Neurotransmitters. With the regard to the process of the neural transmission, a refractory period refers to the time in interval in which. the Positively charged sodium ions are to pumped back to outside a neural membrane.
 Neurotransmitters are the chemical messengers that your body can't function without it. Their job is to carry out chemical signals (“messages”) from one of the neuron (nerve cell) to the next target cell. The next target of the cell can be another nerve cell, a muscle cell or the gland.
Fortunately, the seven “small molecule” are neurotransmitters (acetylcholine, dopamine, the gamma-aminobutyric acid (GABA), or glutamate, histamine, norepinephrine, and the serotonin) do the majority of the work.
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In light reactions, a molecule of chlorophyll absorbs one photon of light, causing a chlorophyll electron to transfer to a higher energy level. ... Chlorophyll then replaces the lost electrons from water molecules. The oxygen atoms form oxygen gas while the hydrogen atoms form protons and electrons.
        
             
        
        
        
Answer:
<u>the bottleneck effect</u>
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Explanation:
Genetic drift has an important impact on the small populations. mutations, which are spontaneous heritable changes in the genetic code, made up of DNA. Here, mutations accumulate over time in a group, modifying the distribution of alleles or various forms of a gene. Natural selection may result in a loss of diversity in a population called genetic drift; one trait's allelic frequency rises while others become less prevalent. Typically such differences exist because of occurrences of mutation and recombination.
Some mutations or alleles may become extinct from the population.
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Variants of a gene accumulate and are transmitted across generations; the frequencies of these occurrences are altered and become more stable in genetic drift- they become genetically distinct and may eventually form a new species after isolation. This may be further compounded through other  phenomena such as the founder effect where a group separates and genetic diversity decreases; and the bottleneck effect where barriers to reproduction or the die-off a population increases genetic drift. 
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1. the digestive system breaks down food and take the nutrients your body needs