B5.2 - Natural selection and Evolution

Question 1

Define evolution

Answer 1

The natural gradual change in a species over time

Question 2

Describe what is meant by natural selection

Answer 2

Idea that….

• organisms in a species show variation (random mutations in genes)
• organisms with characteristics best suited to environment survive and reproduce (others may die)
• well adapted genes passed onto offspring (so are successful too)
• process keeps repeating (over time leads to new species)

Question 3

Examples of evolution (moths)

- 19th century vs Industrial revolution

Answer 3

• in 19th century most moths were pale (able to camouflage against trees)
• random black mutation occurred (but easily seen to prey)
• during Industrial revolution, trees covered in soot (black)
• so black moths more camouflaged, more survived
• more black moths in urban areas than pale moths

Question 4

How does bacteria become antibiotic resistant?

Answer 4

• random mutation of anti-biotic bacteria
• so antibiotics do not kill it, so more likely to reproduce
• does kill normal bacteria
• eventually, all bacteria will be resistant (weaker ones die)

(not the best definition tbf)

Question 5

Why is bacteria a good organism to view evolution in?

Answer 5

As it reproduces very rapidly, and produces a lot of offspring (so can pass on mutations very fast)

Question 6

Describe how a fossil forms

Answer 6

Organism dies 
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flesh rots and skeleton covered in sand/clay 
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Skeleton becomes mineralised + turns to rock 
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Fossil emerges as rock moves or erodes

Question 7

How does the fossil record provide evidence for evolution?

Answer 7

• fossils of simplest organisms found in OLDEST rocks (complex in younger rocks) - complex organisms evolved from simple
• plant fossils appeared before animal fossils (animals need plants to survive)
• scientists can analyse bone structure, show how they are related to current ancestors

Question 8

Reasons for gap in fossil record?

Answer 8

• many soft bodied organisms (worms ie. no skeleton), decompose before fossilised
• destroyed by volcanic eruptions
• may be buried too far in ground

Question 9

Other evidence for evolution? (3)

Answer 9

• rapid change in species
  ie. antibiotic bacteria (how helpful characteristic takes over)
  ie. Atlantic tomcod (in 40 yrs, resistance to PCBs - industrial waste)
• extinction (evolution by natural selection)
  ie. could not adapt for environmental changes
• molecular comparison (compare DNA and proteins of different species)
  or order of nucleic acid bases/order of animo acids

Question 10

Outline the basic idea of how the theory of evolution was formed (6)

Answer 10

Darwin on expedition around the world
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He read a book about the theory that fossils were evidence of animals
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He made observations of finches on one of the islands
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Came up with the idea of ‘natural selection’
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Darwin and wallace teamed up and proposed the theory of evolution in a joint presentation

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                             \/ Darwin wrote ‘on the origin of species’ and told the world abt evolution

Question 11

Where and when did Darwin go to study finches, and what did he observe exactly?

Answer 11

• In 1831
• Galápagos Islands
• observed the design of finches’ beak and claws were linked to the food available. Ie. Long thin beaks for catching insects

Question 12

Who did Darwin propose the theory of evolution with?

Answer 12

Alfred Russel Wallace

- he originally sent his ideas for peer review, but since they were so similar they published it together

Question 13

Why is Darwin more well known than Wallace?

Answer 13

Since Darwin published a book in 1859 about it (so even non-scientists read it)

So they heard about Darwin and not Wallace

Question 14

Name key scientists involved in developing the theory of evolution

Answer 14

• Darwin
• Wallace
• Charles Lyell

Question 15

State what is meant by classification

Answer 15

The process of sorting living organisms into groups

Question 16

What are 3 uses of classifying organisms (to scientists)?

Answer 16

• identify species
• predict characteristics
• find or show evolutionary links

Question 17

Why must scientists use a single classification system?

Answer 17

• they can share their research worldwide

- links between different organisms can be seen (even if they live on different continents)

Question 18

What is artificial classification? (and give an example)

Answer 18

• where systems group organisms using observable characteristics NOT EVOLUTIONARY CHARACTERISTICS
• difficulties in accurate classification
• ie. roses have flowers with five petals, so black currant flowers also have five petals so they are roses

Question 19

What is natural classification?

Answer 19

• when scientists use DNA sequencing to link relationships between organisms
• used to group organisms based on a common ancestor

Question 20

What is phylogeny? (and how is it established)

Answer 20

• The study of evolutionary links
• by studying similarities and differences in DNA between species
• more similar DNA = more closely related the species

Question 21

What is speciation?

Answer 21

When random mutations cause a population of species to become so different that they can no longer interbreed to produce fertile offspring

Question 22

State levels in the taxonomic levels:

8

Answer 22

Domain 
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Kingdom 
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Phylum 
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Class 
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Order 
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Family 
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Genus 
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Species

Question 23

What is the mnemonic to remember the eight taxonomic levels

Answer 23

Don’t kids prefer chips over fresh green salad

or (Atharv’s version)
Domain…
Killing People Can Obviously Fetch (a) Good Salary

Question 24

What two levels do you use when naming an organism, and what’s its name?

Answer 24

Genus, species

BINOMIAL SYSTEM (2)

Question 25

What are the 3 domains

Answer 25

Eukarya/Archaea/Bacteria

Question 26

What can cause a species to develop into another one?

Answer 26

• isolation (ie. physically, mountain in the way, or deepness of sea), prevent them from interbreeding
  |- may lead to independent evolution but may not

Question 27

Why is the theory of evolution agreed upon now compared to when Darwin first published it?

Answer 27

Back then….

• went against religious views
• had little evidence

Now….

• have multiple sources (more evidence, ie. fossils, DNA links)
• has been proven by many scientists (ie. peer reviewed)

Question 28

how does evolution occur?

Answer 28

through the natural selection of variants that have given rise to phenotypes best suited to their environment

Question 29

how have developments in biology affected classification systems?

Answer 29

DNA sequencing has allowed molecular phylogenetics to be used to classify organisms

Question 30

what are the 5 kingdoms

Answer 30

animals (all multicellular animals)
plants (all green plants)
fungi (moulds, mushrooms, yeast)
protists (Amoeba, Chlorella and Plasmodium)
prokaryotes (bacteria, blue-green algae)