Natural selection and adaptation

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Key Concepts

Variation refers to differences in traits among individuals of the same species, often due to genetic differences.
Inherited traits are passed from parents to offspring through genes.
Adaptations are traits that help organisms survive and reproduce in their environment.
Natural selection is the process where individuals with traits best suited to their environment are more likely to survive and reproduce, passing on those traits.
Mutations are natural changes in DNA that can introduce new variations; they can be harmful, neutral, or beneficial.
Survival of the fittest means the organism most fit for its environment, not necessarily the strongest or fastest.

Students demonstrating tongue rolling, an inherited trait.

Mutations and Variation

Most organisms of the same species have some physical differences because their genes differ.
Variations in traits, like hair color, come from mutations that occurred in the past.
Mutations are natural changes to DNA; some are harmful, many are neutral, and some are beneficial.
Harmful mutations may reduce survival or reproduction; beneficial mutations may increase survival and reproduction.
Genetic mutation is central to the creation of biological diversity.

Mutation creates variation; unfavourable mutations are selected against and favourable ones are passed on.

Adaptations

Adaptations are traits that help organisms survive and reproduce.
Many adaptations protect organisms from the external environment.
Adaptations beneficial in one environment may not be beneficial in another.
Examples include camouflage, body shape, speed, agility, and drought tolerance.
Adaptations can be structural (physical features), functional (life processes), or behavioral (instinctive or learned behaviors).

Lithops plants, also known as stone plants, showing their upper and underneath surfaces, and a cross-section of a Lithops plant.

How Adaptations Develop

In a population, individuals with mutations that help them survive in a changing environment are more likely to survive and reproduce.
Their offspring may inherit the favorable mutation, so over time the trait becomes more common in the population.
Traits that hinder survival eventually disappear.
Example: Oak trees with a mutation for fungus resistance survive and pass on the trait, changing the population.
Other examples: reindeer hooves for snow, deep-sea fish small size, plant toxins, skunk odor.

Charles Darwin and the Galápagos

Charles Darwin published 'The Origin of Species' based on 20 years of research, including a voyage on the HMS Beagle.
On the Galápagos Islands, he observed that similar animals differed between islands, such as iguanas and finches.
Darwin's finches had different beak shapes adapted to different food sources on different islands.
Each finch beak was well-matched to the seeds available on its island.
Darwin concluded that organisms are well-suited to their particular environments.

Four Galápagos finch species with differently shaped beaks, adapted to different food sources.

Natural Selection

Natural selection occurs when: (1) there is variation in inherited traits, (2) some traits give individuals an advantage in surviving and reproducing, and (3) those individuals have more offspring, passing on the beneficial trait.
It increases the presence of beneficial traits in a species over time.
Camouflage is a common adaptation in both predators and prey.
Example: In snowy environments, white fur in rabbits is beneficial, so over time dark fur becomes uncommon.
Natural selection works over very long periods.

Camouflage in predator and prey species: a snowshoe hare in snow, and camouflaged crab, gecko and zebras.

Examples of Natural Selection

Peppered moth: Before the Industrial Revolution, light-colored moths were camouflaged on lichen-covered trees; dark moths were rare.
During the Industrial Revolution, soot killed lichen and darkened trees, making dark moths better camouflaged; they survived and reproduced more, so dark moths became common.
After pollution controls, light-colored moths increased again as trees became lighter.
Tawny Owls in Finland: As temperatures rose, brown-feathered owls became more common over 30 years because they were better suited to the changing environment.
Arctic hares: Their fur turns white in winter for camouflage against snow.

Peppered moths on trees before and during the Industrial Revolution

Adaptations in Animals and Plants

Animals have structural, functional, and behavioral adaptations to survive in their habitats.
Examples: Aardvark's long tongue and claws for digging; desert beetles collect mist on their backs; gemsbok conserve water and avoid heat; ostriches run fast and use strong claws; stick insects use mimicry.
Migration is a behavioral adaptation to move to areas with better resources.
Hibernation is an inactive state to survive winter or dry periods.
Plants have adaptations like deep roots, water storage, and reflective bark.
Lithops ('living stones') look like pebbles to avoid being eaten and store water in fleshy leaves.

Wildebeest migration and sardine run as examples of animal adaptations.

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1.A mutation is always harmful to an organism.
Easy
True or false?
2.Adaptations that are beneficial in one environment are always beneficial in another.
Easy
True or false?
3.Natural selection can cause traits that help organisms survive to become more common in a population over time.
Easy
True or false?
4.The term 'survival of the fittest' refers to the fastest, strongest, or biggest organism.
Easy
True or false?
5.Inherited traits are characteristics that are passed down from parent organisms to their offspring.
Easy
True or false?
6.Natural selection requires that there is no variation in inherited traits within a species.
Easy
True or false?
7.An organism that blends with its background is more likely to avoid predators and pass on this beneficial trait to its offspring.
Easy
True or false?
8.Which of the following is an example of a behavioural adaptation?
Easy
- AA camel storing fat in its hump
- BA bird building a nest
- CA fish having gills
- DA plant having thick leaves

Plus de questions

9.Which of the following are conditions required for natural selection to occur? (Select all that apply)
Easy
- AThere is variation in inherited traits within a species
- BSome traits give individuals an advantage in surviving and reproducing
- CIndividuals with advantageous traits produce more offspring
- DAll individuals in a population are identical
- EThe environment is constant and unchanging
10.Match each type of adaptation to its correct description.
Easy
- Structural
- Functional
- Behavioural
- Physical characteristics like long legs
- Special way of carrying out life processes like producing hard-shelled eggs
- Instinctive or learned behaviours like making nests
11.Arrange the following steps of natural selection in the correct order.
Medium
- Variation exists in inherited traits
- Individuals with advantageous traits survive and reproduce
- Advantageous traits become more common in the population
- Environmental change or pressure occurs
12.In the Tawny Owl example, why have brown feathers become more common in recent years?
Medium
- ABrown feathers are always better than gray feathers
- BThe environment changed, making brown owls more likely to survive and reproduce
- CGray owls migrated away from Finland
- DBrown owls are larger and stronger than gray owls
13.A population of rabbits in a snowy area has both white and dark fur. If the climate becomes warmer with less snow, what is most likely to happen over many generations?
Medium
- AWhite fur will become more common because it is always beneficial
- BDark fur will become more common because it provides better camouflage in the absence of snow
- CThe rabbit population will become extinct
- DThere will be no change in fur color frequency
14.Put the following events in the order they occurred in the peppered moth story.
Medium
- Industrial Revolution increases pollution
- Trees become dark with soot
- Light-colored moths become more visible to predators
- Dark-colored moths become more common in the population
15.Match each organism to its adaptation.
Medium
- Desert beetle
- Gemsbok
- Stick insect
- Ridges on back to collect mist
- Does not sweat and sleeps in shade
- Looks like a stick to avoid predators
16.In the oak tree example, what caused the population to change so that most trees eventually had the trait to survive the fungus?
Medium
- AThe fungus caused all trees to mutate
- BTrees with the mutation survived and reproduced, passing on the trait
- CThe fungus disappeared from the environment
- DThe trees without the mutation developed the trait through use
17.Match each Galápagos finch beak shape to its food source.
Medium
- Large strong beak
- Small beak
- Pointed beak
- Large seeds
- Small seeds
- Insects
18.Arrange the following steps in the process of natural selection for the impala example.
Medium
- Some impala inherit a mutation for faster running
- Faster impala escape predators more often and live to reproduce
- The swift running characteristic is passed to offspring
- Slower impala are caught and removed from the population
19.What is the main reason that the Lithops plant is called a 'living stone'?
Medium
- AIt is very hard and rocky
- BIt looks like pebbles to avoid being eaten
- CIt grows only on stones
- DIt has a stone-like smell
20.Which of the following are true about mutations? (Select all that apply)
Medium
- AThey are natural changes to DNA
- BThey can be harmful, neutral, or beneficial
- CBeneficial mutations can be passed to offspring
- DThey always cause a change in the organism's phenotype
- EThey are caused by the environment
21.In the peppered moth example, the proportion of dark moths increased because they were better camouflaged against the soot-covered trees.
Medium
True or false?
22.In a desert environment, a species of beetle has two color variations: light and dark. The desert soil is light-colored. Which variation is more likely to survive and reproduce?
Medium
- ALight-colored beetles, because they are less visible to predators.
- BDark-colored beetles, because they absorb more heat.
- CLight-colored beetles, because they can reflect sunlight to stay cool.
- DDark-colored beetles, because they are more common.
23.A population of fish in a lake has two color forms: bright and dull. The lake water is clear. A new predator that hunts by sight is introduced. Over many generations, what is most likely to happen to the population?
Medium
- AThe proportion of dull-colored fish will increase.
- BThe proportion of bright-colored fish will increase.
- CBoth color forms will become equally common.
- DThe population will become extinct.
24.A scientist studies a population of birds over 20 years. The average beak size increases after a drought that reduces the number of small seeds but leaves large seeds plentiful. What is the most likely explanation?
Hard
- ABirds with larger beaks could eat the available large seeds and survived to reproduce, passing on the trait.
- BBirds grew larger beaks during their lifetime because they needed to eat large seeds.
- CThe drought caused a mutation that made all birds' beaks larger.
- DBirds with smaller beaks migrated to another area.
25.What was the original color form of most peppered moths before the Industrial Revolution?
Medium
- ALight speckled
- BDark grey
- CBlack
- DGreen
26.In an experiment to model natural selection, a student places 50 dark and 50 light-colored paper moths on a dark cloth. A partner randomly removes 20 moths to simulate predation. Which of the following statements about this experiment are correct? (Select all that apply)
Medium
- AThe dark moths are expected to be removed less often because they are less visible on the dark cloth.
- BThe light moths are expected to be removed more often because they are more visible.
- CThe experiment can show how the proportion of dark moths increases in the population over several trials.
- DThe experiment proves that light moths cannot survive in any environment.
- EThe experiment demonstrates that the moths can change color to avoid being eaten.
27.What is the term for the natural changes to DNA that can introduce new variations in traits?
Easy
28.In 1895, what percentage of peppered moths in Manchester were dark coloured?
Easy
29.Complete the sentence using the correct terms.
Easy
The Galápagos finches have different ____ and ____ that are adapted to the different food resources on their islands.
30.What term describes the ability of an organism to blend in with its environment because of its inherited traits?
Easy
31.Complete the sentence about the impala example.
Medium
In the impala example, faster impala are more likely to ____ predators and ____ to pass on the swift running characteristic.
32.What is the name of Darwin's book that described his observations and evidence on evolution?
Easy
33.Complete the sentence about the key concepts.
Easy
Organisms from the same species can reproduce sexually and produce offspring that are ____ and can reproduce.
34.The aardvark can collect up to how many termites in one night?
Easy
35.What is the term for the process where animals move between different areas at different times?
Easy
36.In a population of 500 moths, 125 are dark-colored. Calculate the percentage of dark-colored moths in this population.
Medium
37.Complete the sentence about natural selection.
Medium
Natural selection occurs when individuals with traits that are better suited to their environment are more likely to ____ and ____.
38.Explain why it takes a long time for a species to adapt to a changing environment.
Medium
39.Use the example of the Tawny Owl to explain how genetic variation in a population can affect the probability of survival and reproduction in a changing environment.
Hard
40.Explain why the dark-colored peppered moths became more common after the Industrial Revolution.
Hard
41.In 1895, what percentage of peppered moths in Manchester were dark coloured?
Easy
- A48 %
- B68 %
- C88 %
- D98 %
42.The aardvark can collect up to how many termites in one night?
Easy
- A50000 termites
- B45000 termites
- C55000 termites
- D60000 termites
43.In a population of 500 moths, 125 are dark-colored. Calculate the percentage of dark-colored moths in this population.
Medium
- A22 %
- B28 %
- C25 %
- D31 %
44.Sherpas have lived in the high-altitude Himalayas for thousands of years. Over that time, natural selection has changed how common certain inherited traits are in the Sherpa population. Which of these best describes that change?
Medium
- AA favourable trait became less common, passed on through asexual reproduction
- BA favourable trait became less common, passed on through sexual reproduction
- CA favourable trait became more common, passed on through asexual reproduction
- DA favourable trait became more common, passed on through sexual reproduction
45.Modern giraffes have much longer necks and legs than their short, antelope-like ancestors. This long-necked trait becoming common across the whole population over many generations is the result of:
Easy
- ANatural selection
- BExtinction
- CSelective breeding by humans
- DFossil evidence
46.Sensitivity to an antibiotic is an inherited trait in bacteria. The graph shows how the percentage of a bacteria population that is sensitive to an antibiotic changed from about 95% in 1999 to about 67% in 2015. Which best explains this change?
Medium
- AThe bacteria are becoming more sensitive because they were killed each time they were exposed to the antibiotic.
- BThe bacteria are becoming more sensitive because they changed their genes to protect themselves from the antibiotic.
- CThe bacteria are becoming less sensitive because some bacteria were able to survive and pass on traits that protect them from the antibiotic.
- DThe bacteria are becoming less sensitive because some bacteria reproduced very rapidly when they were aware of the antibiotic in their environment.
47.Explain how blending into its environment most likely helps a snowshoe hare survive.
Easy
48.The timing of a snowshoe hare's colour change from white to brown is influenced by genetics, and some hares change colour earlier in spring than others. Because of climate change, the areas where snowshoe hares live are expected to have fewer days of snow on the ground in spring. Describe how the number of hares that change colour early in spring is expected to change, and explain your reasoning using natural selection.
Hard
49.A population of guppies was moved from their natural environment into a large aquarium. The graph shows how the percentage of male guppies with two variations of a colour trait changed over time: Variation A increased, while Variation B decreased. Explain how natural selection could have caused both of these changes.
Medium

Notes de révision

## Natural Selection & Adaptation Natural selection is the **differential survival and reproduction** of individuals due to differences in their traits. It is a key mechanism of evolution that changes heritable traits in a population over generations. ### Key Ideas - **Variation**: Individuals in a population have different traits (genotypic and phenotypic). - **Inheritance**: Traits are passed from parent to offspring. - **Differential survival & reproduction**: Individuals with traits better suited to the environment are more likely to survive and reproduce, passing on those traits. - **Adaptation**: Over time, beneficial traits become more common in the population, leading to adaptation. ### How It Works 1. **Struggle for existence**: Competition for resources and mates. 2. **Variation exists**: No two individuals are exactly alike. 3. **Some traits are advantageous**: They increase fitness (ability to survive and reproduce). 4. **These traits are passed on**: Offspring inherit them. 5. **Population changes**: The frequency of advantageous traits increases over generations. ### Types of Selection - **Natural selection**: Environment favors certain traits. - **Sexual selection**: Traits favored because they attract mates. - **Fecundity selection**: Traits that improve reproductive success. ### Important Notes - Natural selection is **not intentional**; it is a result of variation, inheritance, and differential success. - It acts on **phenotypes** (observable traits), but changes **genotypes** (genetic makeup) over time. - New species can arise if traits become very different (macroevolution). - Natural selection is the **primary explanation for adaptive evolution**. ### Example In a population of rabbits, some have thicker fur. In a cold environment, thick-furred rabbits survive better and have more offspring. Over generations, the population becomes thicker-furred — an adaptation to cold.

Natural selection: The differential survival and reproduction of individuals due to differences in their traits, leading to changes in heritable characteristics of a population over generations.
Adaptation: A trait that increases an organism's chance of survival and reproduction in its environment, becoming more common in a population over time through natural selection.
Variation: Differences in traits (genotypic and phenotypic) among individuals in a population.
Fitness: The ability of an individual to survive and reproduce in its environment.
Sexual selection: A form of natural selection where traits are favored because they increase mating success.
Fecundity selection: Selection for traits that improve reproductive output or health.

Cartes mémo

What is natural selection?

Natural selection is the differential survival and reproduction of individuals due to differences in their traits, leading to changes in heritable characteristics of a population over generations.

Who popularized the term 'natural selection'?

Charles Darwin popularized the term 'natural selection', contrasting it with artificial selection.

What are the three processes that result in natural selection according to Darwin?

Inheritance (passing traits from parent to offspring), variation (differences in traits among individuals), and the struggle for existence (competition and cooperation).

What is variation?

Variation refers to differences in traits (genotypic and phenotypic) among individuals within a population.

How does natural selection affect trait frequencies in a population?

Traits that improve survival and reproduction become more common over generations, while less beneficial traits become less common.

What is an adaptation?

An adaptation is a heritable trait that increases an organism's fitness in its environment, becoming more common through natural selection.

What is the difference between natural selection and artificial selection?

Artificial selection is intentional breeding by humans for desired traits, while natural selection is non-intentional, driven by environmental pressures.

What is sexual selection?

Sexual selection is a form of natural selection where traits are favored because they are preferred by mating partners.

What is fecundity selection?

Fecundity selection favors traits that lower the cost to an organism's reproductive health, often influenced by female choice.

What is the difference between microevolution and macroevolution?

Microevolution is small-scale change within a species due to new traits favored in a specific niche; macroevolution is large-scale change that can lead to new species.

What is the modern synthesis?

The modern synthesis is the union of Darwinian evolution with classical genetics, developed in the mid-20th century.

What is evolutionary developmental biology (evo-devo)?

Evo-devo compares developmental processes across organisms to understand how developmental processes evolved.

What is genetic drift?

Genetic drift is a random change in allele frequencies over time, which can cause evolution but is not driven by natural selection.

What did Charles Darwin's book 'On the Origin of Species' explain?

It explained natural selection as the mechanism for evolution, using evidence from artificial selection and observations of nature.

What is the struggle for existence?

The struggle for existence includes competition for resources and cooperation (mutual aid) among organisms, influencing survival and reproduction.

How does natural selection lead to adaptation?

Natural selection favors traits that improve survival and reproduction in a given environment, causing those traits to become more common and thus the population becomes better adapted.

What is the role of heritability in natural selection?

Heritability ensures that favored traits are passed from parents to offspring, allowing natural selection to change trait frequencies across generations.

What is the difference between genotype and phenotype?

Genotype is the genetic makeup of an organism; phenotype is the observable characteristics resulting from genotype and environment.

What is fitness in the context of natural selection?

Fitness is the ability of an individual to survive and reproduce in its environment, relative to other individuals.

Can natural selection occur without genetic variation?

No, natural selection requires variation in traits; without variation, there is no differential survival and reproduction.

What is an example of natural selection?

Peppered moths: dark-colored moths became more common in polluted areas because they were better camouflaged from predators.

What is the extended evolutionary synthesis?

The extended evolutionary synthesis is a 21st-century update that challenges the gene-centered view, emphasizing organisms' roles in evolution.

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