Answer:
sieve-tube elements, companion cells
Explanation:
Sieve-tube elements and companion cells are responsible for the movement of photosynthes through a plant.
The sieve tube elements are shorter (almost organelle-free) living cells, placed end to end, forming the sieve tubes. Their transverse cell walls are called sieve plaques that make connections between cells and through openings called sieves establish the connection between the cytoplasm of adjacent cells. Each sieve is coated with calose (glucose polymer), which in winter can completely clog the vessel and then dissolve in spring. When infections occur or the vessel is parasitized, it can also be clogged with callose.
Companion cells are specialized parenchymal cells, which contain all the components that exist in living cells, including the nucleus, are the cells most closely linked to the sieved tube element. The Screened Tube Element and its companion cells are related in development, are derived from the same mother cell, and have several cytoplasmic connections to each other. Due to the many connections, the potential function of the companion cells is to release substances into the sieved tube element and, when the nucleus is absent, to include information molecules, proteins and ATP. When a screened element dies, its companion cells also die, which is a demonstration of this interdependence.
The answer that best describes the relative refractory period in the neuron is The resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.
The refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. Thus, because Na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.
In my opinion
Mass extinctions happen because of climate change, asteroid impacts, massive volcanic eruptions or a combination of these causes. One famous mass extinction event is the one that lead to the extinction of dinosaurs, 65 million years ago.
I hope it’s help
The correct option is C.
if two organisms are in the same class then they will be in the same phylum. The biological classification hierarchy is arranged in such a way that, two organisms who belong to a lower division on the hierarchy will automatically be in the same group in the higher division.
The arrangement from the smallest to largest hierarchy is this: specie, genus, family, order, class, phylum and kingdom.
The amount of DNA present in the system of an organism that does not necessarily relate to how complex that certain organism is. There are single-celled microorganism with very few amount of DNA but are very complex with respect to arrangement of certain amino acid component of the DNA strands.
