What type of data is primarily used to determine the

existence and appearance of early animal species?

a. molecular data

b. fossil data

c. morphological data

d. embryological development data

Fossils are impressions or traces of organisms of the past geological period. They are the evidence of life forms that had existed decades back and were preserved by the earth's crust.

Fossil data are a significant source that provides evidence about the evolution of organisms with respect to their various environmental adaptation. A clear outline of an evolutionary tree can be constructed by fossil data.

Molecular data is represented by the molecular composition of an organism like the nucleotide sequences of DNA. It helps to find the relationship between organisms with their molecular characteristics which plays a significant role in phylogeny.

Morphological data can be collected from the structural organization of organisms. It helps to understand the relationship between organisms with respect to their appearance. These data plays role in elucidating the evolutionary history of organisms.

Embryological development data is the data related to the formation and development of the embryo. The relationship between organisms can be drawn by the similarities in the formation and development of embryo, starting from the gamete formation and fertilization.