Final Answer:
a. a fixed inborn pattern of responding that is species-specific
Step-by-step explanation:
An instinct is a fixed inborn pattern of responding that is species-specific, indicating behaviors that are genetically programmed and emerge without the need for prior learning. These innate behaviors are crucial for the survival and adaptation of a species in its environment.
Instincts are deeply rooted in an organism's biology, serving as automatic and often complex responses to specific stimuli. Unlike learned behaviors, instincts are not acquired through experience; instead, they are hardwired in the genetic makeup of the species. For example, the migratory patterns of birds, the web-spinning of spiders, and the nesting behaviors of various animals are all manifestations of instincts.
These innate patterns of behavior are essential for the survival and reproductive success of a species. They have evolved over time through natural selection, ensuring that organisms exhibit behaviors that increase their chances of thriving in their specific ecological niches. While instincts provide a foundational framework for behavior, it's important to note that they can also interact with learned behaviors, environmental factors, and individual variations, contributing to the complexity of an organism's overall behavioral repertoire.