thebiotutor.com 5B Selective breeding Time: 40 minutes Total marks available: 40 Total marks achieved: Andy Todd

Transcription

1 thebiotutor.com 5B Selective breeding Time: 40 minutes Total marks available: 40 Total marks achieved:

2 Q1. (a) Describe the stages that are used to genetically modify a bacterium that is able to manufacture human growth hormone. (b) BST is a hormone that increases milk yield in cows. (i) Explain what is meant by the term hormone. (ii) In some countries BST from genetically modified bacteria has been injected into cows to improve milk production. In other countries selective breeding has been used to improve milk production. Describe how selective breeding could be used to increase milk production. (5) (2) (3) (Total for question = 10 marks)

3 Q2. (a) Crop plants have been developed by a process called selective breeding. (i) Describe the process of selective breeding. (4) (ii) Give one example of a desired characteristic developed by selective breeding in a named crop plant. desired characteristic crop plant (2) (b) Give two ways in which natural selection differs from selective breeding. (2) (Total for question = 8 marks) Q3. The passage describes selective breeding. Complete the passage by writing a suitable word in each of the spaces. Selective breeding involves... choosing organisms (4) with desired.... These organisms are allowed to breed and produce.... The process is... for several generations.

4 (Total for question = 4 marks)

5 Q4. The table describes four different geographical regions. It also gives the amount of energy converted into plant biomass each year in each region. (a) Plot a bar graph on the grid to show the amount of energy converted into plant biomass each year in each region. (5)

6 (b) The amount of energy converted into plant biomass each year depends on the effect that abiotic (non-living) factors have on the rate of photosynthesis. Carbon dioxide is one of these abiotic factors. Name three other abiotic factors likely to affect the rate of photosynthesis. (3) (c) Regions C and D have the same climate. Plants grown in region D have more energy converted into plant biomass than plants grown in region C. One reason for this is the use of selective breeding to produce high yielding crops. (i) Suggest two other reasons for more energy being converted into plant biomass in region D. (2) (ii) What is meant by the term selective breeding? (d) Describe how you could use a quadrat to estimate the plant biomass in one of the regions. (4) (4)

7 (Total for question = 18 marks) Q1. In part (a) students did less well with a few seeming to have no idea about genetic modification. The better responses included extraction of the gene, that codes for growth hormone, from human DNA using a restriction enzyme. Using the same restriction enzyme to cut a bacterial plasmid and using ligase to insert the human gene into the plasmid to make a vector contain recombinant DNA. In part (b)(i) students had to explain what is meant by a hormone. The majority of students earned some credit. The best responses clearly stated that a hormone is released by endocrine glands into the blood stream carried to target cells upon which it has an effect. In part (ii) students had to describe how selective breeding could be used to increase milk production. About half of the answers scored full marks. Some responses had cows mating with other cows, some referred to cloning and some had cows marrying! The best responses described selecting cows with high milk yield and mating these with bulls from mothers who had high milk yield. This process could then be repeated with their offspring for many generations. Q2. This question was on selective breeding. In part a) most candidates were able to describe selective breeding although some confused this with genetic modification or micropropagation. Few candidates were able to give a sensible example of a desired characteristic from a crop plant. In part b) most candidates could give two ways natural selection differs from selective breeding. Q3. This question provided candidates with a passage on selective breeding into which to fill in the appropriate words. Here performance varied between centres. Many candidates scored full marks but others scored poorly. Q4. In part (a) of this question most students were able to score at least 4 marks with excellent bar charts. The most common loss of a mark was for not labelling the axes fully, including appropriate units. Part (b) was well answered with most showing good understanding of abiotic factors that affect photosynthesis, temperature and light being the most common responses. A few gave vague references to humidity and wind speed confusing it with transpiration. Part (c)(i) was challenging for many. The mark scheme rewarded students who appreciated that farming practices improve primary production. The better students made the connection and scored well but the weaker students made bland references to photosynthesis or made vague references to farming intensity. Student understanding of selective breeding in part (ii) was impressive with many appreciating that human involvement is part of the process. In part (d), many students had no understanding of how to use quadrats. Students who were familiar with the technique scored at least two marks for mentioning the importance of random sampling and repeats. The question asked for an estimate of biomass not numbers but most students referred to counting plants

8 rather than weighing them.

9 Q1.

10 Q2. Q3.

11 Q4.