Answer: All the above options are correct about the characteristics of Lumbriculus variegatus.
Explanation:
Lumbriculus variegatus also called the black worm belongs to the phylum Annelida and is used by biologists to illustrate:
-blood vessel pulsations,
-swimming reflex,
-peristaltic crawling behavior,
-giant nerve fiber action potentials.
These studies where carried out on them due to the characteristics they possess. These includes:
-its blood circulates in a closed circulatory system
-Freshwater worm found throughout North America and Europe
-Prefers the shallow habitats found at the edges of ponds, lakes, or marshes
-Feeds on decaying vegetation and microorganisms.
Difference # Open Store System:
1. There is no specific storage area. Stores are maintained in the form of Suitable/convenient locations.
2. Every individual has access to anystorage facility.
3. After the receipt of the material it is delivered to respective department to expedite the production activity.
4. Chances of Pilferage high.5. Less emphasis on accounting control of the material.
Difference # Closed Store System:
1. All materials are stored in a closed/controlled area.2. No other person than the stores personnel is permitted in the area.
Materials can leave or enter the storage area only by authorised documents.
4. Maximum Physical Security.
5. Tight accounting control of inventory material.
Answer: Mesopotamia, china, indus River Valley, the mesoamerican empires..... in this case, the two rivers are the tigris and Euphrates. Mesopotamia. The name Mesopotamia was given to the middle eastern civilizations that existed between the Euphrates and Tigris Rivers. :)
<u>Answer:</u>
Cyanobacteria start producing pure oxygen around 200 million years ago.
<u>Explanation:</u>
Many scientists believed that Earth did not have any oxygen. Cyanobacteria or the blue green algae are the microbes which produced oxygen for the first time with the help of photosynthesis. This was around 4.5 billion years ago: after Hadean eon.
They were very simple, but they produced oxygen in the early earth’s atmosphere. So, they brought evolution on earth. This “blue-green algae” exists in salt water, rocks and soils and play a major role in maintaining the ecosystem.
