Introductory Biology III: Animal Development

Comprehensive vocabulary flashcards covering the stages of animal development, cleavage patterns, germ layers, coelom formation, and metamorphosis based on the lecture notes.

Animal development

The process by which a single-celled zygote transforms into a multicellular organism with organized tissues, organs, and organ systems.

Fertilization

The fusion of sperm and egg to form a zygote.

Cleavage

A series of rapid mitotic cell divisions of the zygote that occurs without an overall increase in size.

Blastulation

The developmental stage involving the formation of a hollow ball of cells called a blastula.

Gastrulation

The process by which the blastula is reorganized into a three-layered embryo called a gastrula.

Neurulation

The developmental stage characterized by the formation of the neural tube and notochord.

Organogenesis

The stage of development where organs develop from the three germ layers.

Blastomeres

The smaller cells created when the large single-celled zygote is progressively subdivided during cleavage.

Isolecithal (oligolecithal)

Eggs with little, evenly distributed yolk that undergo holoblastic cleavage, such as in sea urchins and mammals.

Mesolecithal

Eggs with moderate yolk concentrated at the vegetal pole, typical of amphibians.

Telolecithal

Eggs with a large amount of yolk at the vegetal pole, resulting in meroblastic cleavage, seen in birds and reptiles.

Centrolecithal

Eggs with yolk concentrated at the centre, undergoing superficial cleavage, characteristic of insects.

Holoblastic cleavage

Complete cleavage where the entire egg is subdivided into cells.

Meroblastic cleavage

Partial or discoidal cleavage where only a portion of the egg cytoplasm divides due to high yolk volume.

Radial cleavage

A pattern where cleavage planes are parallel or perpendicular to the polar axis, characteristic of deuterostomes.

Spiral cleavage

A pattern where cleavage planes are oblique to the polar axis, characteristic of protostomes.

Morula

A solid ball of cells produced by repeated cleavage before the blastula forms.

Blastocoel

The fluid-filled cavity that develops within the blastula.

Archenteron

The primitive gut formed during gastrulation that opens to the outside via the blastopore.

Protostomes

A major animal group where the blastopore becomes the mouth; examples include molluscs, annelids, and arthropods.

Deuterostomes

A major animal group where the blastopore becomes the anus and the mouth forms secondarily.

Ectoderm

The outermost germ layer that gives rise to the epidermis, nervous system, and sense organs.

Mesoderm

The middle germ layer that develops into muscles, skeleton, circulatory system, kidneys, and gonads.

Endoderm

The innermost germ layer that forms the lining of the gut, liver, pancreas, lungs, and bladder.

Notochord

A rod-like structure derived from mesoderm that provides axial skeletal support and induces the formation of the neural plate.

Neural induction

The process by which the notochord induces the overlying ectoderm to thicken and form the neural plate.

Neural crest

A migratory population of cells from the neural folds that gives rise to peripheral neurons, pigment cells, and parts of the skull.

Coelom

A fluid-filled body cavity that is completely lined by mesoderm.

Acoelomate

An animal with no body cavity, where the space between the gut and body wall is filled with mesenchyme (e.g., flatworms).

Pseudocoelomate

An animal with a body cavity that is only partially lined by mesoderm (e.g., roundworms).

Schizocoely

A mode of coelom formation where the cavity arises from the splitting of a solid block of mesoderm, typical of protostomes.

Enterocoely

A mode of coelom formation where the cavity arises as outpocketings of the archenteron wall, typical of deuterostomes.

Primitive streak

A thickened linear band of epiblast cells in birds and mammals that is functionally equivalent to the blastopore.

Hensen's node

The anterior tip of the primitive streak through which cells migrate to form the notochord.

Blastocyst

The mammalian embryo at the stage of implantation, consisting of an inner cell mass, trophoblast, and blastocoel.

Trophoblast

The outer layer of the mammalian blastocyst that forms the fetal portion of the placenta and chorion.

Amnion

The innermost extraembryonic membrane that encloses the embryo in amniotic fluid for protection and hydration.

Chorion

The outermost extraembryonic membrane involved in gas exchange in birds and placenta formation in mammals.

Allantois

An outgrowth of the hindgut that stores nitrogenous waste in birds/reptiles and helps form umbilical blood vessels in mammals.

Larva

A distinct, sexually immature developmental stage that differs in form, habitat, and feeding niche from the adult.

Holometabolous (Complete) Metamorphosis

A type of metamorphosis involving four distinct stages: egg, larva, pupa, and adult.

Hemimetabolous (Incomplete) Metamorphosis

A type of metamorphosis involving three stages: egg, nymph, and adult, with no pupal stage.

Ecdysone

The moulting hormone in insects that promotes moulting and metamorphosis.

Juvenile hormone

An insect hormone that maintains larval characteristics; its decline allows progression to pupal and adult stages.

Thyroxine

A thyroid hormone that triggers tissue remodelling and metamorphosis in amphibians.