Question

Appearance of teeth in the embryo of a bird proves that
A. Ontogeny repeats phylogeny
B. Evolution has taken place
C. Birds have evolved from reptiles
D. All of the above

Answer 1

To survive and continue their lineage, organisms have to adapt to their environment. These adaptations (changes in the genetic material) are inherited by their offspring and led to the evolution of the organism over a period of time. Various naturalists and evolutionary biologists have proposed theories about the evolutionary process and how natural selection and various other factors have led to evolution.

Complete answer:
Dinosaurs inhabited the earth during a geological time period called the Jurassic period. Dinosaurs are considered to be a part of the reptilian group. A group of feathered, meat-eating dinosaurs called theropods existed during the Mesozoic era. It is believed that birds evolved from them.
Certain anatomical features such as feathers, the skeletal structure, lungs, and heart show a connection between the birds and theropods. The feathers are considered to be the connecting link between both the organisms.
Apart from these features, both organisms showcase certain behaviours that are common to both, whether it’s their sleeping positions or looking after their young ones. The theropod dinosaur eggs resemble the avian eggs the most. In fact, embryonic teeth have been found in certain late Jurassic and late Cretaceous theropods. Theropods are meat-eating dinosaurs so their teeth are permanent.
As mentioned previously dinosaurs are reptiles and fossils of certain dinosaurs like Archaeopteryx are the missing link between the modern-day reptiles and birds.
Ernst Haeckel used the phrase “ontogeny recapitulates/ repeats phylogeny”. This was known as the biogenetic law. This law stated that the stages of development in an embryo repeat the development of its ancestor. This law is considered a law only in theory and got discredited in the early 1900s. It is now believed that certain characteristics of the developing embryo can be used to find out the ancestor and its evolution.
The appearance of teeth in embryos of the bird does not prove that evolution has taken place. Birds lose the embryonic teeth as soon as they hatch or as a youngling. Meanwhile, modern-day reptiles have their teeth even as adults. Both are believed to have a common ancestor that they evolved from.
Thus, the right answer is option C.

Note: The egg tooth is the temporary embryonic tooth found in birds is called the egg tooth. This protrusion at the beak of the bird helps it to break the eggshell. It falls off after some period. The gene that codes for the development of teeth was deactivated. The reason for this is still not clear. It is believed this helped eggs hatch faster as the development of teeth in the embryo took time making the egg more vulnerable to predators. Some believe that teeth loss reduced the overall weight of the bird therefore making its flight easy.