43.Animal Development

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  • Created on: 24-05-21 07:26
Define the Vegetal Hemisphere
The lower portion of some animal eggs, zygotes, and embryos, in which the dense nutrient yolk settles. The vegetal pole is to the very bottom of the egg or embryo.
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Define the Animal Hemisphere
The metabolically active upper portion of some animal eggs, zygotes, and embryos; does not contain the dense nutrient yolk.
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Define the gray crescent
In frog development, a band of diffusely pigmented cytoplasm on the side of the egg opposite the site of sperm entry. Arises as a result of cytoplasmic rearrangements that establish the anterior–posterior axis of the zygote.
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Define Cleavage
The first few cell divisions of an animal zygote.
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State the function of a blastocel
The central, hollow cavity of a blastula.
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State the function of the blastula
An early stage of the animal embryo; in many species, a hollow sphere of cells surrounding a central cavity, the blastocoel.
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State the function of blastomeres
Any of the cells produced by the early divisions of a fertilized animal egg.
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Define complete cleavage
Pattern of cleavage that occurs in eggs that have little yolk. Early cleavage furrows divide the egg completely, and the blastomeres are of similar size.
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Define Incomplete Cleavage
A pattern of cleavage that occurs in many eggs that have a lot of yolk, in which the cleavage furrows do not penetrate all of it.
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Define Discodial Cleavage
In animal development, a type of incomplete cleavage that is common in fishes, reptiles, and birds, the eggs of which contain a dense yolk mass.
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Define Superficial Cleavage
A variation of incomplete cleavage in which cycles of mitosis occur without cell division, producing a syncytium (a single cell with many nuclei).
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Define syncytium
A single cell with many nuclei produced as a result of superficial cleavage.
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Define blastoderm
A layer of undifferentiated cells that are a very early stage of development prior to the specification of the embryonic axis.
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Define radial cleavage
Embryonic development in which the planes of cell division are parallel and perpendicular to the animal-vegetal axis of the embryo.
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Define Spiral Cleavage
A form of complete cleavage in which the cleavage planes are at oblique angles to the animal-vegetal axis.
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Define Rotational Cleavage
The form of complete cleavage that occurs in mammals. The first cleavage plain is parallel to the animal–vegetal axis and the two second cleavage planes are at right angles to each other.
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Define Inner Cell Mass
Derived from the mammalian blastula (blastocyst), the inner cell mass that will give rise to the yolk sac (via hypoblast) and embryo (via epiblast).
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Define trophoblast
At the 32-cell stage of mammalian development, the outer group of cells that will become part of the placenta and thus nourish the growing embryo. (Contrast with inner cell mass.)
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Define Blastocyst
An early embryo formed by the first divisions of the fertilized egg (zygote). In mammals, a hollow ball of cells.
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Define embryonic stem cells
A pluripotent cell in the blastocyst.
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Define Endometrium
The epithelial lining of the uterus.
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Define Implantation
The process by which the early mammalian embryo becomes attached to and embedded in the lining of the uterus.
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Define fate maps
A diagram of the blastula showing which cells (blastomeres) are “fated” to contribute to specific tissues and organs in the mature body.
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Define autonomous specification
Determination of cell fates due to informational molecules originally present in the egg.
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Define mosaic development
Pattern of animal embryonic development in which each blastomere contributes a specific part of the adult body. (Contrast with regulative development.)
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Define Regulative Development
A pattern of animal embryonic development in which the fates of the first blastomeres are not absolutely fixed. (Contrast with mosaic development.)
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Define regulated specification
Determination of cell fates due to signals mostly received from neighboring cells.
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Define pole plasm
Cytoplasm at one end of an insect egg that determines that the cells that form at that location will become germ cells.
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Define Gastrulation
Development of a blastula into a gastrula. In embryonic development, the process by which a blastula is transformed by massive movements of cells into a gastrula, an embryo with three germ layers and distinct body axes.
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Define Germ Layer
The three embryonic layers formed during gastrulation (ectoderm, mesoderm, and endoderm). Also called cell layers or tissue layers.
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Define an endoderm
The innermost of the three embryonic germ layers delineated during gastrulation. Gives rise to the digestive and respiratory tracts and structures associated with them.
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Define an ectoderm
The outermost of the three embryonic germ layers first delineated during gastrulation. Gives rise to the skin, sense organs, and nervous system.
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Define a mesoderm
The middle of the three embryonic germ layers first delineated during gastrulation. Gives rise to the skeleton, circulatory system, muscles, excretory system, and most of the reproductive system.
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Define mesenchyme
Embryonic or unspecialized cells derived from the mesoderm.
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Define archentron
The earliest primordial animal digestive tract.
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Define convergent extension
Movements of cells in the sea urchin blastula that form the archenteron. These cells elongate, flatten, and interdigitate to form a tubular structure.
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Define a blastopore
The opening created by the invagination of the vegetal pole during gastrulation of animal embryos.
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Define a Dorsal Lip
In amphibian embryos, the dorsal segment of the blastopore. Also called the organizer, this region directs the development of nearby embryonic regions.
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Define Involution
Cell movements that occur during gastrulation of frog embryos, giving rise to the archenteron.
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Define Epiboly
The movement of cells over the surface of the blastula toward the forming blastopore.
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Define an organizer
Region of the early amphibian embryo that directs early embryonic development. Also known as the primary embryonic organizer.
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Define hypoblast
The lower tissue portion of the avian blastula which is joined to the epiblast at the margins of the blastodisc.
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Define epiblast
The upper or overlying portion of the avian blastula which is joined to the hypoblast at the margins of the blastodisc.
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Define a primitive streak
A midline ridge that forms in the avian blastula that will become the blastopore.
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Define Hensen's Node
In avian embryos, a structure at the anterior end of the primitive groove; determines the fates of cells passing over it during gastrulation.
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Define organogenesis
The formation of organs and organ systems during development.
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Define neurulation
Stage in vertebrate development during which the nervous system begins to form.
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Define a notochord
A flexible rod of gelatinous material serving as a support in the embryos of all chordates and in the adults of tunicates and lancelets.
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Define a neural tube
An early stage in the development of the vertebrate nervous system consisting of a hollow tube created by two opposing folds of the dorsal ectoderm along the anterior–posterior body axis.
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Define a neural crest cell
During vertebrate neurulation, cells that migrate outward from the neural plate and give rise to connections between the central nervous system and the rest of the body.
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Define a Homebox
180-base-pair segment of DNA found in certain homeotic genes. A specific sequence within the homeobox—the homeodomain—regulates the expression of other genes and through this regulation controls large-scale developmental processes. (See homeotic genes.)
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Define a Hox gene
Conserved homeotic genes found in vertebrates, Drosophila, and other animal groups. Hox genes contain the homeobox and specify pattern and axis formation in these animals.
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Define extraembryonic membrane
Four membranes that support but are not part of the developing embryos of reptiles, birds, and mammals, defining these groups phylogenetically as amniotes. (See amnion, allantois, chorion, yolk sac.)
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Define a yolk sac
In reptiles, birds, and mammals, the extraembryonic membrane that forms from the endoderm of the hypoblast; it encloses and digests the yolk.
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Describe the structure of an allantonic membrane
In animal development, an outgrowth of extraembryonic endoderm plus adjacent mesoderm that forms the allantois, a saclike structure that stores metabolic wastes produced by the embryo.
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Define allantonis
An extraembryonic membrane enclosing a sausage-shaped sac that stores the embryo’s nitrogenous wastes.
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Define an amnion
The fluid-filled sac within which the embryos of reptiles (including birds) and mammals develop.
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Define a chorion
The outermost of the membranes protecting mammal, bird, and reptile embryos; in mammals it forms part of the placenta.
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Define a placenta
The organ in female mammals that provides for the nourishment of the fetus and elimination of the fetal waste products.
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Define amniotic fluid
The fluid in the amniotic sac that contains mammalian and reptilian embryos.
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Define Gestation
The period during which the embryo of a mammal develops within the uterus. Also known as pregnancy.
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Define a trimester
The three stages of human pregnancy, approximately 3 months each in length.
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Other cards in this set

Card 2


Define the Animal Hemisphere


The metabolically active upper portion of some animal eggs, zygotes, and embryos; does not contain the dense nutrient yolk.

Card 3


Define the gray crescent


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Card 4


Define Cleavage


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Card 5


State the function of a blastocel


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