Answer: (B) Pre-zygotic; post-zygotic.
Explanation:
Prezygotic isolation occurs before fertilization of eggs. It occurs between the two sex gametes and deter sexual reproduction between different species.
However, individuals are considered to be diverge on the phylogeny tree and different species, when they cannot reproduce.
Mechanisms of prezygotic isolation include habitat isolation, gamete isolation, mechanical isolation, behavioral isolation, and mating seasons.
Whereas, postzygotic isolation prevents the formation of fertile offspring. This phenomenon leads to production of an hybrid offspring from different species and this is a form of speciation in nature.
Mechanisms of postzygotic isolation include hybrid inviability, hybrid breakdown, and hybrid sterility.
The answer to this question is nitrates. Nitrate is a
compound that is composed of nitrogen and oxygen. Nitrates are used as a
preservatives in food, can be used as fertilizer, an ingredient to make gunpowder,
and also an ingredient in making explosives or bomb.
Answer:C). A phospholipid bilayer with proteins
Explanation: A cell membrane is a phospholipid bilayer with proteins embedded in it. The fatty acyl chains of the phospholipids are non polar and hydrophobic while the phosphate groups are polar and hydrophilic. The hydrophobic regions of the phospholipids interact with each by facing each other, forming a bilayer with a fluid interior. The polar head groups face outward interacting with the external environment of the cell. Proteins are embedded in this bilayer and they float in this sea of phospholipids. Proteins anchored to the membrane through interactions between the hydrophobic regions of the phospholipids and the amino acid side chains of the proteins. These lipids and proteins swim laterally in each face of the bilayer but movement from one face of the bilayer to another is restricted.
Every cell of the organism has the same DNA sequence and same genes. However, not all genes are expressed in every single cell at the same time. Only those genes necessary for a specialised function of a specialised cell are expressed in the specialised cell. For example, skin cells have some different proteins than nerve cells. Genes responsible for those "skin proteins" are activated in skin cells and are turned off in nerve cells.
