Summary
Summary Amphibia
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- University Of South Africa (Unisa)
A summary of amphibia
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By: nitacarstens26 • 4 year ago
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AMPHIBIA:Characteristics of Modern Amphibians:
Quadrupedal limbs in two pairs
No true nails, feet often webbed
Forelimbs with 4 digits and hindlimbs with 5
Skeleton mostly bony
Ectothermic
Skin is smooth, moist and glandular
Integument modified for cutaneous respiration
Pigment cells (chromatophores)
10 pairs of cranial nerves
Separate sexes
Granular glands secrete defensive compounds
Light skull, less ossified, flattened in profile and
with fewer bones
Large mouth with small teeth, jaws and palate
Yolky eggs with jellylike membrane coverings
Respiration by skin and gills or lungs
Heart with sinus venosus, 2 atria, 1 ventricle.
Double circulation.
Tripartite brain: forebrain (telencephalon)
coordinating olfaction, midbrain (mesencephalon) coordinating vision and hindbrain (rhombencephalon)
coordinating hearing and balance
Ear with tympanic membrane and stapes. Cornea, eyelids and lachrymal glands. Internal nostrils
CAECILIANS: ORDER GYMNOPHIONA (APODA)
Elongate, limbless burrowing creatures Sensory tentacles occur on the snout
Small dermal scales Feed on worms and small invertebrates
Many vertebrae Internal fertilisation. Protrusible male copulatory
Long ribs organ - .Eggs deposited in moist ground near
Terminal anus water
Small eyes, mostly blind as adults
SALAMANDERS: ORDER URODELA (CAUDATA)
Tailed, limbs set at right angles to the trunk. Forelimbs and hindlimbs of equal size
Carnivorous
Life cycles:
Aquatic larvae with external gills, finlike tail. terrestrial adults
Eggs are fertilised internally. A female recovers a packet of
sperm (spermatophore) in her cloaca deposited by a male
Terrestrial species bypass the larval stage and hatch as
miniature versions of their parents
Respiration:
Respiration across skin, external gills, lungs, both or neither
Cutaneous respiration increased by penetration of capillary
network into epidermis and by pumping air through mouth
Paedomorphosis:
Descendants retain into adulthood features that occurred
only in preadult stages of their ancestors. Some
characteristics of ancestral adult morphology are
consequently eliminated
The most dramatic form of paedomorphosis occurs in species that become sexually mature while retaining
their gills, aquatic life habit and other larval characteristics
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