BIOLOGY FLASHCARD for class 12 practical

Bio class 12 flashcard

1. HOMOLOGOUS AND ANALOGOUS
ORGANS
Submitted by :- PRATIK TRIPATHY
Signature of the Internal Examiner Signature of the External Examiner

2. HOMOLOGOUS
ORGANS:
The organs found in different
organisms which have a common
origin and same basic structure but
differ in the functions they carry out
are called homologous organs. These
structures have the same origin and
basic structure but differ in the

3. functions they perform. Examples of
homologous organs include the
forelimbs of a man, the forelimbs of a
cat, the flippers of a whale, and the
wings of a bat.
ANALOGOUS ORGANS:
The organs which have similar
functions but are different in
anatomical structures are called

4. analogous organs. Examples of
analogous organs are as follows:
Wings of an insect and bird.
Pectoral fins of shark and
flippers of dolphin.
Eyes of
mammal and octopus.
Thorns of Bougainvillea
and tendrilof Cucurbita

5. Thorns of Bougainvillea and
tendrils of Cucurbita are modified
branches, present
in axil of leaves Tendrils help the
plant in climbing, while thorns
protect the plants from predators
(functionally different). This
makes them
homologous structures.
Forelimb of man, whale, bat,
cheetah
Whales, bats, cheetah and human
share similarities in the pattern of

6. bones of forelimbs. Though these
forelimbs perform different functions
in these animals, they have similar
anatomical structure in their
forelimbs. Hence, in these animals,
the same structure developed along
different directions due to adaptions
to different needs. This is divergent
evolution and these structures are
homologous organs.
Wings of an insect and bird

7. The wings of a bird and the
wings of an insect are
analogous structures and
represent convergent
evolution. Both serve the
same function and are
similar in structure, but
each
evolved independently.
Eyes of mammal and octopus

8. The eyes of octopus and
those of mammals show
convergent evolution .
They are different in origin
and structures which have
evolved for the same
function and hence have
similarity. They are thus
analogous structures
Pectoral fins of shark and
flippers of dolphin

9. Pectoral fins of sharks
and flippers of dolphins
are analogous organs.
Pectoral fins of sharks
are not pentadactyle.
The flippers of dolphins
are pentadactyle.
Scale leaves of onion and spines of prickly
pear (opuntia)

10. Both the scale leaves and spines
are modifications of leaves but are
structurally and functionally
different. Scale leaves of onion are
thick and fleshy and store food. On
the other hand spines of cactus are
defensive organs. This makes them
homologous structures.