SB4 - Natural Selection and Genetic Modification ✓ Flashcards Preview

Edexcel GCSE Biology (9-1) > SB4 - Natural Selection and Genetic Modification ✓ > Flashcards

Flashcards in SB4 - Natural Selection and Genetic Modification ✓ Deck (30)
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SB4a - How do fossil remains provide evidence for evolution?

  • 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


SB4a - How do stone tools provide evidence for evolution?

  • 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.


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

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

Increasing skull volume over time


SB4a - Why is it that fossil evidence may not provide conclusive evidence of human evolution?

  • There are gaps in fossil evidence so scientists aren't sure the species evolved from each other
  • Not all fossils have been discovered
  • Some fossils are destroyed so we cannot draw a conclusion from it


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

  • Fossil remains
  • Stone tools


SB4a - How did Leakey's findings provide evidence for human evolution?

  • He discovered many hominid fossils.
  • In 1984, in Kenya, he discovered an almost complete 1.6 million year old skeleton, providing evidence that humans evolved in Africa
  • The species was tall and strongly built


SB4a - Describe methods used by scientists to date tools

  1. Carbon-14 Dating - estimating the age of carbon-containing material found in the tool, whether it's the handle or the fur
  2. Statigraphy - using the layers of sediment as an indication of the age of the tool


SB4a - What do Ardi and Lucy tell us about human evolution?

  • Ardis 4.4 million years old - she had characteristics both ape-like (long arms, big toes), and human-like (walked upright)
  • Lucy, whereas, is more adapted to walking than climbing. 


SB4b - Describe Darwin's theory of evolution through natural selection (6 marks)

  • variation - most populations of organisms have individuals who are very slightly different to one another due to mutations
  • over-production - most organisms produce mroe offspring than will survive to childhood
  • struggle for existence - because populations do not generally increases rapidly in size, there therefore must be competition for survival
  • survival - those with advantgeous characteristics are more likely to survive this struggle
  • advantageous characteristics inherited - better adapted organisms are more likely to reproduce successfully passing on the advantageous characteristics to their offspring
  • gradual change - over a period ftime, the proportion of individuals with the advantageous characteristic increase and the poorly adapted characteristic will eventually bel ost


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

  • 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


SB4c - Describe how Darwin's theories were developed.

  • 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'


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

  • 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.


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

They will have increasingly similar characteristics and genes.


SB4d- What is the bi-nomial system?

  • Genus + Species


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

  • 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


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

  • 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)


SB4e - Describe the process of selective breeding.

  • 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


SB4e - What is genetic engineering?

The process of changing the genome of an organism by introducing genes from another to create genetically modified organisms


SB4e - What may humans selectively breed an organism for?

  • Disease resistance
  • Increased yield
  • Coping with certain conditions


SB4f - What are the uses of tissue culture in agriculture and medicine?


  • Producing clones of GMOs
  • Growing plants which are going extinct


  • Testing new medical treatment without any affects on life forms
  • Studying viruses as they require host cells to be alive


SB4f - What is tissue culture?

  • 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


SB4f - Describe the steps of plant tissue culture

  1. Tissue removed from the tip of the plant
  2. Tissue is placed on a medium containing agar jelly containg plant hormones and nutrients
  3. Sample grows into hundreds of tiny, identical plants


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

  1. DNA from a human cell is cut into pieces using enzymes from restriction enzymes. These make staggered cuts across DNA, leaving a few unpaired bases at each end called sticky ends.
  2. Bacteria cells contain small circles of DNA called plasmids. The same restriction enzymes are used to cut plasmids open, leaving sticky ends with matching sets of unpaired bases.
  3. The pieces of DNA containing the insulin gene are mixed with the plasmids. The bases in the sticky ends pair up, an enzyme called DNA ligase is then added, linking the DNA back into a continuous circle
  4. The plasmids are inserted back into the bacteria. This can be grow in huge fermenters where they can make human insulin


SB4g - What are the problems with genetically engineering plants?

  • Genes may 'hop' onto wild plants, making them resistant
  • Reduce gene pool
  • Very expensive
  • Some people think its bad for your health to eat GMOs


SB4g - What are the risks of selective breeding?

  • Animals may loose an allele through 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 live in conditions that aren't comfortable (e.g chickens with a lot of meat can't stand up)


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

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


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

  • 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


SB4i - What is a biological control?

When organisms are used to control pests.


SB4i - What are the advantages / disadvantages of fertilisers?


  • Contain nutrients including nitrogen, phosphorus and potassium that helps crops grow well
  • Increase crop yield producing more food
  • Good way to use manure from farms


  • Excess fertiliser can pollute waterways, causing eutrophication
  • Artificial fertilisers can be expensive to make
  • Artificial fertilisers reduce soil biodiversity


What are the advantages / disadvantages of Biological Control?


  • Less insecticide wasted
  • Biological Control is usually specific to the pest
  • Pest cannot become resistant


  • Biological Control may become a pest in itself
  • Doesn't guarantee to kill all the pest