Principles of Reproduction and Development

1
Principles of Reproduction and Development

• Starr/Taggarts
• Biology
• The Unity and Diversity of Life, 9e
• Chapter 44

2
Review

• What is fertilization?
• What is the relationship between the egg, sperm
  and zygote?

3
Embryology

• What is embryology?
• The study of early development in organisms from
  fertilization on through each successive stage.

4
Stages of Embryonic Development
Gamete Formation
frog egg
Fertilization
frog sperm
Cleavage
Gastrulation
midsectional views
Organ Formation
top view
side view
Growth, Tissue Specialization
Fig. 44.3, p. 766
5
Stages of Embryonic Development
Gamete Formation
frog egg
Fertilization
frog sperm

• Cleavage is the process of rapid cell divisions
  that leads the zygote to form a ball of cells
  called a blastula

Cleavage
Gastrulation
midsectional views
Organ Formation
top view
side view
Growth, Tissue Specialization
Fig. 44.3, p. 766
6
Cleavage Patterns
Early protostome embryo. Its four cells are
undergoing cleavages oblique to the original body
axis
Early deuterostome embryo. Its four cells are
undergoing cleavages parallel with and
perpendicular to the original body axis
In-text, p. 436
7
animal pole
gray crescent
vegetal pole
Fig. 44.4a, p. 767
8
dorsal lip
blastocoel
dorsal lip (site of inward migration)
archenteron
Fig. 44.4b, p. 767
9
Gamete Formation
frog egg
Stages of Embryonic Development
Fertilization
frog sperm
The blastula leads to the gastrula through
gastrulation which involves cell divisions, cell
migrations and cell rearrangements
Cleavage
Gastrulation
midsectional views
Organ Formation
top view
side view
Growth, Tissue Specialization
Fig. 44.3, p. 766
10
Cell Differentiation

• Activation of genes and proteins
• Cells migrate to new positions
• Formation of primary tissue layers

11
neural plate
ectoderm
neural tube
endoderm
yolk plug
mesoderm
gut cavity
ectoderm
notochord
Within the gastrula, one can see the germ layers!
Fig. 44.4c, p. 767
12
Primary Tissues

• Ectoderm
• Nervous system
• Integument
• Endoderm
• Gut inner lining and
  organs
• Mesoderm
• Muscle and skeleton
• Circulatory, reproductive, and excretory organs
• Connective tissue

13
What comes after gastrulation?

• Determination progressive restriction of
  developmental potential causing the possible fate
  of each cell to become more limited as the embryo
  develops
• Differentiation
• Controlled by gene expression
• It is the structural and functional divergence of
  cells as they become specialized during
  development
• Induction ability of one group of embryonic
  cells to influence the development of another
  group of cells

14
Embryonic Induction

• Embryonic cells
• Specialized cells and tissues

Ectoderm and mesoderm interaction in a chick wing
15
Neurulation

• Creates neural tube, neural crest, true epidermis
• Neural tube formation