The embryos of reptiles (including birds) and mammals have systems of extraembryonic membranes. What are the functions of these membranes, and how do fish and frog embryos survive without them?

Verified step by step guidance

1. Identify the types of extraembryonic membranes present in reptiles and mammals, such as the amnion, chorion, yolk sac, and allantois, and understand their individual functions. The amnion protects the embryo in a fluid-filled cavity, the chorion facilitates gas exchange, the yolk sac provides food from the yolk, and the allantois handles waste and also aids in gas exchange.
2. Examine the environmental differences between terrestrial and aquatic habitats where these embryos develop. Reptiles and mammals typically lay eggs or carry their young in environments where desiccation (drying out) can be a risk, thus necessitating these protective and supportive membranes.
3. Understand the reproductive strategies of fish and frogs, which generally lay a large number of eggs in aquatic environments. The water provides a medium that supports the eggs and embryos, reducing the need for protective membranes against desiccation.
4. Explore how the gelatinous coatings of frog eggs and the multiple layers of membranes around fish eggs serve as protective barriers against physical damage and predation, and also how these layers facilitate the exchange of gases and disposal of waste.
5. Compare and contrast the developmental stages of these different groups of animals, noting how the presence or absence of extraembryonic membranes correlates with other adaptations to their respective environments, such as egg quantity, parental care, and embryonic development speed.

Key Concepts

Extraembryonic Membranes

Extraembryonic membranes are structures that develop outside the embryo and play crucial roles in its protection and nourishment. In reptiles and mammals, these membranes include the amnion, chorion, yolk sac, and allantois, which facilitate gas exchange, waste management, and nutrient supply, allowing for development in a terrestrial environment.

Amniotic Development

Amniotic development refers to the reproductive strategy of amniotes, which includes reptiles, birds, and mammals. This strategy involves the formation of an amniotic sac that encases the embryo in a fluid-filled environment, providing protection and reducing desiccation, which is essential for survival in dry habitats.

Aquatic Embryonic Development

Fish and frog embryos develop in aquatic environments, where they rely on the surrounding water for support and nourishment. Unlike amniotes, these embryos do not require extraembryonic membranes for gas exchange or waste removal, as these processes occur directly through the water, allowing them to thrive in their respective habitats.