- (a) 21. (d)
- Azolla-Anabaena association is of great
importance to agriculture. Anabaena azollae
resides in the leaf cavities of the fern Azolla
where it fixes nitrogen and increases the yield of
plants by 15-35% in rice fields.
- (a) Anaphase I of meiosis: The homologous
chromosomes separate, while sister chromatids
remain associated at their centromeres.
- (b)
- (d) Bt toxin are solubilised in alkaline pH of the
insect gut causing death.
- (a) Cauliflower plant commonly show whiptail
disease and the leaves finally become flaccid and
brown.
- (b) The diagram is identified as heterophyll in
Buttercup.
- (b) In alternation of generation, the gametophyte
undergoes syngamy to produce spore.
- (b)
- (d) Prophase – formation of cytoplasmic fibres
and proteins, Metaphase – arranged on equatorial
plane, Anaphase – arrangement of chromatids
on the poles, Telophase – nuclear membrane
and other organelles reorganise, Cytokinesis –
formation of syncytium. All of these events occur
in mitosis.
- (a) The two empty boxes on the left would be
Aa and the other two on the right would be
aa. In simple words, 50% of the offsprings
are homozygous recessive (aa) and 50% are
heterozygous (Aa).
- (c) In runner stem grows and spread on the
surface of soil. Roots are developed at lower
side and leaves from upper side from node. But
water hyacinth is a floating aquatic plant which
propagates by fleshy bulbs.
- (b) The breakdown of detritus into smaller
particles by the earthworm is a process called
fragmentation. Others are performed by
heterotrophic microbes
- (c) As the genetic code is universal it is possible
to produce human protein in bacteria by genetic
engineering. Due to the universality trait of
genetic code- a codon codes for the same amino
acid in all the organisms.
- (c) DNA Polymerase has thermostable property.
Hence they are active at high temperature.
- (b) Histogen theory for shoot apical meristem has
been proposed by Hanstein(1870). It advocates
that there are three distinct meristematic zones
(layers) called dermatogen, periblem and
plerome. The dermatogen, periblem and plerome.
The dermatogen is the outermost histogen giving
rise to epidermis, periblem is the middle one
producing the cortex and plerome is the innermost
resulting in central cylinder. (i.e., vascular tissue).
Cork cambium (phellogen) is the secondary
lateral meristem found in outer cortical region. Its
cells divide periclinally cutting off cells towards
the outside (forming cork or phellem) and inside
(forming secondary cortex or phelloderm).
- (b) Pencillin, Chloramphenicol, Tetracyclin
and Erythromycin is produced by Penicillium
chrysogenum, Streptomyces griseus,
Streptomyces aureofaciens and Streptomyces
erythreus respectively.
38.(d) The fixation of CO 2 in C 4 plants takes place
in two places and by two different organic
compounds, PEP is found in mesophyll cells
which primarily fixes atmospheric CO 2 into
Oxaloacetic acid.
- (d)
- (a) Transgenic basmati rice contains β-carotene.
It is precursor of Vitamin A and also gives high
yield.
- (c) Some of the non-leguminous plants also fix
nitrogen, Eg: Alnus plant to which Frankia is
involved in formation of nodule.
- (a) Gibberellic acid is a simple weak acidic plant
growth hormone which promotes cell elongation
of leaves and stem and generally it is growth
promoter not inhibitor. It does not involve in
abscission.
- (b) The tallest tree in gymnosperms is Sequoia
whereas in angiosperms it is Eucalyptus, wolffia
is the smallest flowering plant, a hydrophyte,
pteridophytes are seedless vascular cryptograms
and Macrocystis is the largest perennial algae.
- (b) Condensation of DNA so that chromosomes
become visible and occurs during mid-prophase.
Nuclear membrane disassembly begins at late
prophase or transition to metaphase.
Arrangement of chromosomes at the equator
occurs during metaphase, called congression.
Centromere division or spiltting occurs during
anaphase forming daughter chromosomes.
- (c) The genotype of self-fertilizing trihybrid
would be AaBbCc. It implies that eight different
types of gametes ABC, ABc, AbC, Abc, aBC,
aBc, abC, abc are formed. Therefore, the number
of zygotes would be 8^2 = 64.
