Practise A2 Paper 5 by planning controlled investigations, processing biological data and judging whether results support hypotheses or treatment claims.
The light dependent stage of photosynthesis in a suspension of isolated chloroplasts can be investigated using the Hill reaction.
Dichlorophenolindophenol (DCPIP) can be used to follow the process. DCPIP is a blue dye which turns colourless when it is reduced by accepting hydrogen and electrons.
Explain the reasons for:
the colour standard tube A
covering the beaker containing the chloroplast-DCPIP mixture with foil.
Table 2.1 shows the results of the experiment.
Table 2.1
Complete Table 2.1 by calculating the rate of the light dependent stage of photosynthesis for the orange wavelength, using the formula:
Researchers measured insect biodiversity on Acacia trees in the African savannah using the following method:
- insecticide was sprayed into each tree
- this killed the insects, which fell onto a sheet below the tree
- the dead insects were collected, identified and counted.
Table 5.1 shows summary statistics for some of the trees sampled in this study. The leaf canopy area is a measure of the size of the tree and the extent of its leaf cover.
Table 5.2 shows the diversity and abundance of some different taxonomic groups of insects in the study.
Table 5.1
Table 5.2
Comment on the effects of sample size on the quality and accuracy of the data in Table 5.1.
There is considerable variation in the ecosystems that occur in the continent of North America. These include coniferous forest, prairie grassland, scrub and desert. Large areas of land that once contained natural ecosystems are now used for agriculture.
The diversity of some beetle species that feed on animal dung (faeces) was investigated at two types of grassland site in North America. The first type of grassland site was grazed by cattle and the second type of site was not grazed.
Dung beetles were collected, identified and counted from two areas of the same total size. Some of the results are shown in Table 8.1.
Table 8.1
State the null hypothesis for a statistical test comparing the data from the two types of site.
The light dependent stage of photosynthesis in a suspension of isolated chloroplasts can be investigated using the Hill reaction.
Dichlorophenolindophenol (DCPIP) can be used to follow the process. DCPIP is a blue dye which turns colourless when it is reduced by accepting hydrogen and electrons.
Explain the reasons for:
the colour standard tube A
covering the beaker containing the chloroplast-DCPIP mixture with foil.
The light dependent stage of photosynthesis in a suspension of isolated chloroplasts can be investigated using the Hill reaction.
Dichlorophenolindophenol (DCPIP) can be used to follow the process. DCPIP is a blue dye which turns colourless when it is reduced by accepting hydrogen and electrons.
Table 2.1 shows the results of the experiment.
Table 2.1
Complete Table 2.1 by calculating the rate of the light dependent stage of photosynthesis for the orange wavelength, using the formula:
Malaria is a serious and often fatal disease that is transmitted by the mosquito Anopheles gambiae. One method of reducing the incidence of malaria is to control the numbers of these mosquitoes.
In mosquitoes, as in humans, males have an X chromosome and a Y chromosome, while females have two X chromosomes. Researchers investigated the possibility of producing genetically modified (GM), fertile male mosquitoes in which most of the sperm contained a Y chromosome and not an X chromosome.
They predicted that introducing these males into a population of A. gambiae could greatly reduce the number of females in each generation and therefore reduce the numbers of eggs laid.
The researchers modified the gene for I-Ppol, so that it produced a version of I-Ppol that was active only during meiosis in the males, and was not active in the zygote. They then tested the effect of introducing these GM males into a mosquito population.
- Several cages were set up. 50 adult male mosquitoes and 50 adult female mosquitoes without the I-Ppol gene were placed in each cage.
- 150 adult GM males were introduced into each cage. In half of the cages (A), these GM males had the normal gene for I-Ppol. In the rest of the cages (B), the GM males had the modified gene for I-Ppol.
- The mean number of adult female offspring per cage was determined over the next six generations.
Fig. 3.1 shows the results.
mean number of adult females
Fig. 3.1
Describe and suggest explanations for the differences between the mean numbers of adult females in the two sets of cages during the experiment.