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

2. 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

3. 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

4. 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

6. Class Amphibia
Larva
(tadpole)
Yellow Spotted Salamander
Adult

7. 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

9. 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!

11. 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

12. 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