OCR A Level Biology A Module 5 Test Questions With Correct Answers 2024.

5.1.1 COMMUNICATION AND HOMEOSTASIS - Answer 5.1.1 COMMUNICATION AND HOMEOSTASIS why do multicellular organisms need communication systems? e.g hormonal, nervous - Answer So they can respond to changes in the internal and external environment + coordinate the activities of different organs. responses can be behavioural or physiological How does responding to the environment help organisms survive? - Answer - increase chance of survival by responding to changes in external enviro. e.g by avoiding harmful enviro. (too hot/cold) - respond to changes in internal enviro. to make sure conditions are optimal for their metabolism what factors do cells need to keep constant - Answer - conc. of chemicals e.g glucose and sodium - pH - water potential - temperature - low levels of toxins e.g urea - levels of gases so enzyme-controlled reactions can take place Important that CO[2] does not build up as it reacts with water to form carbonic acid which releases H+ ions which lowers pH --> enzymes why is it so important to maintain core body temperature at around 37 °C ?