NCERT Solutions for Class 11 Biology Chapter 1 - The Living World

Chapter 1 'The Living World' elaborated in the NCERT Solutions for Class 11 Biology explains the fundamental concepts of Biology, like what is Living, Diversification in the World of Living, Taxonomic Classifications, Taxonomical Aids, and others. The living world is substantial in terms of variety as millions of plants and animals have been discovered and described so far, but an innumerable variety of species remains uncovered.

The chapter further talks about the taxonomic studies conducted on different species of plants and animals and the usefulness of those studies in forestry, agriculture, industry, and learning about our natural resources and the diversity it has. Multiple taxonomical aids have been developed by Taxonomists that assist in identifying, naming, and classifying organisms. The sub-topics discussed in this chapter are given below.

• What does Living Mean?

Different aspects of the living world have been taught in this section. Students will find explanations on the characteristics of living organisms that vary concerning size, colour, habitat, physiological, and morphological attributes.

• Diversity in the Living World

Biologists develop certain protocols according to which living organisms are recognized, named (nomenclature), and classified. This subtopic deals with these protocols, which has led to the emergence of different kinds of studies of diversity found in living organisms.

• Taxonomic Categories

Under Taxonomic Categories, various aspects of living organisms are classified and talked about are referred to as Taxonomy.

• Taxonomical Aids

In this subtopic, Taxonomical Aids evolved by biologists have been discussed. These taxonomical aids mean the basis of resemblances and distinctness in every organism according to which each of them is identified and given a biological or scientific name.

Q1. Why are living organisms classified?
Answer:Living organisms are classified because of the following reasons

1. Due to a large variety of life forms on earth, it becomes difficult to study each of the species, thus scientists classify these species into larger groups, wherein by studying a group, we can deduce the characteristics of all the species. Hence living organisms are classified for the ease of studying them.

2. Classifying organisms into groups and sub-groups may also aid in establishing evolutionary relationships between them.

Q2. Why are the classification systems changing every now and then?
Answer: Earth is home to numerous species of plants, animals, and microbes. The exact count of these life forms is still unknown. Scientists have discovered many species present on Earth. These have been properly named and classified as per the existing classification systems. However, there are still so many species to be discovered. Whenever new species are discovered the classification systems are modified according to the requirements. Therefore, the classification systems are always dynamic and they keep on changing as per the needs.

Q3. What different criteria would you choose to classify people that you meet often?
Answer: The people that we often meet can be classified on the basis of their sex or gender, the age group in which they fall, profession, education, hobbies, etc.

Q4. What do we learn from the identification of individuals and populations?
Answer: The identification of individuals based on their characteristics helps us to know how an individual differs from the other members of the population and at what points it is similar to the population. It also helps us in deriving relationships between individuals of different populations. Such relationships help in classifying organisms in their right groups. Learning the characteristics of populations aid in the study of that population as well as how it can be related to the other populations. Through this practice, we can establish evolutionary relationships between different populations.

Q5. Given below is the scientific name of Mango. Identify the correctly written name.
1.Mangifera Indica 2.Mangifera indica

Answer: The correct scientific name of mango is Mangifera indica. As per the binomial system of nomenclature, the first name in a scientific name represents the genus while the second name represents the specific epithet. The scientific name is always written in italics. The first letter of the genus name is written in capitals while that of the specific name is written in small letters.

Q6. Define a taxon. Give some examples of taxa at different hierarchical levels.
Answer: Taxon refers to a particular level of hierarchy in the classification of living beings. The examples of taxa at different hierarchical levels are species, genus, order, family, phylum, and kingdom.

Q7. Can you identify the correct sequence of taxonomical categories:
 

The correct sequence of taxonomic categories from lowest to highest is species, genus, family, order, class, phylum, kingdom. Thus, A and C represent the correct sequence of taxonomic categories with some categories missing in between while B is incorrect as the genus is given before species.

Q8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in case of higher plants and animals on one hand, and bacteria on the other hand.
Answer: Species can be defined in various ways such as

1. Species refer to a group of individuals similar in their fundamental characteristics and can interbreed among themselves.
2. Species is the basic unit of classification which assembles individuals who share a common genetic setup.
3. Species refer to a natural group of individuals similar in morphology, physiology, anatomy, cytology, etc.
4. Since, higher plants and animals show sexual reproduction extensively, in their case first definition of species is applicable i.e. species refers to a group of individuals similar in their fundamental characteristics and can interbreed among themselves. On the other hand, in the case of bacteria, the second and third definitions are applicable.

Q9. Define and understand the following terms: 1. Phylum
Answer: Phylum - A phylum is a large group of animals which is formed of one or more classes. The term phylum is replaced by division in the case of plants. For example, the phylum chordate of animals contains mammals, aves, reptiles, amphibians, etc.

Q9. Define and understand the following terms:2. Class
Answer: Class- It is a taxonomic group higher than order and lower to phylum. A class is made of one or more related orders. For example, the class dicotyledonous of flowering plants contain all dicots which are grouped into several orders like rosales, Solanales, etc.

Q9. Define and understand the following terms: 3. Family
Answer: Family - It refers to that taxonomic category that contains one or more genera. For example, the family Solanaceae contains a number of genera like Solanum, Withania, Datura, etc. All genera of a family are related through some common features or correlated characters.

Q9. Define and understand the following terms: 4. Order
Answer: Order- It is the taxonomic category higher to family and lower to class. An order consists of one or more groups of families which share certain common characteristics. For example, families Felidae and Canidae are included in the same order carnivore.

Q9. Define and understand the following terms: 5. Genus
Answer: Genus- A genus is a group of related species which resemble one another in certain correlated characters. All species of the genus are presumed to have evolved from a common ancestor. The animals like lion, tiger, leopard are closely related species and placed in the same genus Panther.

Q10. How is a key helpful in the identification and classification of an organism?
Answer: A taxonomic key refers to an artificial analytical device used for identifying organisms. Usually, in a key, two contrasting characters are used. The one present in the organism is chosen while the other is rejected. Each statement of a key is called a lead. Separate taxonomic keys are used for each taxonomic category like species, genus, family, etc. Keys are generally analytical in nature.

Q11. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
Answer: Taxonomical hierarchy refers to the classification of organisms into a definite sequence of taxonomic categories starting from the kingdom and going up to species. The illustration of the taxonomic hierarchy is given below.