Primary succession: <u>is a process by which a community arises in a virtually lifeless area with no soil. </u>
Secondary succession:<u> follows a disturbance that destroys a community without destroying the soil.</u>
Answer:
A
Explanation:
Tilling agitates the topsoil and removes ‘unnecessary’ vegetation so the main crop can grow without competition. Tilling improves soil aeration and drainage for plants to grow well. Nonetheless, it can lead to other consequences such as soil erosion because it loosens the soil and makes it easy to be carried away by wind and water.
The correct answer is: the treated glioblastoma cells were cultured in the presence of an inhibitor from umbilical cord stem cells, but the control cells were cultured without the inhibitor.
It has been shown that treatment with injected umbilical cord stem cells has strong therapeutic effects on glioma models. Those cells produce anti-tumour substances, with inhibitory effects.
Control group does not include the treatment in order to observe the treatment.