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Biology > Topic 4 - Natural Selection & Genetic Modification > Flashcards

Topic 4 - Natural Selection & Genetic Modification Flashcards

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1
Q

What did Charles Darwin do and what were his limitations?

A
  • Published his theory of evolution by natural selection in ‘On the Origins of Species’
  • Didn’t know about DNA and genes, so he couldn’t explain how characteristics were passed on to offspring
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2
Q

What did Alfred Russel Wallace do and what were his limitations?

A
  • Came up with the idea of natural selection, independent of Darwin
  • Published papers together with Darwin
  • Didn’t publish a book as famous as Darwin’s
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3
Q

What parts of modern biology have Darwin and Wallace influenced?

A
  • Classification
  • Antibiotic resistance
  • Conservation in genetic diversity
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4
Q

How does natural selection work?

A
  1. Individuals show genetic variation, due to random mutation
  2. Selection pressures affect an organism’s chance of surviving and reproducing
  3. Survival of the fittest - Individuals with characteristics better suited to the selection pressures of their environment will have a higher chance of surviving and reproducing
  4. The alleles responsible for the useful characteristics are more likely to be passed on to offspring for the next generation
  5. Individuals less suited for their environment are less likely to survive and reproduce
  6. Beneficial characteristics become more common in each new generation
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5
Q

Which hominid fossils are used to prove human evolution?

A
  • Ardi from 4.4 million years ago
  • Lucy from 3.2 million years ago
  • Turkana Boy from 1.6 million years ago
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6
Q

What are the characteristics of Ardi

A
  • Short for ardipithecus ramidus
  • Foot structure suggests tree climbing and branch grasping
  • Ape-like, long arms and short legs
  • Leg structure suggests upright walking without the use of hands
  • Low cranial capacity
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7
Q

What are the characteristics of Lucy

A
  • Short for australopithecus afarensis
  • Human-like, arched feet
  • Limb proportions between ape and human
  • Similar brain size to modern chimps, but bigger than Ardi’s
  • Leg structure suggests more efficient upright walking than Ardi
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8
Q

What are the characteristics of Turkana Boy

A
  • Homo erectus
  • Discovered by Richard Leakey, alongside other australopithecus and homo species
  • Human-like, short arms and long legs
  • Human-like brain size and cranial capacity
  • Leg structure suggests more efficient upright walking than Lucy
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9
Q

How do stone tools prove human evolution

A
  • Pebble tools, created by hitting rocks together, used from 2.5 million years ago to scrape meat from bone with sharp flakes
  • Flint tools, used from 200 000 years ago for fish hooks, needles and arrowheads
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10
Q

How are stone tools and fossils dated?

A
  • Observing structural features for complexity
  • Stratigraphy (study of rock layers) - older rock layers and found below younger ones
  • Carbon-14 dating - measures the amount of radioactive decay of C-14 over time, the less C-14 left in the object, the longer the isotope has been decaying for
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11
Q

How does the pentadactyl limb prove human evolution

A
  • A limb with five digits
  • Found in all organisms with four limbs
  • It always has a similar bone structure but usually a different function
  • Suggests that species with a pentadactyl limb evolved from a common ancestor
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12
Q

What are the 5 kingdoms

A
  • Animals
  • Plants
  • Fungi (mushrooms, toadstools, yeasts and moulds)
  • Prokaryotes (all single-celled organisms without a nucleus)
  • Protists (eukaryotic single-celled organisms)
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13
Q

What are the three domains

A
  • Eukarya (eukaryotic organisms)
  • Archaea (similar to bacteria with some differences)
  • Bacteria
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14
Q

What is the order for three domain classification

A
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
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15
Q

Why is the three domain classification prefered over the five kingdom classification

A

Improvements of genetic analysis led to biologists finding members of the Prokaryote kingdom were not closely related in their DNA and RNA sequences

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16
Q

How does selective breeding work?

A
  1. From existing stock, individuals with a wanted characteristic are selected
  2. These are bred together
  3. The best of the offspring are selected and bred together
  4. This is continued over several generations, so the desirable trait gets more expressed after each generation, until all the offspring have it
17
Q

How is selective breeding used for food plants

A
  • Give crops disease resistance to improve yields
  • Cause plants to produce bigger fruits
18
Q

How is selective breeding used for animals

A
  • Improves meat/milk yields by increasing muscle, size, etc
  • Rats have been bred with either a strong or weak preferance to alcohol to allow researchers to compare their behaviour and brain function
  • Improves temperament in dogs
19
Q

What is the risk of selective breeding

A
  • Reducing the gene pool means reducing the number of different alleles in a population, due to inbreeding.
  • This causes health problems because the inheritance of harmful genetic defects becomes more common without genetic variation
  • This exacerbates the impacts of new disease, due to the lower chance of resistance alleles being present in the population
20
Q

How does plant tissue culture work?

A
  1. A plant is chosen due to its beneficial characteristics
  2. Several pieces of tissue are removed from the parent plant from the shoot tip. This is the explant.
  3. The explant is grown on a growth medium, such as agar jelly, containing nutrients and growth hormons under aseptic/sterile conditions - producing plantlets.
  4. The growth medium is placed in micropropagation for light and humidity
  5. The plantlet grows into a callus and is moved into compost to carry on growing with rooting powder, which contains more auxins.
  6. This produces many identical plant clones after asexual reproduction is encrouaged.
21
Q

How does animal tissue culture work?

A
  1. A sample of tissue is extracted from the animal
  2. The cells in the sample are seperated from each other using enzymes
  3. They are placed in a culture vessel and bathed in a growth medium containing nutrients - allowing them to grow and multiply
  4. After several rounds of cell division, the cells can be split up again and placed into seperate vessels to encourage further growth
  5. Once grown, the tissue culture can be stored for further use
22
Q

What are the advantages of plant tissue culture?

A
  • Large numbers of identical plants produced rapidly
  • Easier than producing new plants from their seeds
  • Produced at any time of the year
  • Genetic modification can be introduced quickly
23
Q

What are the disadvantages of plant tissue culture?

A
  • No variation between offspring
  • Loss of diversity of different breeds
  • Costs of lab procedure and propagator
24
Q

What are the advantages of animal tissue culture?

A

Allows for tissues to be experimented on in isolation, without being impacted by complications from other processes in the whole organism

25
Q

What is genetic engineering?

A

The transfering of a gene from one organism’s genome into another organism’s genome, in order to introduce a desirable characteristic. This is then known as a genetically modified organism.

26
Q

What is tissue culture?

A

The practise of growing cells on or in an artificial growth medium.

27
Q

What is selective breeding?

A

The artificial selection of plants or animals that are going to breed so that the genes for a particular characteristic remains in the population.

28
Q

How does genetic engineering work?

A
  1. The gene that is going to be transferred is cut out with a restriction enzyme. These cut out a specific sequence of bases and leave behind a section of the DNA with unpaired bases called sticky ends
  2. The same enzyme is used to cut open the vector DNA, such as a bacterial plasmid or a virus. These are often grown in culture
  3. The vector DNA and the DNA being introduced are left with complimentary sticky ends.
  4. These are mixed together with ligase enzymes, which join the sticky ends together to produce recombinant DNA (2 different bits of DNA stuck together)
  5. The recombinant DNA / the vector is inserted into other cells
  6. The cells can now use the inserted gene to make the protein it codes for
29
Q

What are the advantages of genetic engineering?

A
  • Medicine - GM bacteria can produce insulin easily and cheaply
  • Bt crops produce a Bt toxin that only kill insect larvae - increasing their yields and reducing the need for chemical pesticides
  • GM crops can be herbicide resistant, so farmers can kill weeds with sprays while not harming the crops - increaing their yields
30
Q

What are the disadvantages of genetic engineering?

A
  • It can be hard to predict what effect genetic engineering will have on the organism, eg. many modified embryos don’t survive or face problems later in life
  • Transplanting genes may escape into the environment, such as herbicide resistance being picked up by weeds
  • GM crops may affect food chains and human health
31
Q

What are the effects of fertilisers to increase food security?

A
  • Contain minerals that are essential for plant growth
  • Used if soil is poor
  • Replaces nutrients lost from the soil to previous crops
  • Can cause eutrophication if it leaks into aquatic systems - resulting in algal blooms and the death of aquatic organisms
32
Q

How does the binomial classification system work?

A

First name = genus
Second name = species

33
Q

Define evolution

A

The changing of the inherited characteristics of a population over time

Biology (24 decks)

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