Post Lab Quiz #1 Flashcards
Diploblastic Pattern
Two layers of germs in the embryo ( seen in Cnidaria)
Triploblastic Pattern
Three layers of germs. (Endoderm, Mesoderm, and Ectoderm)
Germ layer on the inside of the embryo
Endoderm
Germ layer on the outside of the embryo
Ectoderm
Layer that forms in the middle
Mesoderm
Organogenesis
The cells of different germ layers interact with each other which leads to the development of tissues and organs
Protostome Cleavage
Spiral; dividing blastomeres rest in the crevices of the other cells
Deuterostome Cleavage
Radial; cells rest directly on top of other cells
Pseudocoelomate
- coelom unlined with peritoneum
- No messentries
- Organs can twist
Eucoelomate
- Coelom lined with peritoneum & mesentries
- Eucoelom and coelom present
Hemocoel
- Blood cavity
- Coelom usually present
- Found in molluscs and arthropods
Acoelomate
Has no body cavity
2 cell stage
The zygote divides into two equal blastomeres
Gastrula stage (spiral cleavage)
After cells form a hollow ball, the next division occurs and creates in indentation in one end of the ball.
-Creates a cavity called the gastrocoel
Morula stage (spiral cleavage)
-16-32 cells
Division continues, embryo looks like a solid ball of cells
Blastula stage (spiral cleavage)
- 64+ cells
- Divided to form a hollow ball of cells
Homologous structures
-Diverged somewhat from their ancestral forms
similarity due to a common ancestor
-look similar but not the same function
Analogous structures
-Same function but look different
Divergent evolution
Groups from the same common ancestor develop new traits that make them into new species
Convergent evolution
Development of similar traits due to the environment. Not from common ancestor
Monophyletic group
A group of species descended from the most recent common ancestor and includes its ancestral population plus all of its descendents.
Paraphyletic group
Includes the most recent common ancestor but not all of the descendents.
Polyphyletic group
Does not contain the most common ancestor
-Group must have at least two separate ancestral origins