Kae Sclafani
Ms. Johnson
Biology
5 December 2012

Compare placental mammals, marsupials, and monotremes.

Placental mammals, marsupials and monotremes are part of the phylum chordata. They are similar in some ways and different in others. These similarities and differences include their habitats, the way they reproduce, the food they eat, and adaptations they have.

Placental mammals (humans, dogs, camels, etc.):
Habitats: Placental mammals live in many different places around the world. Most of the time placental mammals will adapt to the environment they are in. Humans are an example of a placental mammal. They live all over the world and have adjusted their lifestyle based on the climate and resources available to them.
Reproduction: Placental mammals reproduce through internal fertilization. The young are enclosed by a placenta. This placenta allows the young to remain in the uterus for a long time. The placenta connected to the uterus by an umbilical cord. The mother gives birth through her birth canal. After the young is born the mammal produces a new egg through the reproduction cycle.
Food they eat: Placental mammals have to eat constantly to maintain their body temperature. When they are young they depend on their mother for food and drink. Some are herbivores and eat only plants. Examples of these animals are horses, pandas, and sloths. Some are carnivores and eat only meat. Examples of these animals are dolphins, tigers, and lions. Others are omnivores and eat plants and meat. Examples of these animals are humans and some bears. Some are even insectivores. These animals only eat insect. Examples of these animals are aardvarks, anteaters, and pangolins.
Adaptations: Mammals develop adaptations based on the different places they live. Placental mammals in colder climates develop thick fur or blubber. Placental mammals in hotter climates may develop adaptations that help them survive in the heat. These adaptations can be changes in their kidneys or sweat glands that help them survive when water is scarce or unavailable to them. Other placental mammals may use hibernation or estivation. They use this if their food source is scarce in the winter or summer.

Marsupials (kangaroos, wombats, opossum, etc.):
Habitats: During the Mesozoic era, marsupials were common in North America. However, today many of the marsupials in the world live in Australia, and only one lives in the United States. Marsupials have adapted to many different environments and habitats. Some live on the forest floor, some live underground, and some are even aquatic.
Reproduction: Marsupials reproduce through internal fertilization. The newborns they give birth are not fully developed, so they are kept in a pouch called a york sac. The york sac is on the underside of the mother and is used to keep the baby safe so it can grow and develop more.
Food they eat: Marsupials can be carnivores or herbivores. Small amounts of the marsupial population are carnivorous. Most of them are herbivores and eat many plants and fruits.
Adaptations: Different marsupials have different adaptations based on their habitat and how they live. Some, like the ringtail possum, have large eyes for better vision at night. They need this because they are nocturnal. The yapoks have webbed feet that help them swim in the water. The koala uses its sharp claws to climb up trees and get its food. The rock wallaby runs across rocks constantly. Because of this the bottoms of its feet have adapted and become ridged. This makes it easier for the rock wallaby run. Kangaroos have tails that have adapted over time. Their tail is what keeps them balanced.

Monotremes (the platypus and the echidna):
Habitats: Scientists have found fossils that might prove the existence of monotremes in South America a long time ago. Currently they are found in Australia and New Guinea along bodies of freshwater and in mild climate areas.
Reproduction: Monotremes are the only mammals that lay eggs instead of giving birth. The embryo starts to develop before the egg is laid. A female monotreme may lay up to three eggs at a time but usually only raises one a year. The egg shell is leathery and small. They are much like reptile eggs, and are about the size of a grape. The mom and eggs stay together anywhere from twelve to twenty days. After about 10 days the young hatches. The baby stays close to the mother and feeds off her milk.
Food they eat: Monotremes eat invertebrates like termites, ants, worms, and other insects. They eat them with the help of their long sticky tongues.
Adaptations: Both the platypus and the echidna have adapted mouths. The echidna has a pointy beak that was adapted for it to have an easier way to get food. The platypus also has a mouth adapted for the use of getting food. Its beak is very similar to a ducks bill. These monotremes also have a defense adaptation. The echidna has the spines on its back which is also its fur. The platypus has defensive spurs on the inside of the ankles on their rear limbs. They are short, sharp, and hollow. The spurs of the male connect to poison glands and act as stingers.

Placental mammals, marsupials, and monotremes are all in the phylum chordata and all have adaptations based on their lifestyle. The biggest similarity, other than their classification, is the food they eat. The biggest difference between all three of the mammals is how they reproduce. Although placental mammals reproduce through internal fertilization just like the marsupials, they care for them differently. Even though placental mammals, marsupial, and monotremes have their similarities they each have their own distinctive characteristics.

Citations: https://science-kingdoms.wikispaces.com/A-Placental-Mammals http://www.enchantedlearning.com/subjects/mammals/ http://kids.britannica.com/comptons/article-204275/marsupial http://animals.jrank.org/pages/2572/Monotremes-Monotremata.html http://animals.jrank.org/pages/2569/Monotremes-Monotremata-BEHAVIOR-REPRODUCTION.html http://www.ask.com/answers/66134681/what-do-monotremes-eat http://animals.jrank.org/pages/2568/Monotremes-Monotremata-PHYSICAL-CHARACTERISTICS.html http://bcb705.blogspot.com/2006/05/placental-and-marsupial-modes-of.html http://www.conservenature.org/learn_about_wildlife/marsupials/searching_for_marsupials.htm http://www.ucmp.berkeley.edu/mammal/marsupial/marsupial.html
http://www.scienceclarified.com/Io-Ma/Mammals.html