W10 L1 Flashcards
What is allometry?
difference in growth rates of different body parts
causes change in body proportionality
What is heterochrony?
changing in the timing of events
What is paedomorphy? Ex.?
condition of an adult organism retaining juvenile features
ex. axolotl
What is considered the ancestral condition for vertebrates?
ovuliparity
What is ovuliparity?
eggs are released by the female into the environment and fertilized externally by the male
common in fish and many frogs
What is the important part of egg development where there is the deposition of the yolk in each ovum?
vitellogenesis
in ovuliparity, is the yolk in each ovum enough to maintain development of the embryo?
yes
What is oviparity?
fertilization is internal but female lays zygote as eggs outside body
Why are eggs are generally large?
the yolk needs to last the zygote through metamorphosis into a juvenile organism
How much space does the yolk take up in an egg?
20-70% volume
What does albumin contain in the egg?
carbohydrates and water that help sustain the embryo
why is the shell rigid?
egg made up of 98% crystalline calcite which is where the embryo gets most of its calcium
Why is the egg able to have passive gas exchange and allow for moisture to leave?
shell is porous
What creates an air cell at the blunt end of the egg?
as embryo grows, shell becomes thinner and water is lost
What is ovoviviparity? Ex.?
internal fertilization & zygote retained in body. but parent doesn’t provide zygote with any sustenance
ex. seahorses
What type of reproduction is present in lots of sharks?
histotrophic viviparity
do females in histotrophic viviparity provide sustenance to the zygotes developing in their oviduct due to internal fertilization?
NO
How do zygotes in histotrophic viviparity obtain nutrition?
through other tissues like skin, oophagy, or from adelphophagy
what is adelphophagy?
consumption of other embryos in the womb
How are nutrients provided in hemotrophic vivaparity?
through a placenta
What is the period of time required for full development of fetus in utero from fertilization of the egg to birth called?
gestation
When do cells go from totipotent to multipotent in embryogenesis?
during gastrulation, when the three germ layers form
What is the primitive streak?
an indentation along the dorsal surface of the epiblast during embryogenesis
Where in the embryo does it secrete growth factors that direct cells to multiply and migrate?
a node at the tail end of the primitive streak
What cells displace the hypoblast and lie adjacent to the yolk sac?
endoderm cells
does the cells of the epiblast become the mesoderm?
NO, they remain and form the ectoderm
What are the first three layers of cells in the embryo an example of?
Modules
What are modules?
set of cells or set of genes that are intrinsically related to each other than to their surroundings
What are modules related to?
Pleiotropy
What is pleiotropy?
state where a single gene controls multiple traits
