genetics and evolution Flashcards
what did Mendel do
in his garden, he noted how characteristics in pea plants were passed on from one generation to the next
what did mendel pea plant experiment show
he showed that the height characteristics in pea plant were determined by separately inherited hereditary units passed on from each parent and that the ratio of tall and dwarf offspring showed that the unit for tall plats T was dominant over the unit for dwarf plant, t
what were Mendel conclusions about heredity in plants
1) characteristics in plants were determined by hereditary units
2) hereditary units are passed on to offspring unchanged from both parents, with one unit from each parent
3) hereditary units can be dominant or recessive and if an individual has both the dominant and the recessive unit for a characteristic, the dominant characteristic will be expressed
why didn’t scientist believe his work at first
as they didnt have any idea about genes, DNA and chromosomes
how did mendels work help contribute to other observations
1) in the late 1800s scientist became familiar with chromosomes allowing them to observe how they behave during cell division
2) in the early 20th century scientist discovered similarities between the way chromosomes and mendels units acted, this proposed that the units were found on the chromosomes and now these units are known as genes
3) in 1953, the structure of DNA was determined, allowing scientist to go and find out how they work
what does variation mean
differences between individuals of the same species
two types of variations
genetic variation
environmental variation
why do animals and plants have characteristics that are similar to their parents
as an organism’s characteristics are determined by the genes inherited from their parents, these genes are passed on in gametes (sex cells), where the organism develops
what causes genetic variation
the combining of genes from your mother and father
what is environmental variation
differences between individuals that are not inherited but caused by the environment that the organism lives in
what are characteristics determined by
a mixture of genetic and environmental factors
examples of environmental variation
tattoos, scars , amount of sunlight for plants
what do mutations do
they lead to changes in the proteins that a gene code for
what are mutations
changes to the sequence of bases in DNA
how do mutations introduce variation
if the mutation results in a new phenotype being seen in a species and makes the individual more suited for environmental changes it can become common throughout the species quickly through natural selction
what is the theory of evolution
that all of species have evolved from simple life forms that first dtated to develop over 3 billion years ago
how did charles darwin come up with the theory of evolution by natural selection
- he knew that organisms showed a wide variation in their characteristics and that organisms had to compete for limited resources in an ecosystem
- so he made a conclusion that organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive, reproduce and pass on the genes for the characteristics that made them successful to their offspring
- the organisms that are less adapted would be less likely to survive and reproduce so are less likely to pass their genes to the next generation
- over time the beneficial characteristics become more common in the population and the species evolve
cons for darwins theory
- ## as the relevant scientific knowledge wasn’t available at the time so he couldn’t give a good explanation for why the characteristics appeared or exactly how individual organisms passed on their beneficial characteristics
what is a phenotype controlled by
genes
what is natural selection
a process where organisms that are better adapted to an environment will survive and reproduce
what is speciation
when the phenotype of organisms change so due to natural selection that a new species is formed
when does speciation occur
when populations of the same species change enough to become reproductively isolated, this means that they cant interbreed to produce fertile offspring
why do species become extinct
- the environment changes too quickly
- a new predator kills them all
- a new disease kills them all
- they cant compete with another species for food
- a catastrophic event happens that kills them all
why didnt people agree with darwins theory
- it went against religious beliefs on how life on earth was created as it was the first plausible explanation for the existence of life on earth without a God
- Darwin couldn’t explain why these new, useful characteristics appeared or how they were passed on from individual organisms to their offspring
- there wasn’t enough evidence to convince many scientists as not many other studies had been done into how organisms change over time
- there were different theories of evolution
what did Lamarck theory suggest
he thought that if a characteristic was used a lot by an organism then it would become more developed during its lifetime and the organism’s offspring would inherit the acquired characteristic
how do you prove an hypothesis is correct
to find evidence that supports it
why was Lamarck theory rejected
as his experiments didn’t support his hypothesis
why was Darwins hypothesis accepted
- as the discovery of genetics supported darwins idea as it provided an explanation how organisms born with beneficial characteristics can be passed on
- evidence from fossils of different ages allowed you to see how the changes in organisms developed slowly over time supporting his idea
- the recent discovery of how bacteria are able to evolve to become resistant to antibiotics supports the idea of evolution by natural selection
what is selective breeding
when humans artificially select plants or animals that are going to breed so that the genes for the particular characteristcs remain in the population
examples organisms that are selectively bred
- animals that produce more meat or milk
- crops with disease resistance
- dogs with a good, gentle temperament
- decorative plants with big or unusual flowers
process of selective breeding
1) from your existing stock, select the ones which have characteristics your after
2) breed them with each other
3) select the best of the offspring and breed them together
4) continue this process over several generations, and the desirable trait gets stronger and eventually all the offspring will have the characteristic
what is selective breeding used for in agriculture
- improve crop yields
- improve meat yields
cons of selective breeding
- it reduces the gene pool (the number of different alleles in a population) as the farmer keeps breeding from the best animals or plants which are closely related (known as inbreeding), reducing variation
- inbreeding can lead to health problems as there is a more chance of organisms inheriting harmful genetic defects when the gene pool is limited
- a new disease can also affect the whole population as there’s not much variation
how does genetic engineering work
1) a useful gene is isolated (cut) from one organism’s genome using enzymes and is inserted into a vector
2) the vector is usually a virus or a bacterial plasmid depending on the type of organism that the gene is being transferred to
3) when the vector is introduced to the target organism the useful gene is inserted into its cells
examples of genetically modified, GM things
- bacteria has been GM to produce human insulin that can treat diabetes
- GM crops have had their genes modified to improve the quality and size of their fruit or to make them resistant to diseases and insects
- sheeps have been GM to produce substances in their milk that can be used to treat human disease
- for gene therapy where scientists use GM treatments for inherited diseaes by inserting working genes into people with the disease
cons of genetic engineering
- there might be long-term effects as changing an organism’s disease might accidentally create unplanned problems which could be passed on
- growing GM crops will affect the number of wildflowers that live around an in the crops reducing farmland biodiversity
- not everyone believes GM crops are safe and some people are concerned that we may not understand the effects of eating them on human health
- transplanted genes may get into the natural environment
pros of genetic engineering
- increase yield, making more food
- GM crops can be engineered to provide the lack of nutrients developing countries are missing
- GM crops are already being grown in some places without a problem
