Save Save takswan mamalia For Later. Original Title: takswan mamalia. Related titles. Carousel Previous Carousel Next. Digestion and Absorption Article 1-Watermark. Jump to Page. Search inside document. Reproduction of Eutherians Ureters enter into the bladder rather than the cloaca Oviducts fuse anterior to the urogenital sinus to form a uterus All have a single midline vaginam but only a few have a single midline uterus as seen in humans Some have a bipartite uterus for some or all of its length.
Fossorial Limb Morphology Limbs specialized for burrowing underground or digging Digging limbs maximize power at the expense of speed Short forearm with a long olecranon process elbow Retain all five digits, tipped with stout claws Large bone projections on limbs for attachment of strong muscles E.
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Gonads exhibit sesonal variations. Oviparous, except sharks and poecilidae fishes. External fertilisation, except in above fishes Megalecithal eggs. Cleavage is holoblastic, determinate. Parental care is found in fishes eg. Oreochromis is mouth brooder. Brood pouch is found in Hippocampus.
Some fishes are nest builders eg sunfishes. Endoskeleton and exoskeleton was made up of bony-armor Jaws were primitive. Climatius, Palaeospondylus. Class Chondrihcthyes Gr. Development takes place inside the oviduct and in oviparous forms development occurs outside the body Classification The cartilaginous fishes are divided into two extant subclasses: Subclass: Elasmobranchii sharks, rays and skates Subclass: Holocephali chimaera, sometimes called ghost sharks Notes: Members of the chondrichchyes have a backbone that is made of cartilage.
Because of their marine nature, they are not the fishes you come across often. These streamlined works of art range in size from the tiny 8 inch gypsy shark to the 45 foot whale shark.
In contrast to the bad name sharks have, only a handful of the known species are dangerous to humans. In fact, many sharks will stay far from the surface if there are humans above. Only the Great White Shark has been known to rise to the surface and "look around. Anatomy Sharks are covered by a layer of tough skin covered with small tooth-like scales called placoid scales.
Unlike fish scales, placoid scales are embedded within the dermis of the shark's skin. The presence of these scales makes the skin tough like sandpaper. In theory, as a shark swims, a series of whirlpools forms behind each scale. The spinning water reduces water drag and allows the shark to swim fast and efficiently. Placoid scales are also called tentacles because they are thought to be miniature versions of the shark's main teeth.
Shark teeth are some of the most envied teeth in the animal kingdom. Sharks have the amazing ability to replace teeth infinitely during their lifetime. Shark teeth are not set into the jaws, like humans.
Instead, teeth are set into the gums. In addition, below each tooth inside of the gums are layers of replacement teeth. If a tooth falls out, a brand new tooth rises from the storage layer within a few days. Some species of sharks have been known to shed as many as 30, teeth in one lifetime. Figure 12 Anatomy of a shark Feeding The shark is truly the ultimate predator. It is perfectly adapted in every way to locate, hunt and kill prey. The carnivorous diet of the shark consists of fish, other sharks, young seals and whatever else it feels like eating.
The most obvious is the mouth. The tongue is used for tasting the water, as well as for tasting food. Sharks are quite intelligent too. They often feel and investigate objects by gently biting them. In fact, many shark attacks were provoked by people when a shark simply wanted to investigate a person. The next sensory feature is the nose.
Two super-sensitive nostrils lie near the front of the head. They are so powerful they can sense a drop of blood from over a mile away. Shark eyes are also very powerful - they can see 10 times better than humans in darkness.
But shark eyes are also very sensitive, and many species have developed a special membrane called a nictitating membrane to cover the eyes when needed. Sharks also have excellent hearing and are especially attracted to low frequency sounds. The less visible sensory structure is the lateral line that runs the length of the shark. It allows the shark to sense vibrations and movement underwater. Finally the most powerful sensory organ sharks have is located on the nose in the form of two little black "dots.
Sharks use this organ to find prey and sense if the animal is dying. To illustrate another human-provoked shark attack, the faster your heart beats, the more a shark thinks you are a dying animal.
Respiration In the back of every shark's mouth is a set of parallel splits in the skin. These gills are lined with filaments that contain blood vessels. In order to breathe, sharks must keep a constant flow of water through these gills slits.
It was once thought that sharks could never stop swimming - even to sleep, but recent studies show that some sharks can lower their metabolism, allowing them to fall into a meditation-like state of sleep. Mating behavior is very complex. A male shark will select a female and follow her very closely. He may even encircle the female. At a point he will quickly bite the female's pectoral fin to stimulate her. After a while, the female will give in to the male who then positions his ventral surface along the female's ventral surface.
The male then inserts his claspers into the female's cloacae. Fertilization occurs internally. Sharks reproduce in three ways: Oviparity: The female lays eggs that develop over a period of a few months.
Young hatch at sea and are on their own. Oviviparity: The eggs are hatched in the oviduct of the female. The embryos develop in the uterus until fully grown. Then they are released into the sea. Viviparity: The embryo is nourished inside of the female by a placenta. The gestation period lasts almost a year before the newborn is released. Order Batoidei contains about to different species. Rays, like sharks, are found worldwide in every ocean.
They are mainly docile animals. Most are slow-moving bottom dwellers that spend most of their time resting on the ocean floor. Most features of rays are true to skates as well. In fact, the two names are almost interchangeable. Anatomy The main feature that differentiates a ray from a shark is the flat rough-skinned body, with the gill slits and the mouth both found on the underside of the animal.
The pectoral fins of rays have been greatly modified into large wings used for locomotion. The tail has also been greatly modified into a long and slender whip-like tail. Ray tails may have one or a few small spines containing venom. Can swim forwards and backwards Buoyancy Large oily liver Gas-filled swim bladder floating Gills Gill slits but no gill cover Covered gill slits Reproduction Eggs fertilized in female's body. Eggs usually fertilized in the water. Skin Rough, sandpaper-like placoid Slippery, overlapping scales scales Feeding Rays, like sharks, feed on a variety of seafood.
Rays eat mostly fishes and invertebrates with their blunt teeth. Some even consume plankton and small organisms. Between the shark and the ray, the two animals prey on nearly everything that swims. Special Features A flat body allows skates and rays to settle in with the sand at the bottom of the ocean floor and wait for prey to pass overhead. Special colorations on the dorsal surface provide some camouflage with the ray's surroundings.
Most rays lash out with the poison tail barb to catch unsuspecting animals. And the electric ray uses a pair of special electricity- generating organs to shock and kill prey.
The pectoral wings act much like the wings of a bird, gently "flapping" to propel the ray forward. Actually, the wings move by waves of dorsoventrally muscle contractions passing from the anterior end of the wing to the posterior. Respiration There are five gill openings on the underside of a ray's body. Most rays breathe by taking in water through large openings on the upper portion of the head. Oxygen is taken in through the gills. Most species will give birth to live young.
Skates lay flat, rectangular eggs that are enveloped by a leathery shell. Empty egg cases have been found on beaches and have come to be called mermaid's purses. What are the differences between rays left and skates right. Figure 15 Rays left and Skates right The major difference between rays and skates is in their reproductive strategies.
Also, skates typically have a prominent dorsal fin while the dorsal fin is absent or greatly reduced in rays. Most rays are kite-shaped with whip-like tails possessing one or two stinging spines while skates have fleshier tails and lack spines. Rays protect themselves with these stinging spines or barbs while skates rely on thorny projections on their backs and tails to for protection from predators. Skates have small teeth while rays have plate-like teeth adapted for crushing prey.
Another difference is that rays are generally much larger than skates. Subclass Holocephali Chimaera Fish Chimaera fish , common name for members of any of three families of deep-water cartilaginous fishes related to sharks. Reaching more than 2 m 6 ft in length, they feed on smaller animals in temperate oceans.
The color of their scale less skin ranges from black to brownish gray, sometimes with markings, and the eyes are large. The eggs of chimaeras are laid in capsules of hornlike material. Chimaeras constitute the order Chimaeriformes of the subclass Holocephali.
They make up the plownose chimaera family, Callorhynchidae; the longnose chimaera family, Rhinochimaeridae; and the shortnose chimaera family, Chimaeridae, also known as the ratfish family. Ratfish The ratfish is a member of a species of deep-water fish related to sharks. The ratfish is characterized by a long tail and a poisonous spine in front of the dorsal fin.
Class Osteichthyes bony Fish Gr. Various species inhabit waters that are fresh, brackish or salt, and either warm or cold.
Bony fishes reproduce by different mechanisms, may be very complex, involving elaborate nest building and care of the young. Social behavior is shown in shoaling movement, which may be accompanied by interchange of sounds. The majority of bony fishes are carnivorous but others feed on every type of food, from plankton to seaweeds. They have been a staple protein food of mankind since antiquity, and many species provide pleasant sporting recreation.
Details of head structure of the earliest complete bony fish fossils indicate that they probably descended from an ancestor shared with the acanthodians. By the middle of the Devonian the bony fishes already had radiated extensively, with adaptations that fitted them for every aquatic habitat.
The early bony fishes had an operculum over the gill-slits, composed of bony plates attached to the first gill arch. This feature increased respiratory efficiency because the outward rotation of the operculum created water to be drawn across the gills, as well as pushed across by the mouth pump. These earliest bony fishes also had a pair of lungs that served as accessory breathing structures. Several key adaptations of bony fishes contributed to their radiation.
An obvious manifestation of their adaptability is the great diversity of body form among the living bony fishes. Progressive specialization of jaw structure and feeding mechanisms is another key feature in their evolution. Their openings are covered by operculum or gill cover. Separate Oval and urinogenital apertures are present. Conus arteriosus is absent. Lung fishes have an incompletely divided auricle and a ventricle. Pulmonary artery and pulmonary vein are present in lung fishes.
Few are viviparous. Classification 1. Crossopterygii Lobe — finned fishes 2. Latimeria chalumnae. Protopterus, Lepidosiren, Neoceratodus. Acipenser Sturgeon , Polyodon. Super order Holostei Gr. Amia, Lepidosteus Super order Teleostei Gr. They are modern fishes.
Teleostei is divided in to 30 orders. Some important orders and their examples are listed below. Anguilliformes: eg. Anguilla Eel 2. Siluriformes: eg. Wallago attu cat fish 3. Cypriniformes: eg. Labeo rohita Ruhu 4. Syngnathiformes: eg. Hippocampus Sea horse 5. Beloniformes: eg. Exocoetus Flying fish 6. Perciformes: eg. Anabas Climbing perch 7. Tetradontiformes: eg.
Diodon Porcupine fish 8. Lophiiformes: eg. Lophius Angler or fishing frog 9. Pleuronectiformes: eg. Solea Flat fish Channiformes: eg. Channa Murrel Clupeiformis: eg. The Osteichthyes include two major clades, the Actinopterygii and the Sarcopterygii. Differentiate briefly between sharks and bony fish?
Differentiate briefly between Cartilaginous Fish and bony fish? These are the elements of the backbone, which lie under the notochord, and match the basidorsals and interdorsals respectively. State three major characteristic features of Gnathostomes. What is the distinguishing feature of each of the three fish classes? Obtain fish from the market and attempt to classify as either cartilaginous or bony fish. Amphibians, sauropsids and mammals are tetrapods. The ancestors of snakes, glass lizards and other limbless amphibians and sauropsids are tetrapods.
The earliest tetrapods evolved from the lobe-finned fishes in the Devonian. They are now a dominant part of the terrestrial fauna, representing all known larger land animals.
Some groups have even returned to an aquatic existence, including the largest animal known, the blue whale. Class Amphibians In the previous two chapters, we examined the characteristics of fishes, which are aquatic throughout their life.
In this unit, we shall be looking at animals that exhibit dual habitation of being able to live in both water and on land. These are the amphibians amphi - meaning both.
They represent an attempt by animals to colonize land from water. Accordingly, you will find that respiration by gills is being supported by moist skin and not too efficient lung system. Amphibian, animal with moist, hairless skin through which water can pass in and out.
They are the ancestors of reptiles, which in turn gave rise to mammals and birds. Scientists recognize more than 5, species of amphibians, all of which are members of one of three main groups: frogs and toads, salamanders, or caecilians.
Frogs and toads are the most abundant of all amphibians, numbering more than 4, species. Frogs have smooth skin and long limbs. Toads, in contrast, have warty skin and short limbs. There are about known species in the salamander group, which also includes newts and mud puppies. Members of this group have long, slender bodies ending in tails. Some salamanders live entirely on land, whereas others never leave the water, and still others spend some time in the water and some on land.
Caecilians, with about species, are the rarest of amphibians. They have no limbs and look much like earthworms. Most live underground and spend their time burrowing in the soil, but a few are aquatic. Brief evolutionary history The living representatives of this class include frogs, toads, newts, salamanders and limbless caecilians.
The transition from aquatic to terrestrial living is clearly indicated in the class Amphibians. These were the first vertebrates to live on land. They hover between aquatic and land environments. This double life is expressed in their name, amphibian. The slimy nature is due to the presence of mucous secreting glands. Scales are practically absent. The mouth is usually large with small teeth in upper or both jaws. The external nostrils communicate into the anterior part of the mouth cavity.
Respiration is effected by gills, lungs, skin and pharyngeal region. This may not be principal areas of disappearance of the fibre frac- tion of the diet. High concentrations of VFA occur infallible since at least one fully mature female has been observed with erupted tusks Spain et al. Gas samples Mature females have well-developed from the caecum and large intestine axil- contain Iary mammae. These are also noticeable in mature measurable quantities of hydrogen but no methane male animals but are much less developed.
Hungate, , personal communication. The large intestine grows with positive Dugongs feed almost exclusively on marine allometry in relation to body length. As expected, the concentrations of choles- through the preputial orifice between the anus and terol, bile acids cholic, deoxycholic and umbilicus.
However, the bile acid to cholesterol ovarian histology has not been studied. The vagina molar concentration ratios are adequate to hold is long and possesses a raised shield-like region of the cholesterol present in solution Caldwell et al. The histological structure of the gall blad- The anatomy of the dugong reproductive system der and liver is similar to that of other mammals has been described by Home , Owen , Caldwell et al.
In dugong are presented in Table 1. Catch records may be an unreliable modern Paenungulata whose triglycerides display indicator of sex ratio particularly when the whole an unusual intramolecular disposition Duncan 8z size range is considered. The fatty basis of 11 dugongs less than 1. Unrinsed seagrasses, as consumed by the Heinsohn reported that both male and dugong, contain about 15 times more chloride and female dugongs from Townsville, Queensland 30 times more sodium than most terrestrial pasture reach reproductive maturity at about 2.
Anatomical studies suggest ritory 2. The age of reproductive maturity has not been Dugong kidneys are dipelvic with a characteristic established due to the absence of known age bilaminar central transverse plate. The extensive material.
Heinsohn used the body lengths of renal sinus is curious in outline and boundaries 68 sexed dugongs caught throughout the year to Batrawi, , Batrawi considers that the distinguish four age classes. He estimated sexual dugong kidney combines features similar to those maturity at approximately 2 yr.
Scheffer found partly in the camel and partly in the horse. Mitchell counted dentinal growth layers in unerupted In the absence of detailed physiological and incisors and suggested that sexual maturity is behavioural studies, knowledge of dugong reached at a layer number of about ten, or at about reproduction is largely based on anatomical stu- 5 or 10 yr depending on whether the layers are dies or on incidental information.
The testes are annual or biannual. Eight is the lowest number of abdominal and lie caudal to the kidneys. The penis does not show the lowest number in a cycling female Marsh, externally unless erected when it is extruded unpublished data. Table 1. Values are given as molecular percentages of the total acids of the trigly- cerides and of the monoglycerides. The analysis was performed by Mr. Reproductively active animals have been taken in The cow-calf relationship is believed to be well- May, July, August and October but only four of developed and long-lasting Banfield, ; Mac- the eight mature males killed for food by abori- millan, ; Thomas, Heinsohn has ginals at Mornington Island in July-August reported calves up to 1.
The dugong is an unusual, although not unique, The mating season at Mornington Island is diving mammal since its natural habitat seems considered to last from May to August Roughsey, restricted to shallow tropical and subtropical African reports of Damning, Jones described the apparent attemp- found.
This consistently warm environment would ted mating of a pair of captive dugongs, both of reduce the problem of heat loss commonly which were subsequently found to be male Jones, experienced by diving mammals and would permit Firm data on the gestation period are lack- a corresponding metabolic adjustment. In comparison is a reduction of thyroid activity with a consequent the gestation period of the Florida manatee is over lowering of overall metabolic rate accompanied by 1 yr Hartman, Such a dugong and concluded that the placenta is at first reduction of overall metabolism, if it in fact occurs diffuse, becoming zonary later and that the rela- in the dugong, would account for the general tionship between foetal and maternal bloodstreams observation of sluggishness recorded in the lit- is epitheliochorial.
Clearly, such a tee placenta which is typically zonary with a metabolic adaptation would only be suitable to a hemochorial relationship between the maternal species which leads a rather sedentary existence, and foetal bloodstreams.
It is likely that calving found it varied up to a maximum of sec. The mean time for each and unpublished and dugongs with presumably dive was Observations made by the present and October Heinsohn, ; Heinsohn et al.
There have been obliged to surface frequently. Physiology of the dugong By comparison with other marine diving mam- the bronchioli. The answer material is part of the Balbharati 10th Standard Board Exam Books Solutions and is produced according to the most recent exam pattern.
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