Recessive Gene Definition A recessive gene is a gene whose effects are masked in the presence of a dominant gene. Every organism that has DNA packed into chromosomes has two alleles, or forms of a gene, for each gene: one inherited from their mother, and one inherited from their father. A recessive gene is only … Read more
Peptide Bond Definition Peptide bonds are covalent bonds formed between amino acids. In living organisms, amino acids are linked together by peptide bonds to form proteins. Proteins play many roles, including supporting structure, catalyzing reactions, and recognizing molecules in the environment. Most biological reactions are therefore based on peptide bonds. In all forms of life, … Read more
Producer Definition Producers are organisms capable of creating simple carbohydrates such as glucose, from gaseous carbon dioxide. This process of producing organic molecules from inorganic carbon sources is called primary production. The energy for this process can come from solar radiation, chemical reactions or from the heat in deep ocean geothermal vents. On land, most … Read more
Chitin Definition Chitin is a large, structural polysaccharide derived from modified glucose chains. In insects, fungi, and certain invertebrates and fish, chitin is found in their exoskeletons, cell walls, and hard structures. In terms of abundance, chitin is second only to cellulose. Chitin is synthesized by organisms in the biosphere every year in excess of … Read more
Body Cavity Definition A body cavity is a space created in an organism which houses organs. It is lined with a layer of cells and is filled with fluid, to protect the organs from damage as the organism moves around. Body cavities form during development, as solid masses of tissue fold inward on themselves, creating … Read more
Positive Feedback Definition Positive feedback is a process in which the end products of an action cause more of that action to occur in a feedback loop. This amplifies the original action. It is contrasted with negative feedback, which is when the end results of an action inhibit that action from continuing to occur. These … Read more
Negative Feedback Definition Negative feedback is a type of regulation in biological systems in which the end product of a process in turn reduces the stimulus of that same process. Feedback, in general, is a regulatory mechanism present in many biological reactions. By allowing certain pathways to be turned off and on, the body can … Read more
The Basics X-Ray Fish are small, schooling aquatic fish native to the Amazon basin in South America. In addition to being known as the Golden Pristella Tetra, X-Ray Tetra, and Water Goldfinch, they also have translucent skin that allows their organs and skeleton to be observed, much like an X-ray. The description Small, the X-Ray … Read more
Passive Transport Definition Passive transport, also known as passive diffusion, is a process by which an ion or molecule passes through a cell wall via a concentration gradient, or from an area of high concentration to an area of low concentration. It’s like moving from the train to the platform of a subway station, or … Read more
Ventral Cavity Definition The ventral cavity, or ventral body cavity, is a fluid filled space surrounding the organs on the ventral side of humans and other tetrapods. The ventral cavity is one of two main cavities, the other being the dorsal cavity. The ventral cavity, in humans, is actually made up of two separate cavities, … Read more