The size and shape of the vertebrate skull can reveal a great deal about an animal's lifestyle and evolutionary relationships. Consider your own skull. If you put your finger in your ear and move your jaw up and down, you can feel the space near the hinge of your jaw. Nestled in this space are the tiny bones that make your hearing possible: the malleus, incus, and stapes. All mammals have these three ear bones, but reptiles such as this T. rex don't. Where did ear bones come from? How is the opossum related to you? Select True or False for each statement. T/F An opossum is an animal, but I am a human. T/F An opossum is a mammal, but I am a human. T/F An opossum is a marsupial, but I am a placental mammal. T/F The opossum and I are both tetrapods.

Verified step by step guidance

1. Step 1: Understand the question. The question is asking you to determine the relationship between you (a human) and an opossum based on certain biological classifications.
2. Step 2: Analyze each statement. The first statement says 'An opossum is an animal, but I am a human.' This is true because both humans and opossums are animals, but humans are a specific type of animal.
3. Step 3: Evaluate the second statement. 'An opossum is a mammal, but I am a human.' This is also true because both humans and opossums are mammals, but humans are a specific type of mammal.
4. Step 4: Consider the third statement. 'An opossum is a marsupial, but I am a placental mammal.' This is true because opossums are marsupials (they carry their young in a pouch) and humans are placental mammals (they carry their young in a womb that is connected to the mother by a placenta).
5. Step 5: Assess the final statement. 'The opossum and I are both tetrapods.' This is true because both humans and opossums are tetrapods, meaning they are animals with four limbs.

Key Concepts

Evolutionary Relationships

Evolutionary relationships refer to the connections between different species based on their common ancestry and evolutionary history. By studying anatomical features, such as the structure of the skull and ear bones, scientists can infer how closely related different organisms are. For instance, mammals share certain traits, like the three middle ear bones, which indicate a shared lineage distinct from reptiles.

Mammalian Characteristics

Mammals are characterized by specific traits, including the presence of mammary glands, hair or fur, and three middle ear bones (malleus, incus, stapes). These features are crucial for their survival and reproduction. Understanding these characteristics helps differentiate mammals from other vertebrates, such as reptiles, and highlights the evolutionary adaptations that have occurred over time.

Tetrapod Classification

Tetrapods are a superclass of vertebrates that include amphibians, reptiles, birds, and mammals, characterized by having four limbs. This classification reflects a significant evolutionary transition from aquatic to terrestrial life. Both humans and opossums are tetrapods, which underscores their shared ancestry and the evolutionary adaptations that have allowed them to thrive in different environments.