Amphibian Characteristics and Classification

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Questions and Answers

How did amphibians adapt to living on land?

Amphibians replaced gills with another respiratory organ, the lungs. 2. Skin that prevents loss of water. 3. Eyelids that allow them to adapt to vision outside of the water. 4. An eardrum developed to separate the external ear from the middle ear. 5. A tail that disappears in adulthood (in frogs and toads).

What are the three Orders of Class Amphibia?

Urodela, containing salamanders and newts. 2. Anura, containing frogs and toads. 3. Apoda, containing caecilians.

What are tetrapods?

Vertebrates with four limbs.

What is keratin?

A tough, fibrous protein found in the skin, scales, feathers, hair, and nails of tetrapod vertebrates. Signup and view all the answers

What are mucous glands?

Secretes glycoproteins: mucins, absorb water to form slippery mucus. Signup and view all the answers

What is a three-chambered heart?

Has two atria and one ventricle; found in amphibians and reptiles (except crocodilians). Signup and view all the answers

What is a tadpole?

The larval form of a frog or toad. Signup and view all the answers

How do amphibians reproduce?

<ol> <li>Amphibians reproduce sexually with either external or internal fertilization. 2. They may attract mates with calls or scents. 3. They do not produce amniotic eggs, so they must reproduce in water. 4. Amphibian larvae go through metamorphosis to change into the adult form.</li> </ol> Signup and view all the answers

What features distinguish frogs and toads from other amphibians?

<ol> <li>A lack of a tail in adulthood. 2. Have much longer back legs than other amphibians. 3. Their back legs are modified for jumping.</li> </ol> Signup and view all the answers

What are the characteristics of salamanders and newts?

<ol> <li>Keep their tails as adults. 2. Long body with short legs. 3. Ability to regenerate legs.</li> </ol> Signup and view all the answers

What are the characteristics of caecilians?

Long, worm-like body; evolved from a tetrapod ancestor; legless; burrow in damp sand and mud; small jaw, small eyes. Signup and view all the answers

What are the tetrapod characteristics?

<ol> <li>Lungs for efficiently breathing air. 2. Four limbs and feet with digits. 3. Ears for detecting airborne sounds.</li> </ol> Signup and view all the answers

What is double circulation?

A circulatory system consisting of separate pulmonary and systemic circuits. Signup and view all the answers

What is Acanthostega?

Well-developed tetrapod with 4 legs and feet with digits. Signup and view all the answers

What is Ichthyostega?

One of the first amphibian-like tetrapods in fossil records. Signup and view all the answers

What was the Carboniferous period?

354 to 290 mya; cooler period; much of the land covered by forest swamps; very large plants and trees became prevalent. Signup and view all the answers

What was the Devonian period?

Major increase in number of terrestrial species; amphibians emerge; Age of the fishes. Signup and view all the answers

What are the characteristics of Class Amphibia?

Amphibians; bony skeleton; moist, glandular skin; two pairs of limbs; three-chambered heart. Signup and view all the answers

What is Order Gymnophiona?

Gymnopis; do not have legs; shaped like worms; live in tropical areas. Signup and view all the answers

What is Order Urodela?

Salamanders; have four equal-sized feet; heavy feeders of insects. Signup and view all the answers

What is direct development?

The process where organisms develop directly into adults without a larval stage. Signup and view all the answers

Study Notes

Amphibian Adaptations

Amphibians developed lungs to replace gills for breathing air.
Skin adapted to reduce water loss, aiding survival on land.
Eyelids evolved for better vision in terrestrial environments.
Eardrums formed to separate external and middle ear, enhancing hearing capabilities.
Adult amphibians, like frogs and toads, lose their tails.

Classification of Amphibians

Class Amphibia consists of three Orders:
- Urodela (salamanders and newts)
- Anura (frogs and toads)
- Apoda (caecilians)

Key Terminology

Tetrapods: Vertebrates with four limbs, including amphibians.
Keratin: A fibrous protein found in skin and other structures; amphibian skin has low keratin content allowing gas and water permeability.
Mucous Glands: Produce slippery mucus through glycoprotein secretion, aiding in hydration and locomotion.

Cardiovascular Features

Amphibians possess a three-chambered heart with two atria and one ventricle, a characteristic shared with reptiles (excluding crocodilians).
Double Circulation: System features pulmonary and systemic circuits with blood passing through the heart after each circuit.

Life Cycle and Reproduction

Amphibians reproduce sexually via external or internal fertilization.
Mating behaviors may include vocalizations or scent marking.
Eggs are laid in water, ensuring larvae development and metamorphosis into adults.

Distinguishing Features of Frogs and Toads

Adults lack tails and possess elongated hind legs adapted for jumping.
Frogs can leap significantly, up to 20 times their body length.
Frogs typically inhabit more aquatic environments than toads, which prefer terrestrial habitats.
Frogs have smoother and moister skin compared to the drier texture of toads.

Characteristics of Salamanders and Newts

Retain tails into adulthood; possess a long body and short limbs.
Adapted for both walking and swimming; limbs are equal in length.
Notable for regenerative abilities, capable of regrowing lost limbs.

Unique Features of Caecilians

Legless, elongated, worm-like body structure.
Evolved from a tetrapod ancestor, adapted for burrowing.
Possess small jaws and eyes, thriving in damp environments.

Evolutionary Context

Acanthostega: An early tetrapod characterized by its four legs and digits, not strong enough for land walking.
Ichthyostega: One of the earliest amphibian-like tetrapods known from fossil records.
Carboniferous Period: Lasted from 354 to 290 million years ago; featured abundant coal deposits, extensive forest swamps, and large plant species.
Devonian Period: Marked by the diversification of terrestrial species and the emergence of amphibians, known as the "Age of Fishes."

Class Amphibia Overview

Amphibians are defined by a bony skeleton, moist glandular skin, two pairs of limbs, and a three-chambered heart.
Species commonly include frogs and toads, displaying adaptability for life both in water and on land.

Order Features

Order Gymnophiona (Caecilians): Include legless, worm-shaped creatures with moist skin and some bony scales; predominantly found in tropical regions.
Order Urodela (Salamanders): Have four similarly sized limbs, which aid in their waddling gait and are significant insect predators, contributing to ecosystem balance.

Developmental Concepts

Direct Development: A reproductive strategy where young develop directly into the adult form without a larval stage.

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Description

Test your knowledge on the unique characteristics and classification of amphibians. This quiz covers their adaptations for life on land and the three main orders of amphibians. Challenge yourself and learn more about these fascinating creatures.