Download 2. Biological Classification.

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1. State two economically important uses of:
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(a) Heterotrophic bacteria
(b) Archaebacteria
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Solution:
(a) Heterotrophic bacteria
The majority are important decomposers.Many of them have a significant impact on human affairs.
They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots,
etc.
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(b) Archaebacteria
Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is
responsible for their survival in extreme conditions. Methanogens are present in the guts of several
ruminant animals such as cows and buffaloes and they are responsible for the production of methane
(biogas) from the dung of these animals.
2. What is the nature of cell walls in diatoms?
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Solution:
In diatoms the cell walls form two thin overlapping shells, which fit together as in a soap box. The
walls are embedded with silica and thus the walls are indestructible. Thus, diatoms have left behind
large amount of cell wall deposits in their habitat; this accumulation over billions of years is referred
to as ‘diatomaceous earth’.
3. Find out what do the terms ‘algal bloom’ and ‘red-tides’ signify.
Solution:
Algal bloom
A heavy growth of algae in and on a body of water; usually results from high nitrate and phosphate
concentrations entering water bodies from farm fertilizers and detergents; phosphates also occur
naturally under certain conditions.
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Solution:
There are 6 ways in which viroids are different to viruses:
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4. How are viroids different from viruses?
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Red tides
Phenomenon associated with population explosions (blooms) of certain types of dinoflagellates; red
structures inside the dinoflagellates cause the water to have a reddish color.
(i) Contain single circular RNA of low molecular weight (300 to 400 nucleotides).
(ii) RNA is often internally paired (3D) and is therefore protected against cellular Enzymes.
(ii) Viroids contain no capsids or envelopes.
(iii) There is no requirement for helper viruses.
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(iv) Viroids do not produce proteins.
(v) In viroids RNA is always copied in the host cell nucleus.
(vi) Viroids can only be identified by nucleotide sequencing techniques.
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5. Describe briefly the four major groups of Protozoa.
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Solution:
Protozoans:
All protozoans are heterotrophs and live as predators or parasites. They are believed to be primitive
relatives of animals. There are four major groups of protozoans.
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(i) Amoeboid protozoans:
These organisms live in fresh water, seawater or moist soil. They move and capture their prey by
putting out pseudopodia (false feet) as in Amoeba. Marine forms have silica shells on their surface.
Some of them such as Entamoeba are parasites.
(ii) Flagellated protozoans:
The members of this group are either free-living or parasitic. They have flagella. The parasitic forms
cause diseases such as sleeping sickness. Example: Trypanosoma.
(iii) Ciliated protozoans:
These are aquatic, actively moving organisms because of the presence of thousands of cilia. They
have a cavity (gullet) that opens to the outside of the cell surface. The coordinated movement of
rows of cilia causes the water laden food to be steered into the gullet. Example: Paramoecium.
(iv) Sporozoans:
This includes diverse organisms that have an infectious spore-like stage in their life cycle. The most
notorious is Plasmodium (malarial parasite) which causes malaria which has a staggering effect
on human population.
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6. What do the terms phycobiont and mycobiont signify?
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Solution:
The algal component is known as phycobiont and fungal component as mycobiont, which are
autotrophic and heterotrophic, respectively. Algae prepare food for fungi and fungi provide shelter
and absorb mineral nutrients and water for its partner.
So close is their association that if one saw lichen in nature one would never imagine that they had
two different organisms within them.
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7. What are the characteristic features of Euglenoids?
Solution:
Majority of the euglenoids are fresh water organisms found in stagnant water. Instead of a cell wall,
they have a protein rich layer called pellicle which makes their body flexible. They have two flagella,
a short and a long one. Though they are photosynthetic in the presence of sunlight, when deprived of
sunlight they behave like heterotrophs by predating on other smaller organisms. Interestingly, the
pigments of euglenoids are identical to those present in higher plants. Example: Euglena
8. Give a brief account of Viruses with respect to their structure and nature of genetic
material. Also name four common viral diseases.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
EMAIL:2 [email protected] web site www.badhaneducation.in
BADHANEDUCATION D96 MUNIRKA VILLAGE NEW DELHI 110067 & VIKAS PURI NEW DELHI
CONTACT FOR COACHING MATHEMATICS FOR 11TH 12TH NDA DIPLOMA SSC CAT SAT CPT
CONTACT FOR ADMISSION GUIDANCE B.TECH BBA BCA, MCA MBA DIPLOMA AND OTHER COURSES 09810144315
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Solution:
Viruses are obligate parasites. In addition to proteins viruses also contain genetic material that could
be either RNA or DNA. No virus contains both RNA and DNA. A virus is a nucleoprotein and the
genetic material is infectious. In general, viruses that infect plants have single stranded RNA and
viruses that infect animals have either single or double stranded RNA or double stranded DNA.
Bacterial viruses or bacteriophages (viruses that infect the bacteria) are usually double stranded DNA
viruses. The protein coat called capsid made of small subunits called capsomeres. The capsomeres
protect the nucleic acid. These capsomeres are arranged in helical or polyhedral geometric forms.
Viruses cause diseases like mumps, small pox, herpes and influenza. AIDS in humans is also caused
by a virus. In plants, the symptoms can be mosaic formation, leaf rolling and curling, yellowing and
vein clearing, dwarfing and stunted growth.
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CONTACT FOR MATHEMATICS GROUP/HOME COACHING FOR CLASS 11TH 12TH BBA,BCA,
DIPLOMA CPT CAT SSC AND OTHER EXAMS Also home tutors for other subjects in DELHI AND OTHER MAJOR CITIES
EMAIL:3 [email protected] web site www.badhaneducation.in