Primary Succession is when an ecological community experiences a community changing natural disaster (volcano, glacier, etc) primary succession starts from bare rock. Secondary succession starts from pre-existing soil, and occurs from a hurricane, deforestation, etc.
The earthworm has a closed circulatory system, and there are 3 main vessels: <span>aortic arches, dorsal blood vessels, and ventral blood vessels.
aortic arches: It functions as the heart of the earthworm
dorsal blood vessels: Responsible to carry blood to the front of the body
ventral blood vessels: Responsible to carry blood to the back of the body
hope this helps</span>
Answer:
The miRNAs act as post-transcriptional silencers, as they are similar to specific mRNAs and regulate their stability and translation. They are small endogenous non-coding ribonucleic acid (RNA) molecules, with about 22 nucleotides, which act as regulators of gene expression in plants and animals, at the post-transcriptional level through the cleavage of a target messenger RNA (mRNA) or repression of translation.
In general, most miRNA genes are transcribed by RNA polymerase II in the nucleus in primary miRNAs (pri-miRNAs). Individually, a pri-miRNA can produce a single miRNA or contain groups of two or more miRNAs that are processed from a common primary transcript. These long pri-miRNA are cleaved by a complex comprising the double-stranded RNAse III enzyme (DROSHA) and its essential cofactor, the binding protein DGCR8 (DiGeorge Syndrome Critical Region 8 protein) in mammals. DROSHA contains two domains of RNAse III, each of which cleaves a strand of the RNA resulting in the precursor microRNA (pre-miRNA) with about 70 base pairs, which contains a double-stranded stretch and a single-stranded loop, forming a structure in clamp. The pre-miRNA is exported to the cytoplasm by the protein exportin-5 (XPO-5), where it is cleaved by DICER1, an RNAse III that assesses the 3 'and 5' ends of the pre-miRNA, generating a mature miRNA with about 22 nucleotides. The processing of pre-miRNA by Dicer promotes the unfolding of the RNA duplex in the form of a clamp. The position in the formation of the clamp can also influence the choice of tape.
Explanation:
The answer is; B
Rocks have naturally occurring and spontaneously radioactive atoms in them, such as carbon-14. These element isotopes decay into other types of atoms over millions of years. Therefore, by measuring the amount of these radiometric substances, and knowing the half-life of the isotopes, it is possible to postulate the age of a rock to within certain ranges of error.
