Life Processes: Movement, Nutrition, and Respiration

• Movement is the most important criterion to determine if something is alive.
• Animals move from place to place or move body parts, plants only move parts like leaves, flowers, roots, and shoots.
• Molecular movements are life processes that happen, keeping an organism alive, even though they are not visible.
• Viruses do not show molecular movement until they infect a cell, which contributes to the debate on whether viruses are alive.
• Life processes maintain life on Earth.
• Nutrition, respiration and transport are life processes common to all living organisms.
• Excretion, control & coordination, growth, movement and reproduction are also key life processes.
• All living organisms need energy, which they get from food, to perform life processes.

Nutrition

• Organisms require energy for various activities, and nutrients supply them.
• Organisms need various raw materials, which nutrients provide, for growth and repair.
• A nutrient is a substance an organism obtains from its environment and uses as a source of energy and for biosynthesis.
• Carbohydrates and fats are nutrients organisms use as a source of energy.
• Proteins and mineral salts are nutrients organisms use for the biosynthesis of body constituents like skin and blood.

Modes of Nutrition

• Modes of nutrition are methods of obtaining food.
• There are two main modes of nutrition: autotrophic and heterotrophic.

Autotrophic Nutrition

• Autotrophic nutrition is a mode in which an organism synthesizes its own food from simple inorganic materials like carbon dioxide and water, with the help of energy.
• Organisms that can make their own food from carbon dioxide and water are called autotrophs, such as all green plants and autotrophic bacteria.
• There are two types of autotrophic nutrition: photosynthetic and chemosynthetic.
• Photosynthetic nutrition: Green plants use solar energy, simple inorganic substances like carbon dioxide and water to form simple sugars, a process called photosynthesis.
• Organisms that utilize this form of nutrition are called photoautotrophs.
• Chemosynthetic nutrition happens in bacteria and other organisms.
• Chemosynthetic nutrition involves the use of energy released by inorganic chemical reactions to produce food.

Heterotrophic Nutrition

• Heterotrophic nutrition the mode in which an organism cannot make its own food from simple inorganic materials like carbon dioxide and water and depends on other organisms for its food.
• Organisms that cannot make their own food are called heterotrophs; for example, all animals, most bacteria, and fungi.

Types of Heterotrophic Nutrition

• Saprotrophic (saprophytic) nutrition
• Parasitic nutrition
• Holozoic nutrition

Saprotrophic Nutrition

• Saprotrophic nutrition involves obtaining food from decaying organic matter like dead plants, dead animals, and rotten bread.
• These organisms partake in extracellular digestion, where they secrete enzymes on the decaying matter to break it down for absorption.
• Organisms showing saprotrophic mode of nutrition are called saprophytes, like fungi (bread mould and mushrooms) and many bacteria.

Parasitic Nutrition

• Parasitic nutrition is when an organism derives its food from the body of another living organism without killing it.
• A parasite can be a plant or animal, and it feeds on another living organism called its host.
• Parasites usually harm the host by spreading diseases.

Types of Parasites

• Endoparasites live inside the body, i.e. liver fluke and tapeworm.
• Ectoparasites live on the outer surface, i.e. ticks, mites, and leeches.
• Obligate parasites live parasitically all the time, i.e. Phytopthora (a fungus that causes potato blight disease).
• Facultative parasites feed parasitically or saprophytically, i.e. Candida fungus.
• Parasitic plants like Dodder/Cuscuta/Amarbel lack chlorophyll, have no leaves, roots are modified into haustoria which penetrate into the host and draw nutrition from their vascular system; they are total parasites.
• Viscum album or mistletoe is a partial parasite. It can photosynthesize but also draws water and minerals from the host plant.

Holozoic Nutrition

• Holozoic nutrition is when an organism takes complex organic food materials into its body through ingestion.
• Digestion occurs, followed by absorption, assimilation, and egestion; such as in humans.

Nutrition in Plants

• Green plants are autotrophs.
• Photosynthesis occurs when green plants make their own food using carbon dioxide, water, and sunlight, in the presence of chlorophyll.
• Oxygen is released during photosynthesis.
• Photosynthesis takes place in the green leaves of a plant in the chloroplasts.
• Food is prepared in the form of glucose.
• Extra glucose is stored as starch in the leaves, flowers, fruits, and stem.
• Green plants convert energy of the sun into chemical energy by making carbohydrates.

Events of Photosynthesis

Photosynthesis occurs in three steps

• Absorption of radiant Sun's energy by chlorophyll.
• Conversion of light energy into chemical energy, with water splitting into hydrogen and oxygen.
• Reduction of carbon dioxide by hydrogen to form carbohydrate glucose, utilizing chemical energy.
• Chlorophyll, sunlight, carbon dioxide, and water are necessary for photosynthesis to take place.

Carbon Dioxide

• Plants obtain carbon dioxide through tiny pores on the leaf surface called stomata, which facilitates gaseous exchange and transpiration.
• Carbon dioxide gas enters the leaves of the plant through the stomata present on their lower surface.
• Each stomatal pore is surrounded by a pair of guard cells.
• Guard cells are kidney-shaped in dicots and dumbbell-shaped in monocots.
• The wall of the guard cell surrounding the pore is thickened and inelastic.
• Guard cells contain cytoplasmic lining, central vacuole, nucleus, and chloroplast.
• The guard cells are surrounded by subsidiary cells that support the movement of the guard cells.
• Guard cells regulate the rate of gas exchange during photosynthesis and transpiration by opening and closing the stomata.

Water

• Plants obtain water for photosynthesis through osmosis.
• Plants absorb water through root hairs.
• Water is transported through the xylem.
• Plants need magnesium for chlorophyll formation, manganese for photolysis of water, and zinc for leaf formation.
• Sap ascends up to the leaf due to root pressure, transpiration pull, and capillary force using adhesion and cohesion of water.
• Chloroplasts, containing the green pigment chlorophyll, in the mesophyll cells of green plants are where photosynthesis happens.

Structure of Chloroplast

• Chloroplasts are organelles covered by a double membrane filled with a colourless ground substance called stroma containing ribosomes, starch granules, lipids, circular DNA, and the thylakoids.
• Thylakoids are flattened sac-like structures present in the stroma.
• Chlorophyll is found on the walls of the thylakoid.
• Chlorophyll-a and Chlorophyll-b are the most important pigments.
• Thylakoids pile up to form the granum.
• The grana are held in position by stromal lamellae.

Mechanism of Photosynthesis

• Light and Dark (Light Independent) reactions are involved in the process of photosynthesis.
• The light reaction occurs in the thylakoids of the chloroplast.
• Chlorophyll molecules in thylakoids absorb sunlight and become activated.
• Water molecules are split using the energy from the sunlight (photolysis).
• The energy released during photolysis is used to produce ATP (energy-rich molecule) from ADP by adding one molecule of inorganic phosphate (iP).
• Photolysis of water produces H+ ions.
• In the phase CO2 is reduced to carbohydrates.
• Six turns of the Calvin Cycle lead to the formation of one molecule of glucose.
• Translocation is the movement of food/glucose, amino acids, and other substances from leaves to other parts of the plant and takes place in pholem tissue.
• Bulk pressure in the sieve tubes moves materials in phloem to tissues with less pressure in both directions (source to sink).
• Sucrose can be converted to glucose or stored as starch.

Leaf Adaptations for Photosynthesis

• Large surface area, leaf arrangement, concentrated chloroplasts, stomata, thin leaves, and network of veins.

Factors that effect Photosynthesis

• Light intensity, carbon dioxide concentration, temperature, water, and polluted atmosphere.

Nutrition in Animals

• Animals are heterotrophs dependent on other organisms.
• Animals can be divided on their feeding habits into the three categories: herbivores eat only plants, carnivores eat only animals, and omnivores eat both plants and animals.
• Energy from the sun provides food for plants and animals.
• The steps of nutrition for animals includes ingestion, digestion, absorption, assimilation, and egestion.

Nutrition in Simple Animals

• Amoeba and Paramecium are two unicellular animals.
• Nutrition is performed by a single cell.
• Amoeba eats tiny plants and animals for food,.
• The mode of nutrition in Amoeba is holozoic where the process of obtaining food is called Phagocytosis.
• Amoeba ingests food by forming pseudopodia (finger like projections), where the food is digested in the food vacuole through a digestion process with digestive enzymes.
• Digested products pass through the cytoplasm in a process of obsorption.
• This is followed by assimilation where food materials are used to produce energy.
• The remaining undigested material is removed through egestion by exocytosis.
• Paramecium also partakes in the same steps; digestion, absorption, assimilation and egestion.
• Paramecium uses hair-like structures (cillia) to sweep food into its mouth.