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)
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)
- closely related species have evolved from the same ancestor - scientists can analyse bone structure, show how they are related to current ancestors
Reasons for gap in fossil record? (3)
- 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?
- 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
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 another scientists teamed up and proposed the theory of evolution in a joint presentation
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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
How did Darwin figure out the natural selection theory?
- he concluded taht a bird born with a beak more suited to the food availible would survice linger than a bird whose beak was less suited
- therefore it would have more offspring, passing on its beak characteristics
- over time the finch population on that island would all share this characteristic —> natural selection
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
