(1) The Making of a Body and a Field: Part 1 Flashcards
zygote
single fertilized egg
blastocyst
a ball of identical cells (same shape as enbryo bc cells aren’t growing, just dividing)
what is developmental biology
the gradual process of change within cells and tissues of the body; it is directed by intrinsic and extrinsic factors; a process taking us from genotype to phenotype
what are six stages of development?
- fertilization
- cleavage
- gastrulation
- organogenesis
- metamorphosis
- gametogenesis
fertilization
fusion of haploid gametes (sperm and egg); results in a diploid zygote with unique genome
cleavage
period of rapid mitotic cell division to produce multicellular blastula; cells of blastula are blastomeres
gastrulation
period of cellular rearrangement to produce specialized tissues and organs
metamorphosis
major alteration of body plan in a new hatchling or newborn that transforms a sexually immature larval form to a sexually mature adult (ex: tadpoles to frogs)
gametogenesis
formation of haploid gametes by meiosis
what is polarization when it comes to eggs
one side is different from the other
animal pole
animal cap (brown; the white part is the nucleus); the majority of the frog
vegetal pole
provides nutrients
fertilization in Xenopus laevis (African clawed frog)
fertilization is external; mating is amplexus
what does fertilization accomplish (3 things)
- joins haploid sperm and egg
- activates biochemical events in fertilized egg (ACTIVATION); allows the development of the embryo
- cause rearrangements of cytoplasmic structures and contents in fertilized egg (set up axes of future organism)
3 body axes of bilaterians
- ant/post
- dors/vent
- left/right
cleavage in Xenopus laevis (frog)
- mitosis is very rapid so there is no growth between divisions; the embryo becomes multicellular but doesn’t grow bigger2
- biphasic (M & S); no G1 or G2
Gastrulation in Xenopus Laevis
- cells on the surface involute (tuck into center)
- create a dimple, called a blastopore
- blastopore is initiated at a stop that denotes future dorsal side, so upper ridge of tissue is called dorsal blastopore lip
- blastopore becomes deeper, but also extends laterally and ventrally
Organogenesis in Xenopus Laevis: Neurulation
- Neurulation is the formation of nervous system
- forms on outside from ectoderm along dorsal midline
- deepends to form a neural groove
- circularizes to form a neural tube and is covered over by surface ectoderm