IGCSE Biology Paper-4: Specimen Questions with Answers 100 - 101 of 120

Question number: 100

Essay Question▾

Describe in Detail

What are the major processes involved in hydrological cycle


Many processes work together to keep earth’s water moving in a cycle. 75 % of earth surface is covered with water. Steps involved in water cycle are-

  • Evaporation- Heat from the sun change from liquid to gas
  • Transpiration- Evaporation of water from leaves of plant
  • Condensation- Changing of water vapor in liquid form
  • Precipitation- Falling of water back to the surface of earth
  • On Ground- Runoff- Transfer of water in rivers and oceans
  • Infiltration- Water is soaked into soil

Question number: 101

Essay Question▾

Describe in Detail

Write the main functions and types of Cell Organelle Plastid?


Plastid are the part of cell and semiautonomous cell organelles, which are surrounded by double membrane envelope. Its main functions are related to take part in storage and synthesis of organic compounds, which present in plants. Types of plastids-

Plastids are of three main types- (i) Leucoplasts (ii) Chromoplasts (iii) Chloroplasts

(i) Leucoplasts-Colorless plastids, which present in many shapes. These are found in those organs where light is not present e. g. Underground roots and underground stems. Leucoplasts can be of many types like- Amyloplasts, Elaioplasts, nd Aleuroplasts.

(ii) Chromoplasts- Such plastids are found in colored other than green because presence of carotenoids but lack chlorophylls. For example-

Red chilies, Tomatoes. These can be of many types-

Phaeoplasts, Rhodoplasts and Chromatophores of blue green algae

(iii) Chloroplasts-These are green colored plastids, which are mainly used for the process of photosynthesis. A double membrane covers each chloroplast. Internally it contains stroma and thylakoids. Thylakoids are structural elements of chloroplasts. They are membrane lined flattened sacs. At places, they form stacks called grana.