Life Processes
The essential activities performed by an organism for the maintenance of the body are called life processes. These are the 7 processes all living things do – movement, reproduction, sensitivity, nutrition, excretion, respiration, and growth.
Nutrition: It is the process of intake of food to gain energy and nutrients for the body. Life on earth depends on carbon-based molecules. Most of the food sources are also carbon based.
Through breathing, swallowing etc. various chemical compounds enter our body. Chemical reactions inside our body breakdown these chemical compounds that will help to maintain the various life processes. One of the most common chemical reactions inside our body is Oxidising reduction reaction. Oxygen is required for this reaction. Most of the organisms acquire oxygen from outside the body.
The process of acquiring oxygen from outside the body and to use it in the process of breakdown of food sources is known as respiration.
In single celled organisms entire surface of organism is in contact with the environment. So, such organisms don’t need any specific organs for taking in food, exchange of gases or removal of wastes. A single celled organisms can depend on diffusion to move substances into and out of the cell.
But in case of multicellular organisms all cells are not in direct contact with surroundings so that it requires body parts/ tissues for intake of food and oxygen, and a well transportation systems to carry these food and oxygen from one place to another in the body. During chemical reaction, some of the by- products it generates are not useful for our body. They are removed from us by the process of excretion.
Nutrition
It is the process of intake of food to gain energy and nutrients for the body. There are two types of nutrition:
- Autotrophic Nutrition- organisms make food by themselves.
- Heterotrophic Nutrition- organisms depend on others to make food.
Autotrophic Nutrition
- Autotrophic organisms make food through the process of photosynthesis.
- It is a process by which autotrophs (plants and other organisms) convert light energy into chemical energy in the presence of sunlight and chlorophyll.
- Here they convert simple substances carbon dioxide and water into complex substances carbohydrates and oxygen.
Photosynthesis is represented as:
- The carbohydrate (glucose) obtained from photosynthesis is utilised for providing energy to these organisms. The extra glucose not utilised immediately gets stored in the form of starch. This starch serves as the internal energy reserve.
Events during photosynthesis:
- Chlorophyll absorbs light energy(sunlight). Light energy gets converted to chemical energy and, water molecule gets split into hydrogen and oxygen.
- Reduction of carbon dioxide to carbohydrates.
- Finally, oxygen gets released into the atmosphere.
How does a plant obtain Carbon dioxide?
- Plants have a tiny pore on the surface of the leaves called Stomata.
- The exchange of gases takes place through these pores on leaves.
- The guard cells that cover the stomata also; control the opening and closing it.
- The plants take up water from roots. When the water reaches the guard cells, they start to swell and move apart, causing the pores to open.
- Site of Photosynthesis- inside the chloroplast within the Thylakoid membrane. The green colour of plants is due to the presence of chlorophyll pigment. Besides these, autotrophs require other raw materials for building their body. Water is taken up from the soil by roots.
- It also takes materials like nitrogen, phosphorous, iron, and magnesium from the soil. Synthesis of proteins and other compounds requires nitrogen.
Heterotrophic Nutrition
- Heterotrophs depend on other organisms for food as they are unable to make food of their own. In heterotrophic nutrition, complex food materials get broken into simpler absorbable substances.
How do organisms obtain their Nutrition?
- The digestive system is different in various organisms.
- Single-celled organisms use the entire surface of the body to take food.
- As the complexity of organism increases, various parts become specialised to perform different functions.
Amoeba
- Amoeba takes in food using a finger-like extension of the cell surface called pseudopodia.
- It fuses with the food particle to form a food vacuole.
- The complex substances get broken into simple substances inside this vacuole, which diffuse into the cytoplasm.
Paramoecium
- Paramoecium obtain their food using tiny hairs called cilia
Nutrition in Human Beings
- We humans obtain nutrition by the process of digestion of food. Digestion involves various steps and takes place in the digestive system. The digestive system has two parts:
- Alimentary canal-A 30ft long tube running from mouth to anus.
- Associated glands- release chemicals or enzymes for digestion to happen.
- The alimentary canal consists following parts:
- Mouth
- Buccal cavity- contains teeth, tongue, and salivary gland
- Pharynx
- Oesophagus
- Stomach
- Small intestine- the longest part of the alimentary canal
- Large Intestine
- Anus
- Food enters our mouth and gets crushed by our teeth. The fluid called saliva secreted by the salivary glands wets this food to make its passage smooth. Salivary amylase, an enzyme in saliva, breaks starch (a complex molecule) into simple sugar. The saliva mixes the food well while the tongue pushes it to the throat. The linings of the canal have muscles that contract rhythmically to make the food movement forward.
- The food now passes through the Oesophagus(food-pipe) to the stomach. The stomach expands when the food enters it.
- The gastric gland present in the stomach helps in digestion. It releases hydrochloric acid (HCl), a protein-digesting enzyme called pepsin, and mucus. The hydrochloric acid creates an acidic medium which in turn activates the pepsin. The HCL helps to maintain the pH of the stomach. The mucus helps in protecting the inner lining of the stomach from the action of acid.
- The food now enters the small intestine. It is the longest part of the alimentary canal. The complex digestion of carbohydrates, proteins, and fats takes place here. For this purpose, it receives secretions of the pancreas and liver. The food from the stomach is acidic.
- For the pancreatic enzyme to act, the food must be made alkaline. Bile juice from the liver helps in this process and, it also helps with fats. The large globules of fats present in the intestine are broken down into smaller globules by bile salts.
- The pancreas secrets pancreatic juice that contains enzymes like trypsin and lipase.
- Trypsin is for digesting proteins and lipase for breaking down fats.
- The enzymes present in the small intestine convert:
- Proteins to amino acids.
- Complex carbohydrates into Glucose.
- Fats into fatty acid and glycerol.
- The walls of the small intestine take the digested food.
- The inner linings of the small intestine have many finger-like projections called villi that help in increasing the surface area for absorption.
- The villi have blood vessels that take the absorbed food to every cell of the body.
- The unabsorbed food goes to the large intestine. The walls of the large intestine absorb water from this food. The remaining material gets removed through the anus.
Respiration
Anaerobic respiration
- Within the cytoplasm, the glucose (a six-carbon molecule) gets broken into pyruvate (a three-carbon molecule). In organisms like yeast, during fermentation, this pyruvate is converted to ethanol and carbon dioxide.
- Since this process takes place in the absence of oxygen it is called anaerobic respiration. The pyruvate gets converted to lactic acid (a three-carbon molecule) when there is a lack of oxygen in our muscle cells. Cramps are caused in our muscles during sudden activities due to the build-up of lactic acid.
Aerobic respiration
- In mitochondria, the pyruvate breaks down to give carbon dioxide and water. Since this process takes place in the presence of oxygen (air), it is called aerobic respiration. ATP gets synthesised using the energy released during cellular respiration.
- The energy released during the aerobic process is higher than in anaerobic respiration.
Respiration in Human Beings
- Air enters our body through the nostrils. This air gets filtered by the fine hairs inside the nose. The passage also has mucus which helps in this process. The air then passes through the throat and into the lungs. The throat has rings of cartilage to ensure that the air passage does not collapse.
- Inside the lungs, the passage gets divided into smaller tubes that end in balloon-like structures called Alveoli. The exchange of gases can take place on the surface of alveoli. The walls of alveoli contain a network of blood vessels.
- When we breathe air, our ribs are lift and diaphragm gets flattened and, the chest cavity becomes large. Because of this, the air is sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body and releases it into the alveoli. The blood in the alveolar blood vessels absorbs the oxygen in the alveolar air. It then transports to all the cells in the body.
Transportation
Transportation in Human beings- Circulatory System
- It helps transport nutrients, oxygen, carbon dioxide, hormones, blood cells from one part to other parts of the body. Double circulation takes place in humans that is blood goes through the heart twice during one cardiac cycle. The heart has different chambers to prevent the mixing of oxygen-rich blood and carbon dioxide-rich blood. There are four chambers in our heart- two atria(atrium) and two ventricles.
- The Vena cava carries the carbon dioxide blood to the upper right atrium. As the right-side atrium contracts, the blood gets pushed to the lower right ventricle. The right-side ventricle contracts, it thrust the blood to the pulmonary artery. The pulmonary artery carries the blood to the lungs for oxygenation.
- The pulmonary vein carries the oxygen-rich blood to the left atrium, and the moment the left atrium contracts, the blood flows to the left ventricle. As the left ventricle contracts, blood flow to the Aorta. From the aorta, blood gets carried to all the cells in the body.
Transportation in Plants
- A proper system of transportation is requisite in plants. The transport system will transfer energy from leaves and raw materials from roots. The two pathways get constructed as independent tubes. One is the xylem and, the other is the phloem.
Transport of water
- The vessels and tracheids of roots, stems, and leaves get interconnected in the xylem tissue. Thus, forming a continuous system of water-conducting channels reaching all parts of the plant.
- The cells (at the roots) in contact with soil take up the ions. It causes a difference in the concentration of ions between the root and the soil. The water moves to the root from the soil to eliminate this difference. Now there is a steady movement of water into the root xylem. Thus, water gets pushed upwards.
Transport of food and other substances
- Phloem transports food produced during photosynthesis from leaves to other parts of the plant. This process is Phloem transports amino acids and other substances, which get transported to the organs of roots, fruits, and seeds.
- The translocation of food and other substance happens in a sieve tube in the upward and downward direction. In phloem, translocation takes place with the use of energy from ATP. It increases the osmotic pressure of the tissue, making the material in the phloem move to tissues with less pressure. Thus the materials are moved according to the plant’s needs.
Excretion
- The process of removal of undigested or harmful metabolic substances from the body is called Excretion. Unicellular organisms remove waste by simple diffusion. The complex multicellular organism has specialised organs to perform this function.
Excretion in Humans
- Our excretory system includes
- A pair of kidneys- located in the back abdominal region.
- A pair of ureters
- A urinary bladder
- A urethra
- Our excretory system includes
The urine gets produced to filter waste products from the blood. In the kidney, nitrogenous waste like urea or uric acid gets removed