This set of Class 12 Biology Chapter 14 Multiple Choice Questions & Answers (MCQs) focuses on “Ecosystem – Xerarch Succession”.
1. What is a medium water condition called?
a) Mesozoic
b) Mesic
c) Hydric
d) Xeric
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Explanation: Mesic means an area having a moderate or well-balanced supply of moisture. The hydrarch, as well as xerarch succession finally leads to the formation of a mesic community. It is neither to wet nor too dry.
2. What are conditions having too much dryness called?
a) Xeric
b) Hydric
c) Mesic
d) Mesozoic
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Explanation: The habitat having too much dryness is known as a xeric habitat. It is deficient in moisture and is characterized by limited water availability. Desert region is an example of a xeric habitat.
3. What are conditions having too much hydration called?
a) Mesic
b) Hydric
c) Mesozoic
d) Xeric
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Explanation: The habitat having an excess of hydration is known as a hydric habitat. They have wet soils and are characterized by an abundance of moisture. Wetland area is an example of a hydric habitat.
4. What is the sequence of successional stages occurring on bare rocks called?
a) Biological succession
b) Ecological succession
c) Hydrarch succession
d) Xerarch succession
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Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. It is also known as xerosere and starts in a newly formed rocky area.
5. Who acts as a pioneering species in a xerarch succession?
a) Phytoplankton
b) Pteridophytes
c) Lichens
d) Bryophytes
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Explanation: The first biotic community to invade a bare land or area is known as the pioneer community. In a xerarch succession, lichens in the temperate region act as pioneering species. Some examples of lichens are Rinodina, Lecanora, Parmelia, etc.
6. Who replaces the lichens in a xerarch succession?
a) Herbs
b) Mosses
c) Shrubs
d) Forest
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. The pioneering species lichens are replaced by mosses in a xerosere. Some examples of mosses are Tortula, Grimmima, Polyerichum, etc.
7. In a xerarch succession, who secrete acids to dissolve rock?
a) Shrubs
b) Herbs
c) Mosses
d) Lichens
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. In a xerarch succession, the pioneering species lichens release acids to dissolve rocks. This helps in weathering and soil formation.
8. In a xerarch succession, who helps in weathering and soil formation?
a) Mosses
b) Herbs
c) Lichens
d) Shrubs
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. In a xerarch succession, the pioneering species lichens release acids to dissolve rocks. This helps in weathering and soil formation.
9. Who replaces the mosses in a xerarch succession?
a) Angiosperms
b) Reptiles
c) Shrubs
d) Herbs
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. The mosses are replaced by the herbaceous plants in a xerarch succession. Some examples of xeric grasses are Aristida, Solidage, Poa, etc.
10. Who replaces the herbaceous plants in a xerarch succession?
a) Angiosperms
b) Lichens
c) Shrubs
d) Forest
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. The herbaceous plants are replaced by the shrubs in a xerarch succession. Some examples of shrubs are Phytocarpus, Rhus, etc.
11. Who replaces the shrub stage in a xerarch succession?
a) Herbs
b) Forest
c) Lichens
d) Mosses
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. The shrub stage is replaced by a forest in a xerarch succession. The trees found in the forest are Acacia, Prosopis, Boswellia, etc.
12. What are pioneers?
a) The organisms of the second seral stage
b) The organisms of the third seral stage
c) The organisms of the first seral stage
d) The organisms of the fourth seral stage
View Answer
Explanation: The first biotic community to invade a bare land or area is known as the pioneer community. These are the organisms of the first seral stage. They further grow and expand to form a climax community.
13. Xerarch succession is observed in which of the following area?
a) Terrestrial area
b) Desert area
c) Aquatic area
d) Marshy area
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. It occurs in an area where there is less amount of moisture. It is mostly observed in the desert area.
14. In a plant succession, which is the last stabilized community?
a) Pioneer community
b) Seral community
c) Ecosphere
d) Climax community
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Explanation: The changes in the community are constant, orderly and sequential. These changes lead to the formation of a stable, self-perpetuating and final biotic community that developed during the end of biotic succession known as a climax community.
15. What will happen to biomass in an ecological succession from pioneer to climax community?
a) Increase and the decrease
b) Increase
c) Decrease
d) Become zero
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Explanation: Ecological succession is the gradual change in the species composition of a given area which can be predicted. Biomass is the total organic material required for energy production.
16. Which of the following is the correct sequence of xerarch succession?
a) Forest → Shrubs → Herbs → Mosses → Lichens
b) Shrubs → Herbs → Mosses → Forest → Lichens
c) Lichens → Mosses → Herbs → Shrubs → Forest
d) Lichens → Mosses → Shrubs → Forest → Herbs
View Answer
Explanation: The sequence of successional stages occurring on bare rocks is known as xerarch succession. It mostly starts with the invasion of lichens and ends with the formation of the forest. The pioneering species grow with time leading to a formation of a climax community called a forest.
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