Earth Science: Mammals – Mammals: Diversity
From the fingernail-size Etruscan shrew to the almost a hundred-foot-long blue whale, the mere size differences among mammals are remarkable. Diverse modes of life have created a diversity of forms and functions.
Distinct adaptations to a particular way of life are, for example, revealed by the various shapes of limbs. The aquatic whales are fishlike in form. Bats in flight display a leathery skin extending between large fingers.
Life beneath the earth produces the cylindrical, compact body of the mole, where the forelimbs have changed into short, powerful digging tools. The outer body envelope of mammals gives an idea of their diversity. This ranges Color of skin and hair is often adapted to habitat conditions, as for example, with snow hares.
Skunks, on the other hand, give off strongly contrasting optical warning signals. With whales and sea cows, the furry coat has almost completely regressed. With respect to diet, there are pure plant and meat eaters and species that will feed on anything.
Meat-eaters have a short digestive tract, while plant-feeders break down and metabolize their hard-to-digest food in a longer digestive tract or, like ruminants, in a multichambered stomach.
Sensory diversity
The sense of smell, which is important for finding food, for territorial behavior, and for the recognition of other members of the same species, is particularly well developed in nose-oriented animals such as dogs or horses. In these animals the olfactory membrane is often extended onto the outside of the nostrils.
Eye-oriented animals, such as cats and humans, have a highly developed visual faculty. Many diurnal animals are able to recognize colors, and nocturnal animals are able to enhance their visual acuity with a special reflection layer in their eyes. Cats also use extremely sensitive tactile hairs for orientation.
Toothed whales and bats can orient themselves by means of echolocation, and the tip of an elephant’s trunk has delicate sensors for mechanical stimuli.
SURVIVAL IN THE DESERT
The humps in camels serve as fat and energy reservoirs These animals can take in enormous volumes of water within a few minutes, since the oval shape of their red blood cells prevents possible bursting.
Special rectal cells remove liquid from fecal matter almost completely; the kidney and bladder condense urine to a point where only a single drop is released.
The nostrils can be closed off, and special reticulating tissue in the nose cools the blood supply flowing to the heat-sensitive brain and eye cells.
BASICS
MAMMAL DENTITION consists of four distinct types of teeth: incisors, canines, and two types of molar teeth.
Most species initially have a set of milk teeth, so-called deciduous teeth, that fall out and are replaced by permanent teeth during the second dentition.