21.How do or gan isms cope with stress ful ex ter nal
en vi ron men tal con di tions which are local ised or of
short duration?
22.What is the equa tion of spe cies area re la tion ship?
Also write down the significance of the slope of
regression in a species-area relationship?Section-D
23.Prateek’s mother wondered why the mos qui toes
were not re spond ing to the mos quito re pel lant,
which she had been us ing for the last sev eral years.
Raj sug gested Prateek’s mother to change the brand
of re pel lant she was us ing. It worked and was
ef fec tive, to which his mother con cluded that the
ear lier repellent might have been ex pired or
degraded over time. Prateek ob jected to her opinion
and explained to her the reality.
(a)What values were reflected by Prateek?
(b)Why did mosquitoes not respond to the repellant?
Explain on the basis of natural selection.
(c)Cite any two examples of natural selection which
you often come across.Section-E
24.A flower of to mato plant fol low ing the pro cess of
sex ual re pro duc tion pro duces 240 vi a ble seeds.
Answer the following questions giving reasons:(i)What is the minimum number of pollen grains
that must have been involved in the pollination of
its pistil?
(ii)What would have been the mininum number of
ovules present in the ovary?
(iii)How many megaspore mother cells were
involved?
(iv)What is the minimum number of microspore
mother cells involved in the above case?
(v)How many male gametes were involved in this
case?
Or
Give a schematic representation of oogenesis in
humans. Mention the number of chromosomes at
each stage. Correlate the life phases of individual
with the stages of the process.
25.A pea plant pro duc ing yel low col oured and round
seeds is given with un known ge no types. Ex plain
how you would find the cor rect ge no types of the
plant with re spect to the traits men tioned.
Work out the cross and name it.
Or
How did Griffith proved transforming principle in
genetics. Explain the procedure.
26.Ex plain how tol er ance to en vi ron men tal fac tors
de ter mines dis tri bu tion of species.
Or
What are the various components of biodiversity?
Explain each of them.Answers of Board Exam Corner (December Issue)
- Sahiwal
- 6 × 106 bp.
- Coelacanth has evolved into the first amphibians, they are fish with
stout and strong fins that could move on land and go back to water. - He is suffering from AIDS. The virus is HIV.
- Biopiracy.
- No, the uterine environment is not congenial for the survival of
gametes. If directly transferred to the uterus they will undergo
degeneration or could be phagocytosised and hence, viable zygote
would not be formed. - (i)High yield
(ii)Disease and pest resistance
(iii)Desirable quality
(iv)Drought resistance
10.
Primary Carnivore Secondary Carnivore
These are the animals which feed on
the herbivores.These are the animals, which feed
on the primary carnivores.
They occupy the third trophic level. They occupy the fourth trophic level.Or
The function of reservoir is to meet the deficit that arises due to the
imbalances in the influx and efflux of nutrients.
The two types of nutrient cycles are :
(i)Sedimentary cycle (ii) Gaseous cycles- Components of biodiversity
(i)Species diversity (ii) Genetic diversity
(iii)Ecosystem diversity