calling all biology whizzes.......?

Question

could you answere these questions for me?

where does gas exchange between the environment and body take place?

describe a negative feedback loop.what does it regulate?

compare and contrast our 2 control systems in the body.

what role do bacteria play in the nitrogen cycle?

what 2 processes cycle carbon and oxygen in an ecosystem?

explain why lethal allelles are able to remain in a gene pool.



it would be much appretiated!
thanx

Answer 1

Ask each question separately, lazy girl.

Answer 2

Are you taking a test or something? Anyway..

1) Gas is primarily exchanged between the atmosphere and the body in the lungs. A small amount diffuses across the skin.

2) a negative feedback loop is a means of regulation in which part of the output of a system is fed back to the input (thereby reversing the flow -- the "negative" portion) An example is blood pressure regulation: a rise in blood pressure is sensed by baroreceptors (special nerves that sense blood pressure), which send an impulse to the brain to release hormones that lower blood pressure by causing blood vessels to relax.

3) By "control systems," I'm going to assume you're talking about the somatic and autonomic nervous systems. The somatic nervous system controls muscles and receives input from sensory organs, and is the portion of the nervous system under conscious control, while the autnomic nervous system controls portions that you typically do not have conscious control over: heart rate, digestion, hormone secretion, and the ever-popular "Fight or Flight response"

4) Bacteria in the soil are responsible for fixing nitrogen in a usable form; many plants are incapable of simply absorbing nitrogen from the air efficiently, and require it in the soil to utilize it. Bacteria take atmospheric nitrogen and convert it into ammonia, nitrates or nitrogen dioxide

5) Carbon and oxygen are cycled in an ecosystem through photosynthesis and respiration

6) Lethal alleles can be passed on to children without ill effect due to their recessive nature -- most of them do not express when a healthy gene is donated by one of the parents, but they carry the trait in their DNA. The next generation of children can still inherit the defective gene, and can actually express it if both parents donate the defective version of the gene. In this way, a defective gene can be passed from generation to generation without the disease itself popping up until several generations down the line, or it can weed itself out of the family line over time if each generation marries someone without the defective gene.