Biology

Microorganism Definition A microorganism is a living thing that is too small to be seen with the naked eye. Examples of microorganisms include bacteria, archaea, algae, protozoa, and microscopic animals such as the dust mite. These microorganisms have been often under-appreciated and under-studied. Indeed, until Anton von Leeuwenhoek invented the microscope, we did not know … Read more

Gap Junction Definition An adjacent cell is connected through a protein channel at a gap junction. Molecules, ions, and electrical signals pass between these channels that connect the cytoplasm of each cell. Almost all cells within the body have gap junctions as they are located between all cells that touch one another directly.  Sperm cells … Read more

Isotonic Solution Definition Isotonic solutions are those with the same solute concentration, or osmolarity, as another solution. The water will flow in equal amounts out of each solution and into the other if the two solutions are separated by a semipermeable membrane. As a result, there is no water flow between the two solutions, even … Read more

Definition ‘Plantarflexion’ refers to the downward movement of the top of the foot away from the leg. A plantar flexion is, for example, pointing your feet and standing on the tips of your toes. Runners, cyclists, and walkers also use plantar flexion to a lesser extent. The range of plantar flexion motion is usually between … Read more

Hyphae Definition Hyphae are comprised of hypha, which are the long filamentous branches found in fungi and actinobacteria (shown below). Hyphae are important structures required for growth in these species, and together, are referred to as mycelium. Hyphae Structure Each hypha is comprised of at least one cell encapsulated by a protective cell wall typically … Read more

Simple Squamous Epithelium Definition Surfaces are lined with simple squamous epithelia, which are formed from one layer of squamous cells. The nucleus of a squamous cell is rounded and large, thin, and flat. They possess polarity and a distinct apical surface with specialized membrane proteins, like other epithelial cells. Functions of Simple Squamous Epithelium These … Read more

Homologous Structures Definition By virtue of their similarity, homologous structures suggest that they share a common ancestor with animals and organisms. It is not necessary for these structures to look or function exactly the same. Their name hints at their structural similarity, which is the most important factor. Examples of Homologous Structures A Tale of … Read more

Modern biology has called into question some of the tenets of cell theory, but they still serve as a good general model. Below we discuss the three tenets of cell theory. 1. All organisms are made of cells Life consists of cells, which are the smallest units. A cell is made up of a membrane … Read more