16. Development of organisms and continuity of life
A section of Biology, 5090
Listing 10 of 348 questions
The diagram shows a pollen grain with a pollen tube growing from it. Pollen grains from the same type of plant were placed in sucrose solutions of different concentrations for a fixed amount of time. After this time, the pollen grains and tubes were examined using a microscope. The following observations were made for each concentration of sucrose: • the number of pollen grains that had germinated to produce a pollen tube, • the length of each pollen tube. The table shows the results of the investigation. % sucrose concentration % of pollen grains germinated mean pollen tube length / mm 0.005 0.008 0.015 0.040 0.030 0.018 0.006 A total of 12 pollen grains were placed in the 20% sucrose solution. Use the information in the table to calculate the number of pollen grains that germinated to produce a pollen tube in the 20% sucrose solution. Suggest why the mean pollen tube length was calculated for each sucrose concentration. Use the information in the table to suggest the optimum concentration of sucrose solution for pollen tube germination and growth. % Explain how the information in the table enabled you to reach this conclusion. The germination of a pollen grain to form a pollen tube requires the movement of water into the pollen grain from its surroundings. Suggest why placing a pollen grain in a solution with a higher sucrose concentration than in your answer to may result in a lower percentage of germination. Describe the route taken by a growing pollen tube in a plant and explain its importance in plant reproduction.
5090_w18_qp_22
THEORY
2018
Paper 2, Variant 2
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Cultivated banana plants produce fruits with seeds that are infertile (unable to develop). Wild banana plants produce fruits with large, fertile seeds. Suggest the type of reproduction usually found in • cultivated bananas • wild bananas State two commercial advantages that result from the type of reproduction found in cultivated bananas. 1. 2. ‘Black sigatoka’ is a fungal disease of banana leaves. The hyphae of the fungus spread through the intercellular spaces as shown in . hyphae lower epidermis of leaf spores leaf mesophyll cells Suggest ways by which the fungus would eventually cause the leaf to die. Explain why fungal diseases tend to kill a higher percentage of cultivated than of wild banana plants.
5090_w11_qp_21
THEORY
2011
Paper 2, Variant 1
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The castor oil plant is a flowering plant which produces seeds. The seeds have an additional structure called an oil body that contains oil. shows a castor oil seed with its oil body. testa oil body The testa protects the seed contents from environmental damage. Name parts of the seed protected by the testa and describe their functions. Describe a laboratory test that can be used to show that the oil body contains oil. When the fruits of the castor oil plant are ripe, they burst open, scattering the seeds onto the soil. Ants feed on the oil bodies, but not the rest of the seeds. They either remove the oil bodies where the seeds have fallen or they take the seeds and oil bodies back to their nest. Colonies of five different ant species, A – E, were supplied with the same number of castor oil seeds near to their nests. shows the results of this experiment into the behaviour of these different ant species. oil body only taken to nest oil body and seed taken to nest key A B C D E ant species percentage taken to nest Only a small number of flowering plant species produce seeds with oil bodies. Suggest one advantage and one disadvantage to the castor oil plant of producing seeds with oil bodies. advantage disadvantage Use information from to explain how useful the different ant species are to the castor oil plant. The ants feed on the oil bodies and digest the oil. Name the products of this digestion. Ant species A is Solenopsis geminata. shows a diagram of S. geminata. S. geminata is an arthropod. The arthropods are classified into a number of groups. State the name of the group to which S. geminata belongs. State two visible features used to classify S. geminata in this group of arthropods.
5090_w24_qp_21
THEORY
2024
Paper 2, Variant 1
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Questions Discovered
348