Question

What is the missing link?

Answer 1

Hint: These are actually organisms that represent or possess the characters of two or sometimes more consecutive phylums, or between groups of organisms. Like consider an organism that does not fall either in phylum Arthropoda or phylum Mollusca but in between mid of these two. It shares characters of both the phylums. These organisms are very important from the evolutionary aspect of view. They serve as specimens which can teach us how evolutions of organisms occurred.

Complete Answer:
The missing links are the fossils of those organisms that shared characters of two phylums, or sometimes different groups of organisms. They became extinct a long time ago and their fossils were found during excavation and research field works. The most common example of missing links is Archaeopteryx.
It was found in the rocks of the Cretaceous period. Archaeopteryx lithographica was discovered in the year 1861 by Andreas Wagner from a lithographic quarry at Solnhofen, Bavaria, in Germany. It displays the characters of both the reptiles and birds.
Reptilian characters of Archaeopteryx:
1. The body axis is more or less lizard-like.
2. A long tail is present.
3. The bones are non-pneumatic.
4. The jaws are provided with teeth.
5. Presence of a weak sternum.
6. Presence of free caudal vertebrae as found in lizards.
7. The hand bears typical reptilian plan and each finger terminates in a claw.
Avian (bird) characters of Archaeopteryx:
1. Presence of feathers on the body.
2. The two jaws are modified into a beak-like structure.
3. The forelimbs are modified into wings.
4. The hind limbs are built on the typical avian plan.
5. Fusion of skull bones as observed in birds is evident.

Note:
Learners must note the fact that connecting link and missing link denote the same definition. Connecting links are also organisms that share common characters of two different groups of organisms. The only major difference between the two is that the connecting links are still living. They are still found on this planet, and the missing links have become extinct a long time ago and their fossils are studied.