Intro to living world

Cells: The basic unit of life. Cells come in all sorts of shapes and sizes and contain different combinations and numbers of organelles. Examples of specialized cells include epithelial cells, muscle cells, and glandular cells.

Tissues: A group of similar cells that work together to carry out a particular function. Examples of tissues include epithelial tissue, muscle tissue, and glandular tissue.

Organs: A group of different tissues that work together to perform a particular function. Examples of organs include the stomach, pancreas, liver, skin, teeth, lungs, spleen, bones, testes.

Organ Systems: A group of organs that work together to perform a particular function. Examples of organ systems include the digestive system, cardiovascular system, and reproductive system.

There are about 12 different organ systems in the human body, including the immune system, nervous system, respiratory system, endocrine system, and urinary system.