Answer:
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The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
Answer & explanation:
Fungi have long been regarded as organisms that were part of the <em>Plantae</em> kingdom (plants), mainly because they have cell walls in their cells, reproduce by spores, and the fact that some of them are sessile (attached to the ground).
However, fungi are no longer considered as plants because they do not have chlorophyll or specialized cells, such as chloroplasts and vacuoles. In addition, fungi have heterotrophic nutrition (plants are autotrophic), needing to absorb organic substances to survive.
Nowadays, fungi are studied in isolation and are inserted in their own kingdom, the <em>Fungi</em> kingdom.
Blood is considered<span> a </span>connective tissue<span> for two basic reasons: ( 1 ) embryologically, it has the same origin ( mesodermal ) as do the other </span>connective tissue types<span> and ( 2 )</span>blood<span> connects the body systems together bringing the needed oxygen, nutrients, hormones and other signaling molecules, and removing the wastes .</span>
