Embryonic and Postembryonic Development
You can now identify the main components, explain the mechanism step by step, interpret an observation and distinguish related ideas.
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: 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: Ectoderm, mesoderm and endoderm form in characteristic positions.
3. Differentiation
Selective gene expression gives cells different structures and functions despite a shared genome.
Observation: A precursor cell activates a program that produces a neuron or muscle cell.