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Showing posts with label XI Biology. Show all posts

The Living World - Solutions of CBSE Class 11 NCERT Biology Chapter 1 Exercise Questions

 

CBSE Class 11 Biology - NCERT Solutions

Unit 1: Diversity in The Living World

Chapter 1, The Living World

 Solutions of CBSE Class 11 NCERT Biology Textbook Lesson 1 Exercise Questions

Question 1: Why are living organisms classified?
Solution: Organisms are classified because of the following reasons:
(i). Easy identification.
(ii). Study of organisms of other places.
(iii). Study of fossils.
(iv). Grouping helps in study of all types of organisms while it is impossible to study individually all of them.
(v). It brings out similarities and dissimilarities.
(vi). They help in knowing relationships among different groups.
(vii). Evolution of various taxa can be known.

Question 2: Why are classification systems changing every now and then?
Solution: Scientific study has been ever progressing due to continuous addition of newer tools and techniques. Earlier workers relied on only habitat and habits for classifying organisms. External morphology then became an important tool for classification. Anatomy and then embryology were used in classification. Subsequently cellular structure, chromosomes, biochemical analysis and now DNA matching are being carried out to find relationships and classify organisms. Therefore, classification systems have been changing, rather evolving with time. They have never been static.

Question 3: What different criteria would you choose to classify people that you meet often?
Solution: Different criteria are:
(i). Family members.
(ii). Relatives.
(iii). Family friends.
(iv). School mates.
(v). Classmates.
(vi). Adults, seniors, same age and juniors.
(vii). Sex.
(viii). Height.
(ix). Playmates.

Question 4: What do we learn from identification of individuals and populations?
Solution: Individuals: Each individual possesses a specific combination of traits not found in other members of the population.
Populations:
(i). Each population is reproductively isolated.
(ii). Members of a population interbreed amongst themselves.
(iii). Members of a population resemble one another more than they resemble members of other populations.
(iv). Karyotype is similar in all the individuals of a population.
(v). There is a complete anatomical similarity amongst members of a population.

Unit 1: Diversity in The Living World

Lesson 1, The Living World

CBSE Class 11 Biology NCERT Solutions of Chapter 1 Exercise Questions

Question 5: Given below is the scientific name of Mango. Identify the correctly written name name Mangifera Indica, Mangifera indica.
Solution: Mangifera indica.

Question 6: Define a taxon. Give some examples of taxa at different hierarchical levels.
Solution: Taxon is a unit of classification which may represent any level of grouping of organisms based on certain common characteristics like Maize (species), Roses (genus), grasses (family), conifers (order), dicots (class), seed plants (division), etc.  The term was introduced for the first time by ICBN during 1956. Mayr (1964) has defined taxon to be a taxonomic group of any rank that is sufficiently distinct to be worthy of being assigned to a definite category. Simpson (1961) recognises taxon to be a group of real organisms recognised as a formal unit at any level of hierarchical classification. Examples,
Division  - Angiospermae
Class - Monocotyledonae
Order - Poales
Family - Poaceae
Genus - Triticum
Species - aestivum

Question 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
Solution: (c).
Species----> Genus----> Order----> Phylum
OR
Species---> Genus---> Family---> Order---> Class---> Phylum---> Kingdom.

Question 8: Try to collect all the currently accepted meaning 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.
Solution:
Species
(i). It is a natural population or group of natural populations of individuals having similar morphology, anatomy, physiology and cytology.
(ii). It is a basic unit of classification where individuals share a common genetic set up.
(iii). Species is an assemblage of structurally similar individuals which interbreed freely amongst them but are reproductively isolated from members of other species.
Higher Plants and Animals
Higher plants and animals are sexually reproducing organisms.  The criterion of reproductive isolation can be used for them. Therefore, third definition of the species given is applicable to them. Examples, Panthera leo (lion), Panthera tigris (tiger).
Bacteria
The criterion of free interbreeding and reproductive isolation cannot be applied in thier case as they do not reproduce sexually. Only the first definition of the species given above can be applied for them.

Question 9: Define and understand the following terms: (i). Phylum (ii). Class (iii). Family (iv). Order (v). Genus
Solution:
(i) Phylum: It is a higher grouping of organisms which is immediately below that of kingdom and possess some similar correlated characters, e.g., jointed appendages in arthropoda.
(ii) Class: It is a taxonomic grouping of organisms higher than order and lower than phylum. Class is taxon that consists of one or more orders of organisms all of which possess some similar correlated characters, e.g., Order Primata comprising monkey, gorilla and gibbon is put along with order Carnivora representing tiger, cat and dog. Both are placed in class Mammalia.
(iii) Family: Family is a grouping of organisms which is immediately below that of order and above that of genus. Family is a taxonomic category that consists of one or more genera of organisms all of which have some common correlated characters not found in genera of other orders. Among plants for example, three different genera Solanum, Petunia, and Datura are placed in the family Solanaceae. Among animals for example, genus Panthera comprising lion, tiger, leopard is put along with genus, Felis (Cats) in the family Felidae.
(iv) Order: Order is a taxonomic category having one or more families of organisms all of which possess some specific correlated characters not found in others, the families felidae and canidae are included under the order carnivora alongwith hyaenidae (hyaenas) and ursidae (bears).
(v) Genus: Genus is a grouping of organisms having one or more species all of which have common ancestry and share some common correlated characters, e.g., potato, tomato, and brinjal are there different species but all belong to the genus Solanum. Lion (Panthera leo), leopard (Panthera pardus), and tiger (Panthera tigris) with several common features, are all species of the genus Panthera.

Unit 1: Diversity in The Living World

Chapter 1, The Living World

CBSE Class 11 NCERT answers of Chapter 1 Biology textbook exercise questions

Question 10: How is key helpful in identification and classification of an organism?
Solution: Key is a table of alternate characteristics arranged sequence wise which through selection and rejection is used in classification and identification of organisms.
Classification: Keys are available for knowing the phylum / division, class, order, and family of the organisms on each system of classification. With thier help every type of organism can be classified, whether it is known or unknown.
Identification: After knowing the family, identification key is used to know the genus and then the name of the species. If the organism is not already recorded, efforts ares made first to check and recheck about its discovery and then given it a name.

Question 11: Illustrate the taxonomic hierarchy with suitable examples of a plant and an animal.
Solution: Taxonomic hierarchy is the classification of organisms in a definite sequence of taxonomic categories in a descending order starting with kingdom and ending in species.
Kingdom---> Phylum / Division---> Class---> Order---> Family---> Genus---> Species.


The table (Figure) below is examples of the taxonomic hierarchy of mango (plant) and human (animal):
Taxonomic hierarchy of mango (plant) and human (animal)
                
 For more please visit

NCERT Solutions of CBSE Class XI Biology - Chapter 2, Biological Classification

 

CBSE Board, Class 11 Biology

UNIT I : DIVERSITY IN THE LIVING WORLD

Chapter 2, Biological Classification

NCERT solutions of Biology Chapter 2 exercise questions


To see answers of previous questions (1 - 6) visit:

Class 11 Biological Classification - CBSE Guide and Answers of NCERT Biology Chapter 2 Exercise Questions (1 - 6)

Question 7: Plants are autotrophic. Can you think of some plants that are partially heterotrophic?
Solution: Plants contain chlorophyll. But some plants show heterotrophic mode of nutrition. They are:
(a) Insectivorous Plants: Plants have specialised leaves to trap insects. The trapped insects are killed and digested by proteolytic enzymes secreted by the epidermis of the leaves. Example - Pitcher plant, Nepenthes, etc.
(b) Parasitic Form: Cuscutta develops haustoria, which penetrates into the vascular bundles of the host plant to absorb water and solutes.
Question 8: What do the terms phycobiant and mycobiant signify?
Solution: Lichens are the symbiotic association between algae and fungi. The algal partner is called phycobiant whereas mycobiant refers to fungal partner of lichen thallus. Phycobiant makes food while mycobiant provides protection and reproduction to lichen.
Question 9: Give a comparative account of the classes of Kingdom Fungi under the following:
(i) Modes of nutrition, (ii) Modes of reproduction
Solution:
Characters
Phycomycetes
Ascomycetes
Basidiomycetes
Deuteromycetes
Mode of Nutrition
Saprophytic and Parasitic (obligats)
Saprophytic parasitic or coprophilous
Saprophytic and Parasitic
Mostly decomposes, some are Saprophytic and Parasitic
Mode of Reproduction
(a) Asexual Reprodn

(b) Sexual Reprodn
(a) Asexual reproduction through zoospores and aplanospores produced in sporangia
(b) By isogam or oogamy
(a) Asexual spore formed outside sporangium in chain called conidia.
(b) By fusion of compatible gametes or +ve & -ve strain hykhae.
(a) Basidiospore formed on a club shaped basidium exogeneously.
(b) Compatible nuclei fuse to form zygote.
By conidia.


Absent.

Question 10: What are the characteristic features of Euglenoids?
Solution: Euglenoids show the following distinguishing characters:
1. Fresh water, free-living found in ponds and ditches.
2. Absence of cell-wall but contains flexible pellicle made up of protein.
3. All the euglenoids have one or two flagella which help in swimming.
4. Bear a red pigmented eye spot and a gullet near the base of flagellum.
5. Some are green and holophytic like other plants. Few are non-green and saprobic, some are like holotrophic animals.
6. Store carbohydrates in the form of paramylum.
7. The photosynthetic pigments are similar to green algae-chlorophyll a, chlorophyll b, and carotenoids.
Question 11: Give a brief account of viruses with respect to their structure and nature of genetic material. Also name four common viral diseases.
Solution: Viruses are ultramicroscopic infectious particles or smallest entities, composed of nucleoproteins. The structural components of viruses are - Nucleoid, Capsid, and Envelope.
Nucleoid: It represents the viral chromosome. Nucleoid or viral chromosome is made of a single molecule of nucleic acid which is either DNA or RNA but never both. DNA containing viruses are called deoxyviruses while RNA containing viruses are termed as riboviruses. It may be linear or circular with various degrees of coiling.  
Capsid (Sheath, Coat): It is the proteinaceous covering around the virus which protects the nucleoid from damage from physical and chemical agents. It consists of a number of subunits called capsomeres or capsomers.
Envelope: It is a loose membranous converting that occurs in some animal viruses, rarely plant and bacterial viruses. Envelope consists of proteins from (virus), lipids and carbohydrates (from host). Examples are HIV, Herpes Virus, etc.
Enzymes: Enzyme lysozyme is present in the region that comes in contact with the host cell in bacteriophages. Other enzymes are neuraminidase in Influenza Virus, RNA polymerase, RNA transcriptase, reverse transcriptase.
The structural forms found in viruses are mainly three types - helical (elongate body, e.g., TMV), cuboidal (short broad body with rhombic, rounded, polyhedral shape, e.g., Polymyelitis virus) and binal (with both cuboidal and helical parts, e.g., many bacteriophages like T2).
Genetic Material: Nucleoid represents the genetic material of virus. It is also the infective part of virus. Genetic material can be double stranded DNA (e.g., T2, T4 bacteriophages, Herpes Virus, Hepatitis B), single stranded DNA (e.g., Coliphase MS 2), double stranded RNA (Reovirus, Tumour virus) and single stranded RNA (e.g., TMV, Polio Virus). Retroviruses synthesise complementary DNA through reverse transcriptase (e.g., HIV).Others have RNA---> RNA replication.
Common Viral Diseases: Dengue, Cough and Cold, Mumps, AIDS, Influenza, Small Pox, Potato Mosaic.
Question 12: Organise a discussion in your class on the topic - Are viruses living or non-living?
Solution: Viruses are considered as connecting links between living and non-living beings. They possess some living character and some non-living characters.   
Characters of Living Beings:
1. Nucleic acids present in their body, are capable of synthesizing protein for their coat, although they use ribosomes of the host for this purpose.
2. Nucleic acids show similar gene mutations as chromosomes of the living organism.
3. Viruses replicate inside the living cells.
4. Daughter viruses resemble parent viruses.
5. Viruses are host specific.
6. They have antigenic properties.
7. They cause disease, like bacteria and fungi.
8. Ability to control cellular machinery of the host.
9. Viruses are obligate parasites.
10. Viruses are killed by UV radiations, autoclaving and many disinfectants.
11. They follow particular pattern of life cycle and reproduction.
Characters of Non-Living Beings:
1. Absence of cellular structure.
2. Metabolically inert when outside the host cell.
3. Absence of energy storing and energy liberating systems.
4. There is no growth.
5. A virus does not divide.
6. Multiplication occurs by synthesis of parts and then their assembly like those of machines.
7. Irritability is absent.
8. Movements are absent.
9. They can be crystallized.
10. Enzyme system absent.
11. They do not respire.
12. Culture of viruses in different types culture media (outside the cells) have failed.
Conclusions: Viruses are ultramicroscopic infectious particles composed of nucleoproteins and are obligate intracellular parasites where different cellular structures have degenerated due to overtaking of metabolic machinery of host.

To see answers of previous questions (1 - 6) visit:


Class 11 Biological Classification - CBSE Guide and Answers of NCERT Biology Chapter 2 Exercise Questions (1-6)

Class 11 Biological Classification - CBSE Biology Answers of NCERT Textbook Exercise

 

CBSE Class 11, NCERT Biology - DIVERSITY IN THE LIVING WORLD

Chapter 2. Biological Classification

NCERT (CBSE) Solutions - NCERT Answers - Chapter Exercise Questions

Question 1: Discuss how classification systems have undergone several changes over a period of time.
Answer: Classification systems are procedures of arranging organisms into groups and subgroups on the basis of similarities and dissimilariries of certain characters. The earliest systems were artificial. Then came natural systems, phylogenetic and now phenetic systems.
Artificial System of Classification: It is a system of classification which uses one or two morphological characters for grouping of organisms. Theophrastus first proposed Artificial System of Classification.
Natural System of Classification: This system is based on the natural affinities among organisms. These systems used as many taxonomic characters as possible to group organisms. In these systems organisms are classified on the basis of mainly morphological, reproductive, anatomical but cytological, physiological, embryological features, biochemistry etc. John Ray was first to propose a natural system of classification.
Phylogenetic System of Classification: Classification based on evolutionary relationships of organisms is called phylogenetic system of classification. It is based on the Darwin's evolutionary concept. First, Eichler and Endlicher proposed a phylogenetic classification system which was later on developed by others.
Phenetic Classification: It is a system of phylogenetic classification which is based on affinities, similarities, and dissimilariries of characteristics present in the present day organisms without searching for the evolution and diversification of these traits in their fossil ancestors.
Then depending upon the type of system of classification, organisms were also classified into Two Kingdom or Three Kingdom, Four Kingdom, Five Kingdom and now into Six Kingdom System.
Five Kingdom System: On the basis of cell-structure, mode of nutrition, reproduction, and phylogenetic relationship Whittaker proposed Five Kingdom Classification. The five kingdoms were named as - Monera, Protista, Fungi, Plantae and Animalia. But Whittaker’s Five Kingdom System of classification has also some demerits such as, the position of viruses is not clear, algae is placed into monera, protista and plantae.     
Six Kingdom System: On the basis of gene sequences, this system of classification was proposed by Gray and Doolittie.
Thus, classification systems have undergone several changes over a period of time and are still changing.
Question 2: State two economically important uses of:
(a) Heterotrophic bacteria
(b) Archaebacteria
Answer:
(a) Two economically important uses of heterotrophic bacteria are:
1. Nitrogen fixation in roots of legumimous plants.
2. Being decomposers, used in production of antibiotics.
(b) Two economically important uses of archaebacteria are:
1. Production of bio-gas from cow-dung.
2. Lives in guts of ruminant animals & help them in digestion of starch.
Question 3: What is the nature of cell-wall in diatoms?
Answer: The cell wall in diatoms is very tough because it is impregnated with silica which makes characteristic patterns on the cell. The cell wall consists of two overlapping halves like a soap-case, the upper one is called epitheca while the lower or inner one hypotheca. The cell wall is almost indestructible and forms diatomaceous earth.
Question 4: Find out what do the terms "algal bloom" and "red-tides" signify.
Answer:
Algal bloom: It refers to the excess growth of algae especially blue green algae, in polluted waters.
Red-tides: Red-tides refer to the red colour imparted to the sea water by the rapid multiplication of dinoflagellates like Gonyaulax. These marine organisms make a red sheet over seas because of red pigment in their cell.
Question 5: How are viroids different from viruses?
Solution:
Viruses
Viroids
1. Larger than viroids.
2. Nucleic acid can be DNA or RNA.
3. A protein covering or coats called capsomeres are present.
4. Virus is known to infect all types of organisms.
5. Cause diseases like - Mumps, AIDS.
6. It is a nucleoprotein particle.
1. Smaller than viruses.
2. Viroid is formed of only RNA.
3. It is an RNA particle.
4. A protein coat is absent.
5. Viroid is known to infect only plants.
6. Cause diseases like - Potato spindle tuber, chrysanthemum stunt.

Question 6: Describe briefly the four major groups of Protozoa.
Answer: The four major groups of protozoa are:
1. Amoeboid protozoans: They move and capture their prey by pseudopodia as in Amoeba. Many forms have silica shells on their surface. Some of them such as Entamoeba are parasites.
2. Flagellated Protozoans: They have flagella. The parasitic form such as Trypanosoma, cause disease.
3. Ciliated Protozoans: They have cilia. They also have a cavity (gullet) that opens to the outside of cell surface. Food is carried into the gullet as in Paramoecium.
4. Sporozoans: They have an infectious spore-like stage in their life cycle. The most important example is Plasmodium (malarial parasite).


To see answers of remaining questions (7 - 12) please visit: 
NCERT Solutions of CBSE Class XI Biology - Chapter 2, Biological Classification