Iron is the metal found in blood. It is an essential mineral that plays a key role in transporting oxygen from the lungs to the rest of the body and carrying carbon dioxide back to the lungs to be exhaled. Iron is a crucial component of hemoglobin, a protein in red blood cells that binds to oxygen and gives blood its red color. Without sufficient iron, the body cannot produce enough healthy red blood cells, leading to iron-deficiency anemia, a common nutritional disorder.

A pacemaker is a medical device used to regulate the heartbeat in individuals with abnormal heart rhythms (arrhythmias). It is often implanted in the chest to help control the heart's rhythm and treat conditions like bradycardia (slow heart rate) or other rhythm disorders. Pacemakers are typically prescribed by cardiologists, specialized doctors who diagnose and treat heart-related conditions. The decision to implant a pacemaker is made by a healthcare provider based on the patient's specific medical condition and needs.

The longest bone in the human body is the femur, which is located in the thigh. The femur, or thigh bone, extends from the hip to the knee and is the largest and strongest bone in the human skeleton.

In humans, the tailbone, also known as the coccyx, is a small triangular bone located at the base of the spine. It is made up of three to five fused (joined together) vertebrae and is the remnant of a tail that our evolutionary ancestors used for balance and communication. The coccyx is not attached to the colon; rather, it is a part of the vertebral column and provides support for the pelvic organs.

Whereas oxygen, nitrogen, and argon are not examples of greenhouse gases.

Cholera, caused by the bacterium Vibrio cholerae, can be both epidemic and endemic. Epidemic cholera refers to sudden outbreaks affecting large populations, often due to contaminated water. Endemic cholera signifies the continuous, stable presence of the disease in specific regions, indicating a persistent, albeit lower, level of infection over time.

Certain plants, like gymnosperms, produce seeds but lack fruits. Gymnosperms, including pine trees and cycads, have exposed seeds on cone scales, distinguishing them from angiosperms, which produce seeds enclosed within fruits. The absence of a fruit covering the seed is a characteristic feature of gymnosperms, a group of seed-producing plants.

The plants that never produce flowers are called "cryptogams." Cryptogams include plants such as ferns, mosses, liverworts, and algae. Unlike flowering plants (angiosperms), which reproduce through seeds enclosed within flowers, cryptogams reproduce through spores and do not produce true flowers. Cryptogams are considered more primitive in evolutionary terms compared to angiosperms, which are the most dominant group of plants on Earth today.