There are two types of flight - active and passive. Active flight involves animals generating force with their wings to fly for sustained periods, like birds. Passive flight involves animals gliding after leaping from heights, using organs like fins or patagia to cover horizontal distances in the air without exerting locomotive force, exemplified by flying snakes and geckos. Features that enable active flight include streamlined bodies, wings, reduced weight through pneumatic bones, developed flight muscles and air sacs, while passive flight involves enlarged fins or webbed membranes between limbs.

2. Active and passive(gliding) flight
• Active volant :Long and sustained flight through
the air by implying power is active volant .Force is
generated by moving the wings and there is
sustained progress through the aie
• Passive flight: Animals cannot fly for long time in
this type. The animals simply take an initial leap
or jump from a high point to lower level and
just glide in air with the help of certain organs. It
may sometimes cover a horizontal distance of
many meters.There is no involvement
of locomotive force other than gravity

3. Flight
Active flight
• In active flight the animals
actively participate in the
flight process. They can
start flying from any places
they like and land at their
favourable places. Generally
most birds and some
mammals are capable of
flying actively
Passive flight
• In this type of flight, animals
jump from a high point, like
hilltop, treetop etc. and come
down to earth due to the
attraction force of gravity.
During their downward
journey they cover a hori-
zontal distance with the help
of some sustaining organs. In
this type of flight the animal
never exerts any locomotory
force, instead they move
passively.

4. Active volant features
• Body countour
• Wings and feathers
• Reduction in body weight:Pneumatic bone,
development of air sac
• Development of flight muscle
• Development of air sac
• Enlarged optic lobe performs sharp vision

7. Streamlined Body

8. Flight Muscles

9. Fused Vertebrae and Keel

11. Pneumatic Bone

15. Passive volant features
• Enlarged pectoral fins
• Development of patagia
• Webbed feet

18. Flying Snake

23. Flying Gecko