Genetics - Speciation and Classification 186-190 Flashcards
what are fossils
2 points
1) the remains of organisms from thousands of years ago
2) they can tell us how much organisms have evolved over time
what are the ways that fossils form
3 points
1) gradual replacement by minerals
2) from casts and impressions
3) preservation in places where decay doesn’t happen
how are fossils made from gradual replacement by minerals
3 points
1) things like teeth, shells and bones don’t decay easily and last a long time when buried
2) eventually they’re replaced by minerals as they decay forming a rock like substance
3) the surrounding sediments also turn to rick but the fossil stays distinct
how are fossils made from casts and impressions
3 points
1) when an organism is buried in a soft material like clay, the clay later hardens around it
2) when the organism decays it leaves a cast of itself
3) things like footprints can also be pressed into these materials when soft, leaving an impression when it hardens
how are fossils made when no decay happens
3 points
1) in amber and tar pits there’s no oxygen or moisture so decay microbes can’t survive
2) in glaciers it’s too cold for the decay microbes to work
3) peat bogs are too acidic for decay microbes
what are some different hypotheses about how life on earth started
2 points
1) life forms came into existence in a primordial swamp, or under the sea
2) simple organic molecules were brought to earth on comets then become simple life forms
why can’t the hypotheses about how life on earth started be proved
3 points
1) lack of good valid evidence
2) many early life forms were soft-bodied and they tend to decay away completely
3) fossils that did form millions of years ago may have been destroyed by geological activity
what is a species
a group of similar organisms that can reproduce to give fertile offspring
what is speciation
the development of a new species
when does speciation occur
when populations of the same species become so different they can no longer successfully interbreed to produce fertile offspring
how does isolation lead to speciation
4 points
1) isolation is where populations of a species are separated, it can happen because of a physical barrier
2) conditions of either side of the barrier will be slightly different
3) because the environment is different, different characteristics will become more common in each population due to natural selection
4) eventually the populations will have changed so much they won’t be able to breed successfully with each other
who was Alfred Russel Wallace
3 points
1) a scientist working at the same time as Darwin
2) he was one of the early scientists working on the idea speciation
3) he greatly contributed to our understanding of speciation today
what did Wallace do with Darwin
2 points
1) Wallace independently came up with the idea of natural selection
2) then published work on the subject with Darwin in 1858
what observations did Wallace make that supported the theory of evolution by natural selection
2 points
1) he realised warning colours are used by some species to deter predators from eating them
2) this was an example of a characteristic that had evolved by natural selection
how can bacteria evolve to be antibiotic resistant
4 points
1) they sometimes develop random mutations in their DNA, which can lead to changes in the bacteria’s characteristics
2) this can lead to antibiotic resistant strains forming as the gene for antibiotic resistance becomes more common in the population
3) bacteria also reproduce very quickly and can evolve quite fast
4) being able to resist antibiotics means the bacterium can survive in the host longer and reproduces many more times
why is antibiotic resistant bacteria a problem
3 points
1) there’s no effective treatment for them, so the infection can easily spread between people
2) sometimes drug companies can make a new antibiotic that’s effective
3) but ‘superbugs’ that are resistant to most known antibiotics are becoming more common
what is MRSA
2 points
1) a relatively common ‘superbug’ that’s really to get rid of
2) often affects people in hospitals and can be fatal if it enters the bloodstream
why is the problem of antibiotic resistance getting worse
2 points
1) the overuse and inappropriate use of antibiotics
2) like doctors prescribing them for non-serious conditions or infections caused by viruses
why does using antibiotics indirectly cause antibiotic resistance
they create a situation where naturally resistant bacteria have an advantage so increase the numbers
why is it important to take the full course of antibiotics prescribed
it makes sure all the bacteria are destroyed so there are none left to mutate and develop into resistant strains
how are antibiotics used in farming and why is this a problem
2 points
1) they’re given to animals to prevent them from becoming ill and make them grow faster
2) this can lead to resistant strains in the animals which can then spread to humans through meat preparation and consumption
what is the problem with drug companies producing new antibiotics
2 points
1) the production rate is slow, so they’re unlikely to be able to keep up with the demand for new drugs as more resistant strains spread
2) it’s also very expensive
what is classification
organising living organisms into groups
what is the traditional classification system
3 points
1) the Linnaean system made by Carl Linnaeus
2) it groups living things according to their characteristics and strcutures that make them up
3) living things are first divided into kingdoms then phylum, class, order, family, genus and species
what is the three-domain system
3 points
1) proposed by Carl Woese, gathering evidence from new chemical analysis techniques
2) he found some cases species thought to be closely related in the traditional classification system weren’t
3) in the three-domain organisms are first split into 3 large groups - archea, bacteria, eukaryota
what is the archea domain
organisms in this domain are primitive bacteria, often found in extreme places like hot springs and salt lakes
what is the bacteria domain
contains true bacteria like E. coli and Staphylococcus, even though they look similar to archea there are lots of biochemical differences
what is the eukaryota
includes a broad range of organism, like fungi plants, animals and protists
how are organisms named
3 points
1) according to a binomial system, so they have a 2 part Latin name
2) the first part refers to the genus the organism belongs to and the second refers to the species
3) this naming system is used world wide so scientists in different countries who speak different languages can refer to a species by the same name
what are evolutionary trees
3 points
1) they show how scientists think different species are related
2) they show common ancestors and relationships between species - the more recent a common ancestor the closer related they’re
3) scientists use a lot of different data to work out evolutionary relationships - classification data, for extinct species they use fossil records
