5. The Theory of Evolution Flashcards
(23 cards)
Who published the Theory of Evolution
Charles Darwin
When did Darwin publish Theory of Evolution by Natural Selection
1859
What 4 key observations did Darwin make abt the world around him
- Organisms produce more offspring than survive.
- Theres variation in the characteristics of members of the same species.
- Some of these characteristics can be passed on from one generation to the next.
- Individuals that are best adapted to their env are more likely to survive.
What did Darwin use his 4 observations for
Wrote his theory of evolution by natural selection to explain his observations
What is the Theory or evolution by natural selection
- Individuals within a population show variation in their phenotypes.
- Selection pressures (env factors sa predation, disease, competition) create a struggle for survival.
- Individuals w better adaptations are more likely to survive & have reproductive success - reproduce & pass on advantageous adaptions to offspring. (& opposite for organisms w/o these adaptions).
- Overtime, proportion of the population possessing the advantageous adaptions increases.
- Over generations this leads to evolution as the favourable adaptations become more common in the population.
What is one process by which evolution occurs
Natural selection
How are the advantageous adaptations passed on
- Genes determine many of an organism’s characteristics & individuals show variations in their phenotype partly as a result of genetic variation, ie. the diff alleles they have.
- When an organism w advantageous characteristics reproduces, the alleles that determine those characteristics may be passed on to its offspring.
Who else contributed to the Theory of evolution
Wallace, a scientist working at the same time as Darwin, played important part. in developing theory of evolution by natural selection
What did Wallace do
- He independently came up w the idea of natural selection & wrote to Darwin abt it.
- He & Darwin published their papers on evolution TOGETHER & acknowledged each other’s work - although they didn’t always agree abt mechanisms involved in natural selection.
- Wallace’s observations provided lots of evidence to support theory of evolution by natural selection. For eg, he realised that warning colours are used by some species to deter predators from eating them & that this was an eg of an advantageous adaptation that had evolved by natural selection.
Why is Darwin better remembered than Wallace
Unfortunately for Wallace, it wasn’t until Darwin published his famous book, ‘On the Origin of Species’ that other scientists began paying attention to the theory.
In this book, Darwin gave lots of ev to support the theory & expanded on it.
Evidence to support the Theory of evolution by natural selection
- Fossil record evidence
- DNA evidence
- Molecular evidence
Fossil record evidence
- Fossils are the remains of organisms preserved in rocks.
- By arranging fossils in chronological order, gradual changes in organisms can be observed that provide evidence of evolution.
DNA evidence
- The theory of evolution suggests that all organisms have evolved from shared common ancestors.
- Closely related species diverged (evolved to become diff species0 more recently.
- Evolution is caused by gradual changes in the base sequence of an organisms’ DNA.
- Organisms that diverged away from eachother more recently, should have more similar DNA, as less time has passed for changes in the DNA sequence to occur. This is exactly what scientists have found.
see pg128 for eg
MORE on DNA evidence
In eukaryotes, most DNA is found in the cell nucleus. But scientists dont just analyse nuclear DNA to find out abt evolutionary relationships.
Eukaryotic organisms also have DNA in their mitochondria, so scientists can also look at differences in mitochondrial DNA to see how closely related organisms are.
Molecular evidence
- In addition to DNA, the similarities in other molecules provide evidence.
- Scientists compare the sequence of amino acids in proteins, & compare antibodies.
- Organisms that diverged away from eachother more recently have more similar molecules, as less time has passed for changes in proteins & other molecules to occur.
What are pesticides
- Chemicals that kill pests (eg, insects that damage crops).
- Scientists have observed the evolution of pesticide resistance in many species of insect.
eg. some populations of mosquitoes have evolved resistance to pesticide DDT.
How can the evolution of pesticide resistance be explained
By natural selection
How can natural selection explain evolution of pesticide resistance
- There is variation in a population of insects. Genetic mutations create alleles that make some insects naturally resistant to a pesticide.
- If the population of insects is exposed to that pesticide, only the individuals w the resistance will survive & reproduce.
- The alleles which cause the pesticide resistance will be passed on to next generation, so population will evolve - more individuals will carry the allele than in previous generation.
Role of the pesticide in evolution of pesticide resistance
The pesticide acts as a selection pressure - w/o a selection pressure, natural selection wont take place.
What implications does evolution of pesticide resistance have for HUMANS
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Crop infestations w presticide-resistant insects are harder to control - some insects are resistant to lots of diff pesticides. It takes farmers a while to figure out which pesticide will kill the insect & in that time all the crop could be destroyed.
If the insects are resistant to specific pesticides (ones that kill that insect), farmers might have to use broader pesticides (those that kill a range of insects), which could kill beneficial insects. - If disease-carrying insects become pesticide-resistant, the spread of disease could increase.
- A population of insects could evolve resistance to all pesticides in use. To prevent this, new pesticides need to be produced - takes time & money.
What else can impact HUMANS
Evolution of drug resistance
Drug resistance
- Scientists have observed the evolution of antibiotic resistance in many species of bacteria.
- Other pathogens have evolved resistance to specific drugs too. For eg, some of the protoctists that cause malaria are resistant to several drugs used to treat malaria.
How does evolution of drug resistance impact HUMANS
- Infections caused by drug-resistant microorganisms are harder to treat - esp if the microorganism is resistant to lots of diff drugs. Can take doctors a while to figure out which drugs will get rid of the infection, & in that time, patient could get worse/die.
- There could come a point where a pathogen has become resistant to all the drugs we currently. use against it. To prevent this, new drugs need to be developed - takes time & money.
