Chapter 47 Halo

Fertilization

The fusion of an egg and a sperm to form a diploid zygote.

Cleavage

A period of rapid cell division without growth following fertilization.

Zygote

The fertilized egg that is the result of the fusion of sperm and egg.

Blastula

A hollow ball of cells formed during the early stages of embryonic development.

Gastrulation

The process during embryonic development that rearranges the cells of a blastula into a three-layered structure called a gastrula.

Organogenesis

The process of organ formation that arises from the three germ layers.

Polyspermy

The entry of multiple sperm into an egg, which is typically prevented during fertilization.

Acrosomal Reaction

The process by which enzymes from the sperm are released to help fertilize the egg.

Cortical Reaction

A response that occurs after sperm binding to the egg, leading to the formation of a fertilization envelope.

Calcium Ion (Ca2+)

An ion that, when its concentration increases, triggers activation of the egg and promotes cortical reaction.

Amniote

A member of a group of animals that lay eggs on land or retain the fertilized egg in the mother, characterized by the presence of extraembryonic membranes.

Germ Layers

The three layers formed during gastrulation: ectoderm, mesoderm, and endoderm.

Ectoderm

The outer layer of embryonic germ layers that forms the skin and nervous system.

Mesoderm

The middle layer of embryonic germ layers that forms muscles, bones, and the circulatory system.

Endoderm

The inner layer of embryonic germ layers that lines the digestive tract and respiratory tracts.

Neurulation

The process during organogenesis in which the neural tube forms from the neural plate, leading to the development of the central nervous system.

Somites

Blocks of mesoderm located lateral to the notochord, which differentiate to form vertebrae and associated muscles.

Induction

The process by which one tissue influences the development of another tissue.

Blastocoel

The fluid-filled cavity within the blastula.

Fertilization Envelope

The structure formed after egg fertilization that acts as a slow block to polyspermy.

Metamorphosis

The developmental process during which an organism transforms from a larval stage to an adult form.

Extraembryonic Membranes

Structures that form around the embryo to provide protection and support during development, such as the chorion and amnion.

Chorion

The outermost extraembryonic membrane involved in gas exchange.

Amnion

The extraembryonic membrane that encloses the amniotic fluid, providing a cushioning environment for the embryo.

Allantois

The extraembryonic membrane that disposes of waste products and contributes to gas exchange.

Yolk Sac

The extraembryonic membrane that encloses the yolk, providing nutrients to the developing embryo.

Apoptosis

Programmed cell death that occurs at various stages during development.

Blastopore

The opening that forms during gastrulation, which will develop into the digestive tract.

Archenteron

The primitive gut that forms during gastrulation.

Blastomeres

Smaller cells formed from the cleavage of a zygote.

Holoblastic Cleavage

Complete division of the egg, characteristic of species with little or moderate yolk.

Meroblastic Cleavage

Incomplete division of the egg, typical in species with yolk-rich eggs.

Embryonic Development 

The series of processes that lead from a fertilized egg to a mature organism.

Cell Migration

The movement of cells from one location to another during development.

The process following fertilization where the zygote begins to divide is called __________.

Cleavage.

The structure formed by the early division of the zygote, which is a solid ball of cells, is called the __________.

Morula.

__________ is the process by which the cells of the blastula rearrange to form the three germ layers.

Gastrulation.

The layer of embryonic germ layers that forms the skin and nervous system is the __________.

Ectoderm.

The __________ is the part of the embryo that helps in nutrient absorption until the placenta develops (in some species).

Yolk Sac.

During __________, the neural plate folds to form the tube that will become the central nervous system.

Neurulation.

Cells that develop into the heart and blood vessels arise from the __________ layer.

Mesoderm.

The __________ is crucial for preventing multiple sperm from fertilizing the egg at the same time.

Fertilization Envelope.

__________ occurs when certain cells signal others to change their development pathway, often in a tissue environment.

Induction.