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The senior population grows every year. Seniors older than 65 years of age now comprise more than 13% of the total population. However, women outlive men. In the 85-and-over age group, there are only 45 men to every 100 women.
According to research, pregnant women tend to eat more if carrying a baby boy. Male fetuses may secrete a chemical that stimulates their mothers to step up her energy intake.
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Ether was used widely for surgeries but became less popular because of its flammability and its tendency to cause vomiting. In England, it was quickly replaced by chloroform, but this agent caused many deaths and lost popularity.
![The female reproductive system. (a) Sagittal section through the pelvis. (b) Top view of pelvic orga](https://biology-forums.com/gallery/47/medium_14755_16_10_12_12_26_15_9423844.jpeg)
![The cardiovascular system. A schematic view of the closed circulation of blood. The heart is section](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_14_25_100191159.jpeg)