CBSE Class 11 Biology Revision Notes Chapter 2

CBSE Class 11 Biology Revision Notes Chapter 2 – Biological Classification

Biological classification is an important chapter that gives an insight into how various organisms are categorised according to their similarities. Students will find that this chapter has many topics and terms to memorise. In order to prepare for this chapter in a better way, students can use revision notes provided by Extramarks that provide a summary of all the important concepts covered in the chapter. Students can conveniently access these notes from the Extramarks’ website.

Access class 11 Biology Chapter 2- Biological classification Notes

In this chapter, students will learn how different scientists at different points in history have tried to classify living beings into different categories based on certain properties. Aristotle was the first to propose the biological classification of plants and animals on the basis of simple morphological characteristics. Linnaeus later classified all living organisms into two kingdoms namely plants and animals. Later this was changed to a five-kingdom classification. Students will learn about the various characteristics of all the five kingdoms of organisms in this chapter.

Biological Classification

Biological classification is the process of categorising living organisms by certain similarities. Linnaeus identified two kingdoms of classification; he classified the animal kingdom organisms as Animalia and the organisms in the plant kingdoms as Plantae. They have certain limitations as well.

Five Kingdoms Rankings

RH Whittaker suggested the five kingdoms rankings. The classification goes as follows: Monera, Protista, Fungi, Plantae, and Animalia.

Kingdom Monera

The bacteria are significant members of the Kingdom Monera. The organisms found in this Kingdom are called prokaryotes. They can be found in extreme habitats such as hot springs, deserts, snow, and deep oceans. Some of them also act as parasites, needing a cell wall. They are divided into archaebacteria and eubacteria.

Archaebacteria

The cell wall structure of Archaebacteria differs from that of monerans. They can be thermoacidophilic, halophilic, and methanogenic. The category of methanogenic can be found inside the intestines of buffalo and cows, and they assist in producing biogas from animal dung.

Eubacteria

Eubacteria, known as true bacteria, is characterised by the existence of a rigid cell wall and a mobile flagellum. They contain blue-green algae and cyanobacteria and are similar to plants. They are also called photosynthetic autotrophs. 

Kingdom Protista

Kingdom Protista consists of single-celled eukaryotes. They are aquatic and have a real core delimited by the nuclear membrane. Their breathing can be aerobic and anaerobic and can produce sexually and asexually. They are divided into chrysophytes, dinoflagellates, euglenoids, slime moulds, and protozoans.

• Chrysophytes

Chrysophytes contain golden algae and diatoms and live in fresh and marine water bodies. They are generally unicellular flagellates and amoeboids.

• Dinoflagellates

Dinoflagellates are marine organisms that perform photosynthesis. They are of various colours like red, brown, yellow, and blue due to the coloured pigments present in their cells. Their cell wall is made up of cellulose, and they have two flagella. Some examples include gonyaulax catenella and noctiluca scintillans.

• Euglenoids

Euglenoids are found in stagnant water and are organisms found in freshwater. They are surrounded by a film that is rich in protein. They have both a short and long flagellum and can behave as autotrophic and heterotrophic organisms.

• Slime moulds

They form aggregates under favourable conditions known as plasmodium. They are saprophytic. They also form fruiting bodies in unfavourable conditions with spores. They have natural cell walls. Most of them contain chloroplasts, and they can synthesise their food.

• Protozoan like protest

They are heterotrophs and can act as both predators and parasites. They are of four types, they are:

• Amoeboid protozoa
• Flagellate protozoa
• Ciliated protozoa
• Sporozoa 

Kingdom Fungi

They are generally heterotrophic. The saprophytes thrive on dead organic matter, and the Parasites feed on living organisms. Some can live mutually with other organisms like algae and are called symbionts. They can reproduce through budding, fragmentation, fission, and spores. Asexual reproduction occurs through spores known as conidia, zoospores, or sporangiospores. Sexual reproduction takes place with the help of oospores, ascopores, and basidiospores, 

Kingdom Plantae

It includes all the eukaryotic photosynthetic, multicellular plants. Their primary pigment is chlorophyll, and the cell wall is made up of cellulose. They produce food through photosynthesis and reproduce by sexual and asexual means.

Kingdom Animalia

These organisms are multicellular and are heterotrophic, and eukaryotic. They have well-developed organ systems such as the skeleton, circulatory, reproductive, etc. They are bilaterally symmetrical and have well-established locomotive organs, and they breathe through gills, skin, etc. Blood, blood vessels, and the heart help in circulation, and they reproduce through the formation of gametes. 

Viruses

Viruses don’t stand a place in Whittaker’s five kingdom classification because they are acellular structures. They consist of either DNA or RNA surrounded by a protein cell. Viruses can cause severe damage and diseases to the host.

Viroids

They are infectious structures that are considered the smallest and have only nucleic acid without a protein shell.

Lichens

Lichens are the symbiotic coalitions of algae and fungi. The pair of fungi provides food and are autotrophic. The pair of mushrooms promote shelter and protection. 

Biology Notes for Class 11 Chapter 2 Free Download

The Notes of Class 11 Biology Chapter 2 are straightforward and guide students to achieve maximum scores in the examinations. The study materials can be downloaded from the official site of Extramarks and can be used by both the students and the teachers of Class 11 Biology.

Class 11 Biology Chapter 2 Biological Classification Notes Summary

Chapter 2 Biology Class 11 Notes deal with essential topics. The first section of the notes covers the different classifications of the Kingdoms developed by biologists Linnaeus and R.H. Whittaker. Linnaeus was the one to categorise the organisms based on two Kingdoms, the Animalia for animals and the Plantae for plants. Biologist Whittaker proposed the five kingdoms of classification. In the notes available at Extramarks, these Kingdoms are precisely discussed, which will help the students to learn faster and better. Important notes on the topics such as Monera, Fungi, Plantae, Animalia, Viruses, Viroids, Lichens, and many more are explained broadly.

Solved Questions from Class 11 Biology Chapter 2 Notes

Q 1. How many types of Protozoan-like Protists are there?

Ans: There are mainly four types of protozoans. They are as follows:

• Amoeboid protozoans have pseudopodia like amoeba.
• Flagellated protozoans are parasitic or free-living and cause diseases.
• Ciliated protozoans contain thousands of cilia that help in movement.
• Sporozoans are both parasitic and pathogenic and have spores.

Q 2. How many classes are there in Kingdom Fungi?

Ans: There are five main classes of the Kingdom Fungi, which are as follows:

• Asexual reproduction occurs in Phycomycetes or lower fungi like micro, Albugo, and rhizopus.
• Zygomycetes or conjugation fungi are the primitive group and initiate asexual reproduction.
• Deuteromycetes are also known as imperfect fungi. They do not engage in sexual reproduction.
• Basidiomycetes or club fungi have vegetative reproduction through fragmentation.
• Ascomycetes or sac fungi are both saprophytic and parasitic. Sexual reproduction occurs by ascospores in them, and asexual reproduction occurs by conidia.