Printer Friendly

Compare-Contrast-Connect: Marsupial Mammals versus Placental Mammals

NGSS Crosscutting Concepts:

Mammals can be generally classified into three broad groups: egg-laying monotremes, marsupials, and placentals. A marsupial is a mammal that raises its newborn offspring inside an external pouch at the front or underside of their bodies. In contrast, a placental is a mammal that completes embryo development inside the mother, nourished by an organ called the placenta. Both marsupial and placental mammal groups give birth to live young. Each animal in an ecosystem occupies a specific position. Niche is the word used to describe the specific role that an organism (or a population) fills in a specific environment, including the resources it uses and its competitors for those resources.

 

Placental mammals account for the majority of modern mammal species alive today. Most extant marsupials can be found in Australia and South America although the fossil record shows that they were once more widespread.

 

SF Table 1.1. Marsupial mammals
Marsupial Mammal Niche Photo of Mammal
Kangaroo Large herbivore that forages extensively across open grasslands
Wombat Medium-sized diurnal herbivore that feeds on grasses, constructs and dwells in extensive tunnel systems
Thylacine Large, nocturnal fast moving predator that feeds on other mammals
Tasmanian Devil Stocky nocturnal omnivore that primarily scavenges carrion and feeds on insects and plants
Bandicoot Small foraging omnivore that eats insects and plants, small rodents, and lizards
Quoll Small nocturnal carnivore that is an aggressive predator on small mammals, insects, and reptiles
Numbat Diurnal insectivore that uses a specialized tongue to feed on ants and termites found in decaying wood
Dunnart Small, nocturnal burrowing insectivore that builds nests of grass and plant material in dry areas
SF Table 1.2. Placental mammals
Placental Mammal Niche Photo of Mammal
Antelope Large herbivore that forages extensively across open grasslands
Groundhog Medium-sized diurnal herbivore that feeds on grasses, constructs and dwells in extensive tunnel systems
Wolf Large, nocturnal fast moving predator that feeds on other mammals
Raccoon Stocky nocturnal omnivore that primarily scavenges carrion, and feeds on insects and plants
Hedgehog Small foraging omnivore that eats insects, plants, small rodents, and lizards
Weasel Small nocturnal carnivore that is an aggressive predator on small mammals, insects, and reptiles
Anteater Diurnal insectivore that uses a specialized tongue to feed on ants and termites found in decaying wood
Mouse Small, nocturnal burrowing insectivore that builds nests of grass and plant material in dry areas

 

Question Set: 
  1. How are marsupial mammals different from placental mammals?
     
  2. Think of a common placental mammal not listed in SF Table 1.2 and write down its physical characteristics and ecological niche. What marsupial species might have filled this same niche?
     
  3. With the exception of Australia, marsupials largely declined or went extinct in many regions, while placental mammals dominate to this day. Provide your own explanation for this phenomenon.

Special Feature Type:

Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.