B-14 Genetics And Evolution Flashcards
(12 cards)
Theory of evolution
-Darwin’s theory of evolution by natural selection is now widely accepted
-evidence of Darwin’s theory of evolution is now avaialable as it has been shown that characteristics are passed on to offspring genes
-our understanding of genetics has made clear the mechanism by which natural selection can occur
Theory of evolution:
-variation exists within species as a result of mutations of DNA
-organisms with characteristics most suited for environment are more likely to survive to reproductive age and breed successfully-survival of fittest
-the beneficial characteristics are then passed down to next generation
-over many generations the frequency of alleles for this advantageous characteristic increase within a population
How are fossil formed
From parts if organisms that have not decayed because one or more of the conditions needed for decay are absent:
-in amber and tar puts a lack of oxygen moisture means that decomposers cannot survive there to break down dead organisms
-in glaciers and permafrost regions it is too cold for decomposers to survive
-peat bogs are too acidic for decomposers to survive
When parts of the organism are replaced by minerals as they decay:
-body parts such as teeth,shells and bones don’t decay easily and can last a long time after the organism has died
-they are slowly replaced by minerals that form a rock-like substance in the same shape as the original body
part
-they can often be seen distinctly within the surrounding rock
As preserved traces of organisms, such as footprints, burrows and rootlet traces:
-an impression can be left in a soft material like clay
-the impression becomes fixed as the clay hardens
-sometimes an organism may be buried in clay but decays after the clay bas hardened, leaving a cast of the organism
Gaps in fossil records
-many early forms of life were soft-bodied which means they have left few traces behind-soft tissues often decay fully,leaving no trace in the fossil record
-what traces there were have been mainly destroyed by geological activity
-this is why scientists cannot be certain about how life began on earth
Changing planet
-evidence for early life forms on earth can be found in fossil record
-we can learn from fossils how much or how little different organisms have changed as life developed on earth
Evolutionary trees:
-diagrams that show relationship between species over evolutionary time
-a new branch in tree shows where speciation has occured
Extinctions
-occur when there are no remaining individuals of a species still alive
-species that are poorly adapted to their environment are less likely to survive and reproduce compared to species that are well adapted to environment
-if they are unable to survive and reproduce sufficiently to maintain their population numbers they will eventually go extinct
Factors that cause extinction
New disease:
-a species that has previously had to evolve resistance to particular disease or pathogen may not have any resistant alleles within its population
-will lewd to very large numbers of the species dying very quickly and the species may not have time to develop immunity to the new disease before it is wiped out completely
New predators:
-a species that has previously not had to evolve defence mechanisms to a particular predator will be very vulnerable if the new predators appears
Factors that cause extinction
New disease:
-a species that has previously had to evolve resistance to particular disease or pathogen may not have any resistant alleles within its population
-will lewd to very large numbers of the species dying very quickly and the species may not have time to develop immunity to the new disease before it is wiped out completely
New predators:
-a species that has previously not had to evolve defence mechanisms to a particular predator will be very vulnerable if the new predators appears
-will lead to species being heavily predated and the species may not have time to adapt before it is wiped out completely
New,better adapted and more successful competitors:
-a species will have to compete for resources if a new competitor species appears that requires the same resources
-if a new competitor species is better adapted to take advantage of these resources, then it will out-compete the original species
-may eventually lead to original species being wiped out completely
Changes to environment over geological time:
-if change to environment occurs, a species may not be well adapted to this change and may be wiped out as a result
-e.g climate change-temp rising
Single catastrophic events:
-certain events may be catastrophic enough to wipe out entire ecosystems or habitats and therefore the species that liver there as well
-this is especially likely to occur if species have limited range close to where the event occurs
-e.g asteroid collisions
Mutations and antibiotic resistance
-bacteria reproduce at a fast rate
-mutations during reproduction can result in new genes, such as gene for antibiotic resistance-this creates a new strain
-when the population is treated with this antibiotic, the resistant bacteria do not die
-as a result those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring
-this population of antibiotic resistant bacteria increases
-bacterial diseases spreads rapidly because people are not immune to these new resistant bacteria and there is no treatment for it
MRSA
-increases in the population of antibiotic-resistant bacteria causes infections and diseases which are harder to control as it is difficult to find antibiotics that certain strains of bacteria are not resistant to
-example is MRSA,very dangerous bacterial strain that is resistant to most antibiotics
-if someone gets infected with MRSA they cannot be treated easily
How to slow the development of resistance in bacteria
-antibiotics should not be given for viral or non-serious infections
-specific antibiotics should be given for specific bacteria
-patients should complete their course of antibiotics-if they do not some bacteria may survive and mutate to become antibiotic resistant
-antibiotics should be used less in agriculture-farmers currently use them to prevent their livestock dying from disease,but this overuse leads to antibiotic resistant bacteria which are then transferred to humans when they consume the meat
How to slow transmission of bacteria:
-maintain high standards of hygiene in hospitals
-medical staff and visitors should wash hands regularly
-medical staff should wear disposable clothing or clothing that is regularly sterilised
Antibiotic development
-the number of new antibiotics discovered has slowed signifcantly
-developing new antibiotics is also very costly
-some scientists are worried we may not be able to keep up with the demand for new antibiotics as more and more antibiotic-resistant strains evolve
