B5.2 - Natural selection and Evolution Flashcards
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Define evolution
The natural gradual change in a species over time
Describe what is meant by natural selection
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)
Examples of evolution (moths)
- 19th century vs Industrial revolution
- 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
How does bacteria become antibiotic resistant?
- 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)
Why is bacteria a good organism to view evolution in?
As it reproduces very rapidly, and produces a lot of offspring (so can pass on mutations very fast)
Describe how a fossil forms
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 erodesHow does the fossil record provide evidence for evolution?
- 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
Reasons for gap in fossil record?
- many soft bodied organisms (worms ie. no skeleton), decompose before fossilised
- destroyed by volcanic eruptions
- may be buried too far in ground
Other evidence for evolution? (3)
- 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
Outline the basic idea of how the theory of evolution was formed (6)
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
Where and when did Darwin go to study finches, and what did he observe exactly?
- 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
Who did Darwin propose the theory of evolution with?
Alfred Russel Wallace
- he originally sent his ideas for peer review, but since they were so similar they published it together
Why is Darwin more well known than Wallace?
Since Darwin published a book in 1859 about it (so even non-scientists read it)
So they heard about Darwin and not Wallace
Name key scientists involved in developing the theory of evolution
- Darwin
- Wallace
- Charles Lyell
State what is meant by classification
The process of sorting living organisms into groups
