genetics and evolution

Question 1

what did Mendel do

Answer 1

in his garden, he noted how characteristics in pea plants were passed on from one generation to the next

Question 2

what did mendel pea plant experiment show

Answer 2

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

Question 3

what were Mendel conclusions about heredity in plants

Answer 3

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

Question 4

why didn’t scientist believe his work at first

Answer 4

as they didnt have any idea about genes, DNA and chromosomes

Question 5

how did mendels work help contribute to other observations

Answer 5

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

Question 6

what does variation mean

Answer 6

differences between individuals of the same species

Question 7

two types of variations

Answer 7

genetic variation
environmental variation

Question 8

why do animals and plants have characteristics that are similar to their parents

Answer 8

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

Question 9

what causes genetic variation

Answer 9

the combining of genes from your mother and father

Question 10

what is environmental variation

Answer 10

differences between individuals that are not inherited but caused by the environment that the organism lives in

Question 11

what are characteristics determined by

Answer 11

a mixture of genetic and environmental factors

Question 12

examples of environmental variation

Answer 12

tattoos, scars , amount of sunlight for plants

Question 13

what do mutations do

Answer 13

they lead to changes in the proteins that a gene code for

Question 14

what are mutations

Answer 14

changes to the sequence of bases in DNA

Question 15

how do mutations introduce variation

Answer 15

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

Question 16

what is the theory of evolution

Answer 16

that all of species have evolved from simple life forms that first dtated to develop over 3 billion years ago

Question 17

how did charles darwin come up with the theory of evolution by natural selection

Answer 17

• 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

Question 18

cons for darwins theory

Answer 18

• ## 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

Question 19

what is a phenotype controlled by

Answer 19

genes

Question 20

what is natural selection

Answer 20

a process where organisms that are better adapted to an environment will survive and reproduce

Question 21

what is speciation

Answer 21

when the phenotype of organisms change so due to natural selection that a new species is formed

Question 22

when does speciation occur

Answer 22

when populations of the same species change enough to become reproductively isolated, this means that they cant interbreed to produce fertile offspring

Question 23

why do species become extinct

Answer 23

• 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

Question 24

why didnt people agree with darwins theory

Answer 24

• 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

Question 25

what did Lamarck theory suggest

Answer 25

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

Question 26

how do you prove an hypothesis is correct

Answer 26

to find evidence that supports it

Question 27

why was Lamarck theory rejected

Answer 27

as his experiments didn’t support his hypothesis

Question 28

why was Darwins hypothesis accepted

Answer 28

• 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

Question 29

what is selective breeding

Answer 29

when humans artificially select plants or animals that are going to breed so that the genes for the particular characteristcs remain in the population

Question 30

examples organisms that are selectively bred

Answer 30

• animals that produce more meat or milk
• crops with disease resistance
• dogs with a good, gentle temperament
• decorative plants with big or unusual flowers

Question 31

process of selective breeding

Answer 31

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

Question 32

what is selective breeding used for in agriculture

Answer 32

• improve crop yields
• improve meat yields

Question 33

cons of selective breeding

Answer 33

• 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

Question 34

how does genetic engineering work

Answer 34

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

Question 35

examples of genetically modified, GM things

Answer 35

• 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

Question 36

cons of genetic engineering

Answer 36

• 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

Question 37

pros of genetic engineering

Answer 37

• 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