Ecological Factors
Short Questions and Answers
One Mark Questions with Answers
1. Soil salinity is measured by
(a) porometer
(b) photometer
(c) conductivity meter
(d) calorimeter
Answer: (c) conductivity meter
2. The factor governing the structure of earth surface is
(a) topographic
(b) edaphic
(c) biotic
(d) temperature
Answer: (a) topographic
3.What is the main causative factor of desertification?
(a) developmental activities
(b) tourism
(c) overgrazing
(d) irrigated agriculture
Answer: (c) overgrazing
4. Prickly pear (Argemone mexicana) is an ecological indicator of
(a) iron rich soil
(b) poorly drained soil
(c) nitrate rich soil
(d) recently flooded soil
Answer: (d) recently flooded soil
5. Plants which can withstand wide range of temperature are called
(a) stenothermic
(b) monothermic
(c) mesothermic
(d) eurythermic
Answer: (d) eurythermic
6. Ephemerals are
(a) drought enduring plants
(b) drought resistant plants
(c) drought escaping plants
(d) drought evading plants
Answer: (c) drought escaping plants
7. Halophytes are peculiar in having
(a) pneumatophoric stem
(b) velamen tissue
(c) vivipary
(d) saline water
Answer: (c) vivipary
8. Heliophytes are plant growing in
(a) saline soil
(b) shade
(c) extreme dry condition
(d) full sunlight
Answer: (d) full sunlight
9. Study of interrelationships between environment and a community is known as
(a) synecology
(b) autecology
(c) phytoecology
(d) ecosystem
Answer: (a) synecology
10. A habitat with long severe winter and growing season restricted to a few months of summer forms
(a) Savannah
(b) Taiga
(c) Grasslands
(d) Tundra ecosystem
Answer: (d) Tundra ecosystem
11. Physical and chemical conditions of soil are studied under
(a) biotic factors
(b) edaphic factors
(c) climatic factors
(d) topographic factors
Answer: (b) edaphic factors
12. The science dealing with soil is called
(a) pedology
(b) aerology
(c) geology
(d) palaeontology
Answer: (a) pedology
Two Marks Questions with Answers
1. What do you mean by ecological factors? Mention the major ecological factors.
Answer: Environment is a complex of large number of living (biotic components) and nonliving (abiotic components). Each part, substance or stage of environment is known as environmental factor or ecological factor. Following are the four major ecological factors:
- Climatic factors.
- Physiographic or topographic factors.
- Edaphic factors.
- Biotic factors.
2. Define the terms holard, chresard and echard.
Answer: The total amount of water present in the soil is termed as holard. Of this, the amount of water that plants use is termed as chresard or available water. The remaining water which the plants cannot absorb is termed as echard or non-available water.
3. What are the effects of humidity on plant life and climate?
Answer: Following are some of the major effects of humidity on plant life and climate.
(a) Evaporation of water and its condensation and precipitation depends upon relative humidity.
(b) Humidity affects structure, form, and transpiration in plants.
(c) Plants like orchids, mosses and lichens depend on atmospheric humidity for the requirement of moisture.
4. How does wind influences plant life?
Answer: Following are common effects of wind on plants and environment.
- Wind helps in dispersal of pollen grains, seeds and fruits.
- It is a chief agent of soil erosion.
- High velocity wind, flowing constantly, causes mechanical damage and changes in plant morphology.
- The process of transpiration increases due to wind.
Three Marks Questions with Answers
1. What are the components of soil?
Answer: Soil is made of five major components. These include mineral matter, soil air, soil water, organic matter or humus and soil organisms.
(a) Mineral matter. There are three major types of soil particles, namely, clay, silt and sand. Clay particles are very small. These fit together very closely and, therefore, leave very less pore space. These spaces fill up with water easily. Hence, the clay soil becomes easily waterlogged. Sand particles are larger in size. These have large pore spaces. Most of the water quickly drains off and reaches deep into the soil. As a result, roots spread and also reach a great depth. The mixture of clay, silt and sand is known as loam. It is a fertile soil because it contains available nutrient elements in sufficient amounts.
(b) Soil air. The amount of soil air and its distribution depends upon the size of the soil particles. The soil made of large particles has more air while the soil with small particles has lesser pore space and hence lesser amount of air. The main components of soil air are CO2, oxygen and nitrogen. The concentration of CO2 in the soil increases as the depth increases while the amount of oxygen decreases. Oxygen in the soil is essential for the respiration of roots. In waterlogged soils, plants die due to deficiency of oxygen. Higher concentration of CO2 is toxic for the roots.
(c) Soil water. The amount of water in the soil depends upon the size of the soil particles, their volume and aggregation. The pore space between large sand particles is more and, therefore, water drains quickly.
2. What are the different types of soil water?
Answer: The major source of water for the soil is rain water. Most of this water flows and collect into rivers and lakes. This is termed as run off water. The remaining water gradually percolates deep into the soil and occurs in the following forms:
i). Hygroscopic water: This form of water occurs as a thin film around the soil particles. AS such hygroscopic water is not useful for the plants and is termed as unavailable water.
ii). Capillary water: This form of water is present in the thin and narrow capillaries formed between the soil particles. This is the major source of water for the plants. Thus it is termed as available water.
iii). Gravitational water: Some amount of water, percolates deep into the soil due to gravitational force. This forms ground water or water table.
iv). Chemically bound water: This water occurs in the form of hydrated oxides of iron, aluminium, silicon etc.
3. What is soil profile? Mention the different horizons.
Answer: Soil shows many layers or horizons placed one over the other. The sequence and nature of these layers or horizon is termed as soil profile. The smallest three dimensional volume of soil which shows all the horizons is known as pedon. A typical soil profile consists of five horizons.
(a) ”O” horizon-This is the uppermost horizon made of organic matter. It may further be divided into two sub-layers. (a). O1 region- This is the top most layer. It consists of freshly added organic matter such as dead leaves, branches, flowers, fruits etc. (b). O2 region- This layer is present below the freshly added organic matter. The organic matter in this layer is in different stages of decay.
(b) ”A” horizon- This horizon is present just below ”O” horizon. It is rich in mineral elements. A large amount of humus, i.e., completely decomposed organic matter, is also present in this region. It shows downward loss of soluble salts, clay, aluminium, iron etc. Therefore, this region is also called zone of leaching or zone of eluviation.
(c) ”B” horizon- This horizon is often dark in colour due to accumulation leached substances like clay ,aluminium, iron etc from horizon”A”. Therefore, this region is also called zone of accumulation or zone of illuviation. Horizons O, A and B are together known as top soil while horizons A and B constitute mineral soil or solum.
(d) ”C” horizon- This is a layer of mineral substances. However, it consists of only rocks. This horizon is also termed as sub-soil.
(e) ”R” horizon- This is the lowermost layer. It is made of bed rocks.
4. What is photoperiodism?
Answer: The duration of light affects flowering and plants. This is termed as photoperiodism. Plants have been grouped into following three categories on the basis of their requirement of critical photoperiod.
- a) Short-day plants: These plants flower when the photoperiod (length of the day) received by them is less than the critical limit (tobacco, soybean, xanthium)
- b) Long-day plants: These plants require a photoperiod more than the critical limit of flowering. These plants include beetroot, radish etc.
- c) Day-neutral plants: Flowering in these plants is not affected by length of the day or photoperiod (cottons, sunflower, tomato etc.)