Understanding Natural Selection and Brain Functions

Natural Selection: Principles of Adaptation

Natural selection is the principle that variations in the biology or behavior of a species result in some individuals possessing traits that confer an advantage in survival. This process is highly dependent on the environment.

Individuals with these advantageous traits are more likely to survive, prosper, and reproduce. Over time, the population becomes dominated by individuals exhibiting these beneficial biological or behavioral characteristics. Offspring of the same species can be born with mutations, introducing new variations. Natural selection drives populations to become adapted, or increasingly well-suited, to their environments over time. This process relies on the environment and requires existing heritable variation within a group. The study of how natural selection influences human behavior is called evolutionary psychology. An evolutionary psychologist might argue that domestication, for instance, began with wild animals that displayed an inherent ability to tolerate human contact.

1. Variation in Traits

   For example, some beetles are green and some are brown.

2. Differential Reproduction

   Since the environment cannot support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do.

3. Heredity

   The surviving brown beetles have brown baby beetles because this trait has a genetic basis.

4. End Result: Population Adaptation

   The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown.

The Human Brain and Nervous System

Neurons and Brain Functions

The cells in the brain and nervous system responsible for sensing, perception, thinking, and memory are called neurons. A neuron sends its own electrical signal through its axon. The axon is connected to the dendrites of other neurons via the axon terminal. Our body has both involuntary and voluntary functions. Involuntary functions occur automatically, without conscious thought (e.g., breathing, heartbeat). Voluntary functions require conscious attention and control.

Key Brain Structures

Brainstem

The brainstem attaches to the brain and controls vital involuntary functions such as breathing and heartbeat.

Thalamus

The thalamus is responsible for receiving and relaying all sensory information (except smell) from our senses to the appropriate cortical areas.

Cerebellum

The cerebellum is responsible for coordinating voluntary movements, balance, posture, and motor learning.

Visual Cortex

The visual cortex receives and processes visual information from the eyes.

Frontal Lobe

The frontal lobe is involved in conscious processing of ideas, information, planning, decision-making, and personality.

Cerebral Hemispheres: Lateralization

The brain is divided into left and right hemispheres. For sensory processing, the right hemisphere processes data from the left side of the body (and visual field from the left eye), and vice versa for the left hemisphere.

Motor Control and Hemispheres

For motor control, the opposite hemisphere of the brain sends signals to coordinate movements of our arms and legs. For example, the left hemisphere controls the right side of the body, and the right hemisphere controls the left side.