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In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization. The fertilized egg cell is known as the zygote. [2] [5]
The development of plants involves similar processes to that of animals. However, plant cells are mostly immotile so morphogenesis is achieved by differential growth, without cell movements. Also, the inductive signals and the genes involved are different from those that control animal development.
Fate mapping shows which tissues come from which part of the embryo at a certain stage in development, whereas cell lineage shows the relationships between cells at each division. [12] A cell lineage can be used to generate a fate map, and in cases like C. elegans, successive fate mapping can be used to develop a cell lineage. [13]
A germ layer is a collection of cells, formed during animal and mammalian embryogenesis.Germ layers are typically pronounced within vertebrate organisms; however, animals or mammals more complex than sponges (eumetazoans and agnotozoans) produce two or three primary tissue layers.
Tissue growth is the process by which a tissue increases its size. In animals, tissue growth occurs during embryonic development, post-natal growth, and tissue regeneration. The fundamental cellular basis for tissue growth is the process of cell proliferation, which involves both cell growth and cell division occurring in parallel. [1] [2] [3] [4]
Some animals, like cnidarians, produce two germ layers (the ectoderm and endoderm) making them diploblastic. Other animals such as bilaterians produce a third layer (the mesoderm) between these two layers, making them triploblastic. Germ layers eventually give rise to all of an animal's tissues and organs through the process of organogenesis.
These cells include vulval cells as well as muscle and neurons. This research also led to the initial observations of programmed cell death, or apoptosis. After mapping various sections of the C. elegans' cell lineage, Dr. Brenner and his associates were able to piece together the first complete and reproducible fate map of cell
During embryonic development, cells are restricted to different layers due to differential affinities. One of the ways this can occur is when cells share the same cell-to- cell adhesion molecules . For instance, homotypic cell adhesion can maintain boundaries between groups of cells that have different adhesion molecules.