Mapping our Genes
Q1.
Fill in the blanks
1. In ___________ mode of reproduction the
offsprings are with minor differences. (asexual)
2. Both the parents contribute equal amount
of ___________ material to the offspring. (genetic)
3. Dominant character masks the ___________
characters. (recessive)
4. Selection by nature is not ____________
but ____________. (deliberate, natural)
Q2.
Give scientific reasons:
1. In sexual mode of reproduction greater
diversities are generated.
Ans.
i.
In
sexual mode of reproduction two parents are involved.
ii.
Each
one has its own DNA copies that are passed on through their nuclei at the time
of fertilization of gametes.
iii.
Therefore
more diversity is produced.
iv.
Moreover,
the process of meiosis at the time of gamete formation, also produces
variations. Hence in sexual mode of reproduction greater
2. Phenotypic and genotypic ratios are
different.
Ans.
i.
Phenotype
is the appearance or any detectable characteristic feature of an individual
life red and white flowers.
ii.
Genotype
is the genetical composition of individuals like RR, Rr and rr.
iii.
Hence,
phenotypic and genotypic ratios are different.
3. In human beings the gametes from the male
parent decides the sex of the baby.
Ans.
i.
In
human male gametes, two dissimilar chromosomes XY are present whereas in
females two similar chromosomes XX are present.
ii.
All
children inherit ‘X’ chromosomes from their mother and ‘X’ or ‘Y’ from their
father.
iii.
Hence
the gametes from the male parent decide the sex of the baby.
4. Paleontological evidence suggests that
invertebrates came into existence before the vertebrates.
Ans.
i.
A
systematic study of fossils and its occurrence revealed that the deepest layers
of land were found to have fossils of invertebrates.
ii.
In
layers above them were found vertebrates such as fish – like animals,
amphibians, reptiles, birds and mammals.
iii.
This
suggests that invertebrates came into existence before the vertebrates.
Q3.
With the help of a diagram (Punnett square) show a Mendelian experiment where
tall pea plant bearing red flowers is crossed with a short pea plant bearing
white flowers. Write both the phenotypic and genotypic ration for F2
generation.
Q4.
Write a short note on:
Darwin’s
theory of evolution.
i.
Darwin’s
theory of evolution is based on natural selection.
ii.
Darwin’s
theory of natural selection suggests that only the fittest survive.
iii.
All
those plants and animals which are not fit die.
iv.
These
fit species reproduce and pass on the relevant characteristics to the following
generation which in turn would make them fit for survival.
v.
This
process of selection of characteristics that contribute to the fitness for
survival was called natural selection by Darwin.
vi.
The
criterion for the natural selection is the only one i.e. successful adaptation
for growth and reproduction in the given environment.
Do
You know?
Charles
Darwin (Feb. 12, 1809 - April 19, 1882) was an
English naturalist renowned for his documentation of evolution and for his
theory of its operation, known as Darwinism. His evolutionary theories,
propounded chiefly in two works--On the Origin of Species by Means of Natural
Selection (1859) and The Descent of Man, and Selection in Relation to Sex
(1871)--have had a profound influence on subsequent scientific thought.
Darwin was the son of
Robert Waring Darwin, who had one of the largest medical practices outside of
London, and the grandson of the physician Erasmus Darwin, the author of
Zoonomia, or the Laws of Organic Life, and of the artisan-entrepreneur Josiah
Wedgwood. Darwin thus enjoyed a secure position in the professional upper
middle class that provided him with considerable social and professional
advantages.