Life Cycle of a Frog
A female frog lays hundreds of eggs, after which the male fertilises them. A layer of jelly holds the eggs together and provides protection to the eggs. This whole mass of fertilised eggs in the jelly is called a spawn. After a few days, the tadpoles hatch out of these eggs. They then feed on the yolk of the egg from which they hatched. After a few days, the tadpole develops External gills for breathing and fins and a tail for swimming. After a few weeks external gills disappear and tadpole develops hind limbs. After a few days tadpole develops into a froglet. It develops forelimbs. It also develops lungs for breathing. Final stage: Tail of the frog becomes smaller and finally disappears. Frog has entered the adult stage. This entire transformation from the egg into an adult frog through drastic changes is called metamorphosis. Once again, the adult frogs mate and the life cycle of a frog continues.
Frogs tend to lay hundreds of eggs inside a jelly cup. Then the male frog fertilize them The life starts right as the central yolk splits in two. It then divides into four, then eight, until it looks a bit like a rasberry. Soon, the embryo starts to look more and more like a tadpole, and hatch out from the jelly cup. It will take about 6-21 days. after being fertilized, the egg will hatch. Most eggs are found in calm or static waters.
Tadpole with hind legs
Over about a 24 hour period, the tadpole develops into a frog. This means almost every organ has to change so the tadpole can go from living underwater to living on land as an adult frog. In this picture you can see the tadpole has started to grow hind legs.
Shortly after hatching, the tadpole still feeds on the remaining yolk. The tadpole at this point consists of poorly developed gills, a mouth, and a tail. It’s really fragile at this point. They usually will stick themselves to floating weeds or grasses in the water using little sticky organs between its’ mouth and belly area. By the fourth week, tadpoles can actually be fairly social creatures. Tadpoles aquatic, the metamorphosis is initiated by a hormone produced by the thyroid gland
Tadpole with front and hind legs
After the hind legs have started to form, a pair of front legs will begin to develop and the tail will start to disappear. You might also notice that the tadpole has started to form a frog-like face. The tadpole’s skull is made out of cartilage (the same stuff your nose and ears are made out of) but during metamorphosis, the cartilage is replaced with bone
When the tadpole reaches the froglet stage, it is almost a full adult. At this point, the tadpole’s gills have disappeared, and its lungs have enlarged. This means it is ready to leave the water and live on land. Once its tail disappears, it will become an adult frog.
This is a fully grown frog. As you have just read, frogs go through a lot to get to this phase. They even go through changes that aren’t visible in these pictures. The tadpole’s horny teeth, once used to tear up plants, disappear and tongue muscles develop to catch insects. The tadpole’s large intestine, important for digesting algae and plants, shrinks to suit the frog’s meat-eating diet.