Difference Between Mammals and Amphibians

Main Difference – Mammals vs Amphibians

Mammals and amphibians are two classes of the phylum Chordata. Mammals live in the ground and on the sea. Amphibians live the shady environments. In addition, mammals are warm-blooded animals and amphibians are cold-blooded animals. Internal fertilization occurs in mammals during sexual reproduction while external fertilization occurs in amphibians. Hence, mammals develop the embryo inside the body of the mother. The main difference between mammals and amphibians is that mammals produce milk to feed their babies whereas amphibians do not produce milk.

Key Areas Covered

1. What are Mammals
     – Definition, Characteristics, Classification
2. What are Amphibians
     – Definition, Characteristics, Classification
3. What are the Similarities Between Mammals and Amphibians
     – Outline of Common Features
4. What is the Difference Between Mammals and Amphibians
     – Comparison of Key Differences

Key Terms: Amphibians, Chordata, Fertilization, Hair, Mammals, Skin

Mammals – Definition, Characteristics and Classification

Mammals are warm-blooded, vertebrate animals, distinguished by the possession of fur or hair and mammary glands. Generally, mammals live every habitat on the earth such as tropical rainforests, deep sea, and deserts. The size of mammals varies from one-ounce (shrews) to 200 tons (whale). Mammals are warm-blooded animals, maintaining their body temperature independent from the external environment through their endothermic metabolism. One of the main characteristic features of a mammal is the presence of fur or hair, which grows from some parts of the body. Hair can be in different forms such as thick fur, horns, long whiskers, and defensive quills. The main function of the hair is the insulation of the body against the cold. Mammals are shown in figure 1.

Figure 1: Mammals

The lower jawbone of mammals is a single piece of bone directly attached to the skull. Diphyodonty refers to a unique pattern to mammals in which the teeth are replaced once during their lifetime. Mammals have three bones in their middle ear for the transmission of sounds to the inner ear. The other characteristic feature of mammals is the presence of mammary glands to feed the babies. Mammary glands are a type of enlarged sweat glands. Mammals exhibit internal fertilization, and they carry the embryo inside the mother.

Amphibians – Definition, Characteristics and Classification

Amphibians are the cold-blooded, vertebrate animals that possess an aquatic gill-breathing larval stage and terrestrial, lung-breathing adult stages. Generally, amphibians are cold-blooded (ectothermic) animals and depend on external sources such as sunlight for the regulation of body temperature. The skin of amphibians is thin, soft, hairless, and porous. It contains both mucus and poison glands. Some amphibians have four legs. Each limb consists of webbed feet and a varying number of digits. But, true nails and claws are absent. Some amphibians such as caecilian are limbless. Some amphibians such as tadpoles use their lateral line to sense water pressure changes, determining the location of the prey. An amphibian is shown in figure 2.

Figure 2: A Leaf Green Tree Frog

As amphibians are unisexual animals, they exhibit external fertilization. Their eggs are laid in moist environments. The larval stage of amphibians is aquatic, and their respiration occurs through gills. The adult stage is morphologically different from the larva. It moves to the terrestrial environment and breath through lungs. Amphibians are the only vertebrates that undergo complete metamorphosis. 

Similarities Between Mammals and Amphibians

• Mammals and amphibians represent two classes of the phylum Chordata.
• Both mammals and amphibians consist of a notochord, dorsal central nervous system, pharyngeal gill slits, and a post-anal tail. 
• Both mammals and amphibians are deuterostomes with bilateral symmetry.
• Both mammals and amphibians have two eyes with colored vision.

Difference Between Mammals and Amphibians

Definition

Mammals: Mammals are warm-blooded, vertebrate animals, distinguished by the possession of fur or hair and mammary glands.

Amphibians: Amphibians are cold-blooded, vertebrate animals who possess an aquatic gill-breathing larval stage and terrestrial, lung-breathing adult stages.

Significance

Mammals: Mammals produce milk to feed their babies.

Amphibians: Amphibians are animals with dual modes of existence.

Habitat

Mammals: Mammals live in both terrestrial and aquatic environments.

Amphibians: Amphibians live partly in both water and shady land.

Skin Covering

Mammals: The skin of mammals consists of a dead layer of keratin-filled cells and fur/hair.

Amphibians: Amphibians have soft skins protected by a slippery secretion of mucus.

Size of the Body

Mammals: Mammals grow into large body size.

Amphibians: Amphibians have small body sizes.

Vertebrae in the Neck

Mammals: Mammals have several vertebrae, allowing the head to move in a wide range.

Amphibians: The neck consists of a single vertebra, limiting the head movement.

Method of Breathing

Mammals: Mammals use lungs to breathe.

Amphibians: Amphibians use gills or lungs to breathe.

Type of Blood

Mammals: Mammals are warm-blooded animals.

Amphibians: Amphibians are cold-blooded animals.

Vision

Mammals: Mammals have either dichromatic or trichromatic vision.

Amphibians: The vision of amphibians is restricted to a narrow range of the color spectrum.

Mouth

Mammals: Mammals have teeth to chew the food.

Amphibians: Amphibians have a large mouth with small teeth. Some amphibians swallow their food as a whole.

Fertilization

Mammals: Mammals undergo internal fertilization.

Amphibians: Amphibians undergo external fertilization. 

Eggs

Mammals: Babies are carries inside the body of the females.

Amphibians: Eggs of amphibians are covered with a transparent gelatinous covering.

Birth

Mammals: Mammals are born on the land or in the sea.

Amphibians: Amphibians are born in water or mushy lands with gills and tails.

Type of Metamorphosis

Mammals: Mammals undergo incomplete metamorphosis.

Amphibians: Amphibians undergo complete metamorphosis.

Parental Care

Mammals: Mammals take care of their babies very well.

Amphibians: Amphibians do not take care of their babies.

Limb

Mammals: Some mammals have four limbs. Others may have fins or wings.

Amphibians: Amphibians have four short limbs.

Cranial Nerves

Mammals: Mammals have twelve pairs of cranial nerves.

Amphibians: Amphibians have ten pairs of cranial nerves.

Excretion

Mammals: Mammals excrete urea through kidneys.

Amphibians: The main nitrogenous waste of amphibians is ammonia.

Conclusion

Mammals and amphibians are two classes of animals that belong to the phylum Chordata. Mammals are well-developed animals than amphibians. Mammals mainly live in terrestrial environments while amphibians live in shady environments. Mammals exhibit internal fertilization while amphibians exhibit external fertilization. Mammals have mammary glands for the production of milk to feed their babies. But, amphibians do no exhibit such parental care. This is the main difference between mammals and amphibians.

Reference:

1. Prakash, Mohini. Characteristics of Class Amphibian, Available here.
2. Strauss, Bob. “These Eight Traits Separate Mammals From Other Vertebrates.” ThoughtCo, Available here.

Image Courtesy:

1. “3040870” (Public Domain) via Pixabay
2. “Litoria phyllochroa” By User:Froggydarb – English wikipedia (CC BY-SA 3.0) via Commons Wikimedia