Cell biology is the study of cells and cell organelles. Cell and organismal biology primarily concerns itself with understanding the interactions between the various systems of a cell, including the interrelationship of cell to cell interactions, the anatomy and physiology of cell organelles, the reproductive functions of cells, tissues, organs, organ systems, and individual organisms.

In cell biology, organelles are small discrete structures inside of a cell having specialized functions. As the name implies, organelles function as 'small organs.' All living cells are divided into one of two groups depending on their cellular structure. Prokaryotes have no membrane bound organelles while eukaryotes have a complex internal structure that allows thousands of chemical reactions to proceed simultaneously in various organelles.

Animals and plants differ in various ways. Most animals can move and are mobile, while plants tend to stay in one location. Animals obtain nutrients by eating other organisms, while plants synthesize their food from elements (i.e. photosynthesis). Differences in the organelles (which include vacuoles and chloroplasts) reflect these different modes of functionality.

Cellular respiration is the process in which the chemical bonds of energy-rich molecules such as glucose are converted into energy usable for life processes. All living organisms on Earth undergo cell respiration. There are two general types of cellular respiration processes: anaerobic and aerobic respiration. Anaerobic respiration refers to the breakdown of molecules in the absence of oxygen to produce energy. Anaerobic respiration is often used interchangeably with fermentation.

Mitosis is the process by which the nucleus of a cell divides to create two new nuclei, each containing an identical copy of DNA. Almost all of the DNA duplication in humans are through mitosis. Meiosis is the process by which certain sex cells are created. In males meiosis creates sperm cells; in females meiosis is used to create egg cells. All other cells in the human body contain 46 chromosomes, but egg (or sperm) cells contain only half that number -- a total of 23 chromosomes. When an egg and sperm unite to make a fertilized egg, the chromosomes then add up to 46.

Single celled organisms are also known as unicellular organisms and cannot be seen with the 'naked' eye. Multicellular organisms are living things composed of more than one cell, and having specialized or differentiated cells that perform specialized physiological functions. Most life that can be seen with the unaided eye is multicellular, as are all animals (i.e. members of the kingdom Animalia) and plants (i.e. members of the kingdom Plantae). Cellular differentiation is a concept from developmental biology which refers to the process by which cells acquire a specific 'cell type'.

A group of organs which perform a specific task(s) for a specific physiological function within the human body are known as an organ system. Organs within a system may be related in a variety of ways, however relationships of function are most commonly used in determining the organ system. For example the urinary system comprises organs that work together to produce, store, and carry urine.

Plants primarily contain three organ systems, compared to eleven in vertebrate animals. Plants have three tissue types which include ground, dermal, and vascular tissue. Animals have four tissue types which include epithelial, connective, muscle, and bone tissue.

Biological reproduction refers to the biological processes by which new individual organisms are produced and in which the genetic code of one generation is passed on to the next. Reproduction is a fundamental feature of all known life on Earth. Each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main categories which include sexual and asexual reproduction.

A flower, also known as a bloom or blossom, is the reproductive structure found in flowering plants. Flowering plants are also called angiosperms. The flower structure contains the plant's reproductive organs, and its function is to produce seeds through reproduction.