Direct development is when the newborn offspring of a species is similar in most regards to the adult, according to Encyclopedia Britannica. The newborn is born or emerges from its egg as a miniature version of the adult. It looks like the adults of its species, and it also feeds like an adult of its species. The newborn differs from the adult only in minor details, especially size.
Examples of species that display direct development include humans, horses, cats and dogs. These species give birth to progeny that is similar to the adults in most ways, with the exception of the fact that they are much smaller. The size of the offspring is not a factor in determining if a species undergoes direct development. How the baby appears compared to the adults is how scientists determine if a species undergoes direct development. Though human infants look different from adults, these are relatively minor differences, such as the babies having less hair.
Examples of species that do not show direct development include those that undergo metamorphosis. This occurs in species such as frogs. A baby frog (tadpole) is unquestionably different from an adult frog, until metamorphosis. Most insects are also an example of species that undergo metamorphosis.