<span>One important mechanism of evolution, natural selection, </span>does<span> result in the evolution of improved abilities to survive and reproduce; however, this does not mean that evolution is progressive — for several reasons
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Answer:
Macrophages are part of your innate immune system, which is antigen-independent and does not require activation.
Explanation:
Macrophages phagocytize (internalize) all non-self pathogens it encounters. These do their job without activation. Other cells in the innate immune system include basophils, neutrophils, eosinophils (these cells are polymorphonuclear leukocytes), mast cells, and dendritic cells, which act as the bridge between your innate and adaptive immune system.
All of the other entities listed above are part of your adaptive immune system. The adaptive immune system is antigen-dependent and requires activation. This section of your immune system responds differently to different pathogens, and has the bonus of having immunologic memory, the ability to remember pathogens after infection and respond much quicker upon secondary and tertiary encounters.
Note: All lymphocyte types begin as naïve cells, which then differentiate into their fully matured form upon activation.
Helper T cells are a type of CD4+ T cell that has the job of activating B and T lymphocytes. There are two different types of T helper cells: Th1 and Th2. Th1 cells secrete the cytokine interferon-gamma (IFNγ), and is primarily involved with the stimulation and activation of cytotoxic T cells, while Th2 cells secrete a variety of cytokines and are responsible for activating and assisting with B cells to make antibodies. To make a long story short, Th cells interact with APC (Antigen Presenting Cells), specifically their Class II MHC (a group of genes that present exogenous proteins). The Th cells then proliferate and gain the ability to activate these APC cells and provide the necessary signals to activate B and T cells and make them proliferate and do their specific function.
Answer:
it has dna that is not contained within a nucleus
Explanation:
The word prokaryote is of Greek origin and means “anterior nucleus” or “before having nucleus”. This meaning gives the impression that it is a primitive structure, and that is exactly what these organisms are about. When compared to eukaryotes, prokaryotic cells are simpler, which leads to the belief that they are more primitive elements in evolutionary history. Thus, it is believed that the first cell was that of a prokaryote being.
The composition of this cell group has few membranes, in general, the only one present is the one that delimits the cell. The prokaryotic cell is characterized by the absence of very well-known and common membranous organelles, such as mitochondria, chloroplast, Golgi complex and nucleus. Regarding the absence of a nucleus, the DNA of this cell is not separated from the cytoplasm by a nucleus.
The prokaryotic cell has a plasma membrane, cytoplasm, free and non-compartmented genetic material (DNA) and ribosomes.
1. Frequency
2. Amplitude
3. Wavelength
