CBSE Class 11 Biology Revision Notes Chapter 4

CBSE Class 11 Biology Revision Notes Chapter 4 – Animal Kingdom

Class 11 Biology Chapter 4 talks about the importance and classification of the Animal Kingdom. The Animal Kingdom is one of the largest in the five kingdoms classification proposed by ecologist R.H. Whittaker. In this chapter, students will learn about how biologists classify different species of animals on the basis of factors like level of organisation, symmetry, cell organisation, coelom, etc.

Extramarks Class 11 Biology Chapter 4 notes provide a comprehensive overview of the Animal Kingdom chapter by covering all the important topics that students need to know. Students can refer to these notes to comprehend this chapter in-depth.

Dissection of Chapter 4 Animal Kingdom

Notes of Class 11 Biology Chapter 4 give a brief understanding of multicellular eukaryotic species in the Kingdom Animalia. The chapter introduces the unique characteristics of each animal species. Animals enlisted in the animal kingdom obtain their energy either by feeding on other animals or plants. Kingdom Animalia is home to millions of identified species. However, a few species share similar characteristics, while others differ radically.

CBSE Class 11 Biology Chapter 4 notes summarise the characteristics of Phylum Porifera, Coelenterata, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata, and Chordata.

Basis of Classification

The animal kingdom classification is based on the different critical and essential characteristics such as level of organisation, symmetry, habitat, and pattern of organ systems.

Levels of Organisation

There are four levels of organisation:

• Cellular organisation level

• Level of tissue organisation

• Body Level of organisation

• Organ system level of organisation

Cellular Level of Organisation

At the level of cellular organisation, cells are arranged in loose aggregates. An example of a group of cellular organisations is that of sponges.

Tissue Level of Organisation

At the tissue level of organisation, cells that perform the same function are organised into tissues. An example of a group of tissue organisations is that of the coelenterates.

Organ Level of Organisation

At the level of organ organisation, tissues are grouped to form organs. Each organ is specialised for a particular function. An example of an organ-level organisation is Platyhelminthes.

Organ System Level of Organisation:

At the organ system level of organisation, organs associate to form functional systems such as arthropods, annelids, chordates, echinoderms, and molluscs. An example of an organ system level of organisation is the circulatory system.

Body Symmetry

There are three levels of body symmetry:

• Asymmetric

• Radial symmetry

• Bilateral symmetry

Asymmetrical Body Symmetry

Organisms under asymmetric body symmetry cannot be divided into two halves by a median plane. Sponges are an example of asymmetrical body symmetry.

Radial Body Symmetry

Organisms falling under radial body symmetry can be divided into two identical halves by any plane through the central axis. An example of radial body symmetry are coelenterates, echinoderms, and ctenophores.

Bilateral Body Symmetry

Organisms falling under bilateral body symmetry can be divided into two identical left and right halves through a single plane. An example of bilateral body symmetry is that of annelids and arthropods.

Germ Layers

Based on the germ layers, animals are classified as follows:

Diploblastic

The cells are arranged in two embryonic layers: outer ectoderm and inner endoderm. Also, an undifferentiated layer known as the mesoglea is present.

Triploblastic

The developing embryo has a third mesoderm of the germ layer, between the ectoderm and the endoderm.