11.7. Ovis canadensis nelsoni: Desert Bighorn Sheep http://www.ck12.org
- Genus:Ovis
- Species:O. canadensis
Habitat
The desert bighorn sheep lives in eastern California, Nevada, northwestern Arizona, New Mexico and southern
Utah. The desert bighorn sheep mostly lives in the high desert areas. It is very hot in the desert, and the highest
temperatures can be in July, when it can get to be well over 100°F, sometimes over 120°F. The lowest temperatures
during winter can easily be lower than 40°F. They have also been seen is Yellowstone National Park in Wyoming.
They live in high, steep, rocky mountains and open terrain with rocky slopes. They have a home range but not a
territory. They climb up the mountains every day and have to be good swimmers because there are many oases
around the desert mountains.
Biology
Cell Biology
The desert bighorn sheep has eukaryotic cells. There are two different types of cells: eukaryotic and prokaryotic.
Eukaryotic cells are found in animals (including humans) and plants (and protists and fungi), and prokaryotic cells
are in bacteria. Most eukaryotic cells are larger than prokaryotic cells. A eukaryotic cell is a cell that has a nucleus,
whereas prokaryotic cells have no nucleus. The nucleus contains DNA, and the DNA carries the genetic information.
There are also ribosomes in the cell which make proteins. The soft, outer shell of the cell is called the cell membrane
or plasma membrane. The cell membrane is semipermeable, allowing only certain molecules to pass in or out of the
cell. To give the cell energy, the mitochondria burns sugars (glucose) during cellular respiration. Those are some
examples of organelles, or cell parts, that have different functions in the cell.
Evolution
The desert bighorn sheep is a mammal. The earliest mammals evolved from the cynodonts, but they continued to
evolve. The desert bighorn sheep is a placental mammal. The first placental mammal evolved about 110 million
years ago. The oldest placental mammal, now extinct, belonged to the genusEomaia. TheEomaialived in China
and were only 10 cm (about 4 inches) long. They ate bugs and worms and climbed trees. Placental mammals
became the more dominant animals, and the marsupials and monotreme mammals started dying out. Interestingly,
today marsupials are still the largest type of mammals on the continent of Australia.
Ecology
The desert bighorn sheep have their breeding season in the early winter. When they are born, they feed on their
mother’s milk. After about 6 or 7 months the lambs are fully grown. As herbivores, they feed on grasses, small baby
plants, and leaves such as yucca and agave. They graze on different species of grass and shrubs. They drink from
surface water such as springs and creeks.
Anatomy and Physiology
Like all mammals, the desert bighorn sheep have hair on their bodies. Once a year the desert bighorn sheep shed
their fur. The desert bighorn sheep can go long periods of time without water. They can get water from snow and