Oviparity is the rule in the animal kingdom. It is common in insects, fishes, amphibians, and reptiles, and universal in birds. Among mammals, the most primitive species (the echidna and the platypus) are also oviparous. However, all mammals that evolved later (marsupials and placentals) are viviparous. What do you think was responsible for this major shift in reproductive strategy?

Oviparity is the rule in the animal kingdom. It is common in insects, fishes, amphibians, and reptiles, and universal in birds. Among mammals, the most primitive species (the echidna and the platypus) are also oviparous. However, all mammals that evolved later (marsupials and placentals) are viviparous. What do you think was responsible for this major shift in reproductive strategy?

Biology (MindTap Course List)

11th Edition

ISBN:9781337392938

Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Publisher:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Chapter51: Animal Development

Section: Chapter Questions

Problem 7TYU: Which of the following are mismatched? (a) endoderm; lining of the digestive tube (b) ectoderm;...

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Mammals have unique reproductive adaptations that have contributed to their evolutionary success. One of the distinguishing characteristics of mammals is their mammary glands, which allow for the production of milk. Even the more primitive mammals, such as the duck-billed platypus and the kangaroo, have some type of mammary glands. However, only the placental mammals (e.g. humans, horses, dogs) have a placenta, which supports the internal development of the embryo. The most primitive mammals have no placenta and can’t support the internal development of the embryo. Describe one advantage for an offspring to develop internally as opposed to developing externally (this means inside vs. outside the female’s womb/body)
Mammals have unique reproductive adaptations that have contributed to their evolutionary success. One of the distinguishing characteristics of mammals is their mammary glands, which allow for the production of milk. Even the more primitive mammals, such as the duck-billed platypus and the kangaroo, have some type of mammary glands. However, only the placental mammals (e.g. humans, horses, dogs) have a placenta, which supports the internal development of the embryo. The most primitive mammals have no placenta and can’t support the internal development of the embryo. Describe one function of the placenta found in mammals such as humans, horses, and dogs.
Mammals have unique reproductive adaptations that have contributed to their evolutionary success. One of the distinguishing characteristics of mammals is their mammary glands, which allow for the production of milk. Even the more primitive mammals, such as the duck-billed platypus and the kangaroo, have some type of mammary glands. However, only the placental mammals (e.g. humans, horses, dogs) have a placenta, which supports the internal development of the embryo. The most primitive mammals have no placenta and can’t support the internal development of the embryo. Identify one factor, besides genetic factors, that could influence the development of human offspring.
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