Evolution Flashcards
what did Darwin propose in his theory of natural selection?
-individual organisms within a particular species show a wide range of variation for a characteristic
-individuals with characteristics most suited to the environment are more likely to survive and to breed successfully
-the characteristics that have enabled these individuals to survive are then passed on to the next generation
why can bacteria evolve quickly?
and what do mutations of bacteria produce?
because they produce at a fast rate
new strains
what happens when a bacteria (through a mutation) becomes resistant to an antibiotic?
it cannot be destroyed by it
what are the main steps in the development of resistance? (3)
1- random mutation occur in the genes of individual bacterial cells
2- some mutations protect the bacterial cell from the effects of the antibiotic
3- bacteria without the mutation die or cannot reproduce when the antibiotic is present
what should be done in order to reduce the rate of development of antibiotic resistant strains? (3)
1- doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections
2- patients should always complete the full course of antibiotics to ensure all bacteria are killed and none survive to mutate and form resistant strains
3- the agricultural use of antibiotics should be restricted
why is it difficult to produce new antibiotics?
they are costly and very slow to develop
what are fossils?
preserved remains of a dead organism from millions of years ago
what can fossils be formed from?
-hard body parts, such as bones and shells, which do not decay
-parts of organisms that have not decayed due to conditions
-preserved traces of organisms
why do hard body parts, such as bones and shell, NOT decay?
they do not decay easily or are replaced by minerals as they decay
why do some organisms not decay despite not being hard body parts?
one or more of the conditions needed for decay are absent
how are preserved traces of organisms, such as footprints, burrows and rootlet traces produced?
these become covered by layers of sediment, which eventually become rock
where are the fossils of simple and complex organisms found?
simple organisms = oldest rocks
complex organisms = newer rocks
why are there gaps in fossil records?
because many early forms of life were soft-bodied, which means that they have left few traces behind
why does the fact that ‘Fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms in the newest rocks’ help to defend Darwin’s theory?
it supports his idea that simple life forms gradually evolved into more complex ones.
what does Charles Darwin’s theory state?
all organisms alive today evolved from more simple life forms
