Quiz 2 Flashcards
Fertilization
male & female gametes fuse to form zygote.
Cleavage
Zygote divides into a larger & larger number of small cells that eventually form a hollow spheres of many cells.
Gastrulation
cells of the sphere formed during the cleavage continue to divide and move inward to form 3 cellular layers
Holoblastic
cleavage of the entire zygote
External fertilization
Small amount of yolk in the eggs distributed evenly – isolecithal (yolk distributed evenly)
blastocoel
fluid filled cavity within the blastula
Gastrulation
Occurs after the blastula has matured and consists of many cells
archenteron
Cells invaginate to form gastrula and a new cavity
skin & nervous system
Ectoderm
digestive tract
Endoderm
Mesoderm
muscular tissue, reproductive organs & circulatory system
Organogenesis
Gastrulation is followed by organogenesis
Frequency
the propotion of individuals in a certain category relative to the total number of individuals considered
fitness
The ability of an individual to produce, fertile offspring relative to that ability in other individuals in the population
Adaptation
A heritable trait that increases an individual’s fitness in a particular environment relative to individuals lacking that trait
