Answer:
Forest floor
Explanation:
Tropical rainforest is characterized by high rainfall that allows a diverse growth of plant species. The different species of plants and animals species that make up a rainforest are found in different layers. There are four layers or sections in the rainforest from top to bottom viz: emergent layer, canopy, understory and forest floor. 
Since the layers are classified from top to bottom, each layer receives different amount of rainfall and sunlight. According to the question, the FOREST FLOOR receives the least amount of sunlight making it the darkest section of the rainforest. Due to the inhibited penetration of sunlight into this layer, it usually does not support any plant growth.
 
        
             
        
        
        
Answer:
A particular genotype does not necessarily guarantee a particular phenotype. Understanding what factors can change this expression is quite complex.. What is what i believe that above statement meant.
Explanation:
Error is the stochastic variation associated with a particular observation of the phenotype (and is managed by use of replication and and appropriate experimental design). The phenotype is the result not only of the average effect of the different alleles at a given locus across test units and across environments, but is impacted by the interaction between the different alleles and the environments (including genetic backgrounds) in which they are evaluated. Phenotype is not simply the sum of the genotype effect and the environment effect, as indicated in the mathematical formula that you provide.
Hope I Helped!!!
 
        
             
        
        
        
Natural Selection. 
An easy and important way to remember this is by thinking of a species - let’s say a bright white moth. For ages, these moths have survived beautifully, matching perfectly with the white tree bark they live on, until one day, a smoky building begins pumping its soot into the air. This air begins to change the color of the tree bark to black and the once hidden white moths are now plainly visible to birds who eat them easily. Fortunately, every now and then a moth is born who is darker than the rest - black as soot even. And so, the birds keep eating the white moths but missing the soot-colored ones. As time goes by, the soot-colored moths produce more and more similarly colored moths, who are well hidden from the birds AND after enough time, the only moths that remain are soot-colored. This is why so many species “fit” exquisitely into their environment. They have ALL adapted in some way similar to the soot-colored moth.
        
             
        
        
        
They replicate fast - producing more of the useful proteins such as the hormone insulin.