Answer:
A rise in blood carbon dioxide concentration.
Explanation:
The feedback regulation may be defined as the process in which the end product of the metabolic pathway regulates the homeostasis of the body. Two main types of feedback are positive feedback and negative feedback.
The negative feedback mechanism occurs when the end product of the reaction is responsible for the shutdown of the metabolic pathway and decreases its concentration. The breathing is controlled by the negative feedback mechanisms, the increase in carbon dioxide concentration acts as the negative sensor as this sensor is mainly responsible for the increase in amount of oxygen level and maintain homeostasis of the body.
Thus, the correct answer is option (c).
 
        
             
        
        
        
Answer:
Because the offspring of a male and female are always going to be xx, xx, xy, or xy.
Explanation:
Remember that men have different reproductive chromesomes than women. Women have 2 x chromesomes(xx) while men have 1 x and 1 y(xy). These are given down to their offspring.
So we can write the this out in a punnet square as(link down below). 
After you see the visual, you will find that the genotypes are xx, xx, xy, xy.
As I said above, women have sex chromesomes xx, while men have sex chromesomes xy. When you match the genotypes on the punnet square with the ones we know from men and women, we find that two of them match with men and two match with female.
So with this, we can conclude that 2/4 of offspring will always be male and 2 will be female. And as you well know 2/4 is 1/2 which is 50%.
 
        
             
        
        
        
The answer is D 
One way to remember this is when you are building a bridge there is one piece right in the middle that keeps the whole thing from collapsing that is called the key-stone. If a keystone species goes extinct then the rest of the ecosystem will crumble around it.
 
        
                    
             
        
        
        
I am taking the test right no and I picked the answer C. But I am not 100% sure that it is the correct answer. It just seems to be the one that makes the most sense.
        
                    
             
        
        
        
An organism that eats other organisms is called a <u><em>heterotroph</em></u>.