Trophic Level Definition A trophic level is the group of organisms within an ecosystem which occupy the same level in a food chain. There are five main trophic levels within a food chain, each of which differs in its nutritional relationship with the primary energy source. The primary energy source in any ecosystem is the … Read more

Dihybrid Cross Definition A dihybrid cross is an experiment in genetics in which the phenotypes of two genes are followed through the mating of individuals carrying multiple alleles at those gene loci. Most sexually reproducing organisms carry two copies of each gene, allowing them to carry two different alleles. Historically, an organism with parts from … Read more

What Are Peripheral Proteins Peripheral protein, or peripheral membrane proteins, are a group of biologically active molecules formed from amino acids which interact with the surface of the lipid bilayer of cell membranes. Unlike integral membrane proteins, peripheral proteins do not enter into the hydrophobic space within the cell membrane.  Instead, peripheral proteins have specific … Read more

Polygenic Inheritance Definition Polygenic inheritance, also known as quantitative inheritance, refers to a single inherited phenotypic trait that is controlled by two or more different genes. In a system which differs from Mendelian Genetics, where monogenic traits are determined by the different alleles of a single gene, polygenetic traits may display a range of possible … Read more

Krebs Cycle Definition The Krebs Cycle, also called the citric acid cycle, is the second major step in oxidative phosphorylation. After glycolysis breaks glucose into smaller 3-carbon molecules, the Krebs cycle transfers the energy from these molecules to electron carriers, which will be used in the electron transport chain to produce ATP. Krebs Cycle Overview … Read more

Parenchyma Cells Definition In plants, parenchyma is one of three types of ground tissue. Ground tissue is anything that is not vascular tissue or part of the dermis (skin) of the plant. In contrast to collenchyma and sclerenchyma cells, parenchyma cells primarily consists of all of the simple, thin walled, undifferentiated cells which form a … Read more

Selective Breeding Definition Selective breeding is the process by which humans control the breeding of organisms in order to exhibit or eliminate a particular characteristic. Selective breeding uses artificial selection to direct the genetic transfer of desirable traits. As opposed to natural selection, selective breeding focuses on traits which will benefit humans. Selective Breeding Overview … Read more

Vertebrae Definition Vertebrae are bones located within the vertebral column. In humans, they are a series of 33 bones that run from the base of the skull to the coccyx. The irregularly shaped bones form the roughly S-shape of the spinal cord. Between each vertebra is an intervertebral disc, which helps provide shock absorption and … Read more