1.
Who was the first to propose a scientific
basis for classifying organisms?
A) Linnaeus
B) Aristotle
C) Whittaker
D) Darwin
Answer:
B) Aristotle
2.
What is the main component of the cell
wall in fungi?
A) Cellulose
B) Chitin
C) Silica
D) Protein
Answer:
B) Chitin
3.
Which kingdom includes unicellular
eukaryotic organisms?
A) Monera
B) Protista
C) Fungi
D) Animalia
Answer:
B) Protista
4.
What type of spores do fungi produce
during asexual reproduction?
A) Conidia
B) Zygospores
C) Ascospores
D) Basidiospores
Answer:
A) Conidia
5.
What structure allows cyanobacteria to fix
atmospheric nitrogen?
A) Heterocysts
B) Flagella
C) Mycelium
D) Gullet
Answer:
A) Heterocysts
6.
Which kingdom is characterized by the
presence of chlorophyll?
A) Animalia
B) Plantae
C) Fungi
D) Monera
Answer:
B) Plantae
7.
Which organism causes red tides?
A) Nostoc
B) Gonyaulax
C) Anabaena
D) Euglena
Answer:
B) Gonyaulax
8.
What are lichens an example of?
A) Parasitism
B) Symbiosis
C) Commensalism
D) Saprophytism
Answer:
B) Symbiosis
9.
Which agent lacks a protein coat and
consists only of RNA?
A) Virus
B) Viroid
C) Prion
D) Bacterium
Answer:
B) Viroid
10.
Which class of fungi includes mushrooms
and rusts?
A) Phycomycetes
B) Ascomycetes
C) Basidiomycetes
D) Deuteromycetes
Answer:
C) Basidiomycetes
11.
Which of the following kingdoms contains
prokaryotic organisms?
A) Fungi
B) Protista
C) Monera
D) Plantae
Answer:
C) Monera
12.
The term "diatomaceous earth"
refers to the deposits of:
A) Fungal
spores
B) Silica
walls of diatoms
C) Dead
lichens
D) Cellulose
from plants
Answer:
B) Silica walls of diatoms
13.
What is the role of plasmogamy in fungal
reproduction?
A) Spore
formation
B) Fusion
of protoplasm between gametes
C) Meiosis
in zygote
D) Production
of conidia
Answer:
B) Fusion of protoplasm between gametes
14.
Which of the following organisms lack a
cell wall?
A) Bacteria
B) Euglenoids
C) Fungi
D) Protozoa
Answer:
B) Euglenoids
15.
Which disease is caused by Plasmodium?
A) Cholera
B) Malaria
C) Tetanus
D) Typhoid
Answer:
B) Malaria
16.
What is the characteristic feature of red
dinoflagellates?
A) Cause
algal blooms
B) Produce
biogas
C) Form
dikaryotic cells
D) Produce
red tides
Answer:
D) Produce red tides
17.
What is the nature of genetic material in
plant viruses?
A) Double-stranded
DNA
B) Double-stranded
RNA
C) Single-stranded
RNA
D) Single-stranded
DNA
Answer:
C) Single-stranded RNA
18.
Which of the following groups contains
both unicellular and multicellular organisms?
A) Protista
B) Monera
C) Fungi
D) Plantae
Answer:
C) Fungi
19.
What type of nutrition is exhibited by
slime molds?
A) Autotrophic
B) Saprophytic
C) Holozoic
D) Parasitic
Answer:
B) Saprophytic
20.
Which scientist proposed the five-kingdom
classification system?
A) Aristotle
B) Carl
Woese
C) R.H.
Whittaker
D) Linnaeus
Answer:
C) R.H. Whittaker
21.
Which kingdom does not contain organisms
with a cell wall?
A) Monera
B) Protista
C) Animalia
D) Fungi
Answer:
C) Animalia
22.
What are the reproductive structures
formed during the sexual phase of fungi called?
A) Zoospores
B) Conidia
C) Ascospores
D) Sporangiospores
Answer:
C) Ascospores
23.
Which group of bacteria can survive in
extreme environments like hot springs or high salinity?
A) Cyanobacteria
B) Eubacteria
C) Archaebacteria
D) Mycoplasma
Answer:
C) Archaebacteria
24.
What type of reproduction is common in
protozoans like Amoeba?
A) Sexual
B) Binary
fission
C) Budding
D) Spore
formation
Answer:
B) Binary fission
25.
Which fungus is commonly used for the
production of antibiotics?
A) Rhizopus
B) Aspergillus
C) Penicillium
D) Puccinia
Answer:
C) Penicillium
26.
What is the primary mode of nutrition in
Kingdom Plantae?
A) Saprophytic
B) Parasitic
C) Holozoic
D) Autotrophic
Answer:
D) Autotrophic
27.
Mycoplasma is unique among bacteria
because:
A) It
can fix nitrogen
B) It
lacks a cell wall
C) It
produces methane
D) It
has a nucleus
Answer:
B) It lacks a cell wall
28.
What are the symbiotic associations of
algae and fungi called?
A) Prions
B) Viroids
C) Lichens
D) Mycorrhiza
Answer:
C) Lichens
29.
What is the role of heterocysts in
cyanobacteria like Nostoc?
A) Photosynthesis
B) Reproduction
C) Nitrogen
fixation
D) Motility
Answer:
C) Nitrogen fixation
30.
Which feature is unique to viruses and not
found in living organisms?
A) Cellular
structure
B) DNA
and RNA present together
C) Crystalline
form outside a host
D) Independent
reproduction
Answer:
C) Crystalline form outside a host
31.
Which organism is considered a connecting
link between plants and animals in the kingdom Protista?
A) Dinoflagellates
B) Euglenoids
C) Slime
molds
D) Protozoans
Answer:
B) Euglenoids
32.
What type of sexual reproduction occurs in
fungi when there is a dikaryotic stage?
A) Immediate
karyogamy
B) Gametangial
fusion
C) Delayed
nuclear fusion
D) Binary
fission
Answer:
C) Delayed nuclear fusion
33.
Which of the following is an example of an
imperfect fungus?
A) Penicillium
B) Alternaria
C) Agaricus
D) Rhizopus
Answer:
B) Alternaria
34.
Which group of Protists contains organisms
with silica-embedded cell walls?
A) Chrysophytes
B) Dinoflagellates
C) Euglenoids
D) Protozoans
Answer:
A) Chrysophytes
35.
Which disease is caused by a prion?
A) Tuberculosis
B) Mad
cow disease
C) Smallpox
D) Influenza
Answer:
B) Mad cow disease
36.
The structure responsible for
photosynthesis in cyanobacteria is:
A) Chloroplast
B) Chlorophyll-containing
thylakoids
C) Pellicle
D) Flagella
Answer:
B) Chlorophyll-containing thylakoids
37.
What type of association is found in
mycorrhiza?
A) Algae
and fungi
B) Fungi
and plant roots
C) Bacteria
and plant roots
D) Protozoans
and animals
Answer:
B) Fungi and plant roots
38.
In Whittaker's five-kingdom
classification, which kingdom contains decomposers?
A) Plantae
B) Protista
C) Fungi
D) Animalia
Answer:
C) Fungi
39.
Which type of algae forms a symbiotic
association in lichens?
A) Green
algae
B) Brown
algae
C) Blue-green
algae
D) Red
algae
Answer:
A) Green algae
40.
What is the infectious agent in potato
spindle tuber disease?
A) Bacteria
B) Virus
C) Viroid
D) Prion
Answer:
C) Viroid
41.
Which of the following Protists can form
harmful algal blooms?
A) Chrysophytes
B) Dinoflagellates
C) Slime
molds
D) Protozoans
Answer:
B) Dinoflagellates
42.
What is the function of the protein coat
(capsid) in a virus?
A) Replicate
the virus
B) Protect
genetic material
C) Infect
host cells
D) Produce
energy
Answer:
B) Protect genetic material
43.
The term "holozoic nutrition"
refers to:
A) Absorption
of nutrients
B) Ingestion
of food particles
C) Symbiosis
with algae
D) Decomposition
of matter
Answer:
B) Ingestion of food particles
44.
Which kingdom includes both autotrophic
and heterotrophic organisms?
A) Animalia
B) Plantae
C) Protista
D) Fungi
Answer:
C) Protista
45.
What is the primary mode of reproduction
in bacteria?
A) Sexual
reproduction
B) Spore
formation
C) Binary
fission
D) Budding
Answer:
C) Binary fission
46.
Which fungus is used extensively in
genetic research?
A) Neurospora
B) Rhizopus
C) Mucor
D) Ustilago
Answer:
A) Neurospora
47.
What is the outer protein coat of a
bacteriophage called?
A) Capsid
B) Cell
wall
C) Sheath
D) Tail
fibers
Answer:
A) Capsid
48.
Which organism has pseudopodia for
movement and feeding?
A) Paramecium
B) Amoeba
C) Euglena
D) Trypanosoma
Answer:
B) Amoeba
49.
Which algae can fix atmospheric nitrogen?
A) Dinoflagellates
B) Green
algae
C) Cyanobacteria
D) Brown
algae
Answer:
C) Cyanobacteria
50.
What are the spore-producing structures in
slime molds called?
A) Heterocysts
B) Fruiting
bodies
C) Ascocarps
D) Zoospores
Answer:
B) Fruiting bodies
Assertion
and Reason Questions:
Q.1 Assertion (A):
Bacteria exhibit extensive metabolic diversity compared to other organisms.
Reason (R): Bacteria are
autotrophic or heterotrophic and can survive in extreme conditions.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.2 Assertion (A): Fungi
are placed in a separate kingdom from plants.
Reason (R): Fungi are
autotrophic organisms with cell walls made of chitin.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: C
Q.3 Assertion (A): Red
tides are caused by certain types of dinoflagellates.
Reason (R):
Dinoflagellates multiply rapidly and release toxins, which may harm marine
life.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.4 Assertion (A):
Mycoplasma are considered the smallest living cells.
Reason (R): Mycoplasma
completely lack a cell wall and can survive without oxygen.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.5 Assertion (A):
Diatoms are referred to as "producers" in aquatic ecosystems.
Reason (R): Diatoms
perform photosynthesis and form the base of the aquatic food chain.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.6 Assertion (A):
Viruses are considered living organisms.
Reason (R): Viruses can
replicate only inside the host cells.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: D
Q.7 Assertion (A): Slime
molds are classified as saprophytic protists.
Reason (R): Slime molds
feed on decaying organic matter and form plasmodium under favorable conditions.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.8 Assertion (A):
Kingdom Monera includes only unicellular organisms.
Reason (R): All members
of Monera are prokaryotic.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.9 Assertion (A):
Euglenoids can act as both autotrophs and heterotrophs.
Reason (R): Euglenoids
have a protein-rich pellicle instead of a cell wall.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: B
Q.10 Assertion (A):
Cyanobacteria are included in the Kingdom Monera.
Reason (R): Cyanobacteria
are eukaryotic, photosynthetic organisms.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: C
Q.11 Assertion (A):
Kingdom Fungi includes both unicellular and multicellular organisms.
Reason (R): Fungi are
autotrophic organisms with cell walls made of cellulose.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: C
Q.12 Assertion (A):
Lichens are good indicators of air pollution.
Reason (R): Lichens
cannot grow in areas with high levels of sulfur dioxide pollution.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.13 Assertion (A):
Prions are infectious agents composed of abnormally folded proteins.
Reason (R): Prions cause
diseases like bovine spongiform encephalopathy and Creutzfeldt-Jakob disease.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.14 Assertion (A): The
alternation of generations is a characteristic feature of plants.
Reason (R): Plants
alternate between a diploid sporophytic phase and a haploid gametophytic phase
in their life cycle.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.15 Assertion (A):
Cyanobacteria can photosynthesize like green plants.
Reason (R): Cyanobacteria
contain chlorophyll a, which is also present in green plants.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.16 Assertion (A):
Basidiomycetes produce sexual spores called basidiospores.
Reason (R): Basidiospores
are exogenously produced on structures called basidia.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.17 Assertion (A):
Viruses cannot be classified under any kingdom in the five-kingdom system.
Reason (R): Viruses are
acellular and cannot reproduce outside a host cell.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.18 Assertion (A):
Euglenoids are capable of photosynthesis in the presence of sunlight.
Reason (R): Euglenoids
have chloroplasts, which allow them to photosynthesize.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.19 Assertion (A):
Chrysophytes are chief producers in aquatic ecosystems.
Reason (R): Chrysophytes
like diatoms have indestructible silica cell walls and perform photosynthesis.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: A
Q.20 Assertion (A):
Dinoflagellates have stiff cellulose plates on their outer surface.
Reason (R):
Dinoflagellates are primarily parasitic organisms.
A) Both A and R are true,
and R is the correct explanation of A.
B) Both A and R are true,
but R is not the correct explanation of A.
C) A is true, but R is
false.
D) A is false, but R is
true.
Answer: C
Short
Answer Questions
Q.1: Who proposed the
five-kingdom classification system?
Answer: R.H. Whittaker
proposed the five-kingdom classification system in 1969.
Q.2: What is the primary
component of the fungal cell wall?
Answer: The primary
component of the fungal cell wall is chitin.
Q.3: What are
heterocysts, and what is their function?
Answer: Heterocysts are
specialized cells in cyanobacteria that are involved in nitrogen fixation.
Q.4: Name two diseases
caused by bacteria.
Answer: Cholera and
typhoid are two diseases caused by bacteria.
Q.5: What is the mode of
nutrition in Kingdom Fungi?
Answer: The mode of
nutrition in fungi is heterotrophic, including saprophytic, parasitic, and
symbiotic forms.
Q.6: What is the
composition of the cell walls of diatoms?
Answer: The cell walls of
diatoms are made of silica and form a rigid, indestructible structure.
Q.7: What causes red
tides in marine environments?
Answer: Red tides are
caused by rapid multiplication of red dinoflagellates, such as Gonyaulax.
Q.8: How do viruses
differ from living organisms?
Answer: Viruses are
acellular, cannot reproduce independently, and are inert outside a host cell.
Q.9: What is the economic
importance of yeast?
Answer: Yeast is used in
baking (to make bread) and brewing (to produce alcohol).
Q.10: What are lichens,
and why are they significant?
Answer: Lichens are
symbiotic associations between algae and fungi. They are significant as
indicators of air pollution since they do not grow in polluted environments.
Q.11: What is the
smallest living cell known?
Answer: Mycoplasma is the
smallest known living cell.
Q.12: What type of spores
are produced in Ascomycetes during sexual reproduction?
Answer: Ascomycetes
produce ascospores during sexual reproduction.
Q.13: What is
diatomaceous earth?
Answer: Diatomaceous
earth is the accumulation of silica-rich cell wall deposits from diatoms over
billions of years.
Q.14: How do Euglenoids
survive in the absence of sunlight?
Answer: Euglenoids behave
as heterotrophs and feed on smaller organisms in the absence of sunlight.
Q.15: Name a pathogenic
protozoan and the disease it causes.
Answer: Plasmodium is a
pathogenic protozoan that causes malaria.
Q.16: What are viroids?
Answer: Viroids are
infectious agents made up of free RNA molecules without a protein coat, smaller
than viruses.
Q.17: How are
archaebacteria different from eubacteria?
Answer: Archaebacteria
have a unique cell wall structure that allows them to survive in extreme
environments, unlike eubacteria.
Q.18: What are prions,
and which diseases do they cause?
Answer: Prions are
infectious agents made of abnormally folded proteins. They cause diseases like
mad cow disease (BSE) in cattle and Creutzfeldt-Jakob disease (CJD) in humans.
Q.19: Name two examples
of slime molds.
Answer: Plasmodial slime
molds and cellular slime molds are two examples of slime molds.
Q.20: What are conidia,
and in which fungi are they found?
Answer: Conidia are
asexual spores found in fungi such as Aspergillus and Penicillium.
Q.21: What is the mode of
reproduction in bacteria under favorable conditions?
Answer: Bacteria
reproduce primarily by binary fission under favorable conditions.
Q.22: What is the
significance of cyanobacteria in agriculture?
Answer: Cyanobacteria
like Nostoc and Anabaena fix atmospheric nitrogen, enriching soil fertility.
Q.23: Name the pigments
responsible for the coloration in dinoflagellates.
Answer: The pigments
responsible for coloration in dinoflagellates are carotenoids and chlorophyll.
Q.24: What type of
genetic material is present in viruses?
Answer: Viruses can have
either DNA or RNA as their genetic material, but never both.
Q.25: What is the
dikaryotic stage in fungi?
Answer: The dikaryotic
stage in fungi is a phase where each cell contains two haploid nuclei from
different mating types.
Q.26: What are algae
blooms, and how do they affect aquatic life?
Answer: Algae blooms are
rapid growths of algae in water, which deplete oxygen levels and can harm
aquatic organisms.
Q.27: Name two edible
fungi.
Answer: Two edible fungi
are Agaricus bisporus (mushroom) and truffles.
Q.28: What are
saprophytes? Provide an example.
Answer: Saprophytes are
organisms that obtain nutrients by decomposing organic matter. Example:
Rhizopus.
Q.29: Name the
reproductive structure of basidiomycetes.
Answer: The reproductive
structure of basidiomycetes is the basidium.
Q.30: What is the
significance of the protein coat (capsid) in a virus?
Answer: The capsid
protects the genetic material of the virus and aids in its attachment to the
host cell.
Q.31: What are slime
molds, and where do they typically grow?
Answer: Slime molds are
saprophytic protists that typically grow on decaying organic material, such as
leaves and logs.
Q.32: Name the component
of the fungal hyphae that allows it to be multinucleated.
Answer: Coenocytic hyphae
allow fungal cells to be multinucleated as they lack cross walls (septa).
Q.33: What is the term
used for viruses that infect bacteria?
Answer: Viruses that
infect bacteria are called bacteriophages.
Q.34: How does
Trypanosoma cause sleeping sickness?
Answer: Trypanosoma
causes sleeping sickness by infecting the bloodstream and central nervous
system, transmitted by the tsetse fly.
Q.35: What is a pellicle
in euglenoids?
Answer: The pellicle is a
flexible, protein-rich layer that provides shape and flexibility to euglenoids.
Q.36: Name a fungus used
in the production of antibiotics.
Answer: Penicillium is a
fungus used in the production of the antibiotic penicillin.
Q.37 What role do
chemosynthetic bacteria play in the environment?
Answer: Chemosynthetic
bacteria oxidize inorganic substances and help recycle nutrients like nitrogen
and sulphur in the environment.
Q.38 What is the role of
mycorrhiza in plants?
Answer: Mycorrhiza is a
symbiotic association between fungi and plant roots that enhances nutrient and
water absorption for the plant.
Q.39 What is the
composition of the cell wall in archaebacteria?
Answer: The cell wall of
archaebacteria is made of polysaccharides and proteins, lacking peptidoglycan.
Q.40 Name a pathogenic
fungus and the disease it causes.
Answer: Puccinia is a
pathogenic fungus that causes wheat rust.
1. Question: Explain the
five-kingdom classification system proposed by R.H. Whittaker. What were the
criteria used for classification?
Answer:
R.H. Whittaker (1969)
proposed the five-kingdom classification system to organize living organisms
based on specific criteria such as cell structure, mode of nutrition, body
organization, and phylogenetic relationships. The five kingdoms are:
Kingdom Monera:- Includes
all prokaryotic organisms (e.g., bacteria, cyanobacteria).
These organisms are
unicellular, lack a true nucleus, and reproduce asexually.
Mode of nutrition can be
autotrophic (photosynthetic or chemosynthetic) or heterotrophic (saprophytic or
parasitic).
Kingdom Protista:- Comprises
single-celled eukaryotes like algae, protozoans, and slime molds. The organisms
have a well-defined nucleus and membrane-bound organelles.
Nutrition can be
autotrophic (e.g., diatoms) or heterotrophic (e.g., Amoeba).
Kingdom Fungi:- Includes
heterotrophic, eukaryotic organisms such as molds, yeast, and mushrooms. Their
cell walls are made of chitin. Nutrition is saprophytic, parasitic, or
symbiotic.
Kingdom Plantae:- Includes
multicellular, autotrophic eukaryotes (e.g., algae, bryophytes, gymnosperms,
angiosperms). They have a cell wall made of cellulose and perform photosynthesis.
Their life cycle exhibits alternation of generations.
Kingdom Animalia:- Includes
multicellular, heterotrophic eukaryotes (e.g., mammals, insects). They lack a
cell wall and have specialized tissue and organ systems.
Nutrition is holozoic
(ingestion of solid food).
Criteria Used:
·
Cell type: Prokaryotic or eukaryotic.
·
Body organization: Unicellular or
multicellular.
·
Mode of nutrition: Autotrophic, heterotrophic
(saprophytic, parasitic, or holozoic).
·
Reproductive strategy: Asexual or sexual
reproduction.
·
Phylogenetic relationships: Evolutionary
history and relationships.
Q.2. Describe the viruses'
structure and explain their reproduction mode.
Answer:
Structure of Viruses: Viruses
are acellular entities that cannot independently reproduce. Their structure
includes:
Genetic Material: Either
DNA or RNA, but never both. Plant viruses usually have single-stranded RNA. Animal
viruses can have single or double-stranded RNA or DNA. Bacteriophages usually
have double-stranded DNA.
Protein Coat (Capsid): Made
of protein subunits called capsomeres. Protects the genetic material and
facilitates attachment to host cells.
Envelope (in some
viruses): Derived from the host cell membrane. Contains lipids
and proteins that assist in infecting host cells.
Shape: Viruses
can have various shapes such as helical (e.g., Tobacco Mosaic Virus),
polyhedral (e.g., adenovirus), or complex (e.g., bacteriophage).
Mode of Reproduction: Viruses
can only reproduce inside a host cell. The process involves:
Attachment:
The virus binds to specific receptors on the host cell's surface.
Penetration:
The viral genetic material enters the host cell, either by injection
(bacteriophages) or fusion with the cell membrane (enveloped viruses).
Replication and Synthesis:
The viral genetic material hijacks the host cell machinery to replicate its
genome and produce viral proteins.
Assembly:
Newly synthesized genetic material and proteins assemble into new virus
particles.
Release:
The viruses are released from the host cell by lysis (rupturing the cell) or
budding (in enveloped viruses).
Viruses are obligate
intracellular parasites, meaning they cannot survive or reproduce outside a
host.
Q.3 What are lichens? Describe
their structure, types, and ecological significance.
Answer:
Lichens are symbiotic
associations between a fungus (mycobiont) and an alga or cyanobacterium
(phycobiont). The fungal partner provides shelter, water, and nutrients, while
the algal or cyanobacterial partner performs photosynthesis and provides food.
Structure of Lichens: Composed
of intertwined fungal hyphae and algal cells. The algal partner is usually
embedded within the fungal tissue.
Types of Lichens:
Crustose: Thin,
crust-like lichens tightly attached to the substrate (e.g., rocks).
Example: Graphis.
Foliose: Leaf-like
lichens loosely attached to the substrate with distinct upper and lower
surfaces.
Example: Parmelia.
Fruticose: Shrub-like
or branched lichens, often hanging from trees or growing upright.
Example: Cladonia.
Ecological Significance
of Lichens:
Bioindicators:
Lichens are sensitive to air pollution, particularly sulfur dioxide, and are
used as indicators of air quality.
Soil Formation:
Lichens secrete acids that break down rocks, helping in soil formation.
Primary Producers: In
harsh ecosystems like tundras, lichens act as primary producers.
Food Source:
They serve as food for animals like reindeer and some insects.
Medicinal Uses:
Some lichens produce antibiotics and are used in traditional medicine.
Q.4 Discuss the
differences between archaebacteria and eubacteria.
Answer:
Archaebacteria and
eubacteria are both prokaryotes but differ in many structural and functional
aspects:
Archaebacteria's ability
to thrive in extreme conditions makes them distinct, while eubacteria include
the more commonly known bacteria.
Q.5 What are protozoans?
Explain their classification with examples.
Answer:
Protozoans are
unicellular, heterotrophic eukaryotes that are either free-living or parasitic.
They are considered primitive relatives of animals.
Classification of
Protozoans:
Amoeboid Protozoans: Move and capture
food using pseudopodia (false feet). Found in freshwater, marine water, or
moist soil.
Example: Amoeba,
Entamoeba (causes amoebic dysentery).
Flagellated Protozoans:
Move using flagella. Can be free-living or parasitic.
Example: Trypanosoma
(causes sleeping sickness).
Ciliated Protozoans:
Use cilia for movement and feeding. Contain a gullet for ingesting food
particles.
Example: Paramecium.
Sporozoans:
Lack locomotory structures.
All are parasitic and
have an infectious spore-like stage.
Example: Plasmodium
(causes malaria).