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Biology Y9 > Variation > Flashcards

Variation Flashcards

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1
Q

What does variation mean

A

the differences between organisms

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2
Q

where is there variation

A

there is variation between species and within species (between members of the same species)

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3
Q

what are the different variation within species

A

continuous variation and discontinuous variations

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4
Q

what is continuous variation

A

variation shows a range which are affected by genes and environmental factors

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5
Q

What are examples of continuous variation

A

height and body mass

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6
Q

what is discontinuous variation

A

small number of distinct groups- not a range which are affected by genes

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7
Q

what are examples of discontinuous variation

A

tongue rolling or not, blood groups and ears with or without lobes

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8
Q

what are the causes of variation

A

variation is due to inherited factors (genes) and environmental factors

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9
Q

what are the examples of causes of variation

A

height is affected by genes and by the nutrition during developement
skin colour is affected by genes and by exposure to light

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10
Q

What is the DNA

A

the DNA is the genetic material which organisms inherit characteristics from their parents through

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11
Q

where is the DNA found

A

in the nucleus in eukaryotes and it contains the information that controls the characteristics

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12
Q

what is the DNA made up of

A

it is made up of a sequence of bases and has the structure of a double helix

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13
Q

what is a change in the base sequence called and what is it

A

it is called a mutation. Mutations can confer new characteristics to organisms and if they are passed on in the next generation they can lead to new varieties.

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14
Q

what does the DNA have and what are they.

A

it has genes which are lengths of DNA that code for protein and control

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15
Q

what is the DNA organised as

A

it is organised in thread-like structures called chromosones

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16
Q

what does each chromosone have

A

many genes

17
Q

how many chromosones does a human have

A

humans have 46 chromosones and in particular 23 pairs

18
Q

all human cells have 23 pairs of chromosones except for

A

the gametes: the sperm and the egg/ovum which do not have pairs but 23 chromosones in total. So when they fuse at fertilisation, the zygote formed has 46 chromosones.

19
Q

what is selective breeding

A

choosing organisms with specific characteristics to breed together and produce an offspring with more desirable characteristics

20
Q

why is selective breeding done?

A

to create new varieties of plants and animals with desirable characteristics e.g. dog breed, racing horses, wheat producing many grains

21
Q

how is selective breeding done?

A
  • organisms with the desirable charcteristic are selected
  • they are bred together
  • offspring with the desirable characteristics are selected and bred together
  • this is repeated for many generations
22
Q

how are plants bred together

A

artifitual pollination is done; pollen is transferred from anther to stigma with a brush and the plant is covered so that no more pollen lands

23
Q

what is genetic modification

A

to make plant and animal varieties with desirable features, humans have also transferred genes to a plant/animal from another species

24
Q

what is an organism called with a foreign gene

A

genetically modified organism (GMO)

25
Q

examples of genetic modification

A

crops that are resistant to herbicides, crops that grow in saline soil, crops that produce a toxin to kill a pest, crops that have high vitamin content, bacteria that produce human insulin, etc.

26
Q

what is natural selection

A

it is evolution. the mechanism by which species evolve

27
Q

who discovered natural selection

A

Charles Darwin years after his trip to the Galapagos islands

28
Q

what is needed for natural selection

A

a variation between members of the same species

29
Q

how does natural selection work

A
  • species produce more offspring than the environment can support
  • within a population, individuals compete for reasources-there is a struggle for survival.
  • Or there is an environmental change that exerts selelction pressure
  • individuals of a population show variation. some individuals are better adapted than others.
  • the better adapted individuals tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring
  • individuals that reproduce pass on the (alleles that controls the) charcteristic to their offspring.
  • over many generations species change and become better adapted.
30
Q

what are alleles

A

different versions of a gene

31
Q

examples of natural selection

A

antibiotic resistance and industrial melanism

32
Q

what is an antibiotic

A

chemical substance used to treat bacterial infections

33
Q

how does antibiotic resistance develop

A
  • bacteria with antibiotic resitance appear in a population of non-resistant bacteria creating variation
  • the can happen by mutation
  • if antibiotic is applied (selection pressure), only the non-resistant bacteria die.
  • The antibiotic resistant bacteria multiply and pass on the resistance gene
  • the more an antibiotic is used, the more resistant bacteria there will be
  • therefore it is important to not use antibiotics if it is not necessary and also to always complete the course of the antibiotic
34
Q

how does industrial melanism develop

A
  • before burning coal the tree trunks are pale
  • the white moths are able to camouflage from the birds and are eaten less
    -the black moths are visible and are eaten more
    -the white moths reproduce and the population of the white moths increase and are more frequent
    -after the burning of coal the tree trunk is darker due to the shoot
    -the dark moth is able to camouflage better and is eaten less therefore survives longer and reproduces more
  • the white moths are eaten and decrease
    the melanistic moth were more frequent
35
Q

what did human do about industrial melanism

A

humans then took measures to reduce pollution and the white moth reappeared.

Biology Y9 (8 decks)

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