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? 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. Evolution can also result in the loss of a trait. Cite three examples from this chapter.

Verified step by step guidance

1. Identify and understand the concept of co-option in evolution, which refers to the process where existing structures are adapted for new functions.
2. Review the chapter to find three examples where preexisting structures were co-opted for new uses in different organisms, noting how each structure's original function was adapted.
3. Understand the concept of trait loss in evolution, which involves the reduction or elimination of certain traits as species adapt to new environments or lifestyles.
4. Search the chapter for three examples of trait loss, documenting each case and explaining why the loss of the trait might have been advantageous or neutral in the evolutionary context.
5. Summarize the findings to reinforce the understanding of how evolution can lead to both the co-option of structures for new uses and the loss of traits, using the examples cited from the chapter.

Key Concepts

Evolutionary Adaptation

Evolutionary adaptation refers to the process by which species undergo changes over time to better fit their environment. This can involve the development of new structures or the modification of existing ones for different functions, such as the evolution of ear bones in mammals from ancestral structures. Understanding this concept is crucial for analyzing how specific traits arise and are maintained in a population.

Co-option

Co-option, or exaptation, is a phenomenon in evolution where a preexisting structure evolves to serve a new function. For example, the bones in the jaw of early vertebrates were repurposed to become the middle ear bones in mammals. This concept highlights the flexibility of evolutionary processes and how traits can be utilized in various ways across different species.

Trait Loss

Trait loss, or evolutionary regression, occurs when a species loses a previously advantageous trait over time, often due to changes in environmental pressures or lifestyle. An example is the loss of limbs in certain snake species, which adapted to a burrowing lifestyle. Recognizing this concept is essential for understanding how and why certain features may disappear in the course of evolution.