The latest update on the number of critically endangered species is from the year of 2014, thus five years ago. As of this year, there have been 4568 species that have been placed in this category, 2464 of which are animal species, and 2104 are plant species. In order for a species of plant or animal to be placed in this category it needs to be on the verge of dying out in the wild because it has only very small number of individuals left in the wild that can produce the new generations. Unfortunately, the number of the critically endangered species has constantly been on the rise, and in the most recent history the blame for that falls on the humans and their activities. Some species that fall into this category are the Chinese alligator, Sumatran rhinoceros, eastern gorilla, vaquita, Iberian lynx...
Related genes from different organism usually translate to proteins of indispensable functions. This means that the proteins must be similar in terms of amino acids produced. Therefore the coding region must be highly conserved. These can be found in the introns. Conversely, exons are not a part of the coding sequence and therefore not required for translation. These sequences may be less conserved.
Organisms that use oxygen need it for cellular respiration, in which energy is released from glucose. Energy is needed by the organism for growth, mobility and reproduction.
