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| to have an accumulation of yolk near the vegetal pole, as the large yolked eggs or ova of reptiles and birds. |
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| having the yolk evenly distributed throughout the egg. |
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| having a centrally located yolk, as certain insect eggs or ova |
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| the yolk in an early developmental stage lies in the center and is enveloped by a layer of blastodermic cells |
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| In embryology, having very little food-yolk: applied to certain ova, such as those of sponges, marine worms, echinoderms, etc |
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| Containing a large amount of food-yolk: said of certain eggs, like those of birds, reptiles, sharks, many insects, crustaceans, etc |
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| The middle embryonic germ layer, lying between the ectoderm and the endoderm, from which connective tissue, muscle, bone, and the urogenital and circulatory systems develop. |
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| The innermost of the three primary germ layers of an animal embryo, developing into the gastrointestinal tract, the lungs, and associated structures. |
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| The outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue, and, in vertebrates, sense organs develop. |
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| hollow ball of cells made from the blastomere |
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| the bastula after invagination and formation of the gut |
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| reproductive cells (sperm and ova) |
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| cavity inside the blastula |
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| the first cells after cleavage; they may form a new organism if seperated. |
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| initial event of sexual reproduction; when the sperm gets inside the egg |
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| a group of genes that control |
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| Any of the genes involved in the early stages of pattern formation in the embryo. |
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| Schizocoely occurs when a coelom (body cavity) is formed by splitting the mesodermal embryonic tissue.[ |
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| a mesoderm is formed in a developing embryo, in which the coelom forms from pouches "pinched" off of the digestive tract (also known as the embryonic gut, or archenteron). This type of coelom formation occurs in deuterostome animals, which for this reason are also known as enterocoelomates. |
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Definition
| change in the egg membrane that prevents additional sperm from fusing with the membrane. |
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| hierarchy of developmental decisions |
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Definition
| steps that are taken in the development of the embryo, making the cells specialized. it is usually irreversable. |
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| the process by which cells or tissues change from relatively generalized to specialized kinds, during development. |
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| A simple life cycle that goes directly from fertilized egg to juvenile without passing through a free-living larval stage |
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| where an egg hatches to a larva, with no resemblance to the adult which it will become. |
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| The opening of an embryo's central cavity in the early stage of development. |
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| The series of mitotic cell divisions by which a single fertilized egg cell becomes a many-celled blastula. Each division produces cells half the size of the parent cell. |
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| the fertilization of an ovum |
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| undergoing cleavage in which the entire zygote participates; dividing completely. |
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| Undergoing partial cleavage. Used of a fertilized egg. |
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| the membrane that forms around a fertilized ovum and prevents penetration by additional spermatozoon. |
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| An immature form of other animals that undergo some metamorphosis, |
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| The portion of an egg that is opposite the animal pole and that contains most of the yolk. |
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| The portion of an egg containing the nucleus and less yolk |
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| Having three primary germ layers, such as ectoderm, mesoderm and endoderm. |
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| Pertaining to a condition in which there are two primary germ layers, such as ectoderm and endoderm. |
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| A fluid-filled body cavity formed from the splitting of lateral plate mesoderm during embryonic development |
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| middle of the three germ layers, gives rise to the musculoskeletal, blood, vascular and urinogenital systems, to connective tissue (including that of dermis) and contributes to some glands. |
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| embryonic cells forming the yolk sac and giving rise to the epithelium of the alimentary and respiratory tracts and to the parenchyma of associated glands. |
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| the outer germ layer that develops into skin and nervous tissue. |
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| a mouth that develops separately from the blastopore. |
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| A multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid or mollusk. |
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| The process in which a previously undifferentiated cell is already programmed to become a specific cell type by following a specified path towards cell differentiation. |
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| central cavity of the gastrula; becomes the intestinal or digestive cavity |
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