THE LIVING WORLD
The fundamental concept of “What is Living” is elaborately discussed in the chapter – The Living World – Term I.
The chapter includes details on Taxonomic Categories, Diversity in the Living World, Taxonomical Aids, etc. Our Living World is a wide and rich variety of diversity. There are millions and millions of flora and fauna present on earth, with equally large numbers of species. The study of plants, animals and their species is known as Taxonomic Study. This study is used in fields like industrial usage, forestry, agriculture. To facilitate mapping, categorization and naming of the organism and its classification, the taxonomists have developed a variety of taxonomic aids.
What are the topics covered in the Class 11 Biology Chapter 1 : The Living World – Term I
The chapter answers mostly about the nature of living itself. Broadly, the chapter talks about –
- Biodiversity
- Need for classification of Biodiversity
- The three domains of life
- Concept of species
- Taxonomical hierarchy
- Binomial nomenclature.
Exercise
1. Why are living organisms classified?
Answer – There are thousands and millions of species of plants and animals in the world. While we name the plants and animals in our area with some common and local names. These names vary from one place to another. To avoid confusion and standardize the naming system of living organisms so that an organism is known by one name all over the world, we need to classify organisms. Also, it is nearly impossible to study all the living organisms, classification makes it possible when organisms are grouped into convenient categories based on observable characteristics.
2. Why are the classification systems changing every now and then?
Answer – Though plants and animal kingdoms have been constant under all different systems, classification systems for living organisms have undergone many changes over time. Because besides gross morphology being used as a criterion, a need was also felt for including characteristics like cell structure, nature of the wall, mode of nutrition, habitat, modes of reproduction, evolutionary relationships, etc, into the classification system.
3. What different criteria would you choose to classify people that you meet often?
Answer – The people we meet often can be categorized by their characteristics like skin colour, gender, name, hobbies, nature, education and career.
4. What do we learn from the identification of individuals and populations?
Answer – By the identification of individuals and populations, we learn their native place, mother language, skin colour, sex, religion, caste, food culture, music and traditions.
5. Given below is the scientific name of Mango. Identify the correctly written name.
Mangifera Indica
Mangifera indica
Answer – The correct scientific name for Mango is Mangifera indica, where Mangifera is the generic name and indica is its species epithet.
6. Define a taxon. Give some examples of taxa at different hierarchical levels.
Answer – A taxon is a hierarchy level in the classification of organisms. The taxa can indicate categories at different levels. Some examples of taxa at different hierarchical levels are –
| Kingdom | Animalia |
| Phylum/Division | Chordata |
| Class | Mammalia |
| Order | Primata |
| Family | Hominidae |
| Genus | Homo |
| Species | Sapiens |
7. Can you identify the correct sequence of taxonomical categories?
(a) Species → Order → Phylum → Kingdom
(b) Genus → Species → Order → Kingdom
(c) Species → Genus → Order → Phylum
Answer – From the above-given options, (a) and (c) are the correct options.
8. Try to collect all the currently accepted meanings for the word ‘species’. Discuss with your teacher the meaning of species in the case of higher plants and animals on one hand, and bacteria on the other hand.
Answer – Species are the group of individual organisms with fundamental similarities and capable of exchanging genes or interbreeding. This is the most basic and principal unit of classification.
Meaning of species in –
Higher plants and animals – The boundary or criteria for interbreeding and reproductive isolation among species can be used for its classification.
Bacteria – The similar gene pool can be used to classify the species in bacteria.
9. Define and understand the following terms:
(i) Phylum (ii) Class (iii) Family (iv) Order (v) Genus
(i) Phylum – It is the group of related classes sharing common characters which comes above Class and below Kingdom. Example- Chordata, Arthropoda, Angiospermae, etc.
(ii) Class – It is the group of related orders of the organisms. It comes above Order and below Phylum. Example- Class Mammalia has orders like Primata and Carnivora.
(iii) Family – Family has a group of related genera, with fewer similarities as compared to species and genus. It comes above Genus and below Order. Example- Family Felidae includes genera like Panthera and Felis.
(iv) Order – Order is the assemblage of families with similar characters. Being a higher taxon, it has fewer similarities as compared to lower taxa. It comes above Family and below Class. Example- Order Carnivora includes families like Felidae and Canidae.
(v) Genus – Genera are the aggregates of related species. It has more similar characters in comparison to species of other genera. For example- potato and brinjal being different species come under the same genera Solanum.
10. How is the key helpful in the identification and classification of an organism?
Answer – The key is a taxonomical aid used for the identification of plants and animals based on their similarities and dissimilarities. They are based on contrasting characters in pairs called couplets. It represents the choice made between two opposite options. This results in the acceptance of only one and rejection of the other when the species, families or genera are identified. Each statement is called a lead. Keys are analytical.
11. Illustrate the taxonomical hierarchy with suitable examples of a plant and an animal.
Answer – The table below describes the taxonomical hierarchy of a plant Mango and an animal Human –
| Common Name | Biological Name | Genus | Family | Order | Class | Phylum/Division | Kingdom |
| Mango | Mangifera indica | Mangifera | Anacardiaceae | Sapindales | Dicotyledonae | Angiospermae | Plantae |
| Human | Homo sapiens | Homo | Hominidae | Primata | Mammalia | Chordata | Animalia |