Reason : The excess of nutrients which are not used
immediately are converted into fats and are stored mainly
in areolar tissue.
- Assertion : Mature mammalian RBCs lack nuclei and other
cell organelles.
Reason : Absence of cell organelles helps in better
accomodation of haemoglobin in RBCs so as to carry out
oxygen transport more efficiently.
- Assertion : Leucocyte extravasation refers to the movement
of leucocytes out of the circulatory system and towards the
site of injury.
Reason : Lymphocytes and monocytes are granulocytes
which produce antibodies to destroy the antigens.
EVOLuTIOn
- Assertion : Hardy-Weinberg Principle states that in the
absence of disturbing influences, gene frequencies of large
populations of sexually reproducing organisms do not
change, provided that matings occur at random.
Reason : The disturbing influences include mutation,
gene flow, genetic drift, genetic recombination and natural
selection pressure.
- Assertion : Herbaceous lycopods and arborescent lycopods
evolved from Zosterophyllum of palaeozoic era.
Reason : Zosterophyllum is a primitive gymnosperm with
vascular tissues.
- Assertion : In sympatric speciation, a new species arises
from an existing species that is living in the same area.
Reason : Temporal and behavioural isolations produce
significant changes in the genetic make-up within a species
so that a new species is formed.
- Assertion : The flippers of seal, patagia of bat, front legs
of horse and arms of man look very different, perform
different functions, but exhibit the same structural plan in
bone pattern.
Reason : These organs are an example of convergent
evolution which involves the tendency of unrelated
organisms to acquire similar structures.
- Assertion :Australia has many species of egg-laying
mammals and pouched mammals that occur only in
Australia.
Reason : Australia separated from the mainland during
mesozoic era, before placental mammals evolved.
- Assertion : Directional selection arises from a changing
environment, it results in reduced variance and a shift in
the mean value of population for the selected character.
Reason : Directional selection results in the organism
being adapted to changed environment.
- Assertion : Seymouria has been considered as a missing
link between amphibians and reptiles.
Reason : Seymouria was a lizard-like animal with relatively
small pointed head with dorsally placed nostril and a short
tail.
- Assertion : Proterozoic era is referred to as the age of
invertebrates.
Reason : All major invertebrate phyla e.g., Mollusca, Arthropoda
etc. were quite abundant during the proterozoic era.
- Assertion : Coacervates were colloidal structures that
were considered to have led to the formation of first living
cells from which more complex cells have evolved today.
Reason : Oparin speculated that coacervates consisted of
only inorganic molecules surrounded by a film of water.
- Assertion : When the population is at decline, the number
of individuals may reduce to a extent that the small group
of population constituting the population becomes isolated
and restricted in distribution.
Reason : This results in a reduction in allelic frequencies,
known as genetic bottle neck effect which often prevents
the species from extinction.
- Assertion : Palaeontological evidences indicated that
evolution has taken place from complex to simple forms in
a gradual manner.
Reason : Rocks of proterozoic era show fossils of great reptiles,
primitive birds and mammals whereas those of palaeozoic era
show fossils of first primates and placental mammals.
- Assertion : Darwin’s finches cites an example of adaptive
radiation.
Reason : Darwin’s finches had common ancestors but then
they evolved different types of modified beaks according to
their food habits.
- Assertion : The rocks of early era (e.g., proterozoic) contain
less number of fossils than the rocks of later era.
Reason : Life first originated in sea as a simple form, so
fossils were not in plenty in the beginning as they were in
later stage.
- Assertion : Vestigial organs are believed to be the
remnants of organs which were complete and functional
in the ancestors.
Reason : Wings of flightless birds, splint bones in feet of
horse, wisdom teeth in human etc. are the examples of
vestigial organs.
- Assertion : Reproductive isolation is the prevention of
interbreeding between the populations of the two different
species.
Reason : Natural selection is the process by which those
organisms which are physically, physiologically and behaviou-
rally better adapted to the environment, survive and reproduce
while those not so well adapted fail to reproduce or die.
ANSWER KEY
- (b) 2. (d) 3. (a) 4. (c) 5. (b)
- (c) 7. (d) 8. (b) 9. (b) 10. (d)
- (c) 12. (a) 13. (c) 14. (a) 15. (c)
- (b) 17. (c) 18. (a) 19. (c) 20. (a)
- (b) 22. (a) 23. (d) 24. (c) 25. (b)
- (d) 27. (a) 28. (a) 29. (b) 30. (b)
