Explanation:
Messenger RNA (mRNA) is transcribed from DNA in the nucleus and carries the codon sequence to ribosomes in the cytoplasm for translation into protein. tRNA brings amino acids, rRNA forms ribosomes, DNA stays in the nucleus. mRNA is the template for protein synthesis.
Consider statements about plant biology: 1. Xylem transports water upwards. 2. Phloem transports food bidirectionally. 3. Cambium is responsible for secondary growth. Which are correct?
Explanation:
Xylem is the vascular tissue responsible for the unidirectional upward transport of water and dissolved minerals from the roots to the aerial parts of the plant. Phloem is the vascular tissue responsible for the translocation of organic nutrients (primarily sucrose) from sources to sinks, which can be bidirectional (up or down depending on the plant's needs). Cambium (vascular and cork) is a lateral meristem responsible for secondary growth, which is the increase in the girth or thickness of stems and roots. All statements are correct.
Consider statements about evolution: 1. Natural selection was proposed by Darwin. 2. Evolution always leads to perfect organisms. 3. Homologous organs indicate common ancestry. Which are correct?
Explanation:
Charles Darwin proposed the theory of evolution by natural selection, where organisms with favorable traits survive and reproduce. Homologous organs share a common structural plan and evolutionary origin, indicating divergent evolution from a common ancestor. Evolution does not lead to perfection; it only results in adaptation to the current environment. Thus, statements 1 and 3 are correct.
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