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Std. XI Sci. Success Biology
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HORIZON Publications
DIVERSITY IN ORGANISMS
Contents
1.0
Introduction
1.1
Diversity in living organisms.
1.2
Systematics : Taxonomy, taxonomic hierarchy and binomial nomenclature
1.3
Five kingdom system of classification
1.4
Lichens
1.5
Viruses and Viroids
Multiple Choice Questions
1.0 Introduction
Q.1.
Ans.
What are the distinguishing characteristics of living organisms?
Distinguishing characteristics of living organisms are :
i.
Growth : Growth is exhibited by all living organisms. Increase in the body mass is considered
as growth. In living organisms growth occurs from inside. Non-living objects also grow. But,
the growth in non-living objects is by accumulation of material on to their surface.
ii. Reproduction : All organisms reproduce asexually or sexually, and produce their own kind.
Thus, helps in continuation of their kind.
iii. Metabolism : There are many bio-chemical reactions which occur simultaneously inside all
living organisms. The sum total of all the reactions occurring in the body of an organism is
called metabolism.
iv. Cellular organization : cell is the basic structural and functional unit of life. Thus, cellular
organization of the body is the defining feature of a living form.
v.
Ability to sense and respond : A very important feature of all living organisms is their ability
to sense their environment and to respond it. Both plants and animals are able to respond to
various environmental factors like light, temperature, water etc. Thus, consciousness becomes
the defining property of living organisms.
Q.2.
Why growth and reproduction are not considered as the defining characters of the living
organisms?
Growth and reproduction are not considered as the defining characters of living organisms because
i.
Non-living objects also grow. They grow by accumulation of material on to their surface. Thus,
growth cannot be considered as the defining character of living organisms.
ii. Though all living organisms can reproduce and continue their own kind. Living organisms like
mule, sterile worker bees, infertile human couples, etc. cannot reproduce. Thus, reproduction
cannot be considered as the defining character of living organisms.
Ans.
1.1 Diversity in living organisms
Q.3.
Ans.
Explain diversity in living organisms.
i.
There are many types of living organisms living on earth, ranging from unicellular prokaryotes
as well as eukaryotes to large multicellular eukaryotes like plants and animals.
ii. There are about 5-30 million species of plants and animals existing on earth at various
locations in many different conditions and also exhibit variations in their size, shape, structure,
mode of nutrition, reproduction.
Diversity in Organisms
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Std. XI Sci. Success Biology
Q.4.
Ans.
www.horizonpublications.in
How many species of plants and animals exist on the earth ?
About 5 to 30 million species of plants and animals exist on the earth.
1.2 Systematics : taxonomy, taxonomic hierarchy and binomial nomenclature
Q.5.
Ans.
Define systematics and taxonomy and mention their objectives.
Systematics : Systematics is the scientific study of similarities and differences among different
kinds of organisms and it also includes their identification, nomenclature and classification.
Taxonomy : It is the branch of biology which deals with the collection, identification, nomenclature,
description and classification of plants and animals.
Objectives of Systematics/Taxonomy :
i.
To know various kinds of plants on the earth with their names, affinities, geographical
distribution, habit, characteristics and their economic importance.
ii. To have a reference system for all organisms with which the scientists can work.
iii. To demonstrate the manifold diversities of organisms and their phylogenetic (evolutionary)
relationship.
iv. To ascertain nomenclature i.e. scientific name for every organism.
Q.6.
Ans.
Define the term : classification.
It is the arrangement of organisms or groups of organisms in distinct categories in accordance with a
particular and well established plan.
Q.7.
Ans.
Who coined the term ‘classification’ ?
The term ‘classification’ was coined by A.P. de Candolle.
Q.8.
Ans.
What is classification of organisms and why is there a need for classification?
i.
Classification is the arrangement of organisms or groups of organisms in distinct categories in
accordance with a particular and well established plan.
ii. The classification is based on similarities and dissimilarities among the organisms. The term
classification was coined by A.P. de Candolle.
iii. There is a large number of living organisms found on earth. All these organisms show
variations in their shape, size, structure, habit, habitat, nutrition, etc.
iv. It is very difficult to remember the characteristics of all the organisms without their proper
arrangement.
v.
The classification helps to explain unity in diversity of the organisms.
vi. It gives specific and scientific names to the organisms which are universal.
vii. It reveals the relationships among various groups of organisms. The classification places an
organism amongst those which have common characteristics.
Q.9.
Ans.
Write a note on the “Three Domains of Life”.
The three domains of life is a system for classifying living organisms.
i.
It was developed by Carl Woese (1990).
ii. From the late 1960’s, organisms are being classified according to a Five Kingdom system.
iii. But now genetic sequencing has given researchers a whole new way of analyzing relationships
between organisms.
iv. The Three Domain System is primarily based on differences in ribosomal RNA structure of
different groups of organisms. Ribosomal RNA is a molecular building block for ribosome.
v.
According to this system, organisms are classified into three domains and six kingdoms.
The three domains are
a.
Archaea
b.
Bacteria
c.
Eukarya
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vi.
The domains Archaea and Bacteria include prokaryotic organisms. These domains include only
one kingdom each i.e. Archaebacteria (ancient bactreria) and Eubacteria (true bacteria)
respectively.
vii. The domain Eukarya includes all eukaryotes. The four kingdoms under this domain are
kingdom Protista, Fungi, Plantae, and Animalia.
Q.10. Define taxonomic hierarchy.
Ans. The manner of scientific grouping of different taxonomic categories in a descending order on the
basis of their ranks or positions in classification is called taxonomic hierarchy.
*Q.11. Define taxon.
Ans. Taxon is a group of living organisms (Pl. taxa) which is used to represent a concrete unit of
classification.
The unit or taxon may be large or small. The term taxon was coined by H. J. Lam in 1948 for plants.
*Q.12. Define category.
Ans. A category is a rank or level in the hierarchial classification of organisms.
Q.13. Give the classification of China rose and Cobra.
Ans. The classification of China rose and Cobra :
Category
Taxon
Kingdom
Plantae
Division/Phylum Angiospermae
Class
Dicotyledonae
Sub- class
Polypetalae
Series
Thalamiflorae
Order
Malvales
Family
Malvaceae
Genus
Hibiscus
Species
rosa-sinensis
Taxon
Animalia
Chordata
Reptilia
Diapsida
Squamata
Elapidae
Naja
naja
Q.14. Give the units of classification.
Ans. Unit of classification are :
Kingdom
↓
Division / Phylum
↓
Class
↓
Sub-class
↓
Series
↓
Order
↓
Family
↓
Genus
↓
Species
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*Q.15. Describe the hierarchy of taxonomic categories.
Ans. i.
Species : Species is a smallest and basic unit in the system of classification. All members
belonging to a particular species show all simillar characters and can breed among themselves
to produce similar type of organisms. e.g. All the China rose (Hibiscus) plants are grouped
under a species rosa sinensis, similarly all the potato plants (Solanum tuberosum) are grouped
under a species tuberosum.
ii. Genus : (Pl. genera) - It is a group of closely related species, which resemble one another in
certain characters, e.g. rosa-sinensis, escuientus, canabinus etc. are different species under the
genus Hibiscus. A genus may be either monotypic (having single species) or polytypic genus
(having many species).
iii. Family : A family represents a group of closely related genera. The genera like Hibiscus,
Malva, Sida, Gossypium, Abutilon, etc. belong to the family Malvaceae .
iv. Order : It is a group of closely related families which resemble in major characters. For
example families Malvaceae, Tiliaceae, Sterculiaceae etc. belong to the order Malvales. (They
show axile placentation in ovary.)
v.
Sub-Class : It is an assemblage of different orders having some similarities. For example the
orders, Malvales, Ranales, Parietales etc. have free petals and hence grouped under the subclass Polypetalae.
vi. Class : It is a group of related sub-classes. For example the class Dicotyledonae includes subclasses as Polypetalae and , Gamopetalae
vii. Division/Phylum : The division is a category composed of related classes. For example,
division Angiospermae includes two classes- Dicotyledonae and Monocotyledonae. In animal
classification instead of Division the category Phylum is used.
viii. Sub Kingdom : Different divisions having some similarities form sub-kingdom. For example
the divisions Angiospermae and Gymnospermae will form the sub kingdom Phanerogams or
Spermatophyta. (All seed producing plants)
ix. Kingdom : It is the highest taxonomic category composed of different sub kingdoms. For
example, sub - Kingdom Phanerogams and Cryptogams, form the Plant kingdom or Plantae
which includes all the plants while all animals are included in Kingdom Animalia.
Q.16. Define a taxon. Give some examples of taxa at different hierarchical levels.
Ans. Taxon is a group of living organisms (Pl. taxa) which is used to represent a concrete unit of
classification.
e.g. The genus Thespesia is a taxon.
The family Malvaceae is a taxon.
The species Panthera is a taxon.
Q.17. Write a short note on the concept of species.
Ans. There are three different concepts of species.
i.
Morphological concept : The morphological concept of species was given by Carolus
Linnaeus. According to this concept species is a group of organisms which are similar in their
morphological characters and is called as morphospecies.
ii. Biological concept : The biological concept of species was given by Charles Darwin.
According to this concept species is a group of organisms that can interbreed under natural
conditions and is called biospecies (True species).
iii. Modern concept : the modern concept of species was given by Ernst Mayr. According to the
modern concept species is a group of actually or potentially interbreeding natural population of
closely resembling organisms.
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*Q.18. Define nomenclature. What is the major purpose of nomenclature.
Ans. The art of naming an object is in fact a science called nomenclature.
The nomenclature has two main purposes :
i.
As an aid to communicate and
ii. To indicate relationship.
*Q.19. What is meant by vernacular name ?
Ans. Vernacular names are the names which are given to organisms in a particular region and language by
local people.
Q.20. What are vernacular names ? Mention their advantages and disadvantages.
Ans. Vernacular names are the names which are given to organisms in a particular region and language by
local people. All plants and animals are known by different common names in different parts of the
world.
Advantages :
i.
Vernacular names help in identifying all plants and animals by different common names in
various parts of the world.
ii. The local or vernacular names are short, familiar and easy to follow.
Disadvantages :
i.
Within the same country, people of different states and regions use different common names
for a single plant. But they do not communicate the necessary information of the organism.
ii. They do not indicate proper relationship and are not universal. For example, in India Ipomoea
batatas is recognized by various names like sweet potato (in English); Shakarkand (in Hindi);
Meetha Alu (in Assamese and Bengali); Kandmul (in Telugu); Ratalu (in Marathi) and Jenasu
(in Kannada), etc.
iii. Thus the local names are different and confusing.
iv. A single vernacular name is used for several species. For example, the name “lily” is used to
describe many bulbous flowering plants like - water lily, spider lily, etc. Vernacular names
may be misleading. For example, starfish, jelly fish, silver fish are not fishes at all. Thus,
vernacular names create confusion.
*Q.21. Why it is said that vernacular names create confusion ?
Ans. Vernacular names are sometimes misleading and in different regions there are different names for
the same organism. Thus these names are not universal and create confusion.
*Q.22. What is binomial nomenclature ? Explain it with a suitable example. Explain the rules
followed for binomial nomenclature. Give its advantages.
Ans. i.
A system of nomenclature of plants and animals in which the scientific name consists of two
words or parts or epithets is called binomial nomenclature.
ii. The binomial system of nomenclature was given by a Swedish naturalist, Carolus Linnaeus.
He introduced this system in his book “Species Plantarum” published in 1753.
iii. According to this system the scientific name of Sunflower is Helianthus annuus. In the above
name the first word Helianthus indicates name of the genus (generic name) and the second
word annuus denotes name of the species (specific name) to which the plant belongs.
Rules of binomial nomenclature :
i.
The name of the organism is composed of two Latin or Latinised or Greek words.
ii. The generic name is a simple noun which should come first and should begin with a capital
letter.
iii. Specific name is the descriptive adjective which should come later and begin with a small
letter.
iv. The names are based on some special characters of the organism.
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v.
These scientific names must be underlined separately if hand written and must be printed in
italics.
vi. The generic as well as specific name does not generally have less than three letters and more
than thirteen letters.
vii. Usually the name of the author, who names a plant or animal, is also written in full or in
abbreviated form after the scientific name. Mention of author’s name after the species name is
called citation. e.g. Mangifera indica L. where L. stands for Linnaeus.
viii. To avoid the confusion, no two generic names in any kingdom can be same. However, the
species name can be repeated when the genera are different, e.g. Mangifera indica, (Mango)
and Azadirachta indica (Neem).
ix. When a single species is described under different names by different authors, then these
names are called synonyms. In such cases the name under which the species is first described is
considered to be valid.
Advantages of binomial nomenclature are :
i.
These names are simple, meaningful, precise and standard as they are accepted universally.
ii. By the use of binomial nomenclature system confusion and uncertainty created by local or
vernacular names is avoided.
iii. The binomials are easy to understand and remember, indicate phylogeny (evolutionary history)
of organisms and help to understand relationships between organisms, and groups of
organisms.
*Q.23. Give diagrammatic representation of the five kingdom system of classification.
Ans. Ecological role
Producers
Decomposers
Consumers
Direction of Evolution
Kingdom
Plantae
Complexity of
organism
Absorption
(Heterotrophs)
(saprophytes)
Kingdom
Fungi
Photosynthesis
(Autotrophs)
Mode of
Nutrition
Ingestion
(Heterotrophs)
Kingdom
Animalia
Multicellular eukaryotes
Kingdom
Protista
Unicellular
eukaryotes
Prokaryotes
Complexity of
cell
Kingdom
Monera
Diagrammatic representation of the five kingdom system of classification
*Q.24. Who proposed binomial system of nomenclature ?
Ans. Swedish naturalist Carolus Linnaeus proposed binomial system of nomenclature.
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1.3 Five kingdom system of classification
Q.25. Who introduced the two kingdom system of classification ?
Ans. The two kingdom system of classification of organisms was introduced by Carl Linnaeus.
Q.26. What was the drawback of two kingdom system of classification ?
Ans. Two kingdom system was found inadequate for classification of some organisms like bacteria, fungi,
Euglena, etc.
Q.27. Who suggested the third kingdom Protista ?
Ans. Haeckel suggested the third kingdom Protista.
Q.28. Who suggested five kingdom classification ?
Ans. R.H. Whittaker suggested five kingdom classification.
Q.29. List the various attempts made for classification of living organisms.
Ans. Classification is the arrangement of organisms or groups of organisms in distinct categories in
accordance with a particular and well established plan.
Various attempts made for accurate classification of living organisms are as follows :
i.
The two-kingdom system of classification of organisms introduced by Carl Linnaeus. The
system recognized two kingdoms of organisms on the earth -Plantae and Animalia. However,
this system was found inadequate for classification of some organisms like bacteria, fungi,
Euglena, etc.
ii. Thus to include the microscopic organisms Haeckel suggested the third kingdom Protista to
include these organisms.
iii. But as more and more unicellular organisms were discovered it increased the need for further
classification of these organisms. So the system of classification proposed by R. H. Whittaker
in 1969 is a five-kingdom system. This system shows the phylogenetic relationship between
organisms. From the late 1960’s, organisms are being classified according to a Five Kingdom
system.
iv. The five kingdoms are :
a.
Kingdom Monera
b.
Kingdom Protista
c.
Kingdom Fungi
d.
Kingdom Plantae
e.
Kingdom Animalia
v.
But now genetic sequencing has given researchers a whole new way of analyzing relationships
between organisms and thus the latest system of classification was presented called The Three
Domain System.
vi. The Three Domain System is primarily based on differences in ribosomal RNA structure of
different groups of organisms. Ribosomal RNA is a molecular building block for ribosome.
According to this system, organisms are classified into three domains and six kingdoms. The
three domains are
a.
Archaea
b.
Bacteria
c.
Eukarya
vii. The domains Archaea and Bacteria include prokaryotic organisms. These domains include only
one kingdom each i.e. Archaebacteria (ancient bactreria) and Eubacteria (true bacteria)
respectively. The domain Eukarya includes all eukaryotes. The four kingdoms under this
domain are kingdom Protista, Fungi, Plantae, and Animalia.
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Q.30. Name the five kingdoms mentioned by whittaker.
Ans. The five kingdoms are :
i.
Kingdom Monera
ii. Kingdom Protista
iii. Kingdom Fungi
iv. Kingdom Plantae
v.
Kingdom Animalia
Q.31. What were the criteria considered by whittaker for classification of the organisms ?
Ans.
i. Cell organization
Whether the organism is prokaryotic or eukaryotic.
ii. Body organization Whether the organism is unicellular or multicellular.
iii. Mode of nutrition
Whether the organism is autotrophic or heterotrophic.
iv. Life style
Whether the organism is producer, consumer or decomposer.
*Q.32. Give the characteristics of kingdom monera with examples.
Ans. i.
The organisms included in this kingdom are microscopic and prokaryotic.
ii. They have a primitive type of nucleus (Pro = first formed, karyon = nucleus). Prokaryotic
nucleus is not well organised. It is without nuclear envelope, nucleolus, nucleoplasm, histone
proteins and true chromosomes. (Only DNA is present). It is also called as nucleoid.
iii. The cell wall is rigid and composed of peptidoglycan.
iv. These organisms are unicellular as in eubacteria or filamentous as in cyanobacteria.
v.
The cells are without membrane-bound cell organelles like chloroplasts, mitochondria, etc.
vi. These organisms are either motile or non-motile. The locomotion is due to gliding movement
or with the help of flagella but cilia is absent.
vii. The organisms exhibit different modes of nutrition like autotrophic, heterotrophic, parasitic or
saprophytic. The autotrophs are either photo-autotrophs e.g. cyanobacteria or chemoautotrophs
e.g. Thiobacillus.
viii. The mode of reproduction in Monera is either asexual or with the help of fission or budding.
Sexual reproduction, mitosis and meiosis are absent.
Examples :
Archaebacteria
Eubacteria
Cyanobacteria
Actinomycetes
Diversity in Organisms
e.g. - Methanobacillus, Thiobacillus, etc.
e.g. - Rhizobium, Clostridium, etc.
e.g. - Nostoc, Anabaena, etc.
e.g. - Streptomyces, Mycobacterium, etc.
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*Q.33. Unicellular prokaryotic organisms are included in which kingdom.
Ans. Unicellular prokaryotic organisms are included in kingdom Monera.
*Q.34. Which kingdom forms a link between prokaryotes and complex eukaryotes ?
Ans. Kingdom Protista forms a link between prokaryotes and complex eukaryotes.
*Q.35. Give the characteristics of kingdom protista and mention their types and examples.
Ans. i.
Organisms belonging to kingdom Protista are unicellular, eukaryotic and mostly aquatic.
However, some are terrestrial.
ii. They can be motile or non-motile. The locomotion is with the help of organs like cilia, flagella,
pseudopodia, etc.
iii. The protists are with or without cell wall. If cell wall is present, it is composed of cellulose.
iv.
They have membrane-bound cell organelles such as mitochondria, chioroplasts, ER, Golgi
complex, etc. The nucleus is well- organized i.e. with nuclear envelope, nucleoplasm,
nucleolus and helical DNA with histone proteins forming chromosomes.
v.
They show either the photosynthetic, holozoic, saprophytic or parasitic mode of nutrition.
vi. The reserve food material can be in the form of glycogen or starch and fat.
vii. The reproduction can be asexual or sexual. Asexual reproduction occurs by mitotic or amitotic
cell division while sexual reproduction is by fusion of male and female gametes forming
zygote. The zygote directly develops into young individual without formation of embryo.
Different types of protists are :
i.
Plant like protists : They are autotrophic (photosynthetic), have celiulosic cell wall and store
reserve food as starch e.g. dinoflagellates, diatoms and desmids (golden algae). They are
together grouped as chrysophytes. The cell wall of diatoms is composed of two overlapping
halves resembling a soap case. The remains of their cell walls is called diatomaceous earth
which is used in chromatography, filtration and polishing. They are chief producers of aquatic
environment.
ii. Animal like protists : These are heterotrophic, ingest food, lack cell wall and store reserve
food as glycogen e.g. Amoeba,Paramoecium.
iii. Fungi like protists : They are saprophytic and lack cell wall e.g. Slime moulds.
iv. Euglenoids : These are primarily photosynthetic aquatic organisms. However, they behave as
heterotrophs in the absence of light, e.g. Euglena
Thus Kingdom Protista is a link between prokaryotic Kingdom Monera and complex
eukaryotic Kingdoms-Plantae, Fungi and Animalia.
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Q.36. Explain the composition of cell wall in diatoms.
Ans. The cell wall of diatoms are composed of two overlapping halves made up of silica resembling a
soap case.
*Q.37. Give the characteristics of kingdom fungi.
Ans. i.
Kingdom fungi are a group of heterotrophic organisms, showing extracellular digestion.
ii. The organisms can be unicellular (yeast) or multicellular and filamentous (Penicillium).
iii. Unicellular organisms have a protoplast with many nuclei e.g. Rhizopus or with a single
nucleus e.g. yeast. Filamentous organisms consist of a body called mycelium in which a
number of thread-like structures called hyphae are present.
iv. The hyphae may be with septa (septate) or without septa (aseptate). They may be uni or multinucleated. The non-septate multinucleated hyphae are called coenocytic hyphae.
v.
The cell wall in fungi is composed of chitin or fungal cellulose.
vi. Fungi contain well-organized membrane-bound cell organelles except the chloroplasts.
vii. The fungi exhibit heterotrophic mode of nutrition. Most of the members are saprophytes, and
absorb food which is decomposed (digested) outside. Thus absorption is the mode of nutrition.
Some are parasites or predators and some are symbiotic.
viii. Reproduction can be vegetative, asexual or sexual.
Q.38. Give the classification of kingdom fungi with examples.
Ans. Kingdom fungi is classified into four classes :
i.
Phycomycetes : They are commonly called algal fungi and consist of coenocytic hyphae. They
grow in moist and damp habitats on decaying organic matter. They reproduce by endogenous
spores produced inside sporangia Examples-Mucor, Rhizopus, etc. Albugo is an example of
parasitic phycomycetes.
ii. Ascomycetes : They are mostly multicellular and are commonly called sac fungi. Their thallus
or somatic body is composed of branched septate hyphae. Reproduction takes place by the
production of endogenous sexual spores called ascospores in saclike structures called asci.
Some produce fruiting bodies (ascocarps) which enclose asci. The asexual and exogenously
produced spores are called conidia which are at the tips of special hyphae called conidiophores.
Examples : Aspergillus, Penicillium, Neurospora etc. Yeast is an example of unicellular ascomycetes.
iii. Basidiomycetes : They are commonly called as club fungi. It includes mushrooms, bracket
fungi, rusts, smuts, etc. They have branched septate hyphae. Asexual reproduction is absent.
Vegetative reproduction takes place by fragmentation. Sex organs are lacking. The fusion of
two vegetative cells or somatic cells (somatogamy) produces a dikaryotic mycelium which
gives rise to basidia or a fruiting body called basidiocarp. Basidiocarp contains many basidia
which exogenously produce sexual spores called basidiospores.
Examples : Agaricus, Ustilago; Puccinia, etc.
iv. Deuteromycetes : They are commonly called imperfect fungi. It is a temporary group of fungi
which are known to reproduce only asexually. When their sexual reproduction is discovered,
they are transferred to the respective groups. They are mostly decomposers while a few are
parasitic. Examples : Alterndria, Colletotrichum, Trichophyton etc.
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*Q.39. What are coenocytic hyphae ?
Ans. In the organisms of kingdom fungi, non-septate, multinucleated hyphae are present which are known
as coenocytic hyphae.
*Q.40. Give the characteristics of kingdom plantae with examples.
Ans. i.
The Kingdom Plantae comprises of all multicellular, eukaryotic and autotrophic organisms like
Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms.
ii. The plants are sedentary in nature.
iii. The cell wall of plant cells is made up of true cellulose.
iv. All the organisms included in this kingdom possess photosynthetic pigments.
v.
The members of Plantae kingdom are the main producers and provide food directly or
indirectly to all living organisms.
vi. Reserve food material is in the form of starch.
vii. Vascular tissues are absent in the lower plants (Algae and Bryophytes) but present in higher
plants (Pteridophytes, Gymnosperms and Angiosperms)
viii. In higher plants cuticle, stomata etc. are present to check the rate of transpiration.
ix. The plants reproduce by vegetative, asexual or sexual methods. Vegetative reproduction occurs
with the help of vegetative parts, asexual reproduction with the help of spores while sexual
reproduction takes place with the help of gametes.
x.
Examples :
Algae
e.g. : Spirogyra, Chara, etc.
Bryophytes
e.g. : Riccia, Funaria, etc.
Pteridophytes
e.g. : Lycopodium, Nephrolepis, etc.
Gymnosperms
e.g. : Cycas, Pinus, etc.
Angiosperms
e.g. : Sunflower, Jowar, etc.
*Q.41. Give the characteristics of kingdom animalia with examples.
Ans. i.
The organisms included in the kingdom animalia are multicellular and eukaryotic. They can be
be aquatic, terrestrial, amphibious or aerial.
ii. Majority of the animals are motile. However, a few like sponges are sedentary.
iii. The animal cells do not possess cell wall, plastids and central vacuole.
iv. The animals possess sense organs, nervous system and they respond to stimuli by exhibiting
certain behaviour.
v.
They are heterotrophic, mostly holozoic while some are parasitic. They are consumers of
various levels which are primary, secondary, tertiary etc.
Examples : Fishes, frog, cats, birds, etc.
vi. The five kingdom system of classification has some advantages as prokaryotes are separated
from other organisms (Eukaryotes), and get the status of kingdom.
Q.42. Which mode of nutrition is observed in kingdom Animalia ?
Ans. Holozoic mode of nutrition is observed in kingdom Animalia.
Q.43. What are the various advantages and disadvantages of whittaker’s five kingdom
classification ?
Ans. The advantages of Whittaker’s five kingdom classification are :
i.
All groups of organisms get proper place and taxonomic status e.g. Rank of kingdom, Monera
and Fungi.
ii. The fungi are separated from Plantae on the basis of their saprophytic mode of nutrition
(absorption).
iii. During redistribution of the organisms among additional kingdoms, the original sub-divisions
of old two-kingdom system are not disturbed.
iv. It also shows phylogenetic relationships among the organisms.
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It is one of the most systematic classification based upon the mode of nutrition, cell structure
and organization.
Euglena is an organism showing photosynthetic mode of nutrition in presence of light and
holozoic mode(ingestion of food) in absence of light, has been placed in kingdom Protista, as it
is unicellular. Thus organisms with doubtful placement like Euglena get proper place in
classification.
The disadvantages of Whittaker’s five kingdom classification are :
i.
Viruses do not find any place in five-kingdom system of classification.
ii. Kingdom Protista includes both, photosynthetic and non-photosynthetic organisms, as well as
those with or without cell wall. Thus it is difficult to imagine them together.
Q.44. Distinguish between the following :
a.
Prokaryotes and Eukaryotes
c.
Monera and Protista
Ans. a.
Prokaryotes and Eukaryotes :
i.
ii.
iii.
iv.
b.
b.
d.
Autotrophs and Heterotrophs
Plantae and Animalia
Prokaryotes
Prokaryotes
include
unicellular
organisms like bacteria, archaebacteria
and blue-green algae.
Prokaryotes possess a distinct cell wall
surrounding their cells.
Prokaryotes lack a definite nucleus.
The nuclear material, i.e. DNA is not
enclosed by a nuclear membrane.
Eukaryotes
Eukaryotes include both unicellular
and multicellular organisms like
protists, fungi, plants and animals.
Cell wall is present in plants, fungi and
some protists but absent in animals.
The eukaryotes possess a definite
nucleus. The nuclear material, i.e.
DNA is enclosed by a nuclear
membrane.
Cell organelles like mitochondria, Cell organelles like mitochondria,
chloroplasts,
Golgi
bodies, chloroplasts,
Golgi
bodies,
endoplasmic reticulum and lysosomes endoplasmic reticulum and lysosomes
are absent in prokaryotes.
are present in eukaryotes.
Autotrophs and Heterotrophs :
i.
ii.
iii.
iv.
Autotrophs
Autotrophs are those organisms which
synthesize their food.
Autotrophs are self-nourishing, i.e.
they consume the food synthesized by
them.
Autotrophs are capable of converting
the light energy into chemical energy.
Heterotrophs
Heterotrophs are those organisms
which do not synthesize their food.
Heterotrophs depend upon other living
organisms or dead and decaying
materials for their food.
Heterotrophs are not capable of
converting the light energy into
chemical energy.
Autrophs are of two types, viz. Heterotrophs are of three types, viz.
photoautotrophs and chemoautotrophs. parasites, saprophytes and holozoans.
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c.
Monara and Protista :
i.
ii.
iii.
iv.
d.
HORIZON Publications
Monera
Protista
Monera
includes
unicellular Protista includes unicellular eukaryotic
prokaryotic organisms.
organisms.
The nucleus lacks nuclear membrane. The nucleus possesses a nuclear
membrane.
Monerans do not possess membrane- Monerans possess membrane-bound
bound cell organelles.
cell organelles.
Reproduction is asexual.
Reproduction is both asexual and
sexual.
Plantae and Animalia :
i.
ii.
iii.
iv.
Plantae
Animalia
Plantae includes all multicellular Animalia includes all multicellular
photosynthetic organisms.
non-photosynthetic organisms.
They possess cell walls and plastids.
They do not possess cell walls and
plastids.
Nonmotile lying anchored to a With the exception of sponges all
substrate.
animals are motile.
They possess autotrophic mode of They possess holozoic mode of
nutrition.
nutrition.
1.4 Lichens
Q.45. Who was the first to use the word lichen ?
Ans. Theophrastus was the first to use the word lichen.
*Q.46. What are lichens ? Mention the types of lichens based upon the fungal component and thallus
organization.
Ans. i.
Lichens are formed by close association of two different organisms one of which is an algal
component and the other is fungal component. The algal component is called phycobiont or
photobiont and it mostly belongs to Chlorophyceae (green algae) or cyanobacteria.
ii. The fungal component is called mycobiont and it mostly belongs to Ascomycetes and rarely
Basidiomycetes or Deuteromycetes. Theophrastus (300 B.C.) was the first to use the word
lichen.
iii. The lichens are slow growing, long living organisms, occurring in wide variety of habitats.
They grow on tree trunks, decaying logs, and on soil too. They are found in extreme climatic
conditions such as on dry exposed rocks and also at snow covered Arctic and Antarctic poles.
iv. They are sensitive to air pollution and generally do not grow near the cities. They are thalloid,
and the thallus is greenish or bluish green in colour. Some lichens have additional pigments
such as yellow, orange, brown and black. The lichens generally reproduce by vegetative,
asexual and sexual methods.
v.
On the basis of fungal component the lichens are divided into three catagories (Alexopoulos
and Mims 1979) as :
a.
Ascolichens : In this category the fungal partner belongs to Ascomycetes.
b. Basidiolichens : Here the fungal partner belongs to Basidiomycetes.
c.
Deuterolichens : In this category the fungal partner belongs to Deuteromycetes. These
are sterile lichens producing no spores.
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On the basis of external form, (thallus organization) the lichens are of three types as :
a.
Crustose Lichens : These are thin and flat lichens occuring as crust on the bark or rock.
e.g. Graphis, Lecanora, Haematomma etc.
b. Foliose Lichens : These are lobed and dorsiventrally flattened, leafy lichens. They are
attached to substratum by hairy rhizoid like structures called rhizines e.g. Parmelia,
Collema, Peltigera.
c.
Fruticose Lichens : These lichens are commonly called shruby lichens. They have
cylindrical, branched and erect or pendulous thallus which gives them a shrub like
appearance. They remain attached to the substratum by basal mucilagenous disc e.g.
Cladonia, Usnea, Alectoria.
*Q.47. Give the economic importance of lichens.
Ans. i.
Lichens as Food : Several species of lichens are used as food as they are edible. The lichens
contain a substance lichenin which is similar to carbohydrate e.g. Lecanora esculenta in Israel
and Umbilicaria esculenta in Japan. Parmelia is used in making curry powder as well as in
making chocolates and pastries.
ii. Lichens as Fodder : Lichens a favourite form of food for reindeers and cattles. Species of
Cladonia, Citraria, Evernia, Parmelia are used as fodder.
iii. Medicinal Uses : Usnic Acid obtained from the Usnea and Cladonia species is used as an
antibiotic against Gram positive bacteria.
Lobaria, Citraria species are useful in respiratory disease like T. B., Peltigera is useful in
hydrophobia, Parmelia is useful in epilepsy and Usnea species in urinary disease.
Some lichens possess anticarcinogenic property.
iv. Industrial Uses of Lichens : In Sweden and Russia, lichens are used for production of alcohol.
Lichens are used in the process of tanning and dying.
In the litmus paper preparation which is an acid-base indicator extract of species of Rocella and
Lasallia are used.
Orcein a biological stain is obtained from Orchrolechia androgyna and O. tortaria.
In perfumery, species of Evernia and Ramalina are the sources of essential oils which are used
in preparation of soaps and other cosmetics.
Q.48. Give the ecological importance of lichens.
Ans. i.
The lichens are the pioneers of vegetation on rocks.
ii. Lichens are the first plants to settle on barren rocks.
iii. Lichens bring about weathering of rocks by releasing carbonic and oxalic acids.
iv. Breaking of the rocks in a stepwise manner leads to formation of soil and is called
Pedogenesis.
v.
After lichens, some bryophytes and then other higher plants can grow on such soil.
Q.49. Why lichens do not grow near the cities ?
Ans. Lichens are sensitive to air pollution thus they do not grow near the cities.
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Q.50. What is meant by the terms phycobiont and mycobiont ?
Ans. Lichens are formed by close association of algal component is called phycobiont, belongs to
chlorophyceae and cyanophyceae.
The fungal component is called mycobiont, belongs to Ascomycetes and rarely basidiomycetes or
Deuteromycetes.
1.5 Viruses and viroids
*Q.51. What are viruses and give their general characters.
Ans. Viruses are acellular, ultramicroscopic, highly infectious microorganisms which are considered to be
on the threshold of life.
General characters of viruses :
i.
The size of viruses ranges from 10 nm to 2000 nm. However some of the viruses are larger.
ii. Viruses show very simple structure i.e. a nucleic acid core surrounded by a protein coat called
capsid to form the nucleocapsid.
iii. The detailed structure of viruses was studied only after the invention of electron microscope.
iv. Viruses possess their own genetic material in the form of either DNA or RNA but never both.
v.
Viruses do not grow, do not eat food or respire.
vi. Viruses are obligate parasites and can multiply only within the living host cells.
vii. Viruses have capacity to transmit the disease from diseased to healthy organisms.
viii. Viruses can be crystallized.
ix. Viruses can be stored for long period.
x.
Outside the body of host they do not show any activity, they are like non-living. They do not
have their own metabolic machinery. They utilize the ribosomes and enzymes of the host cell
for synthesis of protein during reproduction.
xi. Most of the viruses are highly resistant to germicides and extremes of physical conditions.
xii. Viruses exhibit mutations. Viruses cannot be cultured on artificial nutrient medium.
xiii. Viruses are host specific. Viruses show characteristics of living as well as non-living.
Therefore, they are said to be on the threshold of life.
*Q.52. Describe the classification of viruses and give their economic importance.
Ans. Viruses are acellular, ultramicroscopic, highly infectious microorganisms which are considered to be
on the threshold of life.
Classification of viruses [Types of viruses] :
Viruses are classified into three groups on the basis of their hosts.
i.
Plant viruses : The viruses which attack and
infect plants are called, plant viruses. These
viruses consist of ss-RNA or ds-RNA. They
show helical symmetry and are mostly rodshaped or cylindrical.
ii. Animal viruses : The viruses which attack
and infect animals are called animal
viruses. The genetic material is either RNA
or DNA. They show radial symmetry. These
are mostly polyhedral in shape.
iii. Bacterial viruses or Bacteriophages : The viruses which attack and infect the bacteria are
called bacteriophages or bacterial viruses. The genetic material is DNA. They are mostly
tadpole shaped. They were discovered by Twort (1915). Felix d’Herelle named them as
bacteriophages.
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Economic Importance of viruses :
The plant viruses and animal viruses are of great economic importance as they cause various
diseases in plants and animals.
Plant diseases caused by viruses are like :
i.
Little leaf of brinjal
ii. Yellow vein mosaic of lady’s finger
iii. Potato leaf roll
iv. Leaf curl of papaya
v.
Bunchy top of banana
vi. Grassy shoot of sugarcane
vii. Tobacco mosaic disease
Animal diseases caused by viruses are like :
i.
ii.
iii.
iv.
v.
Disease
Common cold
Influenza
Small pox
Mumps
Measles
virus
Rhino virus
Myxo virus
Variola virus
Paramyxo virus
Morbilli virus
Disease
vi. Poliomyelitis
vii. Yellow fever
viii. Swine flu
ix. AIDS
virus
Polio virus
Flavi virus
H1N1 virus
Retro virus/HIV
*Q.53. Who demonstrated tobacco mosaic disease to be infectious ?
Ans. Aldolf Mayer demonstrated the tobacco mosaic disease to be infectious.
Q.54. Who gave the term virus ?
Ans. Louis Pasteur gave the term virus.
Q.55. What was the Ivanowski’s contribution for study of TMV ?
Ans. Ivanowski prepared an extract of infected tobacco plant and showed that this extract could infect
healthy plants even after it was passed through filter that retains bacteria.
Thus Ivanowski confirmed the observation of Mayer about TMV.
Q.56. Who referred virus as ‘contagium vivum fluidum’ ?
Ans. M. W. Beijerink referred virus as ‘contagiam vivum fluidum’.
Q.57. Who discovered viroids ?
Ans. Theodor Diener.
*Q.58. Write a note on viroids.
Ans. i.
Viroids are very small, circular, single-stranded RNAs which are without protein coat.
ii. This RNA is either covalently closed circular RNA or single stranded linear RNA. They are
mainly plant pathogens. They do not show dormant phase.
iii. Viroids were discovered and named by Theodor Diener in 1971 which was the potato spindle
tuber viroid (PSTV) which infects potato. PSTV is composed of 359 nucleotides and thus has
ten times less genetic material than the smallest known virus.
iv. The naked RNA molecule can replicate autonomously in plant cells.
v.
It can also disperse into the environment and produce diseases, at least 11 other plant diseases
have been linked to viroids. These diseases include citrus exocortis, chrysanthemum stunt,
cucumber bale fruit, etc.
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