Q1. The answer is removing metabolic wastes from the body.
Excretion is the process through which metabolic wastes are removed from the body. Skin, lungs, and greatly kidney, which are the part of the excretory system, are responsible for excretion of metabolic waste in vertebrates. Invertebrates have special systems (insects, for example, have Malpighian tubules) or use skin to excrete metabolic wastes while single-celled organisms use the whole surface of the cell.
Q2. The answer is some animals live in dry or salty environments.
Kidneys are important organs in maintaining water balance. Some animals that live in dry and salty environments must preserve water in order to maintain homeostasis. They drink and eat food with more salt in it. If they lose that precious water in such conditions, the amount of different salts in the organism will increase and it will affect a normal functioning of the organism.
Q3. The answer is simple diffusion across the skin. 
Ammonia is very toxic substance and a lot of water is needed for its neutralisation and excretion. Therefore, animals that live in water excrete ammonia directly in the water. Many freshwater invertebrates eliminate ammonia through skin. In animals that do not live in the water, kidneys and liver help conversion of ammonia into urea which is then excreted.,
Q4. They both actively pump salt across their gills. 
Both saltwater and freshwater fishes use gills to eliminate nitrogenous wastes while kidneys have a little role in the elimination of this kind of the waste. Salt that is lost is replaced by active transport of salt ions into the body by the gills.
Q5. The answer is They both convert nitrogenous wastes to uric acid. 
A garden spider and a sparrow are terrestrial organisms. They do not live in the water and do not excrete metabolic wastes in the water. It is known that ammonia is toxic nitrogenous substance and a lot of water is needed for its excretion. For water organisms this is not a problem, they are surrounded by water, but terrestrial organisms, such as the garden spider and the sparrow, have no such amount of water in the environment, so their kidneys and liver must convert ammonia into urine which can then easily be excreted.
        
             
        
        
        
Active Immunity is natural.
Passive Immunity is maternal.
Active Immunity from Vaccination. 
Passive Immunity is Artificial. 
Passive Immunity:
    Does not require previous exposure to a disease agent
    Takes effect immediately
    Does not last long (up to a few months)
Active Immunity is produced inside of the body, whereas passive immunity is introduced from outside of the body.
Active Immunity is from direct infection and vaccination.
Passive Immunity is from Breast milk, Injection, Mother to baby through the placenta.
Active Immunity takes effect over time (typically several weeks).
Passive Immunity takes effect immediately.
Active Immunity's length of efficacy is Long-term to lifelong.
Passive Immunity is short-term.
Active Immunity is produced by memory cells, Passive Immunity is not.
Hope this was insightful and enough information.
 
        
                    
             
        
        
        
Answer:
Taproot systems feature a single, thick primary root, called the taproot, with smaller secondary roots growing out from the sides. The taproot may penetrate as many as 60 meters (almost 200 feet) below the ground surface. It can plumb very deep water sources and store a lot of food to help the plant survive drought and other environmental extremes. The taproot also anchors the plant very securely in the ground.
Fibrous root systems have many small branching roots, called fibrous roots, but no large primary root. The huge number of threadlike roots increases the surface area for absorption of water and minerals, but fibrous roots anchor the plant less securely
Explanation:
 
        
             
        
        
        
The arctic environment is deathly cold, hence the thick blubber on animals so they can handle freezing temperatures