Ecosystem

Group

2

Ecosyste m

Candy Kwok 5B(11), Samantha Li 5B(20), Gloria Ko 5D(6), Katherine Ng

Questions

(a)

Explain the terms ecosystem and habitat. (2 marks)

  (b) (i) With this food web, draw a food chain that has 4 trophic levels. (1 mark) (ii) Construct a pyramid of biomass for this food chain. (2 marks) (iii) Explain the shape of the pyramid of biomass. (4 marks)   (c) Why are there seldom more than 3 or 4 trophic levels in a food chain? (2 marks)   (d) (i) Name the type of ecological relationship between the predaceous insects and the birds. k) (1 mark) (ii) Explain the immediate effect on the number of grasshoppers if most birds

Answers (a). Ecosystem is a natural unit of living and non-living parts which interact to form a stable and self-supporting system. (1) Habitat is the place with a particular set of physical factors in which plants and (b) (i) Plants  (1) grasshoppers  birds  hawk (1) animals live.

(b) (ii) Hawk Birds Grasshoppers

Plants

correct shape (1)

Correct Names (1)

b(iii) Energy is lost along the food chain because some energy is used in the respiration of the organism, and some food is lost in excretion or due to incomplete digestion of food. Thus, the biomass decreases along the food chain. (1 + c. Most energy is lost in each trophic level. After 4 trophic levels, 1 + 1 + 1) there is usually not enough energy left to support the activities of the organisms in the fifth trophic level. (2) (d) (i) Competition. (1) (ii) The grasshoppers will increase in number because there are fewer birds and insects feeding on them. (2) They also have more food because there are (1) fewer birds feeding on the plants. (1) Their birth rate will be higher than the death rate. (1)

(e)

They are bacteria and fungi. (1/2+1/2) The dead bodies of the organisms and their excreta will accumulate in the ecosystem because they cannot be decomposed. (1 + 1) Moreover the recycling of nutrients will be affected because the mineral salts in soil cannot be properly replenished. (1) The growth of the green plants will be severely affected (1) That will affect the supply of food to all the consumers in the ecosystem. (1)