Development Flashcards
What is development?
Development is the events involved in an organism’s gradual changing from a simple to a more complex form.
What are the main stages of embryonic development?
- Fertilization
- Cleavage
- Gastrulation
- Organogenesis
What is the purpose of gastrulation?
Gastrulation gives rise to the embryonic cell layers: ectoderm, mesoderm, and endoderm.
What happens during organogenesis?
Regions of the three embryonic cell layers develop into the rudiments of organs.
What is cleavage?
Rapid cell division of the zygote to produce the blastula with little growth in mass or size.
What is gastrulation?
The formation of the germ cell layers and a primitive gut.
What is organogenesis?
The formation of organs and tissues.
What is the blastocoel?
A fluid-filled cavity in the center of the blastula.
What affects the size of the blastomeres?
The way in which the cleavage furrow forms and distributes the yolk affects the size.
What does it mean for cellular divisions to be holoblastic?
For sea urchins, humans, and frogs, divisions are holoblastic, meaning the cleavage furrow passes entirely through the egg.
What does it mean for cellular divisions to be meroblastic?
In reptiles, birds, and insects, divisions are meroblastic, meaning the large yolk prevents the cleavage furrows from passing through the entire egg.
What are the differences in mitosis during and after cleavage?
During cleavage, there is little protein synthesis, cells are reliant on maternal RNA and proteins, and only S phase (DNA synthesis) and M phase (mitosis) occur. After cleavage, significant protein synthesis and growth during the gap (G1 and G2) phases.
What is the ectoderm?
The outer layer of the gastrula.
What is the mesoderm?
The layer of the gastrula between the ectoderm and the endoderm.
What is the endoderm?
The layer of the gastrula that lines the embryonic gut–the archenteron.
How do the embryonic germ layers form?
- Cells at or near the surface of the blastula move to the interior.
- The three cell layers are established, and the embryo is called a gastrula.
- The cell layers are collectively called the embryonic germ layers.
How does gastrulation begin in sea urchins?
Mesenchyme cells migrate inward from the vegetal pole, and cells at the vegetal plate buckle inward, causing an invagination.
What type of cells form the archenteron in sea urchins?
Endodermal cells.
What type of cells send out filopodia in sea urchins?
Mesenchymal cells.
What do filopodia do during gastrulation for sea urchins?
Filopodia drag the archenteron across the blastocoel, extending away from the blastopore.
What forms the digestive tube in sea urchins?
Fusion of the archenteron with the blastocoel wall forms the digestive tube.
What are protostomes?
Organisms in which the blastopore becomes the mouth
What is the blastopore?
The point at which invagination happens.
What are deuterostomes?
Organisms in which the blastopore becomes the anus.
What type of organisms are protostomes?
Mollusks, annelids, and arthropods.
What type of organisms are deuterostomes?
Echinoderms and chordates (humans, frogs, etc)
What is the difference between the animal and vegetal poles?
The vegetal pole has the majority of the yolk and is much denser.
How does invagination occur in frogs?
Cells from the animal pole invaginate to form the blastopore.
How does gastrulation in frogs begin?
Cells from the animal pole compress the vegetal pole. This causes the dorsal lip of the blastopore to buckle and start pushing some of those cells in.
In chicks, what is the embryo formed from?
The epiblast.
What forms the sac that surrounds the yolk in chicks?
The hypoblast.
How does gastrulation in chicks occur?
A primitive streak forms along the midline of the blastoderm. Epiblast cells migrate inward and down to form the different cell layers.
How does gastrulation in humans begin?
The trophoblast (outer layer) implants in the endometrium.
What does the inner cell mass divide into during human gastrulation?
The epiblast and the hypoblast.
What does the epiblast form during human gastrulation?
The embryo.
What does the hypoblast form during human gastrulation?
The yolk sac.
After the embryo and yolk sac have formed, what happens next during human gastrulation?
A primitive streak forms and cells of the epiblast invaginate, causing the ectoderm, mesoderm, and endoderm to form.
What is the placenta formed from?
Cells from the trophoblast, epiblast, and endometrium.
What are the four extraembryonic membranes in a reptile egg?
- Chorion
- Allantois
- Amnion
- Yolk sac