Many biological processes are cyclical. Examples of cycles can be found at the level of the cell, the organism and the ecosystem.
Explain how changes to the cell cycle can result in tumour formation.
cell cycle is (repeated) sequence of cytokinesis/cell division, (then) interphase (then) mitosis / cell cycle includes the sequence of interphase, mitosis and cytokinesis/cell division (to form new cells which repeat the cycle);
cyclins control/regulate this cycle / ensure the cell moves on to the next stage of the cycle when it is appropriate;
extra cells produced when they are needed;
tumour formation is the result of uncontrolled cell division/ cells growing and dividing endlessly;
repeated mitoses/high mitotic index;
due to mutations in oncogenes / oncogenes may become active and contribute to the development of a cancer cell;
carcinogens/radiation/mutagenic chemicals/mutagens/smoking cause mutations/tumours;