Biology

Simple Columnar Epithelium Definition Simple columnar epithelia are tissues made of a single layer of long epithelial cells that are often seen in regions where absorption and secretion are important features. The cells of this epithelium are arranged in a neat row with the nuclei at the same level, near the basal end.  In a … Read more

Phagocytosis Definition Phagocytosis, or “cell eating”, is the process by which a cell engulfs a particle and digests it. The word phagocytosis comes from the Greek phago-, meaning “devouring”, and -cyte, meaning “cell”.  Cells in the immune systems of organisms use phagocytosis to devour bodily intruders such as bacteria, and they also engulf and get … Read more

Definition Cricoid cartilage is part of the larynx (just below the pharynx), and sits on a level plane just below the thyroid gland and thyroid cartilage. It is a circular piece of hyaline cartilage which wraps completely around the trachea, providing a place of attachment for various ligaments, muscles and other cartilage. Overview While the … Read more

Hermaphrodite Definition A hermaphrodite is an organism with both male and female genitalia. In sexually reproducing organisms, males have organs that produce male gametes, usually sperm. Females have different sexual organs that produce female gametes, usually called eggs. In sexually dimorphic organisms, each organism only has type of reproductive organs, and the population is divided … Read more

Overpopulation Definition Overpopulation refers to a population which exceeds its sustainable size within a particular environment or habitat. Overpopulation results from an increased birth rate, decreased death rate, the immigration to a new ecological niche with fewer predators, or the sudden decline in available resources.  Therefore, overpopulation describes a situation in which a population in … Read more

Microfilament Definition Microfilaments, also called actin filaments, are polymers of the protein actin that are part of a cell’s cytoskeleton. The cytoskeleton is the network of protein filaments that extends throughout the cell, giving the cell structure and keeping organelles in place.  Microfilaments are the smallest filaments of the cytoskeleton. They have roles in cell … Read more

The Basics “Zonkeys” are hybrid animals produced by mating zebras and donkeys. Zonkeys are not a true species because they have an odd number of chromosomes and cannot reproduce. While zonkeys are rare, they are bred in a number of zoos and specialized farms around the world. Zonkeys are also referred to as zebonkey, zebrinny, … Read more

Ovule Definition The ovule is part of the makeup of the female reproductive organ in seed plants. It’s the place where female reproductive cells are made and contained, and it is what eventually develops into a seed after fertilization, only for the seed to then ripen and produce a complete adult plant.  Ovules are contained … Read more

Synapsis Definition Synapsis is an event that occurs during meiosis in which homologous chromosomes pair with their counterparts and remain bound due to the exchange of genetic information. During meiosis, homologous chromosomes are paired and then separated to reduce the genetic content of the resulting gamete cells.  Synapsis does not occur during mitosis, because homologous … Read more