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Edexcel GCSE Biology > SB4 - Natural Selection and Genetic Modification ✓ > Flashcards

SB4 - Natural Selection and Genetic Modification ✓ Flashcards

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1
Q

SB4a - What are the two types of evidence for evolution?

A
  • Fossil remains
  • Stone tools
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2
Q

SB4a - How do fossil remains provide evidence for evolution?

A
  • Fossil remains of humans can show us the bone structure of previous species
  • It also shows how the size of (volume) the skulls, increased over time, suggesting that the size of the brain increased aswell
  • The fossils are dated by the layers under the surface that they are
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3
Q

SB4a - How do stone tools provide evidence for evolution?

A
  • Stone tools show us what previous species of humans did and what they required tools for
  • We can see that over time, they become more sophisticated, going from skining animals/cutting up meat to decorations
  • Stone tools are dated by the rock that they are found in.
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4
Q

SB4a - What are the limitations of using fossil remains as evidence for evolution?

A
  • Not all organisms are fossilised.
  • Any organisms made of soft tissue and any soft tissue in organisms are unlikely to fossilise meaning that there are gaps in the records
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5
Q

SB4a - Name the species of ‘human’ in order of their evolution, and describe the trend in skull volume.

A
  • Adripithecus (Ardi)
  • Australopithecus (Lucy)
  • Homo habilis
  • Homo erectus
  • Homo sapiens

Increasing skull volume over time

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6
Q

SB4b - Describe the process of natural selection.

A
  • The characteristics of different individuals ina species differ due to genetic variation
  • A change in an environmental factor leads to increase in competition between organisms
  • The individuals with varitions that make them adapted to the change, means that they are better at coping and are more likely to survive (survival of the fittest)
  • The survivors will carry this gene that allowed them to cope and once they reproduce, are more likely to pass this onto the next generation
  • Over further generations, this gene will become more prominent in the population
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7
Q

SB4b - Using the theory of natural selection, explain why not completing a course of antibiotics is so dangerous.

A
  • The population of bacteria have variation in their resistance to antibiotics.
  • The course of antibiotics kill most of the bacteria
  • Before the course is finished, the only remaining bacteria are the most resistant
  • If the course isn’t completed, the remaining (more resistant) bacteria will reproduce,
  • This will produce another generation of highly resistant bacteria which the antibiotic will be less effective against
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8
Q

SB4c - Describe how Darwin’s theories were developed.

A
  • After visiting the galapagos islands and seeing differences in the mockingirds of different islands he wondered if spcies changed how they look based on their surroundings
  • After reading an essay by Thomas Malthus, he came to the conclusion organisms produce more offspring than could survive and so only the best suited survive
  • Wallace wrote a letter to him saying he came to the same conclusion
  • They both worked together and Darwin summarised their ideas in a book claled ‘on the origin of species’
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9
Q

SB4c - What is the pentadactyl limb and how does this provide evidence for evolution?

A
  • The pentadactly limb is a limb that has 5 main bone structures and this is visible in many organisms from humans to bats to dolphins.
  • As we all have the same 5 bone base structure, this suggests that we all have a common ancestor.
  • However the layout of these 5 bones changed depending on the surroundings and conditions of a species.
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10
Q

SB4d - What is the order of classification?

A
  • (Domain)
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
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11
Q

SB4d - How is the scientific name of a species made?

A

Name of genus then the name of the species

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12
Q

SB4d - What are the 5 kingdoms and the characteristics of each of these?

A
  • Animalae: Multicellular. Nuclei are present but no cell walls
  • Plantae: Multicellular. Nuclei, chloroplasts and (cellulose) cell walls are present
  • Fungi: Multicellular (apart form yeast). live on dead matter. Nuclei and (chitin) cell walls are present.
  • Protists: Mostly unicellular. Nuclei and cell walls present
  • Prokaryotes: Unicellular. No nucleus, flexible cell walls
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13
Q

SB4d - As you go further down the order of classification, what will happen to the species that are there?

A

They will have increasingly similar characteristics and genes.

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14
Q

SB4d - What are the three domains and the characteristics of each?

A
  • Bacteria: (Cells with no nucleus; containing unused sections of DNA)
  • Archaea: (Cells with no nucleus or unused sections of genes)
  • Eukarya: (Cells with a nucleus and no unused sections of genes)
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15
Q

SB4e - What may humans selectively breed an organism for?

A
  • Disease resistance
  • Increased yield
  • Coping with certain conditions
  • Fast growth
  • Flavour
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16
Q

SB4e - Describe the process of selective breeding.

A
  • Firstly, out of the population, you pick the two organisms that most strongly present your desired characteristic
  • Breed these two together
  • From the offspring choose the two that most strongly show this and repeat
  • After a couple of generations, almost all of the offspring will display the characteristic
  • This is selective breeding/artificial selection
17
Q

SB4e - What is genetic engineering?

A

The process of altering the genes of an organism in order to aquire certian desired characteristics.

18
Q

SB4f - What is tissue culture?

A
  • The growing of cells or tissue in a liquid containing nutrients or a solid medium (e.g nutrient agar).
  • This forms a callus (bunch of unspecialised cells) which can be differentiated and inserte dinto the body
19
Q

SB4f - What are the uses of tissue culture?

A
  • Differentiating cells
  • Producing clones of GMOs
  • Growing plants of very rare species to stop their extinction
  • Testing new medical treatment without any affects on life forms
  • Studying viruses as they require host cells to be alive
20
Q

SB4f - Describe the two processes by which tissue cultures can be grown.

A
  • They both start out by taking a piece of a plant and sterelising it
  • If only a few cells are taken, they are placed on sterile nutrient medium to form a callus
  • They callus is treated with gormones so that the plantlets develop roots and shoots
  • The plantlets are sperated and continue to grow until they can be placed in soil/compost to grow OR
  • If a piece of the plant is taken, its placed in sterile nutrient medium to grow
  • Once it grows bigger, it will be treated with hormones and so on in the same way…
21
Q

SB4g - What are the risks of selective breeding?

A
  • Animals may loose an allele thought this process.
  • This may be needed later on to help them survive/cope
  • All the animals become very similar and so any disease that affects one of them, affects all of them
  • Unethical as some animals liv ein conditions that aren’t comfortable (e.g chickens with a lot of meat can’t stand up)
22
Q

SB4g - What are the risks of genetic engineering?

A
  • Genes may ‘hop’ onto wild plants, making them resistant
  • Loose out on genes that may be required in the future
  • Very expensive
  • Some people think its bad for your health
23
Q

SB4g - Describe the process of genetic engineering of bacteria to produce insulin.

A
  • The insulin gene is to be inserted into the bacteria
  • Once you’ve extracted the DNA containing coding for insulin, use restriction enzymes to cut out the required section of DNA
  • Extract your bacteria’s plasmid, (which will act as a vector) and cut out a section using the same restriction enzymes
  • As you’ve used the same restriction enzymes, it will leave sticky ends (that are complementary to that of the insulin section of DNA)
  • As they are complementary, they will fit together, use ligase enzymes to join the insulin DNA to the plasmid forming hydrogen bonds
  • Re-insert the plasmid (which now has recombinant DNA) into the bacteria and let it reproduce.
  • As bacteris reproduce fast, you will soon have enoguh bacteria to efficiently extract insulin
24
Q

SB4h - What are the advantages of plants that produce ‘their own insecticide’ such as Bt toxin to famers?

A
  • It only affects insects that chew it meaning it targets pests specifically
  • Higher yield
  • Less money spent on insecticides
25
Q

SB4h - What are the disadvantages of plants that produce ‘their own insecticide’ such as Bt toxin, to farmers?

A
  • Insects such as aphids which suck up sap aren’t affected
  • Insects can develop resistance to the toxin
  • GM crops that produce the Bt toxin are expensive
26
Q

SB4i - What is a biological control?

A

When organisms are used to control pests.

27
Q

SB4i - What is the problem with using too much fertiliser?

A
  • Too much fertiliser usage means that its possible not all will be absorbed by the crops
  • Some could flow into water sources
  • This leads to eutrophication
  • And can poison animals/humans that drink from here

Edexcel GCSE Biology (11 decks)

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