SB4a - What are the two types of evidence for evolution?
- Fossil remains
- Stone tools
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 - What are the limitations of using fossil remains as evidence for evolution?
- 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
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
SB4b - Describe the process of natural selection.
- 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
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 - What is the order of classification?
SB4d - How is the scientific name of a species made?
Name of genus then the name of the 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 - 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 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 - What may humans selectively breed an organism for?
- Disease resistance
- Increased yield
- Coping with certain conditions
- Fast growth
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 altering the genes of an organism in order to aquire certian desired characteristics.
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 - What are the uses of tissue culture?
- 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
SB4f - Describe the two processes by which tissue cultures can be grown.
- 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...
SB4g - What are the risks of selective breeding?
- 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)
SB4g - What are the risks of genetic engineering?
- 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
SB4g - Describe the process of genetic engineering of bacteria to produce insulin.
- 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
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 is the problem with using too much fertiliser?