Video answering a question about a refrigerator's defrost cycle. This video answers the question of how often does a refrigerator go into defrost. If you have questions about appliances that you want an answer to, leave them in the comment section below.ideo answering a question about a refrigerator's defrost cycle. This video answers the question of how often does a refrigerator go into defrost. If you have questions about appliances that you want an answer to, leave them in the comment section below.
1 Species Fusion-two species in a hybrid zone may have weak reproductive isolating barriers, and the two species may, over time, eventually share a common gene pool. 2  Species Stability/Hybrid Equilibrium-Hybrids are continually produced by the two parent populations in a hybrid zone.
blood-brain barrier, n barrier formed by epithelial cells in the capillaries that supply the brain and central nervous system. This barrier selectively allows entry of substances such as glucose, some ions, and oxygen, while blocking entry of other substances.he blood-brain barrier prevents or slows the passage of some drugs and other chemical compounds, radioactive ions, and disease-causing organisms such as viruses from the blood into the central nervous system.