The correct option is (a).
Explanation
Forest ecosystems are characterized by a distinct vertical structure known as stratification. This structure consists of different layers of vegetation arranged according to height, which influences the distribution of sunlight and microclimatic conditions within the forest.
Statement-wise Analysis:
- Statement 1 is Correct: The crown is the branchy part of a tree located above the stem (trunk). It consists of leaves, branches, and reproductive structures. The shape and size of the crown vary significantly across different tree species.
- Statement 2 is Incorrect: The roof-like structure formed by the branches of tall trees over the other plants is called the canopy. The root system refers to the underground network of roots responsible for anchoring the tree and absorbing water and nutrients.
- Statement 3 is Incorrect: The forest floor is not the only layer; it is the bottom-most layer consisting of decomposing organic matter, herbs, and fungi. A typical forest exhibits multiple layers, including the canopy, understory (shrubs and small trees), and the forest floor.
Key Takeaway:
A forest is structurally divided into vertical layers: the crown constitutes the top part of individual trees, the canopy forms the upper roof, and the forest floor is the ground layer rich in decomposers.