The Development of Understanding of Genetics & Evolution (AQA GCSE Combined Science: Trilogy: Biology): Flashcards
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What are the main pieces of evidence for evolution?
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What are the main pieces of evidence for evolution?
Fossils
Antibiotic resistance in bacteria
The knowledge that characteristics are passed on in genes.
Why is antibiotic resistance in bacteria good evidence for evolution?
Bacteria reproduce very quickly, so natural selection (evolution) can be observed over a short time span.
How did the understanding of genetics support Darwin's theory?
It showed that characteristics are passed on to offspring in genes, providing the mechanism for how natural selection works.
Evidence for evolution comes from fossils and from resistance in bacteria.
Evidence for evolution comes from fossils and from antibiotic resistance in bacteria.
Briefly, how does antibiotic resistance develop in a population of bacteria?
A chance mutation makes some bacteria resistant. When treated with the antibiotic, the resistant bacteria survive and reproduce, passing on the resistance gene until the whole population is resistant.
True or False?
The theory of evolution by natural selection is now widely accepted.
True.
It is supported by evidence from genetics, the fossil record and antibiotic resistance in bacteria.
Fossil
The remains of organisms from millions of years ago, found in rocks.
What are the three ways in which fossils can be formed?
From parts that have not decayed, because a condition needed for decay is absent.
When parts of the organism are replaced by minerals as they decay.
As preserved traces, such as footprints, burrows and rootlet traces.
Why is the early fossil record incomplete?
Many early organisms were soft-bodied and left few traces, and most traces that did form were destroyed by geological activity.
Many early forms of life were -bodied, so they left few traces as fossils.
Many early forms of life were soft-bodied, so they left few traces as fossils.
Why can scientists not be certain about how life began on Earth?
Because there are gaps in the fossil record — early soft-bodied organisms left few traces, and many traces were destroyed by geological activity.
What can we learn from fossils?
How much or how little different organisms have changed as life developed on Earth.
Evolutionary tree
A diagram showing the relationships between species over evolutionary time; a new branch shows where speciation has occurred.
Extinction
When there are no remaining individuals of a species still alive.
Why are poorly adapted species more likely to become extinct?
They are less likely to survive and reproduce than well-adapted species, so their population falls until none remain.
Give three factors that can contribute to the extinction of a species.
For example:
A new predator
A new disease or a new competitor
A change to the environment (e.g. climate change) or a catastrophic event such as an asteroid strike or volcanic eruption.
A species becomes when no individuals of that species remain alive.
A species becomes extinct when no individuals of that species remain alive.
How have humans increased extinction rates?
By hunting species to extinction (e.g. the dodo) and by out-competing them for resources such as space, food and water.
Why can bacteria evolve rapidly?
They reproduce at a very fast rate (roughly every 20 minutes), so natural selection can act over a short time.
Explain how a population of bacteria becomes resistant to an antibiotic.
A mutation makes some bacteria resistant.
When treated with the antibiotic, the resistant bacteria survive while the others die.
The survivors reproduce and pass on the resistance gene, so the resistant population rises.
What is MRSA?
A strain of bacteria that is resistant to most antibiotics, making its infections very hard to treat.
How can the development of antibiotic-resistant strains be reduced?
Doctors should not prescribe antibiotics inappropriately (e.g. for viral or non-serious infections).
Patients should complete their full course of antibiotics.
The agricultural use of antibiotics should be restricted.
Patients should complete their full of antibiotics so that no bacteria survive to form resistant strains.
Patients should complete their full course of antibiotics so that no bacteria survive to form resistant strains.
Why is the development of new antibiotics a concern?
It is costly and slow, and is unlikely to keep up with the emergence of new resistant strains.
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