B5.2 - Natural selection and Evolution Flashcards Preview

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


How 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?

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



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 figured most birds were very similar to a mainland bird but just had different variations between them.

He figure this must have been by chance, as they could not interbreed (islands are too far apart)


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


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

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


Why must scientists use a single classification system?

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


What is artificial classification? (and give an example)

- 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


What is natural classification?

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


What is phylogeny? (and how is it established)

- The study of evolutionary links

- by studying similarities and differences in DNA between species
- more similar DNA = more closely related the species


What is speciation?

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


State levels in the taxonomic levels:



What is the pneumonic to remember the eight taxonomic levels

Don’t kids prefer chips over fresh green salad


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

Genus, species



What are the 5 domain groups (biggest)

Prokaryotes/ Protoctists/ Fungi/ Animal/Plants


What can cause a species to develop into another one

- isolation (ie. physically, mountain in the way, or deepness of sea), prevent them from interbreeding

- may lead to independent evolution


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

Back then....
- went against religious views
- had little evidence

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


how does evolution occur?

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


how have developments in biology affected classification systems?

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