b14&15 Flashcards
what is variation?
the existence of variety and differences within and betwen species. there are two types of variation - genetic and environmental
what is genetic variation
every person on earth has their own unique genetic make-up (unless they are an identicle twin).
most traits are controlled by more than one gene and variation exists as a result of genetic mutations resulting in changes in proteins
how does an animal evolve by natural selection?
- there is variation that exists as a result of genetic mutation
- some oganisms are better adapted and able to survive in the environment
- these reproduce
- their alleles are passed onto their offspring
- when this process happens over many generations, it results in evolution
when does a different species form?
when two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring
what is selective breeding?
it is the process by which humans breed plants and animals for particular genetic characteristics.
how is selective breeding done?
- first parents with the desired characteristic are chosen.
- they are bred together.
- from the offspring, those with the desired characteristics are bred together.
- this continues over many generations until all the offsprings show the desired characteristics.
how is the characteristic for selective breeding chosen?
disease resistance in crops
so animals can produce more meat/milk
domestic dogs with gentle nature
large or unusual flowers.
what is a disadvantage of selective breeding?
- it can lead to inbreeding where some breeds are particularly prone to disease or inherited defects
- it reduces the number of alleles in the population which reduces the variation between individuals, so if there are problems (disease or climate change) the lack of variation may mean that none of the organisms can cope
what is genetic engineering?
a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
how have bacterial cells been genetically engineered?
to produce useful substances like human insulin to treat diabetes
what is a species?
a group of organisms with similar characteristics that can interbreed to give fertile offspring.
describe the process of speciation - 7 steps.
- a population becomes isolated, there may be different environmental conditions.
- variation exists as a result of genetic mutation.
- some organisms are better adapted to survive in the new environment.
- they reproduce.
- alleles are passed onto their offspring.
- over many generations, the isolated population may become very different to the original population.
- if they become so different they can no longer interbreed to produce fertile offspring - a new species has evolved.
what are ways that populations can be seperated?
- continental drift (islands splitting apart)
- mountain formations
- splitting of habitats - new rivers, deforestation, building of roads.
what are the reasons for differences in characteristics
- genes they have inherited
- the conditions in which they developed
- a combination of both
what is evolution?
a change in frequency of phenotype in a population over many generations
how have plants been genetically engineered?
to be resistant to diseases or produce bigger fruit.
describe the process of genetic engineering
- enzymes are used to isolate the required gene
- this gene is inserted into a vector - a bacterial plasmid/virus
- the vector is used to insert the gene into the required cells
- genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so they develop with the desired characteristics
advatages of GM crops
- reduces the use of chemicals - better for environment
- less time consuming for farmers, cheaper.
- increases yields from the crops as they arent competing with weeds for resources
disadvantages of GM crops
- reduced biodiverisity as there are fewer plant species - impact on insects ann birds
- the effects of eating GM crops on human health not fully explored.
what is tissue culture and why is it important??
using small groups of cells from part of a plant to grow identical new plants
- it is important for preserving rare plant species or commercially in nurseries
what are cuttings?
an older, but simpler method used by gardeners to produce many identicle new plants from a parent plant.
what are embryo transplants?
splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
describe the steps of adult cell cloning
- the nucleus is removed form an unfertilised egg cell.
- the nuleus from an adult body cell, like skin cell, is inserted into the egg
- an electric shock stimulates the egg cell to divide to form an embryo
- these embryo cells contain the sam genetic information as the adult skin cell
- when the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue it’s development
conditions for decay
oxygen, water, warmth, microorganisms
when are fossils formed?
- when the conditions for decay are absent - no water, oxygen, warmth or microorganisms.
- when parts of organisms are replaced by minerals as they decay
examples of preserved traces of organisms
footprints, burrows, rootlet traces
why are fossil records incomplete?
- soft bodied organisms do not fossilise, they decay so fewer traces have been left behind.
- geological activity has destroyed lots of traces.
what is extinction?
the permenant loss of all members of a species.
(when no remaining individuals of a species is still alive)
why do species become extinct?
habitat loss, rapid environmental change, increased competition, new predators, new diseases.
how have living things been classified
depending on their structure and characteristics, using a system developed by Carl Linnaeus
what is the order of classifying living things
domain → kingdom → phylum → class → order → family → genus → species
what is the binomial system
when organisms are named using the genus, then species
why might there be differences in characteristics in a population
- due to genes they have inherited
- due to conditions in which they have developed
- a combination of both genes and environment
what were the observations of charles darwin?
- 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 to breed successfully.
- The characteristics that have enabled these individuals to survive are then passed on to the next generation.
what are 3 reasons why charles darwin’s theory was only gradually accepted?
- the theory challenged the idea that God made all the animals and plants that live on Earth
- there was insufficient evidence at the time the theory was published to convince many scientists
- the mechanism of inheritance and variation was not known until 50 years after the theory was published.
what was lamark’s theory
changes that occur in an organism during its lifetime can be inherited.
we now know that in the vast majority of cases this type of inheritance cannot occur
what is genome
The genome is the entire genetic material of an organism.
what did gregor mendel do?
carried out breeding experiments on plants.
one observation was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged
what happened in 20th century (mendel’s theory)
it was observed that chromosomes and
Mendel’s ‘units’ behaved in similar ways. This led to the idea that the ‘units’, now called genes, were located on chromosomes.
how do resistant bacteria come about?
- mutations of bacteria produce new strains.
- some strains might be resistant to antibiotics, and so are not killed.
- they survive and reproduce so the population of the strain rises
- the resistant strain will then spread because people are not immune to it and there is no effective treatment
how can antibiotic strain development be reduced?
- doctors should not prescribe antibiotics inappropriately, such as treating non-serious or viral infections
- patients should complete their course of antibiotics so all bacteria are killed and none survive to mutate and form resistant strains
- the agricultural use of antibiotics should be restricted.
what is a bacteria resistant to antibiotics?
MRSA
disadvantages of adult cell cloning
- cloned animals may not be as healthy as normal ones
- there is a reduced gene pool so if there was a disease, it could wipe out the whole population
- humans might get cloned, leading to severe health issues
