Indeterminate cleavage

Definition

Indeterminate cleavage is a type of embryonic development in which the fate of each cell formed during the early stages of cleavage is not determined, allowing for the potential of each cell to develop into a complete organism. This process is significant in organisms belonging to the Superphylum Deuterostomia, as it contrasts with determinate cleavage seen in some other groups, leading to unique developmental outcomes such as the formation of identical twins.

5 Must Know Facts For Your Next Test

1. In indeterminate cleavage, each blastomere retains the potential to develop into a complete embryo, making this process crucial for producing identical twins or pluripotent stem cells.
2. This type of cleavage is commonly observed in deuterostomes, including echinoderms (like sea stars) and chordates (like vertebrates), illustrating a key developmental strategy.
3. Indeterminate cleavage contrasts with determinate cleavage found in protostomes, where the fate of each cell is predetermined early in development.
4. During indeterminate cleavage, cell division occurs in a radial pattern, which helps maintain symmetry in the developing embryo.
5. The unique characteristics of indeterminate cleavage can influence various aspects of later development, including patterns of gene expression and organ formation.

Review Questions

• How does indeterminate cleavage differ from determinate cleavage in terms of cell fate and developmental outcomes?
  • Indeterminate cleavage allows each blastomere to retain the potential to develop into a complete organism, meaning that if separated, these cells could form identical twins. In contrast, determinate cleavage results in cells that have specific fates determined early on, limiting their potential and leading to a more fixed developmental path. This fundamental difference affects the organization and eventual structures formed during embryogenesis.
• Discuss the significance of indeterminate cleavage in deuterostome evolution and its implications for developmental biology.
  • Indeterminate cleavage plays a crucial role in deuterostome evolution by enabling greater developmental flexibility and adaptability. This characteristic allows for complex structures and systems to evolve within deuterostomes, contributing to their success in various environments. The ability to form identical twins also raises important questions about genetic variation and evolutionary strategies among species within this group.
• Evaluate how the process of indeterminate cleavage influences the subsequent stages of development in deuterostomes compared to protostomes.
  • Indeterminate cleavage significantly influences deuterostome development by allowing for a more versatile embryonic structure that can respond dynamically to environmental cues. This flexibility contrasts sharply with protostomes, where determinate cleavage leads to more rigid developmental pathways. The differing embryonic processes result in variations in body plan organization, leading to distinct evolutionary adaptations between these two groups. By evaluating these differences, we can better understand how developmental strategies have shaped the diversity of life on Earth.

Related terms

cleavage:

The series of rapid cell divisions that occur immediately after fertilization, leading to the formation of a multicellular embryo.

deuterostome:

A major lineage of animals characterized by indeterminate cleavage, where the anus forms from the blastopore during embryonic development.

blastula:

The hollow ball of cells that forms during early embryonic development, following cleavage and preceding gastrulation.