A hydrometer or areometer is a <span> instrument that always </span><span>measures the specific gravity relative density of liquids and the ratio of density of the liquid to the density of liquid to water.
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Earth's orbit and climate change
The physical characteristics of an organism is its phenotype. I remember this because phenotype and physical both start with 'ph.'
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Answer:
Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
Explanation:
Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete cytokines that regulate or assist the immune response.
The answers are "water and mineral ions" and "amino acids and sucrose" respectively.
For the xylem, it usually transports water and mineral ions that are absorbed from the root hair cells up to the leaves, where photosynthesis take place. Water is one of the necessary substance for photosynthesis to take place, while different mineral ions can help the plant by for example Magnesium ions can help produce chloroplast.
While phloem transports amino acid and sucrose from the location of production (eg. Leaves by photosynthesis) to the place where it is used or stored. Plant needs these substances to generate energy for activities such as growth by for example cellular respiration. This process is called translocation.
Both of these tubes help transport substances in the plant, in order to keep the plant alive.
