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Questions and Answers
What is a transitional fossil?
What is a transitional fossil?
Transitional fossils have features that are intermediate between ancestors and descendants.
Which of the following is a tetrapod?
Which of the following is a tetrapod?
- An amphibian (correct)
- A mammal (correct)
- A bird (correct)
- A reptile (correct)
Which evidence supports the hypothesis that four-limbed animals came from fish?
Which evidence supports the hypothesis that four-limbed animals came from fish?
DNA analysis shows that fish are tetrapods' closest relatives. The fossil record shows more and more tetrapod-like fish before the appearance of tetrapods about 365 million years ago. Both fish and four-limbed animals are vertebrates. Fish and four-limbed animals have very similar embryos.
Why have we NOT found examples in the fossil record of every animal that ever lived on Earth?
Why have we NOT found examples in the fossil record of every animal that ever lived on Earth?
Why did Shubin and Daeschler search in the Canadian Arctic for fossil evidence of the transition from fish to tetrapods?
Why did Shubin and Daeschler search in the Canadian Arctic for fossil evidence of the transition from fish to tetrapods?
What kind of habitat did Tiktaalik live in?
What kind of habitat did Tiktaalik live in?
Which were the tetrapod-like characteristics of Tiktaalik?
Which were the tetrapod-like characteristics of Tiktaalik?
How did the great transition from fish to tetrapod occur?
How did the great transition from fish to tetrapod occur?
Which of the following are considered reptilian characteristics of Archaeopteryx?
Which of the following are considered reptilian characteristics of Archaeopteryx?
Which discovery ultimately overturned the prevailing perception that all dinosaurs were large, slow, and lumbering?
Which discovery ultimately overturned the prevailing perception that all dinosaurs were large, slow, and lumbering?
Which of the following shared characteristics of living birds and theropod dinosaurs provided support to the hypothesis that birds evolved from dinosaurs?
Which of the following shared characteristics of living birds and theropod dinosaurs provided support to the hypothesis that birds evolved from dinosaurs?
How did Dr. Jack Horner's discovery of dinosaur nesting grounds support the hypothesis that birds evolved from a group of dinosaurs?
How did Dr. Jack Horner's discovery of dinosaur nesting grounds support the hypothesis that birds evolved from a group of dinosaurs?
Which pieces of evidence support the hypothesis that the first feathers served a purpose other than flight?
Which pieces of evidence support the hypothesis that the first feathers served a purpose other than flight?
Which of the following statements about bird evolution are accurate based on the evidence presented?
Which of the following statements about bird evolution are accurate based on the evidence presented?
Why was the discovery of organisms, such as Archaeopteryx, that have a mix of traits usually associated with two different groups considered validation of Darwin's theory of evolution?
Why was the discovery of organisms, such as Archaeopteryx, that have a mix of traits usually associated with two different groups considered validation of Darwin's theory of evolution?
Without the taxonomic change of birds being considered as part of the reptile clade, what would be the consequence?
Without the taxonomic change of birds being considered as part of the reptile clade, what would be the consequence?
What is the basis for categorizing the three major groups of mammals?
What is the basis for categorizing the three major groups of mammals?
Vertebrates and tunicates share what structures?
Vertebrates and tunicates share what structures?
Most members of which of the following groups are most closely associated with a wet or moist environment?
Most members of which of the following groups are most closely associated with a wet or moist environment?
What does the presence of a swim bladder allow typical ray-finned fish to do?
What does the presence of a swim bladder allow typical ray-finned fish to do?
Jaws first occurred in which extant group of fishes?
Jaws first occurred in which extant group of fishes?
Which of the following characteristics is shared by a hagfish and a lamprey?
Which of the following characteristics is shared by a hagfish and a lamprey?
How did the evolution of the jaw contribute to the diversification of early vertebrate lineages?
How did the evolution of the jaw contribute to the diversification of early vertebrate lineages?
What is the major feature in coelacanths and lungfish that supports the hypothesis that they are a crucial link between other fishes and tetrapods?
What is the major feature in coelacanths and lungfish that supports the hypothesis that they are a crucial link between other fishes and tetrapods?
Which of the following chordates is most likely to look the LEAST like other chordates?
Which of the following chordates is most likely to look the LEAST like other chordates?
Which of the following represents the strongest evidence that two of the three middle ear bones of mammals are homologous to certain reptilian jawbones?
Which of the following represents the strongest evidence that two of the three middle ear bones of mammals are homologous to certain reptilian jawbones?
With which of the following statements would a biologist be most inclined to agree?
With which of the following statements would a biologist be most inclined to agree?
Which of the following is NOT a diagnostic feature of the Chordata?
Which of the following is NOT a diagnostic feature of the Chordata?
What did chordate pharyngeal slits first function as?
What did chordate pharyngeal slits first function as?
Which of the following are the only extant animals that descended directly from dinosaurs?
Which of the following are the only extant animals that descended directly from dinosaurs?
Which of the following characteristics evolved independently in mammals and birds?
Which of the following characteristics evolved independently in mammals and birds?
In what respect do hominins differ from all other anthropoids?
In what respect do hominins differ from all other anthropoids?
Which of these are amniotes?
Which of these are amniotes?
What group of mammals have embryos that spend more time feeding through the placenta than the mother's nipples, young that feed on milk, and a prolonged period of maternal care after leaving the placenta?
What group of mammals have embryos that spend more time feeding through the placenta than the mother's nipples, young that feed on milk, and a prolonged period of maternal care after leaving the placenta?
What is believed to be the most significant result of the evolution of the amniotic egg?
What is believed to be the most significant result of the evolution of the amniotic egg?
What anatomical change made depth perception possible?
What anatomical change made depth perception possible?
What does the conclusion about Chondrichthyes demonstrate as new evidence emerges?
What does the conclusion about Chondrichthyes demonstrate as new evidence emerges?
Which extant chordates are postulated to be most like the earliest chordates in appearance?
Which extant chordates are postulated to be most like the earliest chordates in appearance?
What does the conclusion about Chondrichthyes demonstrate regarding characteristics in evolution?
What does the conclusion about Chondrichthyes demonstrate regarding characteristics in evolution?
Mammals and birds eat more often than reptiles. Which of the following traits shared by mammals and birds best explains this habit?
Mammals and birds eat more often than reptiles. Which of the following traits shared by mammals and birds best explains this habit?
What is the diagnostic feature of Chondrichthyes?
What is the diagnostic feature of Chondrichthyes?
The Neanderthal DNA discovered in Homo sapiens is best explained by?
The Neanderthal DNA discovered in Homo sapiens is best explained by?
Which of these primate groups is most closely related to humans?
Which of these primate groups is most closely related to humans?
_____ are the oldest known primate group.
_____ are the oldest known primate group.
What primates spend the most time walking upright?
What primates spend the most time walking upright?
Which of these anthropoid groups consists of primates who are mostly tree dwellers and whose forelimbs and hind limbs are about equal in length?
Which of these anthropoid groups consists of primates who are mostly tree dwellers and whose forelimbs and hind limbs are about equal in length?
Which anatomical features of the 3.2-million-year-old Australopithecus fossil known as 'Lucy' suggest she was a bipedal hominid?
Which anatomical features of the 3.2-million-year-old Australopithecus fossil known as 'Lucy' suggest she was a bipedal hominid?
Vertebrates and tunicates have what structures?
Vertebrates and tunicates have what structures?
Living vertebrates can be divided into two major clades. Select the appropriate pair.
Living vertebrates can be divided into two major clades. Select the appropriate pair.
Unlike eutherians, both monotremes and marsupials?
Unlike eutherians, both monotremes and marsupials?
Which clade does not include humans?
Which clade does not include humans?
As hominins diverged from other primates, which of the following appeared first?
As hominins diverged from other primates, which of the following appeared first?
Which of the following could be considered the most recent common ancestor of living tetrapods?
Which of the following could be considered the most recent common ancestor of living tetrapods?
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Study Notes
Transitional Fossils and Evolutionary Evidence
- Transitional fossils display features that bridge gaps between ancestors and descendants, providing insights into evolutionary processes.
- Evidence from DNA analysis indicates that fish are the closest relatives of tetrapods, supporting the evolution of four-limbed animals from fish.
- The fossil record reveals increasing similarities between fish and tetrapod-like creatures prior to the emergence of true tetrapods around 365 million years ago.
- Both fish and four-limbed animals share vertebrate traits and exhibit similar embryonic development patterns.
Fossilization and Discovery
- To fossilize, an organism must be quickly buried in sediment or ash to prevent decomposition, which makes finding fossils rare.
- Many fossils remain buried and can only be uncovered through erosion or excavation processes.
- Shubin and Daeschler targeted Canadian arctic strata older than 365 million years for fossil evidence of the transition from fish to tetrapods.
Tiktaalik: A Key Transitional Species
- Tiktaalik inhabited warm, freshwater swamps and displayed both fishlike and tetrapod-like traits, such as interlocking ribs and a neck.
- The gradual transition from fish to tetrapod was marked by a series of intermediate forms.
Archaeopteryx and the Evolution of Birds
- The Archaeopteryx fossil, dating back 150 million years, combines birdlike features (feathered wings) with reptilian characteristics (teeth, claws, long tails).
- Deinonychus, a small theropod dinosaur, challenged the notion of dinosaurs as large and slow by showcasing agile features.
- Shared traits between birds and theropods, such as hollow bones, feathers, S-shaped necks, and the wishbone, support the hypothesis that birds evolved from dinosaurs.
Nesting and Feather Evolution
- Dinosaur nesting grounds discovered by Dr. Jack Horner suggest that dinosaurs cared for their young similarly to modern birds.
- Some early feathered theropods were not capable of flight, indicating that feathers may have initially evolved for purposes other than flight, such as communication or insulation.
Taxonomy and Classification
- Birds are considered part of the reptile clade; this classification change prevents Reptilia from being paraphyletic.
- Mammals are classified into three major groups based on their reproductive methods, including monotremes, marsupials, and eutherians.
Characteristics and Features of Chordates
- Vertebrates and tunicates share key traits like a notochord and a dorsal, hollow nerve cord.
- Most amphibians are closely associated with moist environments, while a swim bladder in ray-finned fish allows buoyancy without constant swimming.
Evolutionary Milestones
- Jaws first appeared in chondrichthyans, while the evolution of the jaw facilitated access to new food sources.
- Coelacanths and lungfish exhibit limb-like skeletal structures, acting as a critical link between fishes and tetrapods.
- Adult tunicates resemble primitive chordates less than other groups, while early chordates are postulated to be similar to lancelets.
Anecdotes from Evolutionary History
- The movement of ear bones from jaw development in mammals serves as strong evidence for the evolutionary link between reptiles and mammals.
- Hominins distinguish themselves from other anthropoids through bipedalism, with humans most closely related to apes.
Extant Groups and Evolutionary Changes
- The oldest acknowledged primate group is the prosimians, while hominids are recognized for their upright walking.
- Australopithecus fossils, like "Lucy," exhibit anatomical features indicating bipedal locomotion, critical to hominin evolution.
Final Insights into Evolutionary Relationships
- The majority of extant chordates, including humans, fit within established phylogenetic clades, with species descended from common ancestors exhibiting varying adaptations.
- Significant traits like endothermy evolved independently in birds and mammals, enhancing their survival and activity levels compared to reptiles.
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