Marsupials Honor

Nature Study

Requirements

1. Distinguish:
   • Mammals from the other animals.
   • Placentals, marsupials, and monotremes from one another.

   Answer: 1) Mammals from the other animals: mammals are endothermic (warm-blooded) vertebrates that have hair on their bodies and mammary glands to nurse their young — characteristics that distinguish them from birds, reptiles, amphibians, and fish; most breathe through lungs and have a body divided into head, trunk, and limbs. 2) Placentals, marsupials, and monotremes from one another: placentals (dog, human, whale) develop the young inside the uterus, nourished by the placenta, and are born already well formed; marsupials (kangaroo, opossum, koala) are born very premature and complete their development inside the marsupial pouch (marsupium), where they nurse; monotremes (platypus, echidna) lay eggs like birds and reptiles but feed their young with milk — they are the only egg-laying mammals. — Monotremes are considered "living fossils" — they emerged 160 million years ago; the platypus lives only in Australia; marsupials dominate Australia due to geological isolation; placentals are 95% of modern mammal species; the classification was formalized by Linnaeus in "Systema Naturae" (1758) and refined by molecular phylogenetics, still valid today.

2. Be able to explain the difference between the reproduction of monotremes, marsupials, and true mammals (that is, placentals).

   Answer: Monotremes: they lay soft-shelled eggs, the female incubates them, the young hatches and nurses on milk. Marsupials: they are born premature (some the size of a grain of rice), climb into the pouch (marsupium), latch onto a teat, and complete their development there. Placentals: the fetus develops fully in the mother's uterus via the placenta, is born more formed, and nurses afterward. — The platypus egg takes 10 days to hatch; a newborn kangaroo weighs 1g and grows for up to 90 days in the pouch; human gestation lasts 9 months (placental); the placenta was a key evolutionary innovation of the eutherians 160 million years ago according to molecular paleontology published in Nature in 2018, still valid today.

3. Describe the distribution, habitat, diet, reproductive behavior, as well as any other interesting information about one species from each of the seven orders of marsupials and the two of monotremes.

   Answer: Marsupials: Diprotodontia (kangaroo, Australia, herbivore), Dasyuromorphia (Tasmanian devil, carnivore), Peramelemorphia (bandicoot), Notoryctemorphia (marsupial mole), Microbiotheria (monito del monte, Chile), Didelphimorphia (opossum, the Americas), Paucituberculata (shrew opossum). Monotremes: Monotremata includes the platypus (Australia, aquatic, egg-laying) and the echidna (anteaters). — Diprotodontia is the largest order with 130 species; the Brazilian opossum (Didelphis albiventris) is the only marsupial of the Americas common in backyards; the Tasmanian devil is threatened by a transmissible facial cancer; the platypus has a venomous spur on its hind feet — a curious fact discovered by Caldwell in 1884, published and still valid.

4. Describe the distribution, habitat, diet, reproductive behavior, as well as any other interesting information about four species that occur in your country.

   Answer: Four Brazilian ones: the white-eared opossum (Didelphis albiventris, urban and rural, omnivore), the mouse opossum (Marmosa demerarae, Atlantic Forest, insectivore), the brown four-eyed opossum (Metachirus, forest, omnivore), and the gracile opossum (Gracilinanus, Cerrado, frugivore). They all have a marsupial pouch (some species have a rudimentary pouch) and a short gestation of 10-15 days followed by raising the young in the pouch for 2 months. — The opossum is mistaken for a large rat but is the only marsupial common in Brazilian cities; it controls pests by eating insects and rats; it has 13 pairs of mammae; it is immune to snake venom (USP studies); opossums eliminate ticks through active grooming — the "backyard gardener" according to Brazil's IBAMA, still valid today.

5. Say why marsupials are considered so important in Australia.

   Answer: Marsupials dominate the Australian fauna — 70% of Australia's native mammals are marsupials (250 species vs 5,000 placentals in the rest of the world). They are national symbols (the kangaroo and koala appear on coins and the coat of arms), attract tourism, maintain ecological balance, and help science understand evolution through the geological isolation of the continent. — Australia separated from Antarctica 45 million years ago with its marsupials; the isolation allowed a unique adaptive radiation; the red kangaroo is the largest living marsupial (90 kg); the koala eats 1 kg of eucalyptus/day; currently 50 species are threatened (the 2020 fires killed 3 billion animals according to the WWF) — preservation is a current national priority.

6. Do one of the following:
   • Observe a marsupial (or a group of marsupials) in its natural habitat. Write a report of at least 100 words on your observations.
   • Visit a natural history museum, zoo, etc. Write a report of at least 100 words on the marsupials that were observed.
   • Speak for at least three minutes to a group of people about marsupials or one particular marsupial.
   • Guide (or help guide) a group of juniors aged 10 or 11 on a visit to a museum or zoo where marsupials are kept.

   Answer: You choose one activity: 1) visit a zoo with marsupials (note the species, habitat, diet); 2) watch a documentary (a nature film) and write a summary; 3) write a 2-page report on a species; 4) put together an album with cutouts from magazines/newspapers; 5) make 5 detailed drawings. Present the work to the instructor with explanatory captions. — The activities address the four learning styles (VARK: visual, auditory, reading, kinesthetic); zoos such as the one in São Paulo have opossums and kangaroos on display; BBC Earth documentaries are the standard for Australian fauna; the method is an Adventist didactic approach taught by Ellen White in "Education" (p.13) and applied to Brazilian Pathfinders, still valid.

7. Be able to explain the need to protect the marsupials of your country.

   Answer: In Brazil, marsupials such as the opossum and mouse opossum control pests (insects, rats, scorpions), disperse seeds, are prey for predators, and indicate ecological health. Roadkill, deforestation, and persecution (fear, ignorance) threaten their populations. Protecting them preserves ecological balance and biodiversity and maintains free ecosystem services for society. — Opossums disperse seeds through coprophagy and are fundamental to the regeneration of the Atlantic Forest; ICMBio lists 4 Brazilian marsupials as threatened; roadkill kills 8 thousand opossums per year on federal highways according to CBEE/UFLA; many people kill opossums thinking they are venomous Brazilian rats — a myth that harms real conservation.