Class XI Biology (CBSE – 2025–26 Academic Session)

Section A – Diversity of Living Organisms

This section focuses on the diversity of life forms and the scientific need for classification. Since millions of organisms exist on Earth, classification helps in systematic study, identification, and understanding evolutionary relationships.

The Five Kingdom Classification proposed by R.H. Whittaker is discussed in detail.

 The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. The classification is based on cell structure (prokaryotic or eukaryotic), level of organization (unicellular or multicellular), mode of nutrition (autotrophic or heterotrophic), reproduction, and phylogenetic relationships.

Monera includes prokaryotic organisms such as bacteria and cyanobacteria. Protista includes mostly unicellular eukaryotes such as Euglena and Amoeba. Fungi are multicellular organisms with chitin cell walls and saprophytic nutrition. Plantae includes autotrophic multicellular organisms with cellulose cell walls. Animalia includes multicellular heterotrophic organisms without cell walls.

This section also explains plant groups such as Algae, Bryophyta, Pteridophyta, Gymnosperms, and Angiosperms, highlighting their structural and reproductive differences.

Understanding this section helps students grasp biodiversity, evolutionary history, and ecological relationships.

Questions – Section A

Why is biological classification necessary for studying living organisms?

Explain the basis of the Five Kingdom Classification system.

Differentiate between Monera and Protista.

What are the major groups of algae? Mention their distinguishing features.

Compare Gymnosperms and Angiosperms.

Section B – Structural Organisation in Plants and Animals

This section explains the external and internal structure of plants and animals. It emphasizes how structure is closely related to function.

In Morphology of Flowering Plants, the structure of root, stem, leaf, inflorescence, flower, fruit, and seed is described. Different types of roots and leaf modifications are also discussed.

In Anatomy of Flowering Plants, the internal tissue organization is explained. Meristematic tissues are responsible for growth, while permanent tissues perform specialized functions. Vascular tissues (xylem and phloem) help in transportation of water, minerals, and food.

The section on Structural Organisation in Animals focuses mainly on the frog as a model organism. It explains various organ systems such as digestive, respiratory, circulatory, nervous, and reproductive systems.

This section builds a clear understanding of how plant and animal bodies are organized at tissue and organ levels.

Questions – Section B

Describe the different types of roots found in flowering plants.

Explain the structure and function of xylem and phloem.

Describe the digestive system of a frog.

What are meristematic tissues? Mention their types and functions.

Explain the structure and functions of a leaf.

Section C – Cell Structure and Physiology

This section deals with the cell as the basic unit of life and the physiological processes that maintain life.

In Cell: Structure and Function, students learn about prokaryotic and eukaryotic cells, cell organelles such as mitochondria, ribosomes, Golgi apparatus, lysosomes, and nucleus. The differences between plant and animal cells are clearly explained.

In Biomolecules, the chemical composition of cells is discussed. Carbohydrates, proteins, lipids, and nucleic acids are explained in terms of structure and function. Enzymes and their role in biochemical reactions are also covered.

Plant Physiology includes processes such as photosynthesis, respiration, and plant growth regulators.

Human Physiology includes topics such as breathing and exchange of gases, blood circulation, excretion, locomotion, neural control, and endocrine coordination.

This section provides deep insight into how living organisms function at cellular and systemic levels.

Questions – Section C

Differentiate between prokaryotic and eukaryotic cells.

Explain the process of photosynthesis.

Describe the structure and working of the human heart.

What is the cell cycle? Explain its phases.

What are hormones? Explain their functions in the human body.