Stages of Development Flashcards
1
Q
Stages of development
A
- Gamete formation
- Fertilization
- Cleavage
- Gastrulation
- Organogenesis
- Growth
2
Q
Gamete
A
mature haploid male or female germ cell
3
Q
Egg components
A
- Components of a normal somatic cell
- Yolk: Provides energy during development
- Polarity
4
Q
Polarity
A
- Animal pole: contains most of the cytoplasm & nucleus
- Vegetal pole: contains most of the yolk
5
Q
Distribution of yolk in egg
A
- Isolethical
- Mesolethical
- Telolecthical
- Centrolethical
6
Q
Isolethical
A
- Very little yolk evenly distributed through egg
- Typical of placental mammals, tunicates, echinoderms, cephalochordates, and molluscs
7
Q
Mesolethical
A
- Moderate amount of yolk concentrated at vegetal pole
- Typical of amphibians
8
Q
Telolethical
A
- Abundance of yolk densely concentrated at vegetal pole
- Typical of birds, reptiles, fish, monotremes, some amphibians
9
Q
Centrolethical
A
- Large centrally located mass of yolk
- Typical of arthropods
10
Q
Developmental patterns associated with amount of yolk
A
Lots of yolk:
* Direct development
* Telolethical eggs
Little yolk:
* Indirect development
* isolecithal, mesolecithal eggs
11
Q
Fertilization
A
Gametes unite to form a zygote
12
Q
Cleavage
A
- Embryo divides repeatedly without growth
- Occurs more easily in cytoplasm than in yolk
- Egg cell becomes many smaller cells called blastomeres
13
Q
Holoblastic cleavage
A
- Complete and equal division of cells
- Isolethical and mesolethical eggs
14
Q
Meroblastic cleavage
A
- Restricted to a small area of egg
- Telolethical and centrolethical eggs
15
Q
Cleavage direction
A
- Radial cleavage
- Spiral cleavage
