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State what the theory of evolution is
More than 3 billion years ago, life on Earth began as simple organisms from which all the more complex organisms evolved (rather than just popping into existence!)
Looking at the......and......between organisms allows us to......them into groups
Differences, similarities, classify
What are the 3 groups organisms are classified by and what are vague definitions of them that make them different to others?
- Plant - makes their own food (by photosythesis) and are fixed in the ground
- Animals - move about the place and can't make their own food
- Microorganisms - are different to and plants and animals e.g. bacteria are single-celled
Studying the simularities and differences between organisms helps us the understand how all living things are...
Related (evolutionary relationships) and how they interact with each other (ecological relationships)
Species with similar characteristics often have similar genes. Why?
Because they share a recent common ancestor, so are closely related e.g. whales and dolphins
Species with similar characteristics tend to...
Look alike and live in similar types of habitat
Can genetically different species look alike?
In some cases yes - e.g. dolphins and sharks look similar (ish) because they're both adapted to living in the same environment but are not closely related and have evolved from different ancestors
What do evolutionary trees show?
They show common ancestors and relationships between organisms - the more recent the common ancestor, the more closely related the 2 species
If we see organisms in the same environment with similar characteristics, what does it suggest?
That they may be in competition
If we see organisms in the same environment with different characteristics, what does it show?
The predator-prey relationships
What idea did Charles Darwin came up with (2 words)?
How does Charles Darwin's idea of natural selection work?
Individuals within a species show variation because of the differences in their genes. Some individuals are better adapted to their environment than others and these individuals will be more likely to survive and reproduce, passing on their characteristics to the next generation. Over generations, the useful characteristics (that lead to a better chance of survival) will become more common in the population. (N.B individuals in a species are naturally selected for but individuals cannot evolve - only a species as a whole can evolve)
What is a mutation?
A change in an organism's DNA
Are mutations always useful?
No, sometimes mutations have no effect. However, there's occasionally a benefical mutation which produces a useful characteristic. This characteristic may give the organism a better chance of surviving and reproducing. Mutations can also be harmful
Are useful mutations likely to be passed on to future generations and by what?
Yes - the benefical mutation will accumulate in a population and natural selection
Evolution occurs due to...
Why was Darwin's theory controversial at the time?
- It went against religious beliefs
- Darwin couldn't give an explanation on why these new, useful characteristics appeared or how individual organisms passed on benefical characteristics to their offspring - he didn't know about genes and mutation
- There wasn't enough evidence to convince many scientists - not many other studies had been done into how organisms change over time
What did Lamarck argue?
- That if a characteristic was used a lot by an organism, then it would become more developed during its lifetime
- He believed that these aquired characteristics would be passed on to the next generation
Why might scientists develop different hypotheses?
They may have different beliefs (e.g. religious) or be influenced by different people (other scientists and their way of thing) or may just think differently!
How do you find out if a hypothesis is right or wrong?
By finding evidence to support or disprove it
Why was Lamarck's hypothesis rejected?
Because experiments didn't support it (e.g. if you die a hamster's fur pink, its offspring will still be born with a normal fur colour)
Why was Darwin's hypothesis supported?
Because it provided an explanation of how organisms born with beneficial characteristics can pass the on (via their genes). There is so much evidence for it that it's now an accepted hypothesis (theory)
What 2 things can genetic differences be caused by?
Mutations and sexual reproduction
Explain the difference between evolution and natural selection
Evolution is the gradual change/adaption of a population of organisms over time. Natural selection is the process by which evolution occurs
Natural selection, evolution
According to Darwin's theory of evolution, how do new species evolve?
By natural selection
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