Answer:
The trachea, commonly known as the windpipe, is a most important organ as it allows the passage of air into the lungs. Because the trachea has a soft tissue tubular formation, it needs a base of stronger, yet flexible stuff that will give it support, protect it, and still allow the passage of air into the lungs.
This is precisely the task of the tracheal rings, or cartilage rings in the trachea. These rings are made out of cartilaginous tissue, which is much stronger than the soft tissue of the tubule, but are still flexible enough to not close down the tube when air is flowing in. Thus, the tracheal rings have two tasks: one, provide support and protection for the much softer and more vunerable tube of soft tissue through which the air passes, and two, provide flexibility so that air can flow easily.
If these tracheal rings did not exist, if they are crushed, or removed, a person´s trachea would simply collapse and the person would die as air would not be able to flow through to the lungs.
<span>Planaria have a huge regenerative power because of the presence of adult stem cells called neoblasts. If you cut Planaria into pieces, each piece can regenerate into a complete organism and that’s a form of asexual reproduction. Cells which are located on the wound site proliferate to form a blastema-mass of cell that will grow into a new organ. Those cells will differentiate into new tissues and regenerate the missing parts.</span>
<span>The similar thing is happening with starfish.</span>
The abdominopelvic is composed of the abdominal cavity and the pelvic cavity. This cavity contains the organs such as liver, stomach, spleen, gallbladder, pancreas, kidney and most of the intestines along with the internal reproductive organs and urinary tract. The navel is located in the umbilical region of the abdominopelvic cavity.
Hence, the blank can be filled with 'umbilical region'.
Answer: Several homozygous recessive individuals leave the population.
