Answer:
Primary succession is one type of the ecological succession which takes place on the land devoid of vegetation or barren land.
The species which first flourishes on this barren land are known as pioneer species which includes the species of bryophytes and pteridophytes like lichens and mosses.
These lichens and mosses help breakdown the barren rocks through chemical leaching and help increase the nutrient content. This allows the ferns and small pteridophytes to grow.  
Then the area is colonized by the intermediate species which includes herbs, shrubs later trees. These intermediate species help attract the animals and thus help establish the biological community.
Thus, Lichens mosses → herbs→ shrubs →trees.
 
        
             
        
        
        
Answer:
 a. commensalism is the correct answer.
Explanation:
By growing on the trunk or branch of a tree, a lichen gains height and exposure to sunlight for photosynthesis. The tree is not harmed by the lichen but does not benefit either. The relationship between the lichen and the tree is commensalism.
Commensalism is a relationship between two organisms where one organism gets benefits from other organisms without causing any harm or any damage from the relation as it one side symbiotic relation.
In this, we can see lichen is getting benefits from the tree. 
for example, lichen is getting following benefits from the tree such as ( a lichen gains height and exposure to sunlight for photosynthesis.) and they are causing any harm to tree neither any benefits so this is a one-side symbiotic relation and thus the relationship is an example of commensalism.
 
        
             
        
        
        
Answer:
The biological level of organization represented by all of the three steps of gene expression products is <em>the central dogma of molecular biology.</em>
Explanation:
DNA is divided up into functional units called genes. Each of them provides instructions for a functional product, that is, a molecule nedeed to perform a job in the cell. In many cases, the functional product of a gene is a protein. 
The functional products of most known genes are polypeptides.  Genes that specify polypeptides are called protein-coding genes.
Not all genes specify polypeptides. Instead, some provide instructions to build functional RNA molecules, such as transfer RNAs and ribosomal RNAs that play roles in translation.
The construction of polypeptide involves two major steps: transcription and translation. During the transcription, the DNA sequence of gene is copied to make an RNA molecule and in translation the sequence of mRNA is decoded to specify the amino acid sequence of the polypeptide.
 
        
             
        
        
        
Answer:
Stronger; a hydrophobic has lower dielectric constant. The lower the dielectric constant of the interior, the stronger the ionic interactions.
Explanation:
Ionic interactions are the electrostatic interactions between the oppositely charged ions. The strength of ionic interaction depends on the magnitude of the charges on the ions, the distance between the charged groups and the dielectric constant.  
Here, the dielectric constant is the property of the medium in which the ionic interactions are taking place. Dielectric constant represents the number of dipoles present in the medium or solvent. A medium with higher dielectric constant would attract the oppositely charged ions towards its own dipole and would thereby, make the ionic interaction between the ions weaker.
Given that the ionic bonding between substrate and enzyme is taking place in the hydrophobic interior, ionic interactions would be stronger since the hydrophobic medium has a lower dielectric constant.
The lower number of the electric dipoles or their absence in the hydrophobic interior would not attract the oppositely charged groups of substrate and enzyme towards its own dipoles as the water with higher dielectric constant would have done. This would allow stronger ionic interaction between the substrate and the enzyme.