Natural selection and adaptation

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ஆற்றல் சம்பாதிக்க இந்த கேள்விகளுக்குப் பதிலளியுங்கள், பின்னர் மீன் பிடித்து ஆராயுங்கள். கணக்கு தேவையில்லை.

கல்வியாளர்களுக்கு: Natural selection and adaptation (MYP Biology, Year 3)-க்கான தயாரான பாட ஸ்லைடுகள், திருப்புதல் குறிப்புகள் — உங்கள் பாடத்தில் அவற்றைப் பயன்படுத்தவும், அல்லது கற்பவர்கள் நேரலை விளையாட்டாக விளையாடும் ஊடாடும் வகுப்பு செயல்பாடாக தலைப்பை இயக்கவும்.

பாட குறிப்புகள்

Big idea: how populations change over time

Big idea (key concept): Change. Species are not fixed. Over many generations, the features of a population can change, and new species can arise.
Related concept: Adaptation. An adaptation is a feature that helps an organism survive and reproduce in its environment. Natural selection explains how adaptations arise.
Global context: Orientation in space and time. The theory links life across the whole Earth and across millions of years. It came from careful observation in many places.
Charles Darwin sailed round the world on HMS Beagle from 1831 to 1836 and collected plants, animals and fossils. He noticed that related species differed from place to place, for example finches on separate Galapagos islands with different beak shapes.
Alfred Russel Wallace, working in the Malay Archipelago, reached the same idea independently. In 1858 their ideas were presented together. In 1859 Darwin published On the Origin of Species, which set out the evidence at length.

The voyage of HMS Beagle

Adaptations help organisms survive

Structural adaptations are features of the body: the thick fur and fat of a polar bear, the thick waxy cuticle and water-storing stem of a cactus, or the sharp claws of a cat.
Behavioural adaptations are ways of acting: birds migrating to warmer places in winter, or a hedgehog curling into a ball when threatened.
Physiological adaptations are processes inside the body: a camel's body can tolerate losing a lot of water, and some snakes make venom.
A fennec fox shows several adaptations at once: large ears lose heat and give excellent hearing, pale fur camouflages it against sand, and furry feet protect it from hot sand.
Camouflage helps prey avoid being seen and helps predators approach unseen. Adaptations are suited to a particular environment: a fennec fox would struggle in the Arctic.

Adaptations of a fennec fox

Natural selection step by step

1. Variation. Individuals in a population differ, and some of this variation is inherited. New alleles arise by mutation.
2. Competition. Most species produce more offspring than can survive. They compete for food, space, mates and light, and some are eaten or die of disease. This is a selection pressure.
3. Survival and reproduction. Individuals with features that suit the environment are more likely to survive and reproduce. This is sometimes called survival of the fittest, where fittest means best suited to the environment.
4. Inheritance. Survivors pass their alleles to their offspring, so those alleles become more common.
5. Change over generations. Repeat this many times and the frequency of the helpful alleles rises. The population becomes better adapted. If the environment changes, different features may be favoured.
Natural selection acts on variation that already exists. It does not create new alleles, and individuals do not change themselves to survive.

Mutation creates variation and selection favours the better-suited

Worked examples: peppered moths and antibiotic resistance

Peppered moths rest on tree trunks by day. Before the Industrial Revolution most were pale and speckled, which camouflaged them against lichen-covered bark. A rare dark form existed because of a mutation.
In industrial cities, soot killed the lichens and darkened the bark. Pale moths stood out and were eaten by birds, while dark moths survived, reproduced and passed on their dark allele. By the late 1800s most moths in cities such as Manchester were dark.
After clean air laws in the 1950s, bark became lighter again and pale moths became more common. Selection followed the environment in both directions.
Antibiotic resistance is the same process in bacteria. By chance, a few bacteria have an allele that makes them resistant. When an antibiotic is used, susceptible bacteria die, resistant ones survive and divide, and the population becomes mostly resistant.
Bacteria can divide every 20 minutes or so, so selection can change a bacterial population in days. This is why antibiotics should only be used when needed and courses finished: every use is a selection pressure.

Natural selection in peppered moths

Natural selection compared with selective breeding and Lamarck

Selective breeding (artificial selection) is when humans choose which organisms breed, for features they want, such as milk yield in cows or the size of a fruit. The process is the same as natural selection: variation, selection, inheritance, many generations.
In natural selection the environment does the selecting and the features that are favoured help the organism survive. In selective breeding humans do the selecting, and the features may not help survival in the wild.
Before Darwin, Lamarck suggested that features gained during life, such as a giraffe stretching its neck, are passed on. This is wrong. Changes gained during life do not alter the DNA in gametes, so they are not inherited.
The natural selection explanation is that giraffes already varied in neck length. Longer-necked individuals reached more leaves, survived and left more offspring, so the alleles for longer necks became more common.
A common mistake is to say organisms change because they need to. Mutations are random. The environment only selects from the variation that happens to exist.

Giraffes feeding on a tree

Think like a scientist: a model of predation

Question: does the colour of a prey animal affect its chance of being eaten? Model it with 20 pale and 20 dark paper 'moths' scattered on a sheet of dark paper. A student 'bird' picks up as many as possible in 20 seconds.
The independent variable is the colour of the paper moth. The dependent variable is the number of each colour picked up.
Control variables: the size and shape of the moths, the background sheet, the time allowed, the starting numbers and the way they are scattered.
To improve reliability, use several 'birds', repeat the test and calculate a mean for each colour. A model can show that camouflage reduces predation, but it cannot prove what happened in real woodland.
Inquiry task 1: plan this investigation with a table for the results. Inquiry task 2: a student concludes that the model proves pollution caused dark moths to evolve. Evaluate the conclusion and suggest what other evidence you would want.

Light and dark forms of the peppered moth

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இலவச முன்னோட்டம் — 49-இல் 8 கேள்விகள். அனைத்தையும் பார்க்க பதிவு செய்யவும்.

1.Which voyage gave Charles Darwin many of the observations that led to his theory?
Easy
- AThe Mayflower
- BHMS Beagle
- CHMS Victory
- DThe Titanic
2.Who reached the idea of natural selection independently of Darwin?
Easy
- AGregor Mendel
- BLouis Pasteur
- CJean-Baptiste Lamarck
- DAlfred Russel Wallace
3.What is an adaptation?
Easy
- AA feature that helps an organism survive and breed
- BA change an individual makes to itself when it is tired
- CA feature that harms an organism in its habitat
- DAny difference between a parent and its offspring
4.A polar bear has a thick layer of fat and fur. What type of adaptation is this?
Easy
- ABehavioural
- BCellular
- CStructural
- DAccidental
5.Birds flying to a warmer country for the winter is an example of which kind of adaptation?
Easy
- AStructural
- BPhysiological
- CBehavioural
- DMutational
6.An individual animal changes its own features during its life so that its offspring are better suited to the environment.
Easy
True or false?
7.Most species produce more offspring than can survive.
Easy
True or false?
8.Complete the sentence.
Easy
Natural selection is sometimes described as survival of the ____.

மேலும் கேள்விகள்

9.Complete the sentence.
Easy
A fennec fox's large ears help it to lose ____.
10.Before the Industrial Revolution, which type of peppered moth was most common?
Easy
- APale and speckled
- BDark and sooty
- CBright orange
- DPure white
11.Why did dark peppered moths survive better in polluted cities?
Easy
- AThey could fly much faster away from the birds
- BSoot made the moths need less food to survive
- CThey were no longer able to be seen by any animal
- DCamouflage on sooty bark meant birds ate fewer of them
12.How do antibiotic-resistant bacteria first arise in a population?
Easy
- AThe antibiotic makes bacteria mutate on purpose
- BBy random mutation, before the antibiotic is used
- CThe bacteria choose to become resistant
- DThe bacteria learn from the person's body
13.Antibiotics make bacteria mutate so that they become resistant.
Easy
True or false?
14.What is selective breeding?
Easy
- AThe environment decides which animals survive
- BHumans choose which organisms are allowed to breed
- CAnimals choose partners with the same colour
- DGenes are moved from one species into another
15.Match each organism to one of its adaptations.
Easy
- Fennec fox
- Cactus
- Arctic hare
- Camel
- White fur camouflages it in snow
- Stores fat in its hump
- Large ears lose heat
- Thick stem stores water
16.Put these steps of natural selection in order.
Easy
- Their alleles are passed to the next generation
- Those best suited to the environment survive and breed
- Individuals vary, and more are born than can survive
- The helpful alleles become more common over generations
17.In which book did Darwin set out his theory in 1859?
Easy
- AThe Voyage of the Finches
- BA Brief History of Life
- CPrinciples of Heredity
- DOn the Origin of Species
18.What is passed on from parents to offspring in natural selection?
Easy
- AAlleles
- BSkills learned during life
- CScars and injuries
- DMuscle size gained by training
19.Natural selection needs humans to choose which organisms breed.
Easy
True or false?
20.Why do some individuals in a population survive and reproduce more than others?
Medium
- AThey decide to try harder than the others
- BThey have been given extra food by the group
- CTheir inherited features suit the environment better
- DThey have learned to change their DNA
21.Which is the best natural selection explanation for how giraffes came to have long necks?
Medium
- AGiraffes stretched their necks and their children inherited the longer necks
- BGiraffes wanted to be taller, so their DNA slowly changed
- CGiraffes with longer necks reached more food, so survived and passed on their alleles
- DGiraffes grew taller as the trees in the area grew
22.Lamarck thought that features gained during life are inherited. Why is this wrong?
Medium
- ALife changes do not alter DNA in gametes
- BOffspring never look like their parents
- CGiraffes cannot stretch their necks
- DOnly plants can pass features on
23.What does competition mean in natural selection?
Medium
- AOrganisms racing each other to reach a place first
- BOrganisms helping one another to survive in a group
- COrganisms of two different species mating together
- DOrganisms needing the same limited food, space or mates
24.After clean air laws, the bark of trees in cities became lighter. What would natural selection predict about peppered moths?
Medium
- ADark moths would become even more common
- BPale moths would become more common again
- CBoth colours would disappear
- DAll moths would turn pale in one lifetime
25.Why should you finish the whole course of antibiotics you are given?
Medium
- ATo stop the bacteria from mutating at all in the body
- BTo kill all the bacteria so fewer resistant ones are left
- CTo give the bacteria enough time to learn resistance
- DBecause antibiotics make the whole body much stronger
26.A population of bacteria contains one cell with a resistance mutation. An antibiotic is added. What happens?
Medium
- AAll of the cells die because the antibiotic always works
- BThe resistant cell loses its resistance in the antibiotic
- CThe antibiotic changes the other cells into resistant ones
- DSusceptible cells die and the resistant cell divides
27.What is a main difference between natural selection and selective breeding?
Medium
- AIn selective breeding humans choose the features; in natural selection the environment does
- BNatural selection happens in one generation but selective breeding takes many
- CSelective breeding uses variation but natural selection does not
- DOnly natural selection involves inheritance of alleles
28.A water lily has flat leaves with the stomata on the upper surface and large air spaces. Why are these useful?
Medium
- AThe leaves need to keep as much water in as they possibly can
- BThe roots have to take in carbon dioxide gas from the water around them
- CThe leaves float, so stomata on top reach air and air spaces help buoyancy
- DThe leaves must stay hidden below the surface of the water all day
29.Darwin's finches on different Galapagos islands have different beak shapes. What is the best explanation?
Medium
- AFinches changed their beaks to suit their meals
- BEach island has a different species of tree that changes beaks
- CBeak shape was selected by the foods available on each island
- DBeaks changed because the finches stretched them
30.Which statements are part of the theory of evolution by natural selection? (select all that apply)
Medium
- AIndividuals in a species show variation
- BMore offspring are born than survive
- CSome features are inherited by offspring
- DIndividuals change their features by effort
- EEvery individual has an equal chance of survival
31.Camouflage can help prey avoid predators and help predators approach prey.
Medium
True or false?
32.Match each term to its meaning.
Medium
- Adaptation
- Variation
- Selection pressure
- Mutation
- A random change in DNA
- A factor that makes some individuals survive better
- A feature that helps survival in an environment
- Differences between individuals
33.Put these events in order to show how antibiotic resistance spreads.
Medium
- Resistant bacteria divide and become common
- An antibiotic kills the non-resistant bacteria
- A resistance mutation arises by chance
- The resistant bacteria survive the antibiotic
34.In a model of predation, a student scattered 20 pale and 20 dark paper moths on dark paper. A 'bird' picked up 14 of the pale moths and 6 of the dark moths in 20 seconds. What percentage of the pale moths was picked up?
Medium
35.In the paper moth model, the student wants to find out if moth colour affects the chance of being picked up. What is the dependent variable?
Medium
- AThe number of each colour picked up
- BThe colour chosen for the paper moths
- CThe size of the background sheet
- DThe length of time the bird is allowed
36.Which change would make the paper moth model more reliable?
Medium
- AUse a much larger sheet for the dark moths only
- BLet the bird search for longer on the second test
- CUse only one bird who has seen the moths before
- DUse several 'birds' and calculate a mean for each colour
37.Complete the sentence.
Medium
A factor in the environment that makes some individuals survive better than others is a selection ____.
38.Describe two adaptations of a fennec fox and explain how each helps it to survive in the desert.
Medium
39.Use the ideas of variation and inheritance to explain why pale peppered moths became rarer in polluted cities.
Medium
40.
In a model of predation 20 pale and 20 dark paper moths were scattered on dark paper, and a 'bird' picked moths for 20 seconds.
Colour of moth Number picked up
Pale 14
Dark 6
Which conclusion is best supported by these results?
Hard
- ADark moths are always better at avoiding birds in every habitat
- BOn dark paper the pale moths were easier to spot
- CThe pale moths used to be dark and changed colour
- DPale moths are tastier than dark moths to every bird
41.A student says: "The paper moth model proves that peppered moths evolved because of pollution." What is the best criticism?
Hard
- AThe model is useless because it is only made from paper
- BA model shows camouflage matters, but real woodland evidence is needed too
- CPeppered moths have never evolved at all in history
- DOnly one colour of moth should ever be used in a model of this kind
42.Resistant bacteria divide every 20 minutes, and each one divides into two. If there are 10 resistant bacteria at the start and none die, how many are there after 80 minutes?
Hard
43.A student says: "The bacteria became resistant because they needed to survive the antibiotic." Which correction is best?
Hard
- ABacteria cannot become resistant to any drug
- BThe bacteria chose which genes to switch on
- CThe antibiotic created the resistance allele in each cell
- DThe mutation arose by chance and was then selected
44.If every individual in a population were genetically identical, natural selection could not change the population.
Hard
True or false?
45.Why might a dog breed produced by selective breeding survive poorly in the wild?
Hard
- AIt was bred for human-wanted features, not survival ones
- BSelective breeding always removes all of the genes
- CWild animals do not have any variation in their genes
- DBreeds are made by feeding dogs on special diets
46.Why was it important that Wallace reached the same idea as Darwin independently?
Hard
- AWallace found fossils that Darwin did not have access to
- BIt proved that Lamarck's idea had been correct all along
- CTwo scientists in different places reached the same explanation
- DIt showed that evolution is only a guess by scientists
47.Explain how a population of bacteria can become resistant to an antibiotic. Use the words mutation, survive and allele.
Hard
48.Compare natural selection and selective breeding. Give one similarity and one difference.
Hard
49.Plan a fair test with paper moths to find out whether the colour of the background affects how many moths a 'bird' picks up. Say what you change, measure and control.
Hard

திருப்புதல் குறிப்புகள்

## The big idea - Populations change over generations through **natural selection** (**Change**, **Adaptation**). - **Darwin** (HMS Beagle, 1831 to 1836; book in 1859) and **Wallace** reached the idea independently. ## Adaptations - **Structural**, **behavioural** and **physiological** features that help survival in a particular environment. - Example: the fennec fox has large ears, pale fur and furry feet. ## Natural selection 1. **Variation** exists and some is inherited; mutations create new alleles. 2. More offspring are born than survive, so there is **competition**. 3. Those best suited **survive and reproduce**. 4. They pass on their **alleles**. 5. Helpful alleles become more common over **generations**. - Selection acts on existing variation. Organisms do not change because they need to. ## Examples - **Peppered moths:** dark moths favoured on soot-darkened bark, pale moths favoured again after clean air laws. - **Antibiotic resistance:** resistant bacteria survive and multiply, so every use of antibiotics is a selection pressure. ## Contrasts - **Selective breeding:** humans choose. **Natural selection:** the environment chooses. - **Lamarck** was wrong: features gained in life are not inherited. ## Investigating - Paper moth model: change colour, measure number picked, control the rest, repeat and take a mean. A model supports but does not prove an explanation.

Adaptation: A feature that helps an organism survive and reproduce in its environment.
Natural selection: The process by which individuals with features suited to the environment survive and reproduce more, passing on their alleles.
Variation: Differences between individuals of the same species.
Mutation: A random change in DNA that can create a new allele.
Allele: A version of a gene.
Competition: When organisms need the same limited resources, such as food, space or mates.
Selection pressure: A factor in the environment that makes some individuals more likely to survive than others.
Structural adaptation: A physical feature of the body that helps survival.
Behavioural adaptation: A way of acting that helps survival, such as migration.
Camouflage: Colouring or pattern that helps an organism blend into its background.
Antibiotic resistance: The ability of bacteria to survive an antibiotic, because of an allele that arose by mutation.
Selective breeding: Humans choosing which organisms breed so that wanted features become more common.
Lamarck's idea: The incorrect idea that features gained during life are passed on to offspring.
Fitness: How well suited an organism is to its environment, shown by how many offspring survive.

ஃப்ளாஷ் கார்டுகள்

What is an adaptation?

A feature that helps an organism survive and reproduce in its environment.

Name the three types of adaptation.

Structural, behavioural and physiological.

Who was Darwin and what did he do?

A naturalist who sailed on HMS Beagle (1831 to 1836) and published On the Origin of Species in 1859.

Who was Wallace?

A naturalist who reached the idea of natural selection independently of Darwin.

What are the steps of natural selection?

Variation, competition, survival and reproduction of the best suited, inheritance of alleles, change over generations.

Where do new alleles come from?

From mutations, which happen at random.

What is a selection pressure?

A factor, such as predation or disease, that makes some individuals more likely to survive.

What does fittest mean in survival of the fittest?

Best suited to the environment, not necessarily the strongest.

Why were dark peppered moths common in polluted cities?

They were camouflaged on soot-darkened bark, so birds ate fewer of them and they passed on their allele.

What happened to peppered moths after clean air laws?

The bark became lighter and pale moths became more common again.

How does antibiotic resistance arise?

A resistance mutation occurs by chance; the antibiotic kills other bacteria, so resistant ones survive and multiply.

Why should antibiotics only be used when needed?

Every use is a selection pressure that favours resistant bacteria.

What is selective breeding?

Humans choose which organisms breed to make wanted features more common.

How does selective breeding differ from natural selection?

Humans select the features in selective breeding; the environment selects in natural selection.

What did Lamarck suggest, and why is it wrong?

That features gained in life are inherited. Changes in the body do not alter the DNA in gametes.

Why do giraffes have long necks, according to natural selection?

Longer-necked giraffes reached more food, survived and passed on their alleles, so the alleles became common.

Why can bacteria evolve quickly?

They divide very fast, so a resistant mutation can spread through the population in days.

What does a model of predation show, and what can it not show?

It shows camouflage can affect survival, but it cannot prove what happened in real habitats.

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இந்த தலைப்பிற்கான முந்தைய தேர்வு பயிற்சி விரைவில் வருகிறது.

விரைவில் வருகிறது

Colour of moth	Number picked up
Pale	14
Dark	6