Final answer:
In mammals, extensive parental care includes protection and teaching offspring necessary survival skills. The care is particularly significant in mammals like meerkats, humans, kangaroos, and pandas. Mammalian groups, especially eutherians, offer care facilitated by their complex placenta.
Step-by-step explanation:
The type of care that is extensive in mammals is involved, lasting, and includes both protecting and teaching offspring vital survival skills. For instance, meerkat adults instruct their young on how to handle and eat scorpions, a skill essential for their survival. This teaching not only involves how to identify food but also how to deal with potential dangers associated with their prey. Moreover, mammals like humans, kangaroos, and pandas provide significant parental care, often at their own expense, due to their offspring being born relatively helpless and requiring considerable time to develop.
Within the mammalian classification, there are three broad groups - monotremes, marsupials, and eutherians (or placental mammals). Eutherians, or placental mammals, are the most populous and diverse, with about 4,000 species that have adapted to various environments and lifestyles. They have a complex chorioallantoic placenta that provides a critical connection between the fetus and the mother, allowing for essential exchanges to occur during gestation.