Where variation comes from, Darwin and Wallace, speciation, evidence from fossils, extinction, and antibiotic resistant bacteria as evolution you can watch.
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1.What is variation?
The differences in the characteristics of individuals in a population.
2.What are the three causes of variation?
The genes inherited, the conditions the organism has lived in, or a combination of both.
3.What is the only source of new alleles?
Mutation.
4.How often do mutations occur?
Continuously, at random.
5.Do most mutations affect the phenotype?
No. Very rarely a mutation determines a new phenotype, and even more rarely it is beneficial.
6.Define evolution.
A change in the inherited characteristics of a population over time, through natural selection, which may result in the formation of a new species.
7.How long is life thought to have been evolving on Earth?
More than three billion years, from simple life forms.
8.Describe the theory of evolution by natural selection.
Individuals within a species vary. Those with characteristics best suited to the environment are more likely to survive and breed, so they pass those alleles on, and over many generations the population changes.
9.Who proposed the theory of evolution by natural selection?
Charles Darwin, in On the Origin of Species in 1859. Alfred Russel Wallace independently reached the same conclusion.
10.Why was Darwin's theory only gradually accepted?
It challenged the idea that God made all life, there was not enough evidence at the time, and the mechanism of inheritance was not known for another fifty years.
11.What was Wallace best known for?
Working independently on natural selection, publishing jointly with Darwin in 1858, and his work on warning colouration and speciation.
12.What did Lamarck believe?
That characteristics acquired during an organism's lifetime, through use or disuse, were passed on to its offspring.
13.Why was Lamarck wrong?
Changes acquired during a lifetime do not usually affect the genes in the gametes, so they cannot be inherited.
14.What is speciation?
The formation of a new species, when populations become so different that they can no longer interbreed to produce fertile offspring.
15.Describe how speciation happens.
Two populations become isolated, natural selection acts differently on each because conditions differ, and over many generations they become too different to interbreed successfully.
16.What is a species?
A group of organisms that can breed together to produce fertile offspring.
17.What are fossils?
The remains of organisms from millions of years ago, found in rocks.
18.Give three ways fossils form.
From parts that have not decayed because conditions for decay were absent, when parts are replaced by minerals as they decay, and as preserved traces such as footprints or burrows.
19.Why is the fossil record incomplete?
Many early organisms were soft bodied and left few traces, and many fossils that did form have been destroyed by geological activity.
20.Why does an incomplete fossil record matter?
Scientists cannot be certain about how life began, because so little evidence from the earliest organisms survives.
21.What is extinction?
When there are no remaining individuals of a species still alive.
22.Give four causes of extinction.
A change in the environment over geological time, a new predator, a new disease, or a catastrophic event such as an asteroid strike.
23.How do bacteria evolve so quickly?
They reproduce very rapidly, so mutations arise often and beneficial ones spread through the population in a short time.
24.Explain how antibiotic resistance develops.
A random mutation makes one bacterium resistant. When the antibiotic is used the others die, but the resistant one survives and reproduces, so the resistant strain spreads.
25.Why is MRSA a problem?
It is a strain of bacteria resistant to common antibiotics, so infections are very difficult to treat.
26.Give three ways to reduce the rate at which resistant strains develop.
Do not prescribe antibiotics for viral or non-serious infections, always finish the course, and restrict the use of antibiotics in agriculture.
27.Why is developing new antibiotics not a complete answer?
Developing them is slow and expensive, and bacteria eventually become resistant to new ones too.
28.Why is antibiotic resistance good evidence for evolution?
It shows natural selection happening fast enough to be observed and measured directly.
29.How does the environment cause variation?
Conditions during life affect characteristics, for example a plant grown in poor light will be smaller than a genetically identical one grown in good light.
30.Why can a characteristic caused only by the environment not be inherited?
It has not changed the alleles in the gametes, so nothing different is passed to the offspring.
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