Zoology Final a Flashcards
types of Amphibians
- frogs
- toads
- salamanders
- caecilians
What collective monophyletic group are Amphibians a part of?
tetrapods
evolutionary history of amphibians
- movement from water to land
- a non-aquatic environment is more hazardous than an aquatic environment for many life processes (reproduction)
- life originated in water, animals are mostly water in composition, and all cellular activities occur in water
- invasion of land required major modifications of almost every organ system of vertebrate body
from what group of fish did the earliest tetrapods (amphibians) most likely evolve?
lobe-finned fish similar to the modern coelacanth
What fossil fish had an arrangement of its pectoral bones that foreshadowed the forelimb of amphibians?
Eusthenopteron
After Eusthenopteron, Acanthostega appeared with what characteristics?
- forelimb bones
- 8 toes replacing the dermal fin rays
After Acanthostega, Ichthyostega appeared with what characteristics?
- 7 digits on hindlimb
- stronger vertebrae and associated muscles
- muscles raise head off ground
- stronger and more protective skeleton
- resembled aquatic forms
After Ichthyostega, Limnoscelis appeared with what characteristics?
- 5 toes on all limbs
- more adapted for land
life on land
- oxygen is more readily available on land, but need modifications for gills
- much harder to support body on land
- relatively difficult to reproduce away from water
Amphibians are a transitional class. What does this mean?
means that they are still tied to water, particularly for reproduction
respiration in amphibians
- developed lungs, from air-filled swim bladder
- no diaphragm, so air has to be forced into lungs by elevating floor of mouth (buccal breathing)
- supplement lungs with cutaneous respiration through extensive vascular nets in their skin; skin is permeable
buccal breathing
- floor of mouth is lowered
- air flows through the nares into the bottom of the mouth
- glottis opens; air flows from the lungs across the top of the mouth and out of the nares
- floor of the mouth is raised; air is pumped into the lungs; the glottis closes
skin of an amphibian
- permeable skin allows greater water loss,adults require a war or moist environment to prevent desiccation
- permeable skin also allows for absorption of chemicals through skin
reproduction in frogs
- water-permeable eggs mean adults must return to water to breed
- copulatory embrace in frogs is called amplexus eggs are fertilized externally as they are shed by female
- some species use creative ways to allow young to develop on or inside body
where do pygmy marsupial frogs carry their young?
carry developing larvae in dorsal pouch, on the back
where do surinam frogs carry their young?
eggs embedded in brooding pouches; froglets emerge from back
where do male poison arrow frogs carry their young?
carries tadpoles on back for protection
where do darwins frog carry their young?
carries tadpoles around in mouth
where do glade frogs carry their young?
eggs are kept on a leaf and the male urinates on them to keep them moisturized
metamorphosis in frogs
- tadpole is fishlike in structure
- tail of tadpole degenerates as hind limbs first then forelimbs
reproduction in salamanders
- internal fertilization
- female picks up spermatophore
- most are metamorphic with aquatic larvae (with external gills) and terrestrial adults
- terrestrial species lay eggs in moist earth and have direct development
mud puppy characteristics
- Necturus
- exhibit paedomorphosis
- retention of juvenile characteristics in adult
- rarely undergo metamorphosis
characteristics of axolotls
- Ambystoma mexicanum
- only undergo metamorphosis when pond dries up and must travel across land
- nearly extinct
characteristics of newts
- larvae of some species metamorphose to form terrestrial juveniles that later metamorphose again to produce secondarily aquatic, breeding adults
- many species skip the terrestrial “red eft” stage, however remaining entirely aquatic
- other remain terrestrial, returning to water only to breed
- toxic as adult
circulatory system of amphibians
- heart is 3-chambered rather than 2-chambered (2 atrium, 1 ventricle)
- double circulation rather than single
brain in amphibians
- forebrain
- midbrain
- hindbrain
forebrain
- olfactory lobe > smell
- cerebrum > thinking part
midbrain
optic lobe > vision
hindbrain
- cerebellum > coordination and balance (not well developed)
- medulla oblongata
senses in amphibians
- have lateral line system, but only in larval stage of most species, since it doesn’t work in air
- tympanic membrane for hearing (outside of ear)
- sound waves are transmitted to inner ear via collumella
lachrymal glands produce what?
produce tears
eyes in amphibians
- have lachrymal glands, nictitating membrane and eyelids
- cornea assists lens in bending light rays to focus them on retina
- lens moves forward and backward to focus
- change shape of what its seeing in order to focus it
skin glands in amphibians
- mucous glands secrete protective waterproofing
- serous glands produce whitish watery poison that is highly irritating to would-be predators
What family of frogs produces one of most lethal poisons known, more poisonous even than venoms of sea snakes or any most poisonous arachnids?
Dendrobatidae - poison arrow frog
amphibian skin disadvantages
- since it is permeable to water and it is involved in gas exchange, it is restricted them to wet/moist environment
- toxins can easily enter their bodies
amphibian decline
- habitat loss particularly drainage of wetlands
- unscrupulous collecting
- 200 million bull frogs are killed annually for their legs for food > causing rice crops are threatened from resulting explosion in insect pests
legless amphibians
- Caecilians
- threatened due to loss of tropical habitat
- live in underground burrows and are seldom seen
