Zoology

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Zoology
Phylum Chordata Class Amphibia
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General Characteristics

• First vertebrates on land

• 4000 species

• Strong skeleton to support body weight

• Nostrils for breathing through nose

• 3 chambered heart

• Air breathing lungs

• Carnivorous diet

• Eardrum

• Eyelids

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• Important accommodations needed for land because
  of

• Oxygen content

• Density

• Temperature regulation

• Habitat diversity

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Donovan Period

• 400 million years ago

• Mild temperatures and cycles of drought then
  heavy rainfall, then drought

• Unstable environment when many pools evaporated,
  only those able to acquire atmospheric oxygen
  survived

• Gills would collapse, dry, and lose function

• Lobe-finned fish and lungfish were at an advantage

• A kind of lung (extension of pharynex)

• Bones in fins are like that in arms and legs or
  early amphibians

• Came to land to escape predators or get food

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bony or cartiliginous structures in lobed fin
undergoing modificaiton
limb bones of early amphibians
Fig. 27.11, p. 462
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3 Orders of Amphibians 1. Urodela

• Tailed ones

• Salamanders, newts, mudpuppies

• 400 species

• Some are entirely aquatic and some live on land

• Most walk by bending side to side

• Usually internal fertilization female picks up
  sperm packet, spermatophore, and inserts it into
  her cloaca

• Born with gills, but these are usually lost in
  all but aquatic forms

• Some do not have lungs or gills and use only skin
  and mouth for gas exchange

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In-text, p. 463
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2. Anura

• Tail-less ones

• Frogs and toads

• 3500 species

• More specialized for living on land

• Use strong legs to hop

• Flick tongue to catch insects

• Defense from predators

• Camouflage

• Secrete mucus bad tasting or poisonous

• Many with poison have a bright color to warn
  predators

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3. Apoda

• Leg-less ones

• Caecilians

• Nearly blind

• Look like earthworms

• 160 species

• Burrow through soil

• Live in South America, Africa and Southeast Asia

• Internal fertilization

• Viviparous live birth

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Frog
Tadpole
Adults
Aquatic with gills
Gills and tail disappear
Lateral line
Lateral line
Develops legs
Finned tail

• Some frogs do not go through the tadpole phase

• Some are strictly aquatic and some are strictly
  land

• Salamanders and caecilians resemble adults when
  born

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• Even land dwelling amphibians need a moist habitat

• Need to stay moist

• Some breath through skin and mouth because they
  have no lungs

• Eggs do not have a shell and dehydrate in air

• Male causes female to release eggs and spills
  sperm while she does this

• Some incubate eggs on back, mouth or in stomach

• Some are ovoviviparons and viviparons

• Ovoviviparons eggs hatch in uterus

• Viviparons young develop in uterus

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• Frogs are usually quiet, but may call during
  mating season

• Many want to protect territory or attract females