Hich is the first checkpoint in the cell cycle where a cell will be caused to exit the cycle if this point is not passed?

Answer;
G1-phase
The first checkpoint in the cell cycle where a cell will be caused to exit the cycle it this point is not passed is the G1-phase.

Explanation;
The interphase of the cell cycle contains three phases, G1 , S and G2 phases. It begins with G1 phase (G stands for gap). During this phase, the cell makes a variety of proteins that are needed for DNA replication. When the cell passes the G1 checkpoint it enters the S phase of the cell cycle, during which DNA is replicated, after the replication, the cell leaves S phase and enters G2, where the cell prepares for mitosis or meiosis. 

An autotrophic protist - they can perform photosynthesis and mainly consist of unicellular algae. they can be divided into number of systematic group according to the shape of their cell and the type of photosynthetic pigments they use.