PNB 2250 Exam Practice Questions and
Answers
How are plant cells held together? - Ans:-Plasmodesma
Plasmodesma - Ans:-Flow of nutrients between cells
How are animal cells held together? - Ans:-Tight junctions
Tight junctions - Ans:-Unique connections for animal cells
2 absolute requirements o...
Feedback Loop: sensor - Ans:✔✔-A protein based biochemical amplifier
Feedback Loop: Output - Ans:✔✔-Change in physiological variable
Most common type of feedback - Ans:✔✔-Negative
Negative feedback - Ans:✔✔-Reducing the change in physiological variables
In the geological past, there were toxic concentrations of: - Ans:✔✔-NH4, CH4, and CO2
Basis of the food chain for all marine life - Ans:✔✔-Phytoplankton
How did phytoplankton create Earth's capability for animal life? - Ans:✔✔-Converted Earth from a
chemical reducing state to an oxidizing state
When did photosynthesis begin? - Ans:✔✔-2.5 BYA
When did animals appear on Earth? - Ans:✔✔-1.2 BYA
Cambrian Explosion - Ans:✔✔-Once the Earth became more favorable for animal life, there was a rapid
explosion in animal number and diversity
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