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Session 3

EVOLUTION

Continuing with the balance of four(4) Evidence of Evolution
3
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In living organisms, sudden development of new tissues or
organs for living in changing environment is not possible
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Mostly, a specific
structure in the body is useful under certain situation
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Such structure
begins to degenerate under such situation as per the principle of natural selection
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Similarly, muscles of ear pinna, which are useless to human, are useful
in monkeys for movement of ear pinna
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4
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Large number of organisms get
buried due to disasters like flood, earthquake, volcano, etc
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These are called
as fossils
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Carbon consumption of
animals and plants stops
after death and since
then, only the decaying
process of C-14 occurs
continuously
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The time passed since the
death of a plant or animal
can be calculated by
measuring
the
radioactivity of C-14 and
ratio of C-14 to C-12
present in their body
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It is used in
palaeontology and anthropology for determining the age of human fossils and
manuscripts
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It
seems that vertebrates have been slowly originated from invertebrates
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It is difficult to
find out from which invertebrates group the chordates were developed
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Thus is evidence of fatal science among chordates
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Connecting Links
Some plants and animals show some morphological characters by which they can
be related to two different groups; hence they are called as ‘connecting links’
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Similarly, these
animals show tracheal respiration and open circulatory
system similar to arthropods
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Similarly, duck billed platypus lays eggs like reptiles but
shows relationship with mammals too due to presence of
mammary glands and hairs
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These examples indicate that mammals are
evolved from reptiles and amphibians from fishes
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Embryological Evidences:
Comparative study of embryonic developmental stages of various vertebrates
given in the picture shows that all embryos show extreme similarities during
initial stages and those similarities decrease gradually
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I

II

III

Fish Salmander Tortoise chick

pig

cow

rabbit

Embryos during different stages

human

Vestigial
Evidence
Eveidences
Paleontological
Evidences

Home Work:
1
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Vestigial organ _______ present in human body is proof of evolution
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Read the following statements and justify same in your own words with the
help of suitable examples
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b) There is evidences of fatal science among chordates
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Short Notes:
a)Embryology
b)Connecting link
IV) Define vestigial organs
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V) Explain the theory of evolution and mention the proof supporting it
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Explain importance of fossils as proof of evolution
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Annelida : a large phylum(division) that comprises the segmented worms, which
include earthworms, lugworms, ragworms, and leeches
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They have a segmented body, an external
skeleton, and jointed limbs, and are sometimes placed in different
phyla(division)
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Insects, centipedes, spiders, crabs etc

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