Final answer:
Apoptosis, or programmed cell death, can be triggered by internal checkpoints or external signaling. Internal checkpoints monitor cell health, while external signaling, such as moving away from the extracellular matrix, can also initiate apoptosis. These signals work together to ensure cells die in a controlled manner.
Step-by-step explanation:
Apoptosis, or programmed cell death, can be triggered by two different signals: internal checkpoints and external signaling. Internal checkpoints monitor a cell's health and can initiate apoptosis if abnormalities are observed. External signaling can also initiate apoptosis, such as when animal cells move away from the extracellular matrix, causing the signaling to cease and the cell to undergo apoptosis. These two signals work together to ensure cells die in a controlled manner to prevent harm to the organism.
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