An Overview of Ncert Books Class 11 Biology Chapter 6 Free Download
FAQs on Ncert Books Class 11 Biology Chapter 6 Free Download
1. Which topics from Chapter 6, Anatomy of Flowering Plants, are most important for the Class 11 Biology exam 2025-26?
For the CBSE Class 11 Biology exam, you should focus on these high-weightage topics from Anatomy of Flowering Plants:
The anatomical differences between dicot and monocot stems and roots. This is a very frequently asked question.
The process of secondary growth in dicot stems, including the roles of the vascular cambium and cork cambium.
The structure and function of complex permanent tissues like xylem and phloem.
Labelled diagrams of the transverse sections of a dicot stem, monocot stem, dicot root, and monocot root.
2. Differentiate between the anatomy of a dicot stem and a monocot stem. (5 Marks)
The key anatomical differences between a dicot stem and a monocot stem are:
Vascular Bundles: Dicot stems have vascular bundles arranged in a distinct ring (eustele), while monocot stems have them scattered throughout the ground tissue (atactostele).
Cambium: A strip of cambium is present between the xylem and phloem in dicot stems, making their vascular bundles 'open' and capable of secondary growth. In monocot stems, cambium is absent, so the bundles are 'closed'.
Ground Tissue: In dicot stems, the ground tissue is well-differentiated into cortex, endodermis, pericycle, and pith. In monocot stems, there is no such differentiation; it is a mass of parenchyma.
Pith: A large, well-developed pith is present in the centre of a dicot stem. Pith is absent in a monocot stem.
Hypodermis: The hypodermis is collenchymatous in dicot stems, providing flexible support. It is sclerenchymatous in monocot stems, providing rigid support.
3. What is secondary growth and why is it significant? Explain the role of the vascular cambium.
Secondary growth is the process that results in an increase in the girth or diameter of the stem and root of a plant, primarily in dicots and gymnosperms. It is significant because it provides structural support to the growing plant and increases the production of conducting tissues (xylem and phloem). The vascular cambium is the key meristematic layer responsible for this process. It is located between the primary xylem and primary phloem. During secondary growth, the cells of the vascular cambium divide to produce secondary xylem towards the inside and secondary phloem towards the outside, leading to the thickening of the stem.
4. How can the anatomy of a tree trunk be used to determine its age and the climate conditions it has faced?
The age of a tree can be determined by counting the annual rings in a cross-section of its trunk. Each ring represents one year of growth. This is possible because the activity of the vascular cambium is influenced by seasonal changes.
Springwood (Earlywood): In spring, the cambium is very active and produces a large number of xylary elements with wider vessels. This wood is lighter in colour.
Autumnwood (Latewood): In winter/autumn, the cambium is less active and forms fewer xylary elements with narrow vessels. This wood is darker and denser.
These two types of wood appear as a concentric ring, forming an annual ring. The width of these rings can indicate past climate conditions; wider rings suggest favourable conditions (good rainfall, sunlight), while narrower rings suggest stressful conditions like drought.
5. What are the three main tissue systems in flowering plants as per the NCERT syllabus?
Based on their structure and location, there are three main tissue systems in flowering plants:
The Epidermal Tissue System: This forms the outermost covering of the entire plant body. It includes the epidermis, stomata, and epidermal appendages (trichomes and hairs). Its main function is protection.
The Ground Tissue System: All tissues except the epidermis and vascular bundles constitute the ground tissue. It consists of simple tissues such as parenchyma, collenchyma, and sclerenchyma. In stems and roots, it includes the cortex, pericycle, and pith.
The Vascular or Conducting Tissue System: This system consists of the complex tissues, xylem and phloem, which are organised into vascular bundles. It is responsible for the transport of water, minerals, and food.
6. Why are vascular bundles in monocot stems described as ‘closed’?
The vascular bundles in monocot stems are described as ‘closed’ because they lack a layer of cambium between the xylem and phloem. The cambium is a type of lateral meristematic tissue responsible for secondary growth (increase in girth). Since monocots do not have this cambium, their vascular bundles cannot form secondary xylem and phloem. This means their growth in diameter is limited, and the vascular bundle is considered 'closed' to further growth.
7. What are the key anatomical differences between a dicot root and a monocot root?
The main anatomical differences between a dicot and monocot root are:
Number of Xylem Bundles: Dicot roots typically have a small number of xylem bundles, usually 2 to 6 (diarch to hexarch condition). Monocot roots have a large number of xylem bundles, usually more than six (polyarch condition).
Pith: In dicot roots, the pith is very small or completely absent. In monocot roots, a large and well-developed pith is present in the centre.
Secondary Growth: Dicot roots undergo secondary growth due to the formation of a cambium ring. Monocot roots do not undergo any secondary growth.
8. Why are stomata generally more numerous on the lower surface (abaxial side) of a dicot leaf?
Stomata are more numerous on the lower (abaxial) surface of a dicot leaf primarily to minimise water loss through transpiration. The upper (adaxial) surface is directly exposed to sunlight and heat, which would cause excessive evaporation if many stomata were present. By being located on the shaded lower side, the leaf can still effectively perform gaseous exchange (CO₂ intake and O₂ release) for photosynthesis while conserving water. This is a crucial adaptation for plants in terrestrial environments.
