Sarcopterygii Characteristics Quiz

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Questions and Answers

What are the characteristics of Sarcopterygii?

Skeleton with bone of endochondral origin; caudal fin diphycercal in living representatives, heterocercal in ancestral forms, skin with embedded dermal scales with layer of cosine and a thin layer of enamel of fossil species; 2. Paired and median fins present; paired fins with a single basal skeletal element and short dermal rays; muscles that move paired fins located on appendage; 3. Jaws present; teeth covered with true enamel and typically are crushing plates restricted to palate; olfactory sacs paired, may or may not open into mouth, intestine with spiral valve; 4. Gills supported by bony arches and covered with an operculum; 5. Swim bladder vascularized and used for respiration and buoyancy (fat-filled coelacanths); 6. Circulation consisting of heart with a sinus venosus, two atria, a partly divided ventricle, and a conus arteriosus; double circulation with pulmonary and systemic circuits; characteristically five aortic arches; 7. Nervous system of a relatively small brain; 10 pairs of cranial nerves; three pairs of semicircular canals; 8. Separate sexes; fertilization external or internal.

What is Class Sarcopterygii?

Lobe-finned fishes.

Who is considered the ancestor of modern Sarcopterygii?

Class Sarcopterygii; probable ancestor of all tetrapods.

What is the sequence of fossils of Class Sarcopterygii?

Fish -> Fishapod -> Tetrapod. Signup and view all the answers

What is Eusthenopteron?

A fossil lobe-finned fish that has many fin rays. Signup and view all the answers

What is Acanthostega?

A primitive tetrapod with eight toes. Signup and view all the answers

What is Tiktaalik rosae?

The latest 'missing link' fossil. Signup and view all the answers

What were two challenges of terrestrial life?

Dessication risk and structural support. Signup and view all the answers

What adaptations to aquatic life didn't work on land?

Fins, undulatory locomotion, disarticulated appendicular skeleton, gills, external fertilization, filter feeding, 'inhalation' feeding. Signup and view all the answers

What primitive features from aquatic life were retained during the transition to land?

Water permeable skin, splayed gait, horizontal undulation, reliance on water for reproduction and larval stages. Signup and view all the answers

What were the solutions for the adaptations from water to land for fish-type limb structure?

Redirect limbs in a ventral direction, strengthen appendicular skeleton articulations, develop rib cage to support body for belly crawling, selective pressure led to extreme skeletal modification in frogs. Signup and view all the answers

What was the solution for the transition from water to land regarding water-permeable skin that leads to moisture loss?

Secrete mucus and stay in/near moist/wet habitats. Signup and view all the answers

What are the limitations to adaptations of water-permeable skin?

Mucus production costs energy and some water, still somewhat permeable. Signup and view all the answers

What does permeable skin allow?

Permeable skin allows toxin penetration. Signup and view all the answers

What are amphibians similar to regarding their permeable skin?

Canary in a coal mine. Signup and view all the answers

What is the solution to gas exchange through gills causing moisture loss during the transition to land?

Lungs. Signup and view all the answers

What are the limitations of the solution to gas exchange?

No diaphragm, necessitates buccal breathing. Signup and view all the answers

What is cutaneous respiration?

Gas exchange that supplements lung-breathing but adds moisture loss; mucus secreted by skin limits moisture loss. Signup and view all the answers

What is the solution to external fertilization and water-permeable eggs that don't work on land?

Return to water for reproduction. Signup and view all the answers

What is the limitation to the solution of external fertilization?

Required metamorphosis to adult form. Signup and view all the answers

What are additional adaptations to the problem of external fertilization?

Offspring in marsupia and spermatophore deposition for terrestrial sperm transfer. Signup and view all the answers

In salamanders, what does indirect insemination refer to?

Internal fertilization. Signup and view all the answers

Study Notes

Characteristics of Sarcopterygii

Skeleton comprised of endochondral bone; living representatives have diphycercal caudal fins, while ancestral forms possess heterocercal fins.
Presence of paired and median fins; paired fins feature a single basal skeletal element and short dermal rays; muscles for movement are located directly on the appendage.
Jaws are present, with teeth covered in true enamel, often forming crushing plates; olfactory sacs are paired and may not connect to the mouth; intestines exhibit a spiral valve.
Gills are supported by bony arches and protected by an operculum.
Swim bladder serves both respiratory and buoyancy functions, particularly noted in fat-filled coelacanths.
Heart structure consists of a sinus venosus, two atria, a partly divided ventricle, and a conus arteriosus; possesses a double circulation including pulmonary and systemic circuits along with five aortic arches.
Nervous system is characterized by a relatively small brain, ten pairs of cranial nerves, and three pairs of semicircular canals.
Reproduction involves separate sexes with either internal or external fertilization.

Class Sarcopterygii Overview

Known as lobe-finned fishes.

Ancestry

Considered the probable ancestor of all tetrapods.

Fossil Sequence

Evolutionary sequence includes fish, fishapod, and then tetrapod.

Eusthenopteron

Fossil lobe-finned fish known for having many fin rays.

Acanthostega

Primitive tetrapod identified by its eight toes.

Tiktaalik Roseae

Recognized as the latest "missing link" fossil in the evolutionary transition.

Challenges of Terrestrial Life

Risks of desiccation and the need for structural support present major challenges for terrestrial life.

Non-Working Aquatic Adaptations

Features not suitable for land include fins, undulatory locomotion, disarticulated appendicular skeleton, gills, external fertilization, filter feeding, and "inhalation" feeding.

Retained Primitive Aquatic Features

Transitioning to land retained certain characteristics like water-permeable skin, splayed gait, horizontal undulation, and dependence on water for reproduction and larval stages.

Solutions for Water to Land Adaptations

Limb structures redirected ventrally, strengthened appendicular skeleton articulations, developed rib cages for belly-crawling support, and underwent significant skeletal modifications driven by selective pressure (illustrated in frogs).

Addressing Moisture Loss from Skin

Adaptations to combat water loss include secreting mucus and staying in or near moist habitats.

Limitations of Permeable Skin Adaptations

Energy and water costs associated with mucus production, while skin remains somewhat permeable.

Implications of Permeable Skin

Permeable skin can facilitate toxin penetration.

Amphibian Skin Comparison

The permeable skin of amphibians is likened to a "canary in a coal mine," indicating environmental health.

Gas Exchange Solutions

Transitioning to land required lungs due to moisture loss associated with gills.

Limitations of Lung Adaptation

Absence of a diaphragm necessitates buccal breathing to facilitate gas exchange.

Cutaneous Respiration

This form of respiration, which supplements lung-breathing, also increases moisture loss; skin secretes mucus to mitigate this loss.

Reproductive Adaptations to Terrestrial Challenges

To address external fertilization and the limitations of water-permeable eggs, many species return to aquatic environments for reproduction.

Limitations of External Fertilization Solutions

The requirement for metamorphosis into adult forms presents a significant limitation.

Additional Reproductive Adaptations

Some species have developed marsupia for offspring protection and utilize spermatophore deposition to facilitate terrestrial sperm transfer.

Salamander Reproductive System

Indirect insemination in salamanders equates to internal fertilization.

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Test your knowledge on the characteristics of Sarcopterygii with this flashcard quiz. Explore the unique features of these ancient lobe-finned fishes and their evolutionary significance. Perfect for biology students and enthusiasts alike!