Why was it important that the phylogeny in Figure 32.9 was estimated using traits other than the morphology of the limb?
answer
When determining the evolution of a particular trait you need to have independent evidence of the relationship of the species involved.
question
What was the adaptive significance of the amniote egg?
answer
It allows reproduction on land.
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There are four recognized phyla of deuterostomes: Echinodermata, Hemichordata, Xenoturbellida, and...
answer
chordata
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What was the adaptive significance of jaws?
answer
They allowed the fish to be herbivores or predators
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What trait(s) define(s) the vertebrates?
answer
vertebrae and a cranium
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Analyze the morphological data shown below and write a hypothesis to explain the origin of mammalian ear bones
answer
the bones evolved from the jaw bones of an early amniote
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Evolution often results in the co-option of a preexisting structure for a new use. Cite three examples from this chapter to support this statement.
answer
-gill arches were co-opted for use as a jaw
- arms were co-opted for use as wings
- lungs were co-opted for use as swim bladders
question
Evolution can also result in the loss of a trait. Cite three examples from this chapter.
answer
-tails were lost in adult frogs
-limbs were lost in caecilians and snakes
-vertebrae were lost in hagfishes
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Which of the following classes is comprised of carnivorous predators that are able to extend their stomachs through their mouths to feed?
answer
Asteroidea
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If a kelp farmer wanted to maximize her harvest, which type of echinoderm would she be most concerned about in the habitat?
answer
sea urchins
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Vertebrates and tunicates share...
answer
a notochord and a dorsal, hollow nerve cord
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Which vertebrates lay amniotic eggs?
answer
reptiles and some mammals
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Where would the origin of endothermy map on the phylogeny?
answer
Within Mammalia and within Aves.
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What is believed to be the most significant result of the evolution of the amniotic egg?
answer
Tetrapods were no longer tied to the water for reproduction.
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In what way are monotremes similar to more ancestral chordate lineages, as opposed to other mammals?
answer
Monotremes lay eggs; other mammals bear live young.
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Which of these are amniotes?
answer
turtles
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It is believed that the coelacanths and lungfish represent a crucial link between other fishes and tetrapods. What is the major feature in these fish in support of this hypothesis?
answer
Their fins have skeletal and muscular structures similar to amphibian limbs.
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Shared Character of Chordates: notochord
answer
a flexible rod that runs along the anterior-posterior axis; may be associated with a joined skeleton
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Shared Character of Chordates: pharyngeal clefts
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grooves that separate pouches along the side of the pharynx; may develop into parts of the ear
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Shared Character of Chordates: pharyngeal slits
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openings to the outside of the body along the side of the pharynx; may develop into gill slits
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Shared Character of Chordates: dorsal, hallow nerve cord
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a bundle of nervous tissue running the length of the body; may develop into the brain & spinal cord
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Shared Character of Chordates: muscular, post-anal tail
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a structure that contains muscles & extends past the anus; may be used to propel some species in water
question
Lancelets
answer
-all chordate characters present in adults
-adults bury themselves into the sediment of the seafloor
-adults swim by the contraction of a series of muscles along the notochord
-adults feed with the aid of the pharyngeal slit
-adults do not swim using the vertebral column
question
Tunicates
answer
-most chordate characters not present in adults
-larvae swim using the notochord, but adults may be sessile
-in adults, water enters through one siphon & leaves through another
-adults feed with the aid of pharyngeal slits
-adults do not swim using the vertebral column
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What is a transitional fossil?
answer
Transitional fossils have features that are intermediate between ancestors and descendants.
question
Which of the following is a tetrapod?
answer
amphibian, mammal, bird, reptile
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Which evidence supports the hypothesis that four-limbed animals came from fish?
answer
-Fish and four-limbed animals have very similar embryos.
-DNA analysis shows that fish are tetrapods' closest relatives.
-Both fish and four-limbed animals are vertebrates.
-The fossil record shows more and more tetrapod-like fish before the appearance of tetrapods about 365 million years ago.
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Why have we NOT found examples in the fossil record of every animal that ever lived on Earth?
answer
-To become a fossil, an animal must remain buried for thousands or millions of years until it (and the layer around it) turns to rock.
-Many fossils remain buried. We can only find them when they are exposed by erosion or excavation.
-To become a fossil, an animal must be quickly and completely buried in ash or sediment before it has a chance to decompose.
question
Why did Shubin and Daeschler search in the Canadian arctic for fossil evidence of the transition from fish to tetrapods?
answer
Why did Shubin and Daeschler search in the Canadian arctic for fossil evidence of the transition from fish to tetrapods?
They hypothesized that the transitional fossils were in sedimentary rocks older than 365 million years ago, when the first tetrapods appear in the fossil record.
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What kind of habitat did tiktaalik live in?
answer
Tiktaalik lived in a warm, freshwater swamp.
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Tiktaalik had a combination of fishlike and tetrapod-like characteristics. Which were the tetrapod-like characteristics?
answer
- flat head with eyes on top
-a neck
-interlocking ribs
question
How did the great transition from fish to tetrapod occur?
answer
The transition occurred gradually over time, so there are many intermediate forms.
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