BIO 315 Exam 2 comprehensive
Questions and Answers with Verified
Solutions
Question 1:
Lungfishes are considered to be more closely related to tetrapods than
are coelacanths, but for most of the 20th century, coelacanths were
thought to be the sister group of tetrapods. How have new phylogenetic
tools and changes in our ways of thinking about phylogenetic
relationships reversed the older interpretation? What is it about lungfishes
that makes their phylogenetic placement challenging?
Answer:
Molecular phylogenetics helped to clarify these relationships. The
realization that extant lungfishes are highly specialized relative to
Devonian fossils discovered late in the 20th century such as Diabolepis
also made it easier to understand how lungfishes fit on the tree of the
Devonian vertebrates. Finally, many of the changes that occurred during
the evolution of lungfishes can be attributed to paeodmorphosis, which
helped us understand why they look so different from Devonian
lungfishes
Question 2:
What information about Devonian tetrapods leads to the conclusion that
tetrapods evolved in the water rather than on land?
Answer:
Retention of internal gills and polydactylous feet that look more like
flippers than feet for walking on land are characters that suggest an
aquatic origin for tetrapods
,Question 3:
What is the definition (in phylogenetic terms) of a tetrapodomorph?
Answer:
A tetrapodomorph is any fish that is more closely related to tetrapods
than lungfishes
Question 4:
What is the main new piece of information about early tetrapods that
contradicts the old "drying pond" hypothesis of the origins of terrestriality
Answer:
Many early tetrapods are known from marine, or near marine,
environments 1■ã
Question 5:
What are the three groups of Sarcopterygii (lobe-finned fishes)?
Answer:
Actinistia (Coelacanths) - deep-sea, very few extant; paired lobed fins
with internal bones.2■ã Dipnoi (Lungfish) - freshwater; have both lungs
and gills; can aestivate during droughts.3■ã Tetrapodomorphs - the
extinct lobe-finned fish lineage that gave rise to all modern Tetrapods.
Question 6:
What do extant Sarcopterygians (Coelacanths & Lungfish) have in
common?
Answer:
Fleshy paired fins supported by internal bones and muscles (precursors
of limbs). True enamel on teeth. Lungs or lung-like organs that allow gas
exchange. Use lungs for air-breathing and buoyancy control.
, Question 7:
What was the original function of lungs in early fishes?
Answer:
They evolved first for buoyancy regulation and air breathing in
oxygen-poor water environments, not specifically for life on land.
Question 8:
Who were the "fishapods"?
Answer:
Transitional Tetrapodomorphs between fish and land vertebrates, such
as Eusthenopteron, Panderichthys, and Tiktaalik.
Question 9:
When did the first true Tetrapods appear?
Answer:
In the Late Devonian Period (~365 million years ago). 1■ã Lissamphibia -
non-amniotic tetrapods (all modern amphibians).2■ã
Question 10:
Into which two major lineages did early Tetrapods split?
Answer:
Reptilomorphs - amniotes and their extinct ancestors (reptiles, birds,
mammals).
Questions and Answers with Verified
Solutions
Question 1:
Lungfishes are considered to be more closely related to tetrapods than
are coelacanths, but for most of the 20th century, coelacanths were
thought to be the sister group of tetrapods. How have new phylogenetic
tools and changes in our ways of thinking about phylogenetic
relationships reversed the older interpretation? What is it about lungfishes
that makes their phylogenetic placement challenging?
Answer:
Molecular phylogenetics helped to clarify these relationships. The
realization that extant lungfishes are highly specialized relative to
Devonian fossils discovered late in the 20th century such as Diabolepis
also made it easier to understand how lungfishes fit on the tree of the
Devonian vertebrates. Finally, many of the changes that occurred during
the evolution of lungfishes can be attributed to paeodmorphosis, which
helped us understand why they look so different from Devonian
lungfishes
Question 2:
What information about Devonian tetrapods leads to the conclusion that
tetrapods evolved in the water rather than on land?
Answer:
Retention of internal gills and polydactylous feet that look more like
flippers than feet for walking on land are characters that suggest an
aquatic origin for tetrapods
,Question 3:
What is the definition (in phylogenetic terms) of a tetrapodomorph?
Answer:
A tetrapodomorph is any fish that is more closely related to tetrapods
than lungfishes
Question 4:
What is the main new piece of information about early tetrapods that
contradicts the old "drying pond" hypothesis of the origins of terrestriality
Answer:
Many early tetrapods are known from marine, or near marine,
environments 1■ã
Question 5:
What are the three groups of Sarcopterygii (lobe-finned fishes)?
Answer:
Actinistia (Coelacanths) - deep-sea, very few extant; paired lobed fins
with internal bones.2■ã Dipnoi (Lungfish) - freshwater; have both lungs
and gills; can aestivate during droughts.3■ã Tetrapodomorphs - the
extinct lobe-finned fish lineage that gave rise to all modern Tetrapods.
Question 6:
What do extant Sarcopterygians (Coelacanths & Lungfish) have in
common?
Answer:
Fleshy paired fins supported by internal bones and muscles (precursors
of limbs). True enamel on teeth. Lungs or lung-like organs that allow gas
exchange. Use lungs for air-breathing and buoyancy control.
, Question 7:
What was the original function of lungs in early fishes?
Answer:
They evolved first for buoyancy regulation and air breathing in
oxygen-poor water environments, not specifically for life on land.
Question 8:
Who were the "fishapods"?
Answer:
Transitional Tetrapodomorphs between fish and land vertebrates, such
as Eusthenopteron, Panderichthys, and Tiktaalik.
Question 9:
When did the first true Tetrapods appear?
Answer:
In the Late Devonian Period (~365 million years ago). 1■ã Lissamphibia -
non-amniotic tetrapods (all modern amphibians).2■ã
Question 10:
Into which two major lineages did early Tetrapods split?
Answer:
Reptilomorphs - amniotes and their extinct ancestors (reptiles, birds,
mammals).
