EVOLUTION (Genetics and Evolution)
India Study Solution Theoretical
Questions - TQ 2 (Q. No. 7-11)
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Evolution (Syllabus): Origin of life; Evolution of Life Forms; Universe; Origin of Universe; Biological Evolution and Evidences for Biological Evolution from Paleontology, Comparative Anatomy, Embryology and Molecular Evidence; Darwin’s Contribution, Modern Synthetic theory of Evolution; Mechanism of Evolution-Variation (Mutation and Recombination) and Natural Selection with examples, types of Natural Selection; Gene Flow and Genetic Drift; Lamarckism; Darwinism; Mutation Theory of Hugo De Vries; Hardy-Weinberg’s Principle; Adaptive Radiation; Human Evolution.
Long Answer Type Questions
Question.7: How does industrial brownish
explain Darwin's theory of Natural Selection?
Question.8: What are fossils? Mention any
two way in which the study of fossils support biological evolution of an
organism.
Very Long Answer Type Questions
Question.9: Explain Darwinism and
criticism.
Question.10: Explain in brief regarding
origin of source of variation.
Question.11: Explain in brief regarding
human evolution.
Answer 7: In England, it was
observed before industrialization that white-winged moth (Biston betularia)
were more in number than dark-winged moth. But the situation became reversed
after industrialization. It was argued that predator will spot and pick a moth
(Biston betularia) against a contrasting background. In pre-industrialization,
the tree trunk was covered by white lichens and on white background dark colour
moth can be picked up. The situation changed during industrialization, the tree
was covered by dar, dust, coal particles and become dark on which white moth
can easily be picked up. Thus, it is a case of natural selection which built
pressure on population and some members are selected for evolution.
Answer 8: The remains or
evidences of pre-historic life is called fossil.
Two ways in which study of fossils support biological
evolution:
(i) The study of Archaeopteryx reveals that birds have
evolved from reptile, so fossil provide evidence for evolution.
(ii) Phylogeny can be reconstructed from the fossils.
(iii) The habitat and behaviour of extinct organisms
can be inferred from well preserved fossils.
Answer 9: The
Great criticizer Hugo De Vries
criticized Darwinism by the following points:
1. Great
weakness:
He was unable to explain the cause, origin and inheritance of variations.
2. Raw Material for evolution: He regarded all small
and continuous variations, which may be acquired by organism during their life
time due to environmental effect but somatic ones never play this role.
3. Theory
of pangenesis: As it is cleared that Darwin was failed to explain the origin
of variations at genetic level as well their transmission to next generation.
In 1868, Darwin put forward his own theory of inheritance, the Theory
of pangenesis. According to this theory, every organ of the
body produce minute hereditary particles, called Pangenesis
or Gemmules e.g., live Gemmules
from liver, leg Gemmules from leg, and so forth. He thought the Gemmules were carried
through the blood form every organ of the body and were collected together into
the gametes.
4. Certain useful or harmful variations are
brought about by mutation (Sudden changes in genetic material) and Darwin knew
about these sudden changes (Mutation) and called these sports, but
Darwin either ignored these observations or kept silence.
5. The variations of Darwin originated by
natural selection are gradual (not in single step) and certain variations such as electric organ of Torpedoes, light producing organs of luminescent organism (Glow
worm) etc., are functional and useful only in their perfected state (in fully
developed state not in under developed state) and could not be originate
through natural selection while only possible through mutation.
6. There are some examples of overgrowth of
useful cousins beyond the limit of usefulness and bring down extinction of some
species rather than evolution, and it is said clearly that it is not possible
through adaptation and natural selection e.g., Antlers of Iris elk,
teeth of Sweedolon.
7. Darwin was also unable to explain how
does set of coordinated organ evolved through natural selection.
Answer 10: Five
factors regarding origin of source of variation are as follows:
1. Gene migration or Gene flow
If the migrating individuals breed within
the new population, the immigrants will add new alleles to the local gene pool
of the host population called gene migration
(Gene flow).Sometimes two
populations of a species which were separated, come close due to migration. The
genes of two populations mix through breeding and the result causes variations
in the offspring. The random introduction of alleles into the recipient
population and their removal from donor population affects the allelic frequencies
of both the populations. Gene flow decreases the genetic differences between
populations.
2. Genetic Drift
The random changes in the allele frequency
occurring by chance alone are called genetic drift.
3. Mutation
According to Hugo De Vries, it is a sudden
heritable changes. Single step large mutation (saltation) brings speciation.
4. Genetic Recombination
Crossing over or independent segregation
during meiosis followed by random fertilisation are referred to as genetic
recombination.
5. Natural Selection
Organisms which are better adapted to the
environment survive and reproduce. It is of 3 types:
(a) Stabilizing Selection (centripetal selection)
This selection operates in stable
environment. In this process extreme individuals from the two ends of the
phenotypic distribution are eliminated. Stabilizing selection does not promote
evolutionary change that leads to speciation, but tends to maintain phenotypic
stability within the population over generations. It removes deleterious
genotypes from the population.
(b) Disruptive selection
This selection operates in response to
gradual changes in environmental conditions. It works by constantly removing
individuals from one end of the phenotypic distribution. Therefore, average
value of fitness is coherently shifting towards the other end of the phenotypic
distribution.
(c) Disruptive selection (centrifugal selection)
This is a rare selection, but very
important in bringing about evolutionary change. This process operates in the
changing conditions within an environment (heterogeneous environment) which
increases the competition in the population. This can split the population into
two or more sub populations called Species populations. It is also
called as Adaptive radiation.
Answer 11: Humans
were developed from ape like ancestors. Human beings belong to order Primates,
sub order Anthropoidea, super family hominoidea, family Hominidae and sub
family Homininae.
The term "anthropoid apes" is
used for common ancestors of humans, apes and monkeys.
Humans, apes are their common immediate
ancestors.
Human ancestry:
About 15 million years ago, primates called
Dryopithecus and Ramapithecus
were lived on earth.
Dryopithecus was more
ape-like. Ramapithecus was more man-like.
It is believed that most of the human
evolution occurred in Ethiopia,
Kenya, Tanzania (East Africa). Fossils of man like bones were discovered
in Ethiopia and Tanzania, based on these fossils it is believed that man like
primates walked in Eastern Africa about 3-4 million years ago. These were approximately
four feet tall and walked up right.
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