The primary function of the respiratory system is to exchange gases, specifically oxygen and carbon dioxide, between the body and the environment.

The primary function of the respiratory system in mammals is the exchange of gases, specifically oxygen and carbon dioxide.

The primary function of the respiratory system is to exchange gases, specifically oxygen and carbon dioxide, between the body and the environment.

The small intestine is primarily responsible for the absorption of nutrients from digested food.

The primary function of the small intestine is the absorption of nutrients from digested food.

The stomach's primary function is to perform mechanical and chemical digestion of food, aided by gastric juices.

The stomach's primary function is the chemical digestion of proteins through gastric juices.

The swim bladder allows fish to maintain buoyancy and control their depth in the water.

Hemoglobin primarily transports oxygen from the lungs to the tissues of the body.

Progesterone is the primary hormone responsible for maintaining pregnancy.

Estrogen is the primary hormone that regulates the menstrual cycle, influencing the growth and maintenance of the endometrium.

Most mammals reproduce viviparously, meaning they give birth to live young rather than laying eggs.

Most reptiles primarily reproduce through egg-laying, which is a characteristic of their reproductive strategy.

The diaphragm is the primary muscle involved in inhalation, contracting to increase the volume of the thoracic cavity and draw air into the lungs.

The diaphragm contracts and moves downward, increasing the thoracic cavity volume and allowing air to flow into the lungs.

The sinoatrial (SA) node is the primary pacemaker of the heart, initiating the heartbeat.

The primary purpose of prenatal care is to monitor the health and development of the fetus throughout pregnancy.

Amniotic fluid cushions the fetus, providing protection and allowing for movement.

The nasal cavity filters, warms, and humidifies the air we breathe before it enters the lungs.

The umbilical cord connects the fetus to the placenta, allowing for nutrient and waste exchange.

Capillaries are the sites of exchange where nutrients and waste products are exchanged between blood and tissues.

The primary role of the circulatory system is to transport nutrients, gases, hormones, and waste products throughout the body.

The primary role of the nervous system is to coordinate and respond to stimuli from the environment.

The primary role of the nervous system is to coordinate body activities by transmitting signals between different parts of the body.

The placenta facilitates nutrient absorption, gas exchange, and waste elimination between the mother and developing fetus.

The stomach plays a key role in both mechanical and chemical digestion of food.

Villi are small, finger-like projections in the small intestine that increase the surface area for the absorption of nutrients.

The primary site of gas exchange in the respiratory system is the alveoli.

The stomach is the primary site for protein digestion, where pepsin breaks down proteins into peptides.

Natural selection is the process by which organisms change over time through adaptations that enhance survival and reproduction.