Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

40. Circulatory System

Circulatory and Respiratory Anatomy

General Biology

40. Circulatory System

Circulatory and Respiratory Anatomy

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2:22 minutes

Problem 17

Textbook Question

Physiologists speculate about cardiovascular adaptations in dinosaurs—some of which had necks almost 10 m (33 feet) long. Such animals would have required a systolic pressure of nearly 760 mm Hg to pump blood to the brain when the head was fully raised. Some analyses suggest that dinosaurs' hearts were not powerful enough to generate such pressures, leading to the speculation that long-necked dinosaurs fed close to the ground rather than raising their heads to feed on high foliage. Scientists also debate whether dinosaurs had a 'reptile-like' or 'bird-like' heart. Most modern reptiles have a three-chambered heart with just one ventricle. Birds, which evolved from a lineage of dinosaurs, have a four-chambered heart. Some scientists believe that the circulatory needs of these long-necked dinosaurs provide evidence that dinosaurs must have had a four-chambered heart. Why might they conclude this?

Verified step by step guidance

Understand the cardiovascular requirements: Recognize that the long necks of certain dinosaurs would necessitate a high systolic blood pressure to pump blood from the heart to the brain when their heads were raised. This is due to the gravitational pull on the blood moving upwards against gravity over a long distance.

Compare heart structures: Know that most modern reptiles have a three-chambered heart with a single ventricle, which might not efficiently separate oxygenated and deoxygenated blood, potentially leading to less effective blood oxygenation and lower pressure outputs.

Consider the bird-like heart structure: Birds have a four-chambered heart, which allows for complete separation of oxygenated and deoxygenated blood, leading to more efficient pumping and higher pressure capabilities, which could be necessary to meet the physiological demands of long-necked dinosaurs.

Relate to evolutionary lineage: Since birds evolved from dinosaurs, the presence of a four-chambered heart in birds might suggest that their dinosaur ancestors, especially those with extreme physiological demands like long-necked species, could have developed a similar heart structure.

Evaluate physiological evidence: Conclude that the necessity for high blood pressure to reach elevated heads and the evolutionary relationship to birds provide strong evidence supporting the hypothesis that long-necked dinosaurs might have had a four-chambered heart to meet their circulatory needs.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cardiovascular Adaptations

Cardiovascular adaptations refer to the physiological changes in the heart and blood vessels that enable an organism to meet its metabolic demands. In the context of dinosaurs, particularly long-necked species, these adaptations would be crucial for efficiently pumping blood over long distances, such as from the heart to the brain. Understanding these adaptations helps explain how dinosaurs could sustain their large body sizes and maintain proper blood flow.

Heart Structure in Reptiles vs. Birds

The heart structure varies significantly between reptiles and birds, which is essential for understanding dinosaur physiology. Reptiles typically possess a three-chambered heart, which limits the separation of oxygenated and deoxygenated blood, while birds have a four-chambered heart that allows for complete separation and more efficient oxygenation. This difference is critical when considering the metabolic needs of large dinosaurs, suggesting that a more efficient heart structure may have been necessary for their survival.

Systolic Blood Pressure

Systolic blood pressure is the pressure in the arteries during the contraction of the heart muscles, which is vital for understanding how blood is pumped throughout the body. For long-necked dinosaurs, a systolic pressure of nearly 760 mm Hg would be required to ensure adequate blood flow to the brain when the head is elevated. This high pressure raises questions about the capabilities of dinosaur hearts and supports the hypothesis that they may have needed a more advanced circulatory system, similar to that of modern birds.

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