Phylum Chordata: Subphylum Verebrata: Class Amphibia Biology 11 Phylum Chordata: Subphylum Verebrata: Class Amphibia

Class Amphibia Objectives Describe the structural adaptations that allow them to live on land Describe the reproductive, respiratory, circulatory, skeletal and nervous systems of the frog

Class Amphibia Still quite tied to water The amphibians represent the first attempt by vertebrates to live on land; they are only partially successful Their biology does show the beginnings of significant adaptations to their new habitat Due to lack of competition from other species, amphibians were very successful during the Carboniferous period

Class Amphibia Amphibian Biology 1. Reproduction External fertilization and development Larva (tadpole) lives exclusively in water and has gills and fins (no legs!) They later undergo metamorphosis into an air breathing, land dwelling adult

Class Amphibia Larva (tadpole) Yellow Spotted Salamander Adult

Class Amphibia 2. Respiration As adults, they have crude sac-like lungs that come off the pharynx Inefficient: 50% of O2 absorbed through skin (so must stay moist) Larva use gills, adults do not

Class Amphibia 3. Circulatory System Have three chambered heart with the new chamber being a second atrium Beginning of “double pump” Blood mixes in the one ventricle and partially oxygenated blood goes to the lungs INEFFICIENT!

Class Amphibia 4. Skeleton Appendages come off the side of the body As a result, they are “belly draggers” which is inefficient over the rough terrain on land Most still have tail and legs that are not well muscled Cumbersome movement on land

Class Amphibia 5. Nervous system Brain size increases with a notable increase in the size of the cerebrum and cerebellum Senses improved: land based ear and sense of smell