Natural Selection & Evolution Flashcards
All 17 cards in this deck
What is evolution?
The change of inherited characteristics (in a species) over time through natural selection.
What are the key steps of natural selection?
e.g. a population of beetles on dark bark
- Variation: some beetles are darker due to a mutation.
- Competition and survival: the best adapted (dark) beetles survive and reproduce.
- Inheritance: they pass the advantageous allele to offspring, so over generations most beetles are dark.
True or false? Individual organisms change their own characteristics during their lifetime so they can survive better.
False. Variation already exists from mutation; natural selection acts on the individuals that are already best adapted.
How does a population of bacteria become resistant to an antibiotic?
e.g. bacteria treated with Colistin
- Some bacteria have a mutation / gene for resistance.
- The antibiotic kills the non-resistant bacteria; the resistant bacteria survive.
- The resistant bacteria reproduce and pass on the beneficial allele, so eventually all the bacteria are resistant.
True or false? Bacteria become immune to an antibiotic after being exposed to it.
False. They become resistant, not immune — resistance comes from a mutation some bacteria already have.
Why is antibiotic resistance in bacteria strong evidence for Darwin's theory?
Bacteria reproduce very quickly, so natural selection (evolution) can be observed over a short timescale.
How old are the Ardi, Lucy and Richard Leakey hominid fossils?
Ardi — 4.4 million years; Lucy — 3.2 million years; Leakey's fossils — 1.6 million years.
How did brain size and walking change in hominids from Ardi to Leakey's fossils?
Brain size increased and walking became fully upright (bipedal), with shorter arms relative to legs, in the more recent fossils.
In a diagram of rock layers, which layer contains the most recent fossils or tools?
The top layer — younger rock layers are towards the top and older layers lower down.
How was a stone tool made?
By hitting it with another stone / rock / flint (something hard) to knock flakes or chips off — called knapping.
How did stone tools change over time as humans evolved?
Older tools are basic, simple and barely worked; newer tools are more refined, more pointed and more specialised.
Give two ways scientists date stone tools.
Radiometric dating of the rocks they are found in, and comparing them with fossils of a known age found in the same layer.
Name the three domains.
Archaea, bacteria and eukarya.
What type of evidence led scientists to suggest the three domains instead of the five kingdoms?
Genetic analysis — comparing RNA / DNA base sequences of organisms.
True or false? Archaea and bacteria were originally placed in the same kingdom.
True. Genetic analysis showed their RNA/DNA sequences are very different, so they were split into separate domains.
What were organisms grouped by in the five kingdom system?
Features that can be seen (observable characteristics), such as body structure, rather than genetic analysis.
Which organisms belong to the Eukarya domain?
Organisms whose cells have a nucleus: animals, plants, fungi and protists.