Silent Mutation Definition Silent mutations occur when nucleotide bases in DNA are changed without affecting amino acids or overall protein function. A single amino acid can change, but if it has the same properties as the amino acid it replaces, little to no change will occur. There are many ways in which a silent mutation … Read more

Nitrogenous Base Definition Nitrogenous bases, chemicals with similar cyclic structures, play an important role in biology. In addition to building genetic information carrying molecules like DNA and RNA, nitrogenous bases serve various cellular functions, such as signal transduction and microtubule growth. Nitrogenous bases form bonds with 5-sided carbon sugar molecules in DNA and RNA, which … Read more

Skeletal Muscle Definition Skeletal muscle is a specialized contractile tissue that moves the body of an organism. The skeletal muscle is made up of bundles of muscle fibers surrounded by protective membranes. As a result of this arrangement, skeletal muscle can contract and release rapidly without being subjected to too much friction. In most multicellular … Read more

Stabilizing Selection Definition Stabilizing selection refers to any force or forces that push a population toward the average or median trait. Stabilizing selection describes what happens to an individual trait when its extremes are selected against.  This increases the frequency of the trait in the population, as well as the alleles and genes involved. Stabilizing … Read more

Stratified Cuboidal Epithelium Definition Stratified cuboidal epithelium is a type of epithelial tissue found mainly in glands, which specialize in selective absorption and secretion by the gland into blood or lymph vessels. In general, epithelial tissue is any group of cells lining a body cavity or body surface. Stratified cuboidal epithelium describes an epithelial tissue … Read more

Osmosis Definition Osmosis is a type of diffusion that, in biology, is usually related to cells. Diffusion is when molecules or atoms move from an area of high concentration to an area of low concentration. Osmosis is when a substance crosses a semipermeable membrane in order to balance the concentrations of another substance.  In biology, … Read more

Definition Bacillus subtilis, hay bacillus, or grass bacillus was one of the first Gram-positive bacteria to be studied. It is an aerobic, rod-shaped spore-forming microorganism that can spread in extreme cold, heat, and even disinfected environments. It transfers to the gastrointestinal tracts of animals and humans via the soil.  More than 200 Bacillus species exist; … Read more

Simple Diffusion Definition Simple diffusion is the process by which solutes are moved along a concentration gradient in a solution or across a semipermeable membrane. Simple diffusion is carried out by the actions of hydrogen bonds forming between water molecules and solutes. Water molecules move in to surround individual solute molecules, which maximizes hydrogen bonding.  … Read more

Invertebrate Definition Invertebrates are animals that don’t have a backbone. The vertebral column is another name for the backbone. Over 90% of all species on Earth are invertebrates, and invertebrate species have been found in the fossil record as far back as 600 million years ago. Molecular biology studies suggest that all invertebrates evolved from … Read more

Phosphorus Cycle Definition The phosphorus cycle is the process by which phosphorus moves through the lithosphere, hydrosphere, and biosphere. Phosphorus is essential for plant and animal growth, as well as the health of microbes inhabiting the soil, but is gradually depleted from the soil over time. The main biological function of phosphorus is that it … Read more