Phoebes Levine proposed the polynucleic model (around 1910!).
Cell walls are supporting structures that help the plant to have a fixed shape and protect it from injury. Other than that, it helps to keep the plant turgid so that it can stay firm and upright. Because when it enters a high water potential solution, as water moves in, the water exerts turgor pressure on the cell wall and the cell wall thus exerts an opposing pressure to keep water out. Hence cell wall is needed for the plant.
On the other hand, animal cells do not need to keep the structures, as they have the skeletal system to protect the organs and cushion them against any
external injuries.
I hope that helped
22. C
23. C
24. A
25. B
26. D
27. C
28. C
Natural selection is the process by which individuals who are best suited to the environment tend to leave (on average) more offspring than others.
Evolutionary changes take place over many generations and through millions of years of natural selection. For the genes to survive, they must be among the strongest.
