Answer:
a) Acetylcholine is degraded by acetylcholinesterase.
Explanation:
After it binds for its receptor on the plasma membrane of the postsynaptic cell, acetylcholine must be removed in order to prevent repeated stimulation. Acetylcholinesterase is enzyme for the inactivation of acetylcholine, present at all cholinergic synapses. This enzyme hydrolyses acetylcholine and breaks it to the acetate and choline. Choline can be reused for the synthesis of the new acetylcholine molecule so it is taken back into the presynaptic cell.
Biogeographical studies use information for various fields, such as evolutionary biology, geography, geology, and climate science to determine how organisms evolved through time and how the moving of tectonic plates resulting in forming continents, mountain ranges and islands has affected their distribution.
Studies in this field explain how organisms that now live on different continents are very closely related and how the flora and fauna of islands are connected to one of the closest continents etc.
Answer:
Selection is a directional process that leads to an increase or a decrease in the frequency of genes or genotypes. Selection is the process that increases the frequencies of plant resistance alleles in natural ecosystems through coevolution, and it is the process that increases the frequencies of virulence alleles in agricultural ecosystems during boom and bust cycles.
Selection occurs in response to a specific environmental factor. It is a central topic of population and evolutionary biology. The consequence of natural selection on the genetic structure and evolution of organisms is complicated. Natural selection can decrease the genetic variation in populations of organisms by selecting for or against a specific gene or gene combination (leading to directional selection). It can increase the genetic variation in populations by selecting for or against several genes or gene combinations (leading to disruptive selection or balancing selection). Natural selection might lead to speciation through the accumulation of adaptive genetic differences among reproductively isolated populations. Selection can also prevent speciation by homogenizing the population genetic structure across all locations.
Selection in plant pathology is mainly considered in the framework of gene-for-gene coevolution. Plant pathologists often think in terms of Van der Plank and his concept of "stabilizing selection" that would operate against pathogen strains with unnecessary virulence. As we will see shortly, Van der Plank used the wrong term, as he was actually referring to directional selection against unneeded virulence alleles.
Dominant m8 hope this hleps
