Key Concepts in Reproduction and Embryonic Development

Soma Cells: These cells comprise the whole body, excluding the germ cells.

Germ Line: Specialized cells in reproductive organs responsible for producing gametes.

Karyogamy: The fusion of cell nuclei.

Sexual Dimorphism: Morphological differences between males and females of a species.

Fecundity: The ability to produce offspring.

Withers: When two hermaphroditic individuals mate and fertilize each other.

Parthenogenesis: A phenomenon where an unfertilized egg develops into a normal adult.

Receptaculum Seminis: A storage location for sperm after mating.

Spermatophores: Packets containing sperm that are transferred to females.

Segmentation: A series of rapid cell divisions during early embryonic development.

Morula: A solid ball of cells in the early embryo.

Blastomere: Each individual cell within the morula.

Blastocoele: The fluid-filled cavity inside the blastula.

Blastula: An early embryonic stage where blastomeres form a layer around the blastocoele.

Blastocyst: An embryonic form that develops from the morula.

Trophoblast: The outer layer of cells in the blastocyst that aids in implantation and forms part of the placenta.

Yolk Sac: The first embryonic membrane to form, surrounding the yolk mass.

Amnion: A membrane surrounding the embryo, filled with fluid to provide an aqueous environment.

Chorion: A membrane surrounding the amnion and yolk sac, limiting water loss and controlling gas exchange.

Allantois: A sac-like structure that stores metabolic wastes generated by the embryo.

Placenta: A structure formed from maternal and embryonic tissues that nourishes the embryo in the uterus.

Metamorphosis: A drastic change in form during post-embryonic development.

Nymph or Pupa: An inactive stage in the life cycle of some insects.

Albumen: Tissue that surrounds and nourishes some seeds.

Radicle: The embryonic root of a plant.

Plumule: The embryonic shoot of a plant.

Cotyledons: The embryonic leaf or leaves within a seed.