Embryonic and Postembryonic Development
This lesson connects molecular mechanisms, cell behavior and biological evidence. Instead of memorizing isolated terms, follow what changes, what is measured, where the process occurs and why the outcome matters to a living system.
Big idea
Rapid mitotic divisions partition the zygote into many smaller cells and form an early embryo. Coordinated cell movements establish germ layers and the basic body plan.
Learning goals
- Cleavage and blastula: Rapid mitotic divisions partition the zygote into many smaller cells and form an early embryo.
- Gastrulation: Coordinated cell movements establish germ layers and the basic body plan.
- Differentiation: Selective gene expression gives cells different structures and functions despite a shared genome.
- Morphogenesis and organogenesis: Cell division, movement, adhesion and programmed death shape tissues and organs.
- Postembryonic development: Growth, maturation, metamorphosis in some species and aging continue after embryonic stages.
Core concepts
1. Cleavage and blastula
Rapid mitotic divisions partition the zygote into many smaller cells and form an early embryo.
Observation or application: Cell number rises during cleavage while total embryo size changes little.
2. Gastrulation
Coordinated cell movements establish germ layers and the basic body plan.
Observation or application: Ectoderm, mesoderm and endoderm form in characteristic positions.