Life Processes
This chapter covers the basic life processes necessary to maintain life: nutrition, respiration, transportation and excretion, in both plants and animals.
Nutrition is the process by which organisms obtain and utilise food to get energy, build body mass, and maintain body functions. It is broadly classified into autotrophic (self-feeding, e.g. green plants via photosynthesis) and heterotrophic (depending on others for food, e.g. animals).
Food passes through the mouth, oesophagus, stomach, small intestine and large intestine. Digestion is aided by saliva (mouth), gastric juice containing HCl and pepsin (stomach), and bile plus pancreatic juice (small intestine), where most absorption of digested food also occurs.
Q. Why is the small intestine in herbivores longer than in carnivores?
Herbivores eat grass and plant material which contains cellulose, a complex carbohydrate that is harder to digest and requires a longer small intestine to allow more time and surface area for complete digestion and absorption.
Autotrophic nutrition: CO2 + H2O (in presence of sunlight and chlorophyll) -> Carbohydrates + O2. This is the overall equation for photosynthesis.
Q. How is the small intestine designed to absorb digested food?
The inner lining of the small intestine has millions of finger-like projections called villi, which greatly increase the surface area for absorption of digested food into the bloodstream.
Which gas is released during photosynthesis?
Correct answer: (B) Oxygen
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in the _______ of the cell.
Mitochondria
Anaerobic respiration releases more energy than aerobic respiration.
False — aerobic respiration (which uses oxygen) releases much more energy than anaerobic respiration, because the glucose molecule is broken down completely into carbon dioxide and water in aerobic respiration, while anaerobic respiration only partially breaks it down.
Q. What is the role of hemoglobin in human beings?
Haemoglobin is a red pigment present in red blood cells that binds with oxygen in the lungs and transports it to all parts of the body; it also helps carry some carbon dioxide back to the lungs.