(iii) A poster making programme can be held in school
depicting the causes, effects and solutions for air
pollution. The students can use these posters in their
society to make people aware.- (a) The organism that was used by Thomas Hunt Morgan
and his colleagues for their experiments on linkage was
Drosophila melanogaster. Refer to answer 80, page no. 120,
MTG CBSE Champion Biology.
(b) Sturtevant used the frequency of recombination between
the gene pairs on the same chromosome as a measure of
the distance between genes and mapped their position
on the chromosome. This resulted in a chromosome map
which was a linear graphic representation of the sequence
and relative distances of the various genes present in that
chromosome. This relative distance between genes was
indicated by the percentage of their recombination or
crossing over. A 100% cross over was termed as Morgan
(M), 10% as deciMorgan (dM) and 1% as centiMorgan (cM)
or 1 map unit. Today genetic maps are extensively used as
a starting point in the sequencing of whole genomes.
OR
(a) Refer to answer 16(b), page no. 155, MTG CBSE Champion Biology.
(b) Refer to answer 35(b), page no. 160, MTG CBSE Champion Biology.
- (a) (i),(ii) Refer to answer 28(a), page no. 323, MTG CBSE
Champion Biology.
(iii) Migrate : Under unfavourable conditions, some
organisms migrate to more favourable areas and
return when the conditions are less hostile. The
movement can be in search of food, climate, etc.
Many animals, specially birds, migrate during
winters to more favourable areas. E.g., Arctic
tern, Sea lamprey etc. Every winter the Keoladeo
National Park (Bharatpur) in Rajasthan receives
thousands of migratory birds which comes from
Siberia and other very cold northern regions.
(iv) Suspend : To tide over unfavourable conditions,
some organisms suspend their metabolic activities.
Bacteria, fungi and lower plants develop thick
walled spores, which germinate during suitable
conditions. Polar bears go into hibernation during
winter season to escape cold. Some snails and
fish undergo aestivation to avoid summer related
problems like heat and dessication.
(b) Death rate is defined as the number of deaths per 1000 individuals
of a population. Since, total number of butterflies = 80
Number of butterflies that died = 8
Death rate ==
8
8001. butterflies per weekOR
(a) Trophic level in an ecosystem is defined as a specific place for
an organism in the natural surroundings or in a community
according to its feeding relationship with other organisms.
It is based on the source of that organism’s nutrition or food
because of which it occupies a specific position in the food
chain.
Standing crop is the total mass of living material at a
particular trophic level at a specific time. The standing crop is
measured as the mass of living organisms or biomass or the
number in a unit area. The biomass of a species is expressed
in terms of fresh or dry weight and the measurement of
biomass in terms of dry weight is more accurate.
(b) Trophic level of an organism depends upon the source of
food and position in a food chain. The first trophic level
is occupied by the producers which synthesise organic
nutrients from inorganic raw materials with the help of
solar radiations (photosynthesis) not only for themselves
but also for heterotrophic organisms or consumers. They
have this capacity due to the presence of chlorophyll
which can convert solar energy into chemical energy, e.g.,
phytoplanktons, plants, trees, etc.
(c) Refer to answer 29, page no. 345, MTG CBSE Champion Biology.- (a) Flowering plants have developed many devices to
discourage autogamy and geitonogamy. These are :
(i) Dicliny (Unisexuality) : Flowers are unisexual so
that self pollination is not possible. The plants may
be monoecious (bearing both male and female
flowers, e.g., maize) or dioecious (bearing male and
female flowers on different plants, e.g., mulberry,
papaya).Monoecious plants cannot undergo
autogamy, however geitonogamy is possible in
these plants whereas dioecious plants prevent both
geitonogamy and autogamy.
(ii) Dichogamy : Anthers and stigmas mature at
different times in a bisexual flower so as to
prevent self-pollination. (a) Protandry : Anthers
mature earlier than stigma of the same flower.
Their pollen grains become available to stigmas
of the older flowers, e.g., sunflower, Salvia. (b)
Protogyny : Stigmas mature earlier so that they
get pollinated before the anthers of the same
flower develop pollen grains, e.g., Mirabilis jalapa,
Gloriosa, Plantago.
(b) Refer to answer 111, page no. 36, MTG CBSE Champion Biology.
OR
(a) Refer to answer 85(a), page no. 69 and 86(a), page no. 70, MTG
CBSE Champion Biology.
(b) Refer to answer 85(b), page no. 70, MTG CBSE Champion Biology.