Exploring Our World

Similarities and Differences: Amphibians and Reptiles

The lifeform that is considered to most closely resemble amphibians is the reptile family. Amphibians and reptiles both have vertebrates, are cold-blooded, and most hatch from eggs, although a few reptiles give live birth.

Key Changes Needed:

The development of lungs, scaly skin, and amniotic eggs would be needed to allow amphibians to transitionally change into reptiles.

However, to get a better understanding of the unique natures of both reptiles and amphibians, let’s consider how they differ from one another.

1. Body Coverings

Amphibians have smooth, moist and at times rather sticky skin, laden with mucous glands. Reptile skin is dry and scaly.  Scales are made of keratin.  Skin is found underneath the scales.

2. Feeding

Snakes are able to disjoin their upper and lower jaw that will allow them to accommodate swallowing large prey whole.  Amphibians attempt to swallow their food whole, but some have exclusive teeth called pedicellate teeth.

3. Neck Vertebra

Reptiles have multiple vertebra in the neck, allowing articulation.  Amphibians have a single vertebra in the neck which limits head articulation.

4. Eggs

Reptiles have leathery, soft or hard eggs laid on land or maintained inside the body until hatching.  The reptile egg is self-contained and protects the embryo from dehydration. Amphibians have soft eggs normally laid in water or in damp media.  The amphibian egg is a yolk sac enveloped in one or more layers of a clear, jelly-like covering.  The egg capsule is permeable to water and gases.

5. Respiration

Reptiles breath via lungs.  Amphibians breathing via gills, lungs or through the skin which is called cutaneous respiration.  Their vascularised skin must be moist for this to work.

6. Metamorphosis (profound change in form)

Most amphibians use gills while developing their lungs.  Some salamanders such as the mudpuppy retain their gills throughout their lives which is called neoteny.  Reptiles have no larval stages.

7. Reproduction

Amphibians utilize external fertilization; while reptiles utilize internal fertilization.

8. At Birth

Amphibians are born in water or mushy land with gills and tails.  Reptiles are born on land and with strong instincts, and physically look similar to the adult.  Most mother reptiles leave the nest once the eggs are laid.  The hatchlings are independent from the start and must find their own food and shelter.

9. Defense

Amphibians have no nails.  They give off a toxic skin secretion, and they can bite.  If teeth are present, they are pedicellate teeth (Pedicellate teeth consist of a tooth crown and a base separated by a layer of uncalcified dentine).  Reptiles have nails, teeth, and scales.

10. Limbs

Amphibians have short fore limbs and long hind limbs with five webbed digits.  Reptiles usually have four limbs, but some reptiles (snakes) have no limbs.  Reptiles with limbs vary in their ability to move; some move very slowly and crawl, while others can run, jump, and even climb.

11. Skulls

Reptile skulls differ from those of amphibians.  Reptiles lack an otic notch (an indentation at the rear of the skull) and several small bones at the rear of the skull roof.

12. Eyes

Amphibians such as frogs have bulging eyes that provide them a wide range of view.  Reptiles, especially snakes, generally have poor vision.

13. Tongues

Amphibian tongues are broad and specially attached so they can be thrust out and catch insects. Reptile tongues are narrow and forked, to ‘taste’ chemical particles in the air.

14. Skeletons

Although both amphibians and reptiles have a backbone, most frogs have no ribs.

Two Worldview Interpretations:

Undirected Process Formation

Life forms share common traits and body parts with other life forms because they had a common ancestor.

Directed Purpose Formation

Life forms share common traits and body parts with other life forms because of similar purpose and design.