Biology 2 Flashcards
What is embriology
the study of the development of a unicellular zygote into a complete multicellular organism
What are the steps of early development of vertebrates
fertilization
cleavage
gastriculation
What is fertilization
when an egg is entered into by a sperm
What is the window for fertilization for the egg
it can be fertilized between 12 and 24 hours after ovulation
where does fertilization occur
in the lateral, widest part of the oviduct or fallopian tube
What happens if more than one egg is fertilized
fraternal twins may be conceived
What is cleavage
early rapid mitotic division
what does cleavage do
leads to an increase in cell number without a corresponding growth in cell protoplasm (volume is constant)
What are the benefits of more cells to less cytoplasm created by cleavage
in increases the gas and nutrient exchange
What is an indeterminate cleavage
a cleavage that results in cell that maintain the ability to develop into a complete organism
what is a result of indeterminate cleavage
identical twins
What is a determinate cleavage
a cleavage that results in cell who have different pathways that are determined at an early developmental stage
What is differentiation (embryology)
the specialization of cells that occurs during development
When does the first complete cleavage of the zygot occur
32 hours after fertilization
when does the 2nd and third cleavage of the zygote occue
60 and 72 hours after fertilization
how many cells does the embryo have after the first 3 cleavages
8
when does the zygote enter the uterus
after the third cleavage (72 hours)
What is the zygote called when it gets to the uterus
embryo
What is it called when the embryo continues to divide until a solid ball of cells forms
a Morula
What is blastulation
when the morula develops a fluid filled cavity called the blastocoel
What is it called when the morula becomes a hollow sphere of cells
a blastula
when does gastriculation occur
when the blastula has implanted in the uterine wall
What is gastriculation
when the blastula’s cells migrate to form a three layered structure called the gastrula.
What are the three layers of the gastrula called
Ectoderm
Endoderm
Mesoderm