Developmental Stages

Zygote

The initial single cell formed when a sperm and egg fuse, containing a full set of parental chromosomes.

Morula

A solid ball of 16 cells formed after the zygote undergoes division by mitosis.

Blastula

A hollow ball of cells that develops from the morula during embryonic development.

Gastrulation

The process during embryogenesis where the single-layered blastula reorganizes into a three-layered structure.

Endoderm

The innermost germ layer that eventually becomes internal organs.

Mesoderm

The middle germ layer that eventually develops into bone, muscle, and the cardiovascular system.

Ectoderm

The outermost germ layer that gives rise to the nervous system, eyes, ears, and nose.

Complete metamorphosis

A developmental process in some organisms, such as the tobacco hornworm, that includes egg, larva, pupa, and adult stages.

Tadpole

The juvenile stage of a frog that develops legs and loses its tail as it matures.

Dioecious plants

Plants that have separate male and female individuals.

Hermaphrodite with bisexual flower

Plants that have both male and female reproductive structures on the same flower.

Monoecious hermaphrodite

Plants that have separate male and female flowers on the same individual plant.

Gamete formation

The process of creating sex cells (sperm and egg) through meiosis.

Fertilization

The process in which a sperm cell fuses with an egg cell.

Pupa

The developmental stage in insects during which transformation occurs, leading to the adult form.