The statement that the “Cambrian explosion actually consists of three explosions, not one.” Concept introduction : Cambrian explosion refers to the rapid diversification of animals that occurred 535-525 million years ago, during the Paleozoic era. Simple, soft bodied animals also called Ediacaran fauna inhabited the earth before the Cambrian explosion. There are various hypotheses that explain the Cambrian explosion. According to one hypothesis, the appearance of a prey-predator relationship led to the Cambrian explosion. The predators in the Cambrian period acquired novel adaptations for predation. This led to natural selection of prey with hard bodies. The hard bodies helped them in defense from predators. Another hypothesis emphasizes on the increase in atmospheric oxygen. The increase in atmospheric oxygen led to the evolution of animals with high metabolic rate and larger body size. According to another hypothesis, the evolution of Hox genes (developmental genes) and microRNAs led to the evolution of animals with complex bodies. The evidences of first arthropods and chordates come from the rock strata of the Cambrian period.

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Definition Definition Organ system that helps in the digestion of food by mechanical and biochemical processes. The digestive system breaks down food into simpler components that enable the body to then absorb or transport nutrients. The human digestive system includes the gastrointestinal tract or alimentary canal and the associate glands. The organs of the gastrointestinal tract include the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The associated glands include salivary glands, liver, gallbladder, and pancreas.

Chapter 32.4, Problem 3CC

Summary Introduction

To evaluate: The statement that the “Cambrian explosion actually consists of three explosions, not one.”

Concept introduction:

Cambrian explosion refers to the rapid diversification of animals that occurred 535-525 million years ago, during the Paleozoic era. Simple, soft bodied animals also called Ediacaran fauna inhabited the earth before the Cambrian explosion. There are various hypotheses that explain the Cambrian explosion.

According to one hypothesis, the appearance of a prey-predator relationship led to the Cambrian explosion. The predators in the Cambrian period acquired novel adaptations for predation. This led to natural selection of prey with hard bodies. The hard bodies helped them in defense from predators.

Another hypothesis emphasizes on the increase in atmospheric oxygen. The increase in atmospheric oxygen led to the evolution of animals with high metabolic rate and larger body size.

According to another hypothesis, the **evolution of Hox genes (developmental genes) and microRNAs** led to the evolution of animals with complex bodies. The evidences of first arthropods and chordates come from the rock strata of the Cambrian period.

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Answer 2

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Definition Definition Organ system that helps in the digestion of food by mechanical and biochemical processes. The digestive system breaks down food into simpler components that enable the body to then absorb or transport nutrients. The human digestive system includes the gastrointestinal tract or alimentary canal and the associate glands. The organs of the gastrointestinal tract include the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The associated glands include salivary glands, liver, gallbladder, and pancreas.

Chapter 32.4, Problem 3CC

Summary Introduction

To evaluate: The statement that the “Cambrian explosion actually consists of three explosions, not one.”

Concept introduction:

Cambrian explosion refers to the rapid diversification of animals that occurred 535-525 million years ago, during the Paleozoic era. Simple, soft bodied animals also called Ediacaran fauna inhabited the earth before the Cambrian explosion. There are various hypotheses that explain the Cambrian explosion.

According to one hypothesis, the appearance of a prey-predator relationship led to the Cambrian explosion. The predators in the Cambrian period acquired novel adaptations for predation. This led to natural selection of prey with hard bodies. The hard bodies helped them in defense from predators.

Another hypothesis emphasizes on the increase in atmospheric oxygen. The increase in atmospheric oxygen led to the evolution of animals with high metabolic rate and larger body size.

According to another hypothesis, the **evolution of Hox genes (developmental genes) and microRNAs** led to the evolution of animals with complex bodies. The evidences of first arthropods and chordates come from the rock strata of the Cambrian period.

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Answer 3

Question

Definition Definition Organ system that helps in the digestion of food by mechanical and biochemical processes. The digestive system breaks down food into simpler components that enable the body to then absorb or transport nutrients. The human digestive system includes the gastrointestinal tract or alimentary canal and the associate glands. The organs of the gastrointestinal tract include the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The associated glands include salivary glands, liver, gallbladder, and pancreas.

Chapter 32.4, Problem 3CC

Summary Introduction

To evaluate: The statement that the “Cambrian explosion actually consists of three explosions, not one.”

Concept introduction:

Cambrian explosion refers to the rapid diversification of animals that occurred 535-525 million years ago, during the Paleozoic era. Simple, soft bodied animals also called Ediacaran fauna inhabited the earth before the Cambrian explosion. There are various hypotheses that explain the Cambrian explosion.

According to one hypothesis, the appearance of a prey-predator relationship led to the Cambrian explosion. The predators in the Cambrian period acquired novel adaptations for predation. This led to natural selection of prey with hard bodies. The hard bodies helped them in defense from predators.

Another hypothesis emphasizes on the increase in atmospheric oxygen. The increase in atmospheric oxygen led to the evolution of animals with high metabolic rate and larger body size.

According to another hypothesis, the **evolution of Hox genes (developmental genes) and microRNAs** led to the evolution of animals with complex bodies. The evidences of first arthropods and chordates come from the rock strata of the Cambrian period.

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Answer 4

Question

Definition Definition Organ system that helps in the digestion of food by mechanical and biochemical processes. The digestive system breaks down food into simpler components that enable the body to then absorb or transport nutrients. The human digestive system includes the gastrointestinal tract or alimentary canal and the associate glands. The organs of the gastrointestinal tract include the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. The associated glands include salivary glands, liver, gallbladder, and pancreas.

Chapter 32.4, Problem 3CC

Summary Introduction