Why some believe that birds have evolved from reptiles.
Dear student,
Variations leads to the evolution of new organisms but it doesn't means that the already existing species will get extinct. Variation occurs due to changes in the environmental conditions or due to mutations. These variation lead to the generation of new species with better characters. With the passage of time these newly evolved organisms increase in population along with previously existing species. For example- We can say that birds have evolved from reptiles because the connecting link between reptiles and birds are the archeopteryx (flying dinosaurs). Also there are some similarities in birds and reptiles like birds have 4 chambered heart, which is also feature of many reptiles, both birds and reptiles are oviparous, both have separate sexes and fertilization is internal.
Regards
Variations leads to the evolution of new organisms but it doesn't means that the already existing species will get extinct. Variation occurs due to changes in the environmental conditions or due to mutations. These variation lead to the generation of new species with better characters. With the passage of time these newly evolved organisms increase in population along with previously existing species. For example- We can say that birds have evolved from reptiles because the connecting link between reptiles and birds are the archeopteryx (flying dinosaurs). Also there are some similarities in birds and reptiles like birds have 4 chambered heart, which is also feature of many reptiles, both birds and reptiles are oviparous, both have separate sexes and fertilization is internal.
Regards