Answer:
Fascicles
Explanation:
Muscle fibers are arranged into bundles known as fascicles. These are in turn covered by connective tissue called perimysium.
 
        
             
        
        
        
Answer:
Natural selection causes change in allele frequencies within a population.          
So option A is correct one. 
Explanation:
Natural selection generally  work  on an organism’s phenotype, or observable features. Phenotype is often largely a product of genotype (the alleles, or gene versions, the organism carries). When a phenotype produced by certain alleles helps organisms survive and reproduce better than their peers, natural selection can increase the frequency of the helpful alleles from one generation to the next – that is, it can cause microevolution.
 
        
             
        
        
        
Destruction of biodiversity. Water pollution depletes aquatic ecosystems and triggers unbridled proliferation of phytoplankton in lakes — eutrophication —. Contamination of the food chain.Human diseases: Pathogens(viruses,bacteria,fungi,protozoa etc)are biological pollutants of water. They cause typhoid,cholera,dysentery,jaundice,hepatitis.
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Answer:
<h3>Biologists study humans, plants, animals, and the environments in which they live. They may conduct their studies--human medical research, plant research, animal research, environmental system research--at the cellular level or the ecosystem level or anywhere in between.</h3>