Answer:
Most cells within planarians tend to be very close to their gastrovascular cavity, in addition to their external environments. Also, planarians have the ability for oxygen and carbon dioxide to diffuse through the cells on their body walls: this makes it unnecessary for these varieties of flatworms to need a dedicated bodily system.
I think the deficiency of dedicated respiratory and circulatory systems in Planarians does not cause a problem because none of their cells are far removed from the gastrovascular cavity or from the external environment. Planarians are free-living flatworms and form the class Turbellarians in the Phylum Platyhelminthes. Flatworms have three tissue layers, that is the ectoderm, mesoderm, and endoderm.
hope this helps!!!!!....
Explanation:
Answer:
there are 4: paracrine signaling, autocrine signaling, endocrine signaling, and synaptic signaling
Explanation:
paracrine:cells that are near one another communicate through the release of chemical messengers
autocrine: a cell signals to itself, releasing a ligand that binds to receptors on its own surface
endocrine:When cells need to transmit signals over long distances, they often use the circulatory system as a distribution network for the messages they send.
synaptic: nerve cells transmit signals. The junction between two nerve cells where signal transmission occurs.
Answer:
<em>6</em><em> </em><em>minutes</em>
EXPLANATION:
The brain can survive for up to about six minutes after the heart stops. The reason to learn cardiopulmonary resuscitation (CPR) is that if CPR is started within six minutes of cardiac arrest, the brain may survive the lack of oxygen. After about six minutes without CPR, however, the brain begins to die.
