1. When discussing natural selection, the term "increased reproductive success" is used. Explain what this means.
Answer
Where an organism is more likely to survive long enough to reproduce more frequently and pass on their advantageous alleles to their offspring.
2. What changes in allele frequency would be expected over a long period of time when natural selection is acting on a population ?
Answer
Allele frequency for advantageous alleles would increase.
3. Explain what the term "anatomical adaptation" means.
Answer
Anatomical adaptations are physical features that organisms have that help them survive.
4. Explain what the term "behavioural adaptation" means.
Answer
Behavioural adaptations are behaviours that an organism carries out that helps them survive.
5. Suggest how a fall in population could lead to low genetic diversity.
Answer
If a large portion of the population dies, the number of different alleles will decrease. The surviving population will have fewer alleles when repopulating.
6. A poisonous toad was introduced into a new environment to control pests. This caused a decline in local predators that were vulnerable to its toxins. Some snake species were highly vulnerable, yet over time they evolved traits that improved survival. Snakes swallow prey whole, so jaw size affects what they eat. Scientists have observed changes in jaw size that reduce the risk of eating lethal toads. Explain how natural selection could have led to snakes developing the ability to survive in areas where this toad lives.
Answer
There was variation in jaw size among the original population. Those with smaller jaws were more likely to survive, reproduce, and pass on their alleles to offspring. As a result, the allele frequency increased.
7. Name the type of selection shown above.
Answer
Directional selection because it is favouring one extreme, causing the distribution to shift towards smaller head phenotype.
8. A student wanted to find out which brand of bathroom cleaning spray was best at killing bacteria. She used aseptic technique to spread E.coli bacteria over the surface of agar jelly in a Petri dish. The student dipped a filter paper disc into one of the bathroom sprays and placed it on the agar. She repeated this with two other brands of bathroom spray. The student also dipped one filter paper disc in sterile distilled water and placed this on the agar. She incubated the dish for 24 hours at 30°C. The figure below shows the appearance of the dish after incubation. Give some examples of aseptic technique that the student should have used.
Answer
Sterilise spreader by heating in a flame or use disposable sterilised spreader. Use sterile pipette to place bacteria on agar. Clean bench with disinfectant before and after investigation. Wash hands with antibacterial soap before and after. Flame necks of vials, tubes, bottles or cultures of bacteria.
9. The student soaked one filter paper disc in distilled water. Explain why.
Answer
Control for comparison. To show it is the spray that kills bacteria and nothing in water or paper kills bacteria.
10. The student concluded that brand B is the best bathroom spray for killing bacteria. Evaluate this conclusion.
Answer
It has the largest inhibition zone, indicating that it kills more bacteria than the other brands. However, it was only tested against E.coli, so it may not be effective against all types of bacteria. Since the test was conducted on an agar plate, its effectiveness in a bathroom environment may be reduced. In the experiment, the spray remained in contact with bacteria for 24 hours, but in real bathroom use, the contact time is much shorter.