08 Tys Dec Hol (sci) T10 Ms

1/12/09

Unit 13.1: Structured Qn 1 (ai) Algae ii) Young mayfly/ blackfly larvae

Sci Bio nit13 y a d i l Dec Ho ework T10 U m TYS Ho 09

Jan 20

Unit 13.1: Structured Qn 2 (ai) Caterpillars/Flies/Mice; ii) Snakes/Sparrows/Sparrowhawks; (bi) Insecticide kills flies/caterpillars and hence sparrows have less food; Biological amplification of insecticides may occur down the food chain, killing off some of the sparrows; ii) Insecticides have no effect on trees or snakes which are the food source and predator of mice respectively;

Unit 13.1: Structured Qn 3 (ai) Chicken/water flea; (Reject: Human) ii) Corn/algae; (bi) Light energy from the sun ii) Y iii) Energy is lost as it is transferred from one level to another via excretion, egestion and respiration; As the total energy level decreases progressively down the chain; Y being the shortest food chain would give humans the largest proportion of energy absorbed by the producer;

(bi) Population of blackfly larvae would increase; as fewer young stonefly feed on the blackfly larvae; ii) Population of young stonefly and caddis fly larvae would decrease; as they are fed on by the trout;

Unit 13.1: Structured Qn 2 (biii) Snakes have 2 possible food sources, mice and sparrows, whereas sparrowhawks feed solely on sparrows; Hence when sparrows decline in numbers, but the number of mice does not change, the sparrowhawks are more affected than the snakes;

Unit 13.1: Structured Qn 4 (ai) Small insect;  centipede;  frog; ii) Small insect; (b) Energy is lost as it is transferred from one level to another via excretion, egestion and respiration; As the total energy level decreases progressively down the chain, the energy available for the next tropic level can support only a smaller number of organisms; Hence, the average number of frogs is less than the centipedes, and the average number of centipedes is less than the insects; (c) Not possible to count all organisms in entire leaf litter, hence sampling was carried out; Using a few samples increases accuracy;

1

1/12/09

Unit 13.1: Structured Qn 5 (ai) Not in syllabus ii) They secrete enzymes to break down the organic molecules in dead plant material, releasing simple inorganic molecules like nitrates & carbon dioxide, which return to the environment for the plants to use; Notes say: Microorganisms (mainly fungi & bacteria) which are saprophytes and live on dead organic matter. They secrete digestive enzymes onto the material and absorb the products of digestion.

Unit 13.2: Structured Qn 1 (ai) X: Respiration/decomposition; ii) Y: Combustion; (b) Photosynthesis by green plants removes the inorganic carbon dioxide in the air; To form organic glucose by combining with hydrogen from water; In the process, light energy is converted into chemical energy stored in the glucose molecules;

Unit 13.2: Structured Qn 2

Unit 13.1: Structured Qn 5b i) Respiration; ii) From weeks 0-3, bacteria & fungi/ decomposers multiply and breakdown plant material, releasing an increasing amount of heat due to increasing activity; From weeks 3-8, the amount of material available for the decomposers decreases, and the decreasing activity results in a decrease in heat production;

Unit 13.2: Structured Qn 1c (ci) Sunlight; ii) Energy is lost through respiration and in the form of heat to the environment; As the animals do not consume & assimilate the entire plant, energy contained in those molecules are also lost;

Unit 13.2: Structured Qn 2 (b) 1. Combustion; 2. Respiration/Decay;

2a) photosynthesis combustion

decay

respiration

Assimilation

(c) The increased burning of fossil fuels by industries leads to the release of more carbon dioxide into the atmosphere; The increase in deforestation reduces the number of plants in the environment. Hence, less carbon dioxide is absorbed by the plants for photosynthesis;

2

1/12/09

Unit 13.3: Structured Qn 1

Unit 13.3: Structured Qn 1

1 a) sulphur dioxide

  Source: From burning of fossil fuels. eg. Coal in power stations or petroleum products;

  Effect: Causes bronchitis in Man and forms acid rain which can kill aquatic life; b) Sewage

  Source: From raw untreated sewage being dumped into rivers/water bodies;

c) Insecticides

 Source: From farmers using insecticides to eliminate pests;

 Effect: Insecticides accumulate along the food chain and kills birds of prey which are on the top of the food chain due to bioamplification. Also, when left on crops, can cause poisoning when man eats the crops;

  Effect: Causes water to be deoxygenated due to the increase in number of bacteria, hence water is unable to support aquatic life;

Unit 13.3: Essay Qn 2a

 Sulphur dioxide dissolves in rain water to form acid rain which increases soil acidity thus destroying the root system of the plants, killing them/ reacts with minerals in soil, reducing minerals available for plant growth;

 Sulphur dioxide in the air can enter the leaves via the stomata and dissolve in the water covering the cells forming sulphuric acid. The acid causes the leaves to die thus photosynthesis cannot take place;

Unit 13.3: Essay Qn 2a

  From 1980 to 1990, the number of plant species decreased from 537 to 340 as the amount of sulphur released increased from 4.5 to 5.7 tons, which increased the amount of acid rain produced;

  In 1995, the amount of sulphur released decreased from 5.7 to 2.6 tons, hence the number of plant species increased from 340 to 347 as the species could slowly recover from the effects of acid rain;

  In 2000, though there was a slight increase in the amount of sulphur released to 2.9 tons, the number of plant species continued to recover, increasing to 365;

Unit 13.3: Essay Qn 2b

  The increase in nitrates (eutrophication) leads to an excessive growth of algae and aquatic plants as nitrates are used to produce amino acids and proteins;

  The submerged plants then die due to the lack of sunlight as surface plants and algae block entry of light;

  The dead plants are decomposed by bacteria which then multiply and consume more oxygen in the water;

  The lack of oxygen will then lead to the death of aquatic animals and further bacterial decomposition;

  The river will thus be unsustainable to aquatic life;

3