topic five Flashcards
when does evolution occur
when heritable characteristics (allele) of a species change over time
where do fossils typically form
in sedimentary rock, such as limestone and shale
Heritable characteristics
the characteristics that an organism possesses due to its genetic make-up. These characteristics can be inherited by the organism’s offspring.
macroevolution
occurs on a large scale leading to the development of new species.
Fossils that show links between ancestral groups are known as
transitional
Natural selection :
Natural selection occurs when species have variation and certain traits are selected because they help the species to reach a reproductive age and pass on their genes.
Selective breeding :
A form of artificial selection in which organisms with certain characteristics are chosen by humans because they are of some benefit. These organisms are bred to produce offspring that have the same genes and, therefore, the same characteristics.
breed
a group of animals within a species that have specific and similar characteristics.
examples of selective breeding
Breeding egg-laying hens to lay lots of eggs
Breeding race horses for speed
Breeding dogs for herding, hunting or simply for specific physical features
Breeding cattle for increased meat or milk production
Breeding of crops to be disease- or cold-weather-resistant in order to increase production
Breeding of plants to produce larger and sweeter fruits.
microevolution
occurs on a small scale within a species
homologous
similar in position, structure, and evolutionary origin but not necessarily in function.
Divergent evolution
when two separate species have a similar structure, but use it in different ways because of their environment.
Pentadactyl limb
A limb with five digits, found in amphibians, reptiles, birds and mammals.
Adaptive radiation
a process in which organisms rapidly diverge from the form of the original species into several new forms specialised to make use of different environmental niches. This can lead to divergent evolution and the development of a new species.
Analogous:
performing a similar function but having a different evolutionary origin, such as the wings of insects and birds.
convergent evolution
when organisms that are not closely related evolve similar structures that are used for similar purposes
speciation
the process by which new species form, is one of the success stories of evolution.
Discontinuous variation
a type of variation that is influenced by a gene or a few genes, can be put into categories, and is not influenced by the environment.
Continuous variation
a type of variation that is controlled by many genes, has a wide range of variability, and is easily influenced by the environment.
what happened in the 19th century
industrial revolution in the UK led to the widespread burning of fossil fuels by power machinery. This produced large amounts of sulfur dioxide in the atmosphere which killed many plants and lichen. It also produced vast quantities of soot which changed the colour of the tree bark. The result was darker coloured trees.
in biston betularia, which allele is dominant
the dark allele. codes for the moth to make more melanin
change in moth colours
industrial melanism
industry increase led to a change in the frequency of the alleles in the peppered-moth gene-pool.
Transient polymorphism
the gradual change in the allele frequency of a population due to the slow replacement of one gene of another.
balanced polymorphism
a balance between both forms of the allele variations within a population.
causes oof variation
mutation
meiosis
sexual reproduction and random fertilisation
what are missense mutations
may cause variation that benefits the organism by changing a codon, which in turn alters the protein.
silent mutations
those in which the codon still codes for the same amino acid, so no actual change in the protein occurs. These silent mutations do not have any effect on the variation of the species.
Examples of adaptations that have arisen through natural selection include:
Development of special hair structures in the fur coat of polar bears that insulate them from the intense cold of the Arctic and provide camouflage with the snow and ice.
Development of intricate and subtle forms in orchids to entice certain insects to pollinate them, as well as the hairs on the insects that help to collect pollen, which they spread, helping to pollinate other plants of the same species, providing more genetic variation for the orchid.
why was darwins finches a widely accepted theory
For a scientific theory to be accepted it must be able to explain and predict natural phenomena. The increase in the beak length and decrease in the beak width of these finches supports the theory of evolution by natural selection. Natural selection pressures caused adaptive radiation to occur where there were many small changes occurring in the species. This occurred until the species diverged and speciation arose.
what do enzymes do to the beta lactam ring of penicillin and other antibiotics
break down the beta lactam ring
why is antiobiotic resitnce spreading so widely and rapidly
Bacterial generation times are short, ranging from 20 minutes to several hours. This means that evolution can progress rapidly.
There has been widespread use of antibiotics in the general population and in animal feed. People often do not finish a course of antibiotics, leaving residual populations of bacteria in their system that have been exposed and are likely to have developed partial or full resistance.
Antibiotic resistance is often coded for by a gene or genes located on plasmids. The plasmids are easily exchanged between bacteria, even if they are not of the same species or strain.
Hospitals are breeding grounds for antibiotic resistance, because that is where patients with severe infections are treated with high doses of antibiotics, creating enormous selective pressure on the bacteria.
how is natural selection increasing antibitoic rsitance
When exposed to antibiotics, bacterial mutations can occur leading to more variation within the population. Those bacteria with variations that are resistant to the antibiotic are the most fit for their environment and will survive to pass on their resistant genes to their offspring or through plasmids. Those bacteria that are susceptible to the antibiotics will die. The allele for the antibiotic-resistant characteristic will increase in frequency in the gene pool and eventually, more and more bacteria become resistant.
biological classification
