<span>An indicator species is an organism whose presence, absence or abundance reflects a specific environmental condition. Indicator species can signal a change in the biological condition of a particular ecosystem, and thus may be used as a proxy to diagnose the health of an ecosystem. For example, plants or lichens sensitive to heavy metals or acids in precipitation may be indicators of air pollution. Indicator species can also reflect a unique set of environmental qualities or characteristics found in a specific place, such as a unique microclimate. </span>
The common geographic factor for Egypt and the fertile crescent were the big rivers, they made big alluvial deposits on their shores each year and allowed the people to have sufficient amount of food production. That opened the gates for civilizations to flourish in this places.
A or b or c not d you chose
Hey how’s it going man? I’ll be glad to help?
At low latitudes, the thermocline is a zone of rapid temperature
over a relatively short depth. it is associated with a similar depth zone marked by a change in density called the pycnocline.
