produce hybrids. Hybrids can show different traits or genes from either parent species. Those differences can affect survival and reproductive success. Because of this, hybridization can change species diversity and influence speciation within the hybrid zone. Gene flow and natural selection shape what happens in a hybrid zone. Gene flow moves genes between populations and can spread, blend, and preserve genetic...

key terms and concepts

Compare gradualism and punctuated equilibrium, two models that explain how new species form through slow change, isolation, and rapid evolutionary bursts.

Two Paths to New Species | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

LS.Bio.10.1

Pennsylvania State Academic Standards

Life Science

interdependent-relationships-in-ecosystems

Interdependent Relationships in Ecosystems

3.1.9-12.V

Natural Selection and Evolution

3.1.9-12.X

Louisiana Student Standards for Science

High School

Life Sciences

Biological Evolution: Unity And Diversity

HS-LS4-5

Environmental Science

ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy And Dynamics

HS-LS2-7

Virginia  Standards of Learning

HIgh School

LS.11

LS.11.a

Minnesota Academic Standards in Science

4.1.1 9L.4.1.1.1

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

New Jersey Student Learning Standards for Science

Biological Evolution: Unity and Diversity

Next Generation Science Standards

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS4-3

Earth and Space Science

Earth’s Systems

HS-ESS2-6

Florida Department of Education

SC.912.L.15

SC.912.L.15.2

SC.912.L.15.9

Texas Essential Knowledge and Skills

BIO.10

BIO.10.C

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

South Carolina College and Career Ready Science Standards

B-LS4-2.

B-LS4-5.

new-york-state-science-learning-standards

New York State Science Learning Standards

HS-LS4-3.

HS-LS4-5.

Georgia Standards of Excellence

Ecology

SEC3.

SEC3.d

SB6.b

Development of Antibiotic Resistance

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Understanding Species and Reproductive Barriers

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Formation of Species

Speciation describes the formation of one or more new species from one or sometimes multiple original species. The resulting species are discrete from the ...

Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and ...

Genetics of Speciation

Speciation is the evolutionary process resulting in the formation of new, distinct species&#x2014;groups of reproductively isolated populations.The ...

Hybrid Zones

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What is Natural Selection?

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Types of Selection

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Frequency-dependent Selection

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Limits to Natural Selection

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Natural Selection

Fitness
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Simulating Natural Selection
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Artificial Selection

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Observing Artificial Selection in Plants
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Observing Artificial Selection in Plants 
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Analyze and interpret data to summarize how various factors such as geographic isolation, pesticide resistance, antibiotic resistance can influence natural selection.

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The Colonization of Land

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The Evidence for Evolution

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The Fossil Record

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Convergent Evolution

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Gene Evolution - Fast or Slow?

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genome-size-and-the-evolution-of-new-genes

Genome Size and the Evolution of New Genes

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Gene Families

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types-of-genetic-transfer-between-organisms

Types of Genetic Transfer Between Organisms

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Ribozymes

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Construct an explanation to illustrate how common ancestry and biological evolution are supported by multiple lines of empirical evidence.

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.

LS.Bio.9.3

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

LS.Bio.9.4

Extinction

The History of Life on Earth
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Diversity and Extinction during the Paleogene Epoch
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ExpandBegin this procedure by reading the extinction reading supplement that has been printed out for ...

Construct explanations to illustrate how varying environmental conditions may result in: changes in the number of individuals of a species, the emergence of new species over time, or the extinction of other species.

Synteny and Evolution

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Multi-species Conserved Sequences

Next-generation sequencing technologies have created large genomic databases of a variety of animals and plants. Ever since the human genome project was ...

Taxonomy

Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics. It uses a hierarchy of increasingly ...

Phylogeny

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Use models (including dichotomous keys, scientific nomenclature, cladograms, phylogenetic trees) to identify organisms and exemplify relationships.

LS.Bio.10.2

Understand natural selection as a mechanism for biological evolution.

Two Paths to New Species

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