ORGANISM DIAGRAM: LITTLE BROWN BAT - Essay Example

? ORGANISM DIAGRAM LITTLE BROWN BAT (Myotis lucifugus) [Pick the ORGANISM DIAGRAM: LITTLE BROWN BAT (Myotis lucifugus) Figure Morphology of a Bat (http://www.infovisual.info/02/064_en.html) 1. Second digit: second jointed appendage in relation to the head of a bat. 2. Thumb: first jointed appendage in relation to the head of a bat. 3. Ulna: one of the arms bones of a bat. 4. Tragus: bone forming the ear. 5. Ear: organ of hearing. 6. Elbow: joint of the arm. 7. Radius: one of the arm bones. 8. Wrist: joint between the arm and the digits of a bat. 9. Finger membrane: membrane that forms the wing of the bat. 10. Knee: joint of the leg. 11. Foot: end of the leg, which is used to clutch. 12. Toe: jointed appendage of the foot of a bat. 13. Tail membrane: skin connecting the femurs. 14. Tail: extension of the spinal column. 15. Cutaneous muscles of the arm membrane: muscular organs on the surface of the wing. 16. Fifth digit: fifth jointed appendage in relation to the head of a bat. 17. Fourth digit: fourth jointed appendage in relation to the head of a bat. 18. Third digit: third jointed appendage in relation to the head of a bat. INTRODUCTION ‘Bats’ is a term referring to the animals belonging to the order Chiroptera. It is the second largest order of living mammals including 18 families, 202 genera and 116 species broadly classified in to two suborders megachiroptera (large fruit eating bats of old world) and microchiroptera (smaller insectivorous bats found worldwide). The little brown bats (Myotis lucifugus) is a microchiroptera belonging to family Vespertilionidae and abundantly found in Southern Alaska, Canada and across the Pacific and Atlantic coasts in United States. The major characteristics of bats form the defining features of M. lucifugus along with certain additional unique characteristics. Like all chiropterans M. lucifugus is nocturnal, winged and capable of echolocation. Besides these M. lucifugus are insectivorous feeding on free flying insects as well as those found on water surface, and undergo hibernation. Despite the wide abundance of bats, they are ill represented in fossil records. The easy degradability of small light skeletons renders preservation difficult and thus early evolutionary records and information on origin of the mammal is lacking. The earliest known record is that of a microchiropteran fossil obtained from early Eocene rocks in Wyoming, and named Icaronycteris. PHYSIOLOGICAL ADAPTATIONS Flight Adaptations: All bats have wings that are distinct from those of insects and birds in that the bone in the wings is formed by elongated fingers with webbings or membranes (15) connecting the digits (1, 2 & 12, 16, 17, 18), extending to the legs and sometimes even to the tail (14), forming the tail membrane (13). The wings originally evolved from highly moveable mammalian forearm and the skeletal structure of wings in present day bats comprises of the humerus, radius (7) and a reduced ulna (3). Besides these the other digits (1, 16, 17, & 18), too contribute to the wing. Only the thumb (2) features a claw like the mammalian ancestors to hold the prey. The membrane forming the wing (9 & 13)) or the patagium is made of skin, cutaneous muscles and connective tissue. It is richly supplied with blood vessels and can be clearly demarcated in to four regions: Plagiopatagium or membrane extending from side of body and hind limb (11) to forearm and fifth digit (16). Propatagium or membrane extending from shoulder to thumb (2). Chiropatagium (9) or the membrane extending between the digits (1, 16, 17 & 18) Uropatagium (13) or the portion of membrane extending between the tail (14) and hind limbs (11). Body Design & Skeletal Adaptations Small size, with thinner and reduced bone sizes along with complete loss of some bone such as fibula; are weight reduction strategies contributing to morphological adaptations for flight. They do retain teeth contributing to skull mass but the neck of bats is reduced in length to compensate for it. To reduce skull weight and compensate for presence of teeth, the lower skeleton is reduced in size, thereby making the bat incapable of holding itself in upright position. Thus bats are usually found hanging upside down. Besides femur is rotated leading to backward orientation of the knee; further contributing to the upside down position. Cardiovascular adaptations A three times bigger heart than that of mammals of equivalent sizes with higher levels of ATP in its muscle fibers along with highly vascularized wing membranes are adaptation to provide energy for flight. A higher concentration of red blood cells in the blood further ensures high oxygen carrying capacity of the blood. Respiratory Adaptations Though not as large as that of birds; the lungs of bats are larger than comparative size mammals and have developed smaller alveoli providing for larger volumes of gas exchange and therefore richer oxygen supply. Nocturnal habit and Echolocation: Echolocation results as a consequence of production of high pitched sounds through mouth or nostrils thus enabling nocturnal flight ability. The echoes are received by external ears (5) which have evolved large pinna. Besides this, presence of a tragus (4) within the ear canal aids a bat to decipher the origin of echoes or the location of obstacles. Insectivory & Dental Adaptations To enable insectivorous feeding habits, M. lucifugus possess relatively sharp teeth, even the molars. The canines are prominent to grip the hard bodies of insects; however grinding surfaces are lacking. Hibernation and Thermoregulation M. lucifugus have developed the ability to hibernate during seasons with food scarcity and conserve energy by thermoregulation techniques. The little brown bat has brown fat 75% of which is utilized during active waking hours the rest is consumed gradually during the hibernation period. During this period bats lower their body temperature up to 95?F by reducing blood flow to the extremities and thus enter a phase of torpor. This ability of heterothermy enables bat to conserve energy. The condition is reversed during flight to supply energy for power flights. CONCLUSION The rationale underlying the major physiological adaptations acquired and preserved by M. lucifugus rendering it better suited to its environment can be traced back to the period of their origin. This period or the cretaceous was also characterized by the spread of flowering plants. By end of cretaceous period there was a predominance of insects feeding on flowering plants leading to success of insectivorous mammals. To exploit this scenario and to escape predators of small mammals; bats seem to have evolve strategies to survive leading to their nocturnal characteristics and insectivory. Moreover with continuous jumping around aerial insects they evolved membranes acting as wings thus enabling better hunting abilities and a defense mechanism. REFERENCES Morphology of a bat [Image] (n. d.). Retrieved from http://www.infovisual.info/02/064_en.html Read More