amphibian notes
DESCRIPTION
AMPHIBIAN NOTES. EXTERNAL STRUCTURE AND MOVEMENT. Amphibian skin does not have scales , feathers, or hair . It does have secretions that help with protection. These glands also keep skin moist to prevent drying. They also produce toxic chemicals that discourage potential predators. - PowerPoint PPT PresentationTRANSCRIPT
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AMPHIBIANNOTES
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EXTERNAL STRUCTURE AND MOVEMENT
• Amphibian skin does not have scales, feathers, or hair.
• It does have secretions that help with protection. • These glands also keep skin moist to prevent
drying. • They also produce toxic chemicals that
discourage potential predators.
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EXTERNAL STRUCTURE AND MOVEMENT
• Chromatophores are specialized cells in the skin that are responsible for skin color and color changes.
• Cryptic coloration, aposematic(warning) coloration, and mimicry are all common in amphibians.
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Support and Movement
• Animals that live in water are partially supported by water.
• Animals that live on land have to support themselves against gravity.
• Amphibian skulls are flattened, are relatively small, and have fewer bones than water-dwelling animals.
• These changes keep the skull light so it can be supported out of water.
• Amphibians also have changes in jaw structure and muscles to allow them to crush prey held in the mouth.
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Support and Movement
• The amphibian vertebral column is modified to provide support and flexibility on land.
• Amphibians do have a neck. • They also have a sternum which supports the
forelimbs and protects internal organs. • Amphibians have a pelvic girdle that has 3 bones. • These bones attach pelvic appendages to the
vertebral column. • This is very important in providing support on
land.
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Support and Movement
• Amphibians depend more on appendages than on the body wall for movement.
• Therefore, muscles on the body wall are not as strong as muscles in their appendages.
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Support and Movement
• In the water, salamanders move like fish.• On land, they walk and it makes their body curve. • Caecilians move like an accordion, pushing and
pulling at the same time. • Anurans have long hindlimbs that are modified
for jumping. • They also have connective tissue and muscles in
the forelimbs that act as shock absorbers.
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Nutrition and the Digestive System
• Most adult amphibians are carnivores and eat a wide variety of invertebrates.
• Some anurans are more diverse.• The main factors that determine what amphibians
will eat are prey size and availability. • Most larvae are herbivores and eat algae and
other plant matter.
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Nutrition and the Digestive System
• Most amphibians locate their prey by sight and simply sit and wait for it to pass by.
• Water amphibians depend more on their sense of smell.
• Many salamanders use only their jaws to capture prey.
• Some salamanders and most anurans use their tongue and jaw in a “flip-and-grab” method.
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Nutrition and the Digestive System
• Amphibians have the first true tongue. • Mucous and gland secretions make the tip of the
tongue sticky. • When prey comes within range, the tongue
comes out, the tip traps the prey, and then trapped in the mouth.
• This whole process happens in about 0.5 seconds! • The tongue then pushes the food toward the
esophagus, and the eyes sink downward to help force the food.
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Circulation, Gas Exchange, Temperature Regulation
• Gas exchange occurs across the skin in amphibians, as well as in the lungs.
• So blood coming into the right side of the heart has almost as much oxygen as blood coming from the lungs.
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Circulation, Gas Exchange, Temperature Regulation
• In addition to a vascular system that circulates blood, amphibians also have a well-developed lymphatic system that helps return fluids and proteins to the blood vessels and also helps transport water across the skin.
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Circulation, Gas Exchange, Temperature Regulation
• Land animals expend much less energy exchanging gas than water animals do.
• This is because air contains 20 times more oxygen than water.
• There are 2 factors that permit amphibians to exchange gas across the skin: their skin is very moist, and their skin also has a rich supply of capillaries.
• Gas exchange across the skin is called cutaneous respiration and can occur on land or in water.
• This ability allows frogs to spend the winter in mud at the bottom of a pond.
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Circulation, Gas Exchange, Temperature Regulation
• In salamanders, gas exchange can also occur in the mouth and pharynx.
• This is buccopharyngeal respiration. • Most amphibians have lungs. • Salamander lungs are very simple sacs. • Anurans have divided lungs, providing more
surface area for gas exchange. • Amphibians larvae and some adults breathe using
external gills.
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Circulation, Gax Exchange, Temperature Regulation
• Amphibians are ectothermic (they depend on external heat sources to maintain body temperature).
• When in the water, they will take on the temperature of the water.
• On land, their body temperature can be different from the environment.
• Temperature regulation is mainly behavioral.• Many amphibians are nocturnal and remain in
cooler burrows or under leaves during the hottest part of the day.
• They may warm themselves by basking in the sun.
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Nervous and Sensory Functions
• The nervous system of amphibians is similar to that of other vertebrates.
• Their brain has 3 sections: forebrain, midbrain, and hindbrain.
• Amphibians have many sensory receptors on their skin.
• They also have a lateral line system similar to fish and this helps aquatic amphibians.
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Nervous and Sensory Functions
• Chemoreception is an important sense for many amphibians.
• Smell is used in mate recognition, detecting toxic chemicals, and in locating food.
• Vision is one of the most important senses for amphibians because they are primarily sight feeders, often responding to the movements of their prey.
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Nervous and Sensory Functions
• Some amphibian eyes are on the front of the head and some are more to the side.
• The lower eyelid is movable, and it cleans and protects the eye.
• Much of it is transparent and is called the nictitating membrane.
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Nervous and Sensory Functions
• Amphibians auditory system is an adaptation for living on land.
• It transmits both underground and airborne vibrations.
• Anuran ears are made up of tympanic membrane, a middle ear, and an inner ear.
• Anurans can screen out either high or low frequency sounds, depending on the situation.
• Salamanders have no tympanic membrane or middle ear.
• They have no mating calls, and the only sounds they hear are probably low-frequency vibrations.
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Excretion and Water Regulaton
• Amphibians do have kidneys. • Their waste product is either ammonia or urea,
depending on where they live. • One of the biggest problems amphibians have is
controlling the amount of water and salt in their body.
• In water, they must get rid of excess water while keeping essential ions.
• On land, they must conserve water.
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Excretion and Water Regulation
• They can not replace water in the usual ways. • So they limit water loss by using behavior that avoids
exposure to conditions that cause water loss. • For example, many amphibians are nocturnal. • Those that are active day AND night can rehydrate by going
back in the water. • Some amphibians have protective covering that reduce
water loss. • Others may form cocoons that cover the body during
dormancy. • They can also temporarily store water in the urinary
bladder and lymph sacs.
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Reproduction, Development, Metamorphosis
• Amphibians have separate males and females.• Fertilization is usually external, and because the
developing eggs do not have protective covering, development must take place in moist habitats, usually water.
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Reproduction, Development, Metamorphosis
• Some anurans have nests on land that are kept moist by a foam covering or by being near water.
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Reproduction, Development, Metamorphosis
• The main exception to external fertilization are the salamanders.
• All caecilians have internal fertilization and about 75% have internal development.
• Amphibian development usually includes larval stages called tadpoles.
• Tadpoles are different from adults in how they breathe, how they move, and what they eat.
• This helps reduce competition between adults and larvae.
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Reproduction, Development, Metamorphosis
• Reproductive activity is often controlled by outside factors such as temperature (in temperate regions) and seasons (such as the rainy season in tropical regions).
• Courtship behavior helps individuals locate breeding sites and identify potential mates.
• Salamanders rely mostly on smell and vision clues in courtship and mating.
• Anurans, especially males, rely on sound.
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Reproduction, Development, Metamorphosis
• Sound production is mainly used in male anurans.• These sounds will attract females and let other males know
that a certain territory is taken. • These sounds are species specific. • Females respond by making the same call that indicates
her willingness to mate. • Release calls let a frog know that the partner is incapable of
reproducing. • Distress calls are associated with pain or with being seized
by a predator. • Sound production in frogs comes from the larynx and vocal
cords. • Males also have a vocal sac.
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Reproduction, Development, Metamorphosis
• Parental care increases the chance of any one egg surviving but requires a lot of energy from the parent.
• The most common form of care is protecting the egg clutch, usually done by either parent.
• Maternal care occurs in species with internal fertilization (salamanders and caecilians), and paternal care may occur in species with external fertilization (anurans).
• This care may involve providing oxygen to aquatic eggs, cleaning and/or moistening land eggs, protecting eggs from predators, or removing dead or infected eggs.
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Reproduction, Development, Metamorphosis
• Eggs may be transported if development occurs on land.
• Females of genus Pipa carry eggs on their back. • Rheobatrachus females grow tadpoles in their
stomach, and the young emerge from the female’s mouth.
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Reproduction, Development, Metamorphosis
• Metamorphosis is a series of abrupt structural, physiological, and behavior changes that transform a larva into an adult.
• Several conditions influence the time required for metamorphosis, such as crowding and food availability.
• Most changes, however, are controlled by hormones.
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Reproduction, Development, Metamorphosis
• Caecilian and salamander changes are minimal. • They develop reproductive structures, lose their
gills and caudal fin. • Anurans have dramatic changes. • Limbs and lungs develop, tail is reabsorbed, skin
thickens, and noticeable changes in the head and digestive tract occur.
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AMPHIBIANS IN PERIL
• Frogs and salamanders are disappearing at an alarming rate—and no one knows exactly why.
• Local events can affect populations—clear-cutting forests, mining, drilling, and urban sprawl destroy habitats.
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AMPHIBIANS IN PERIL
• Two other factors are thought to be affecting amphibians—acid deposits and UV radiation.
• Embryos are very susceptible to changes in the pH of their water.
• UV radiation also kills eggs and embryos.
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