Comparison between cartilaginous and bony fishes

Cartilaginous fishes (Chondricthyes)	Bony fishes (Osteichthyes)
1.        Exclusively marine.	Marine & fresh water.
2.        Heterocercal caudal fin.	Homocercal caudal fin.
3.        Cartilaginous endoskeleton.	Bony endoskeleton
4.        Gill slits without operculum.	4 pairs of gills covered by an operculum on each side.
5.        Crescent (half moon) shaped ventral mouth	Terminal mouth
6.        Skin with placoid scales. Teeth are modified placoid scales which are backwardly directed.	Scales are Cycloid, ctenoid etc.
7.        No air bladder so they have to swim constantly to avoid sinking.	Air bladder for buoyancy
8.        Sexes are separate. In males pelvic fins bear claspers.	Sexes are separate. No claspers
9.        Internal fertilization.	Fertilisation external
10.     Many of them viviparous	Mostly oviparous
11.     E.g. Scoliodon (Dog fish), Pristis(Saw fish), Carcharodon (Great white shark), Trygon (Sting ray),Torpedo (Electric ray)	E.g. Marine fishes: Exocoetus (flying fish),Hippocampus (sea horse), Sardine, Mackeral, Tuna, Remora (sucker fish), Pomfret, Cybium               Fresh water fishes: Labeo (Rohu), Catla(Katla), Clarias (Magur), Tilapia, Anabas(Climbing perch)               Aquarium fishes: Betta (Fighting fish), Pterophyllum (Angel fish) etc.

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Comparison between male frog and female frog

Male frog	Female frog
1.        Smaller and slimmer in size	Larger and stouter in size
2.        Nuptial pads are present	Absent
3.        Vocal sacs present	Absent
4.        They can make very loud and very frequent during breeding season	More silent

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Comparison between Indian elephant and African elephant

Indian elephant	African elephant
1.       Small sized (3 m)	Large sized (3.45 m)
2.       Small sized ear pinnae	Large sized ear pinnae
3.       Tusks are small sized and seen only in males	Tusks are large sized and seen in both male and female
4.       It can be domesticated	It cannot be domesticated

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Comparison between flying birds and flightless birds

Flying birds (Carinatae)	Flightless birds (Ratitae)
1.         Usually small in size	Usually large in size
2.         Well developed wings	Poorly developed wings
3.         Interlocking mechanism in feathers is present	Absent
4.         Tail quills are present	Absent
5.         Oil gland is present	Absent
6.         Well developed flight muscles	Reduced fight muscles
7.         Keel is present in breast bone	Absent
8.         Short legs	Long and stout legs
9.         Copulatory organ is absent in males	Present
10.     The young are naked without feathers (altricious)	The young are with feathers (precocious)
11.     Cosmopolitan distribution (found everywhere)	Discontinuous distribution
12.     E.g. Crow, Columba, Parrot etc	Struthio, Kiwi, Penguine etc

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Comparison between Lizards and Snakes

Lizards	Snakes
1.        Slightly compresed body	Cylindrical body
2.        Two pairs of limbs	Limbs are absent
3.        Exoskeleton is not removed by moulting	Exoskeleton is removed periodically by moulting
4.        Scales are uniform in size	Scales are differentiated into plates and shields
5.        Nictitating membrane is present	Absent
6.        Tympanic membrane is present	Absent
7.        Tongue is not bifid	Tongue is bifid
8.        They can hear air-borne sound	They cannot hear air-borne sound
9.        Urinary bladder is present	Absent
10.     Jaw bones are fixed	Jaw bones are movable

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