embryology, BIO Lab 3rd Quiz Wrong Folder Flashcards
fertilization
restores the diploid number of chromosomes and forms zygote
Cleavage
zygote that undergoes a series of mitotic divisions
Blastomere
each cell that forms is a blastomere
they are identical in structure and function
-type of cell produced by cell division (cleavage) of the zygote after fertilization;
“genetically equivalent”, all contain the same DNA in the nuclei of their cells, in multicellular organisms the cells are not identical in structure/function. why
they synthesize and accumulate different sets of RNA and protein molecules.
embryology
turns a single fertilised egg into a whole new individual with all the many specialised cell types.
4 stages of embryology
fertilization, zygote, cleavage, morula, Blastula, Gastrula
steps
-morula forms solid ball of cells
-blastula stage which cavity forms within the developing embryo, this cavity is called blastocoel.
-as next stage begins cells begin to specialize
-process of gastrulation form the gastrula stage. (transforms from a one-dimensional layer of epithelial cells (blastula) and reorganizes into a multilayered and multidimensional structure called the gastrula).
-formation of new cavity the archenteron (cells migrating over and into the embryo (where blastocoel once existed) forms cavity.
Cavity is the formation of the blastocoel
3 layers of gastrula, during gastrulation
ectoderm, mesoderm and endoderm.
gastrulation
forms- ectoderm, endoderm, and mesoderm
-The archenteron, lined with endoderm, become the primitive gut tube.
-Gastrulation (and overall movement of cells) differs depending on the type of egg, and the type of organism.
egg types
-Isolecithal: these eggs have a tiny amount of yolk, and cells throughout the embryo are relatively the same size, although there can be differences in the color/pigmentation of cells.
-Mesolecithal: moderate amount of yolk, obvious difference between cells within the embryo.
-Telolecithal: a large amount of yolk.
mesolecithal egg
The animal pole has cells that are smaller and eventually more numerous as these are the cells that actively divide. Yolk cells are larger, less numerous and differ in color as they lack pigmentation that cells of the animal pole generally have.
polarity
defined by distribution of yolk, (the crack of it)
(vegetal pole most yolk) (animals pole has least)
Telolecithal egg
In a telolecithal egg there is a great amount of yolk. The site where cleavage begins is the blastodisc, a tiny area (like a nucleus) on the yolk.
what would determine the amount of yolk found in each egg type
- Microlecithal eggs, 2. Mesolecithal eggs 3. Macrolecithal eggs.
dividing the yolk height by the yolk diameter of the egg broken onto a flat surface.
vegetal pole and animal pole
Isolecithal: tiny amount of yolk,
Mesolecithal: moderate amount of yolk, Telolecithal: a large amount of yolk.
goes from small to big as the cleavage stage starts to begin
name the organism that have those particular egg types
vertebrate eggs can be classified by the relative amount of yolk. Simple eggs with little yolk are called microlecithal, medium-sized eggs with some yolk are called mesolecithal, and large eggs with a large concentrated yolk are called macrolecithal.
