(b) These are six matchstick-sized capsules containing
synthetic progesterone which are implanted subcutane-
ously under the skin of the inner arm above the elbow.
The capsules slowly release the progesterone for about
five years. This blocks ovulation (by inhibiting the release
of FSH and LH from pituitary) and thickens the cervical
mucus to prevent sperm transport.
- (a) & (b) Refer to answer 55 (i) and (ii), page no. 122, `MTG
Excel in Biology’.
OR
(a) Western Ghats have been declared as biological hotspots as
they exhibit exceptionally high levels of biological diversity
and endemism. atleast 325 globally threatened (IuCN red
Data List) species occur in the Western Ghats. They are
under tremendous pressure due to loss of biodiversity.
(b) Chlorofluorocarbons (CFCs) release active chlorine radicals
(Cl, ClO) which remain functional in atmosphere for a long
time and convert ozone molecules into oxygen at a fast
rate. This occurs as :
CFCl 3 →uV-C CFCl + Cl (^2) , CFCl 2 CFCl + Cl
uV-C
→
Cl + OC 32 → lO + O, ClO + O 32 → Cl + 2O
- When a piece of differentiated tissue is cultured on a
suitable nutrient medium, and given external stimuli the
mature and non-dividing cells undergo certain changes
to transform into meristematic cells. This phenomenon of
transformation of mature cells to the meristematic cells
leading to the formation of callus, is called dedifferentiation.
These dividing cells of callus have an ability to form the entire
plants if provided with suitable nutritional and hormonal
requirements. Such a phenomenon of the component cells of
callus to form whole plants is called redifferentiation. These
two phenomena i.e., dedifferentiation and redifferentiation
are the basic requirements of cellular totipotency which is the
basis of tissue culture. - Culture (nutrient) medium can be referred to as a highly
enriched laboratory soil as it consists of all the important
organic and inorganic nutrients (e.g., glucose, sucrose,
amino acids, vitamins, micro and macro elements, etc.), and
growth hormones (auxins, gibberellins, cytokinins, etc.) in
appropriate proportions, which are required for the growth
and development of an organism. - Pathogens often develop resistance to existing antibiotics
so that newer antibiotics are required to be produced. Some
of the factors due to which this resistance is developed
are : (i) Development of copious mucilage. (ii) alteration
of cell membrane so that antibiotic cannot recognise the
pathogen, which prevents antibiotic entry. (iii) Mutation in
pathogen. (iv) Development of pathogen enzyme capable
of modifying antibiotic. - (a) Gaseous nutrient cycles are rapid and more perfect as
compared to sedimentary nutrient cycles. It is because in
gaseous nutrient cycles, nutrients remain in circulation more
or less uniformly, whereas in sedimentary nutrient cycles,
nutrients get out of circulation and constitute a relatively
inactive and immobile reservoir in earth's crust.
(b) Over-exploitation is one of the major causes of loss of
biodiversity. Man for its own economic benefits, kills a vast
majority of animal species that leads to their extinction.
example – Steller's sea cow (Hydrodamalis gigas) was
a large, herbivorous, marine mammal which had been
discovered in 1741 and become extinct by 1768. It became
extinct as it was over-exploited for food, skin and for its
valuable subcutaneous fat.- Plasmid is a circular DNa molecule. When cut with a
restriction endonuclease, it becomes linear but does not get
fragmented. On the other hand, a linear DNa molecule forms
two fragments when cut with restriction endonuclease.
Hence, a single DNa band is observed in case of plasmid
and two DNa bands are observed in case of linear DNa, on
agarose gel electrophoresis. - (a) The biology teacher reflects social and moral responsibility
along with good knowledge of his subject.
(b) a person is classified as having aIDS if :
(i) CD4 T cells count drops below 200/cubic mm of blood.
(ii) an HIV – related infection or HIV - related cancer
develops
an HIV positive patient can live for many years without
even developing aIDS.
(c) Refer to answer 64, page no. 250, `MTG Excel in Biology’. - (a)
(b) Refer to answer 28(i) and 30(i), page no. 293, `MTG Excel
in Biology’.
OR
Refer to answer 12(a), page no. 308, `MTG Excel in Biology’.- (a) Refer to answer 18(a), page no. 54,
MTG Excel in Biology’. (b) Refer to answer 12, page no. 68,MTG Excel in Biology’.
OR
(a) Refer to answer 26 (i) page no. 82,MTG Excel in Biology’. (b) Refer to answer 6 (a) page no. 75,MTG Excel in Biology’. - (a) Refer to answer 11, page no. 359,
MTG Excel in Biology’. (b) Refer to answer 29, page no. 367,MTG Excel in Biology’.
OR
Refer to answer 3 page no. 276, `MTG Excel in Biology’.