Frogs undergo a process called metamorphosis from egg to adult. Metamorphosis is regulated by hormones and allows the frog to transition from an aquatic tadpole with gills and tail to a terrestrial adult with lungs and legs. The life cycle begins with an egg that hatches into an embryo with forming organs; it then emerges as a tadpole that lives in water and feeds on algae. Over several weeks, limbs grow and organs like lungs develop as the tadpole transforms into a froglet. Finally, after 11 weeks, a fully developed frog with lungs and legs emerges from the water to live on land.

1. Frog Metamorphosis
The Life Cycle of Frogs

2. What is Metamorphosis?
A typically marked or more or less abrupt
developmental change in the form or
structure of an animal occuring subsequent
to birth or hatching

3. How does it Work?
Metamorphosis in amphibians is regulated
by thyroxin and prolactin
Development is subject to many adaptations
due to specific ecological circumstances
They also make use of the lateral line organ
Redundant organs are reabsorbed via
apoptosis after metamorphosis

4. A Frog’s Life Cycle

5. The Egg
The egg begins as a single cell
It becomes surrounded by a jellylike
covering, which protects the egg
The female may or may not stay with the
eggs to take care of the young after she had
laid them

6. The Embyo
The mass of cells in the egg come to form
an embryo
Organs and gills begin to form, and the
embryo lives off the internal yolk
This supplies it with nutrients for 21 days

7. The Tadpole
After its 21 day development period, the
embryo leaves its jelly shell, and attaches
itself to a weed in the water
It has external gills like a fish to absorb
oxygen and feeds on algae
It is extremely vulnerable, and must rely on
its camouflage to protect it

8. The Changing Tadpole
About five weeks, the tadpole begins to
change
It starts to grow hind legs, which are soon
followed with forelegs
Lungs begin to develop, preparing the frog
for its life on land

9. The Froglet
Over time, the tadpole becomes even more
froglike
Its mouth widens, it loses its horny
jaws, gills are lost
The tail becomes much smaller, and the legs
grow
The lungs are almost functioning at this
point

10. The Frog
Eleven weeks after the egg was laid, a fully
developed frog with lungs, legs, and no tail
emerges from the water
Eventually, it finds a mate
The female lays the eggs, the male fertilizes
them, and the whole process begins again