What is the Difference Between Amniotes and Anamniotes?

Amniotes and anamniotes are two groups of vertebrates that differ in their reproductive strategies and environmental dependencies. The main differences between them are:

1. Reproductive Strategy: Amniotes are vertebrates that can reproduce on dry land, either by laying shelled eggs or by carrying fertilized eggs within the female. Examples of amniotes include reptiles, birds, and mammals. On the other hand, anamniotes are vertebrates that lay their eggs in aquatic environments and are dependent on water for reproduction. Examples of anamniotes include fishes and amphibians.
2. Presence of Amnion: Amniotes are characterized by the presence of an amnion, an extraembryonic membrane that serves as a carbon dioxide and metabolic waste exchanger and secretes a cushioning fluid during embryonic development. Anamniotes lack an amnion during embryonic development and rely on external water for oxygen and diluting and excreting waste.
3. Environmental Dependency: Amniotes are not dependent on water for reproduction and can reproduce on dry land. However, anamniotes are highly sensitive to chemical and temperature variations in the surrounding water and are more vulnerable to egg predation and parasitism. They are also dependent on an aqueous or at least very moist environment.
4. Life Cycle: During their life cycle, all anamniote classes pass through a completely aquatic egg stage and an aquatic larval stage, during which all hatchlings are gill-dependent. In contrast, amniotes develop directly into a (mostly) terrestrial form.

In summary, amniotes and anamniotes differ in their reproductive strategies, presence of an amnion, environmental dependencies, and life cycle stages. Amniotes can reproduce on dry land and have an amnion, while anamniotes are dependent on water for reproduction and lack an amnion.

Comparative Table: Amniotes vs Anamniotes

Amniotes and anamniotes are two groups of vertebrates that differ in their reproduction and development. Here is a table comparing their key characteristics:

Amniotes are higher vertebrates that lay eggs on land or keep fertilized eggs within the mother's body, while anamniotes are lower vertebrates that lay their eggs in water. The presence of an extra-embryonic membrane called the amnion is the key characteristic that distinguishes amniotes from anamniotes.