The change in the frequency of a phenotype in a population over many generations.

The process by which individuals with characteristics most suited to their environment are more likely to survive and reproduce, passing on those beneficial characteristics to their offspring.

Who proposed the theory of evolution by natural selection, and in which book and year was it published?

Charles Darwin proposed it. It was published in his book On the Origin of Species in 1859.

Outline the steps of evolution by natural selection.

Individuals in a species show variation caused by differences in their genes Individuals with characteristics best suited to the environment have a higher chance of survival and more chances to reproduce These beneficial characteristics are passed on to their offspring at a higher rate Over many generations the beneficial characteristics become more common and the species evolves

Give two reasons why Darwin's theory of evolution was only gradually accepted.

It challenged the idea that God made all the animals and plants on Earth There was insufficient evidence at the time to convince many scientists The mechanism of inheritance and variation was not known until about 50 years after the theory was published

What are antibiotics, and what type of microorganism are they effective against?

Chemical substances made by certain fungi or bacteria that disrupt the structure or function of bacterial cells, or prevent them from reproducing. They are effective against bacteria but not against viruses.

Why do antibiotics not affect viruses?

Antibiotics work by disrupting cell functions (such as respiration) or breaking down cell structures. Viruses do not carry out cell functions and have no cell walls, membranes or organelles, so antibiotics do not affect them.

Explain how a population of antibiotic-resistant bacteria develops.

Bacteria have random mutations in their DNA One of these mutations may give a bacterium resistance to an antibiotic When treated with the antibiotic, the non-resistant bacteria are killed but the resistant ones survive The surviving resistant bacteria reproduce, so the resistant population increases

What does fossil evidence suggest about the origin of modern humans?

That modern humans ( Homo sapiens ) evolved from a common ancestor shared with other apes. For example, humans and chimpanzees evolved from a common ancestor that existed around 6 million years ago.

To which species does the fossil 'Ardi' belong, and how old is it?

The species Ardipithecus ramidus . Ardi is 4.4 million years old and was found in Ethiopia.

Give features of Ardi that show a mixture of ape and human characteristics.

Ape-like features: an ape-like big toe for gripping branches (so she climbed trees), short legs but long arms, and a brain about the same size as a chimpanzee's Human-like features: her leg and hand bone structure suggest she walked upright and did not use her hands when walking

To which species does 'Lucy' belong, and how old is she?

The species Australopithecus afarensis . Lucy is 3.2 million years old and was also found in Ethiopia.

How was Lucy more human-like than Ardi?

She had arched feet better adapted to walking and no ape-like big toe Her brain was slightly larger than Ardi's Her leg bones suggest she walked upright more efficiently than Ardi

Who was 'Turkana Boy', how old is the fossil, and where was it found?

A fossil of the species Homo erectus , more human-like than Lucy. It is 1.6 million years old and was found in Kenya (on Richard Leakey's 1984 expedition).

How do stone tools provide evidence for human evolution?

As different Homo species evolved, their stone tools gradually became more complex over evolutionary time. This reflects their brains evolving to become larger and larger.

Describe three methods used to date hominid fossils and stone tools.

Looking at structural features — simpler tools are probably older than more complex ones Stratigraphy — the study of rock layers; fossils or tools in deeper layers are probably older Carbon-14 dating — using the carbon in fossils or carbon-containing materials found with tools

Arranging living things into groups based on their structure and characteristics.

A domain of primitive bacteria that usually live in extreme environments, such as hot springs and salt lakes.

Who first classified organisms into groups, and what is the sequence of classification groups?

The Swedish naturalist Linnaeus. The sequence is: Kingdom, Phylum, Class, Order, Family, Genus, Species.

Name the five kingdoms traditionally placed at the top of the classification hierarchy.

Prokaryotes, Protists, Fungi, Plants and Animals.

What feature distinguishes prokaryotes, and give an example.

They are single-celled organisms without a nucleus. An example is bacteria.

How did advances in technology change the way organisms are classified?

Improvements in microscopes revealed internal structures, and understanding of biochemical processes and genetics progressed. Genetic analyses such as DNA sequencing then allowed organisms to be classified using a more scientific approach.

How does comparing DNA or RNA base sequences show how closely related two species are?

The more similar the base sequences in the DNA or RNA of two species, the more closely related they are. This also means the more recent in time their common ancestor is.

Who proposed the three-domain system of classification, and in which year?

Carl Woese proposed it in 1990.

Name the three domains, and state which organisms are included in Eukaryota.

The three domains are Archaea, Bacteria and Eukaryota. Eukaryota includes protists, fungi, plants and animals.

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Natural Selection & Evolution (Edexcel GCSE Combined Science: Biology): Flashcards

Exam code: 1SC0

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FrontEvolution by Natural Selection
Evolution

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Cards in this collection (33)

Evolution
The change in the frequency of a phenotype in a population over many generations.
Natural selection
The process by which individuals with characteristics most suited to their environment are more likely to survive and reproduce, passing on those beneficial characteristics to their offspring.
Who proposed the theory of evolution by natural selection, and in which book and year was it published?
Charles Darwin proposed it.
It was published in his book On the Origin of Species in 1859.
Outline the steps of evolution by natural selection.
Individuals in a species show variation caused by differences in their genes
Individuals with characteristics best suited to the environment have a higher chance of survival and more chances to reproduce
These beneficial characteristics are passed on to their offspring at a higher rate
Over many generations the beneficial characteristics become more common and the species evolves
What well-known phrase is used to describe natural selection?
'Survival of the fittest'.
Give two reasons why Darwin's theory of evolution was only gradually accepted.
It challenged the idea that God made all the animals and plants on Earth
There was insufficient evidence at the time to convince many scientists
The mechanism of inheritance and variation was not known until about 50 years after the theory was published
Darwin published his theory in the book On the Origin of , in the year .
Species / 1859
What are antibiotics, and what type of microorganism are they effective against?
Chemical substances made by certain fungi or bacteria that disrupt the structure or function of bacterial cells, or prevent them from reproducing.
They are effective against bacteria but not against viruses.
Why do antibiotics not affect viruses?
Antibiotics work by disrupting cell functions (such as respiration) or breaking down cell structures.
Viruses do not carry out cell functions and have no cell walls, membranes or organelles, so antibiotics do not affect them.
Explain how a population of antibiotic-resistant bacteria develops.
Bacteria have random mutations in their DNA
One of these mutations may give a bacterium resistance to an antibiotic
When treated with the antibiotic, the non-resistant bacteria are killed but the resistant ones survive
The surviving resistant bacteria reproduce, so the resistant population increases
A strain of Staphylococcus aureus that is resistant to the antibiotic is known as .
methicillin / MRSA
Hominids
Humans and their ancestors.
What does fossil evidence suggest about the origin of modern humans?
That modern humans (Homo sapiens) evolved from a common ancestor shared with other apes.
For example, humans and chimpanzees evolved from a common ancestor that existed around 6 million years ago.
To which species does the fossil 'Ardi' belong, and how old is it?
The species Ardipithecus ramidus.
Ardi is 4.4 million years old and was found in Ethiopia.
Give features of Ardi that show a mixture of ape and human characteristics.
Ape-like features: an ape-like big toe for gripping branches (so she climbed trees), short legs but long arms, and a brain about the same size as a chimpanzee's
Human-like features: her leg and hand bone structure suggest she walked upright and did not use her hands when walking
To which species does 'Lucy' belong, and how old is she?
The species Australopithecus afarensis.
Lucy is 3.2 million years old and was also found in Ethiopia.
How was Lucy more human-like than Ardi?
She had arched feet better adapted to walking and no ape-like big toe
Her brain was slightly larger than Ardi's
Her leg bones suggest she walked upright more efficiently than Ardi
Who was 'Turkana Boy', how old is the fossil, and where was it found?
A fossil of the species Homo erectus, more human-like than Lucy.
It is 1.6 million years old and was found in Kenya (on Richard Leakey's 1984 expedition).
How do stone tools provide evidence for human evolution?
As different Homo species evolved, their stone tools gradually became more complex over evolutionary time.
This reflects their brains evolving to become larger and larger.
Describe three methods used to date hominid fossils and stone tools.
Looking at structural features — simpler tools are probably older than more complex ones
Stratigraphy — the study of rock layers; fossils or tools in deeper layers are probably older
Carbon-14 dating — using the carbon in fossils or carbon-containing materials found with tools
Both Ardi and Lucy were found in the country of , while Turkana Boy was found in .
Ethiopia / Kenya
Older rock layers usually lie below younger ones, so fossils found in layers are probably older; this dating method is called .
deeper / stratigraphy
Classification
Arranging living things into groups based on their structure and characteristics.
Archaea
A domain of primitive bacteria that usually live in extreme environments, such as hot springs and salt lakes.
Who first classified organisms into groups, and what is the sequence of classification groups?
The Swedish naturalist Linnaeus.
The sequence is: Kingdom, Phylum, Class, Order, Family, Genus, Species.
Name the five kingdoms traditionally placed at the top of the classification hierarchy.
Prokaryotes, Protists, Fungi, Plants and Animals.
What feature distinguishes prokaryotes, and give an example.
They are single-celled organisms without a nucleus.
An example is bacteria.
How did advances in technology change the way organisms are classified?
Improvements in microscopes revealed internal structures, and understanding of biochemical processes and genetics progressed.
Genetic analyses such as DNA sequencing then allowed organisms to be classified using a more scientific approach.
How does comparing DNA or RNA base sequences show how closely related two species are?
The more similar the base sequences in the DNA or RNA of two species, the more closely related they are.
This also means the more recent in time their common ancestor is.
Who proposed the three-domain system of classification, and in which year?
Carl Woese proposed it in 1990.
Name the three domains, and state which organisms are included in Eukaryota.
The three domains are Archaea, Bacteria and Eukaryota.
Eukaryota includes protists, fungi, plants and animals.
The Linnaean classification sequence is Kingdom, , Class, Order, , Genus, Species.
Phylum / Family
The three-domain system divides organisms into Archaea, and .
Bacteria / Eukaryota

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