Amphibians Biology

Study Notes

Modification to movement, breathing, and skin were necessary for vertebrates to transition from water to land
Amphibians are vertebrates that inhabit both freshwater and terrestrial environments
Examples of modern amphibians include frogs, salamanders, and caecilians
Amphibians are the first tetrapods, possessing four limbs
They are ectothermic, meaning their internal body temperature is the same as their environment
Amphibians have a complex circulatory system featuring a three-chambered heart
Frogs possess a larynx, enabling them to produce sound
Oxygen is absorbed through the skin in amphibians

Amphibians do not produce amniotic eggs
Eggs are laid in water to prevent desiccation
Early larvae stages (tadpoles) resemble fish, with gills, no legs, and a tail for swimming

The limited resources in aquatic environments likely led to the evolution of amphibians into reptiles
Reptiles are tetrapod vertebrates that produce amniotic eggs, enabling them to survive outside water
Examples of reptiles include crocodiles, alligators, lizards, snakes, and turtles

Amniotic eggs consist of a shell, membrane, and other structures that protect and nourish the embryo
The yolk provides a rich, fatty food source for the embryo
The amniotic membrane allows for gas exchange while preventing water loss

Reptiles have scales covering their skin to prevent water loss
They breathe air exclusively through their lungs (not skin)
Crocodiles and alligators possess a diaphragm, a large sheet of muscle controlling breathing
Reptiles are ectothermic, having the same body temperature as their environment
Most reptiles have a three-chambered heart, while crocodiles and alligators have a four-chambered heart
Reptiles inhabit ocean, freshwater, and land environments