Study of Homology and Analogy from suitable specimens

Study of Homology and Analogy from suitable specimens

✅HOMOLOGY

 Homology refers to the traits inherited by different organisms from a common ancestry.

 A homologous structure is an organ, system, or body part that shares a common ancestry in multiple organisms.

Homologous organs perform different functions but basic structure & built on pattern is same.

SET-I

Reason :

 Organs are similar in origin/modification of fore limb.

 Organs contain same set of bones- humerus, radius, ulna, carpals, metacarpals and phalanges.

 They follow the same pattern of development.

 Muscle nerves and blood vessels arranged on the same pattern.

 They are homologous organs.

Functional significance :

 Whales use their flippers for swimming.

 Bats and birds use their wings for flight.

 Divergent evolution.

SET-2

Reason :

 Mouthparts represent modification of the basic structure and have evolved from the same prototype.

 Modification occur due to their different feeding habits.

 They are homologous organs.

Functional Significance:

 Mouth parts of mosquito ,butterfly, cockroach and housefly are modified for piercing, sucking, biting and chewing and sponging type respectively.

 Divergent evolution.

SET-3

Reason :

 Legs are formed of similar five podomeres-coxa ,trochanter, femur, tibia, tarsus.

 During movement the legs form alternating triangles of support.

 Various modifications allow the legs to be used in forms of locomotion.

 They are homologous organs.

Functional significance :

 Legs of honey bee used for pollen-Pollen carrying type.

 Legs of grasshopper used for hopping and jumping-Saltatorial legs.

 Legs of mole cricket used for digging and burrowing-fossorial legs.

 Legs of cockroach used for walking or running-cursorial legs.

 Divergent evolution.

✅ANALOGY

 Superficial similarity in appearance between organs of different animal groups because they carry out the same function.

 They do not share common ancestors and have different origin. They evolve independently of each other.

Analogous organs show superficial similarity in appearance between organs of different animals organs but performs same function.

SET-1

Reason :

 In Bat wing is formed by fold of skin named patagium.

It supported with elongated outspread phalanges of last 4 digits.2nd,3rd,4th and 5th.

 In bird , flight surface is formed by feathers attached to the bones of forelimb.

 Wing of insect are mere expansions of body wall without any skeletal support.

 They are analogous organ.

Functional Significance:

 They all perform same function ,i.e. uplifting the body

in air but basic structure is completely different.

 Found in unrelated organisms lead to convergent evolution.

SET-2

Reason:

 Different internal anatomy.

 Skeletal pattern is different.

 Development is different.

 Analogous organ.

Functional Significance:

 Penguins use their fins to help them navigate through the arctic conditions in which they live including water.

 Fish use their fins to navigate through only water.

 Dolphins fin is filled with a fibrous connective tissue. It serves to keep the animal upright and prevents "roll". Also it has a thermo-regulation function.

 One is a bird, one is a fish and another one is mammal, thus informing us that those species evolved with the best functional feature to use based on their environment.

 Convergent evolution.

SET-3

Reason:

 Similar appearance and both help in swimming but structural details are different.

 Whales move their body through the water with the help of their horizontal tail, which flaps up and down to propel them through the water.

 Fish, on the other hand, have vertical tails, which move from side to side.

 Analogous organ.

Functional Significance:

 They all perform same function but basic structure is completely different.

 Found in unrelated organisms lead to convergent evolution.

Homologous organs	Analogous organs
They are similar in origin & basic structure, but perform different functions in different organisms.	They are different in basic structure but perform same functions.
It shows divergent evolution.	It shows convergent evolution.
They develop in related organisms.	Develop in unrelated organisms
Stages in the development are similar	Stages in the development are different
Example: Forelimb of man, front leg of bull	Example: Wing of insect, tail fin of lobster.