IMPORTANT TERMS

Carnivores-                       Animals which eat only flesh of other animals as their food.

Herbivores-                       Animals which eat only plants as their food.

Omnivores-                       Those animals which can eat both plants as well as animals.

Parasite-                           A plant or organism that lives on or inside other organism and derives its food from that organism. E.g. Cuscuta

Endoparasite-                   Parasites which live inside the body of host.

Exoparasite-                     Parasites which live outside the body of host.

Autotrophs-                       Organisms which make food themselves from simple substances, by the process of photosynthesis. E.g. Mango tree, rose plant etc

Heterotrophs-                    Organisms which cannot prepare their own food and take food from other animals or plants. E.g. Pitcher plant

Saprotrophs-                     Those organisms which feed on dead and decomposed plant and animals as their food are known as Saprotrophs. E.g. Fungi, mushroom, yeast etc.

Autotrophic Nutrition -       Mode of nutrition in which organisms make their own food by simple substances is called autotrophic nutrition. E.g. Green plants

Saprophytic Nutrition-        Mode of nutrition in which organisms take in food from dead and decaying matter is called saprophytic nutrition. E.g. Fungi

Heterotrophic Nutrition-      Mode of nutrition in which organisms take their food from other plants or animals is called heterotrophic nutrition. E.g. Tiger.

Parasitc Nutrition-              Mode of heterotrophic nutrition in which an organism lives on the body surface or inside the body of another type of organism (known as a host). The parasite obtains nutrition directly from the body of the host.

NUTRITION
Nutrition is the mode of intake of food by the organism and its utilization by the body. All organisms need food to perform their life processes. Food comprises of different nutrients which include carbohydrates, proteins, fats, vitamins and minerals. Food provides us energy, help us to grow, repair the damaged parts in our body. Living organisms include microorganisms, plants and animals.

Plants obtain their nutrition by various modes. The mode of nutrition in plants can be autotrophic mode or heterotrophic mode. Plants can be classified into autotrophs and heterotrophs.

• Autotrophic plants can synthesize their own food by the process of photosynthesis. 
• Heterotrophic plants cannot synthesize food on their own but depend on other organisms for their nutrition. Heterotrophic plants can be further classified into parasites, saprophytes and symbiotic and insectivores plants. 

 

Mode of Nutrition in Plants
Heterotrophic	Autotrophic
Parasitic E.g. Cuscutta	Phototrophic E.g. All Green plants
Saprophytic E.g. Fungi, Mushroom	Chemotrophic E.g. Nitrifying bacteris
Insectivores E.g. Venus fly trap
Symbiotic

 

Autotrophic mode of nutrition – Photosynthesis

It is an autotrophic mode of nutrition. Photosynthesis is a process by which green plants can synthesize glucose from raw materials like carbon dioxide and water in the presence of sunlight and chlorophyll. Photosynthesis involves the conversion of solar energy into chemical energy to synthesize starch.

Required Conditions for Photosynthesis are

Presence of the following

• Carbon dioxide                           
• Water
• Sunlight
• Chlorophyll

Facts about photosynthesis

All chlorophyll-containing plants, including algae, and some plants with red, brown or other dominant pigments, make their food by photosynthesis.

• Leaves are considered as food factories of a plant.
• Roots absorb water and minerals from the soil and are transported to different parts of the plant with the help of a vascular tissue called Xylem.
• Roots contains Root Hairs which increase the surface area of roots and hence help in increased absorption of water and minerals.
• Stomata are small pores present in the lower epidermis of the leaf to take-in carbon dioxide from the air. The opening and closing of stomata pores is controlled by Guard cells.
• Leaves have special structures called as chloroplasts. Chloroplasts possess chlorophyll, a green colour pigment present in the leaf captures energy from sunlight. Sun is the ultimate source of sunlight for all the living organisms on earth.
• Plants synthesize glucose using carbon dioxide and water in the presence of sunlight.
• Oxygen and water are released as by-products through the stomata during daytime.
• Glucose is a carbohydrate. Glucose synthesised by the process of photosynthesis is converted into complex compounds like starch and cellulose. Starch is stored in different parts of the plant.
• Plants also prepare proteins with the help of nitrogen which is obtained from the soil.  
• The minerals dissolved in water are used to convert sugar synthesised into carbohydrates, proteins and fats.
• The food synthesized is transported to other parts of the plant for utilisation and storage through another type of vascular tissue called Phloem.
• These food components stored are the source of energy for other heterotrophic plants and animals.

Heterotrophic Mode of Nutrition

Heterotrophic plants do not possess chlorophyll. Therefore, they cannot produce their own food using the process of photosynthesis. Heterotrophic plants obtain food from other plants by following either a parasitic, saprophytic or symbiotic mode.

a) Parasitic mode:

The organisms which exhibit parasitic mode of nutrition are called as parasites. Parasites obtain their nourishment from other living organisms. In parasitic mode of nutrition, plants depend on other plants or animals for their nourishment. Such plants are called as parasites and the ones on which parasites depend are called as hosts. E.g. Wheat rust, Corn Smut.

• Mistletoe is another parasitic plant which depends on other organisms for its nourishment.
• Cuscuta (Amarbel in Hindi) also known as dodder is a parasitic plant which develops special roots called Haustoria. Haustoria penetrate deep into host plant tissues and absorb the nutrients from them.

b) Insectivorous mode:

These are the plants with special leaves that are modified into special structures. These structures have the ability to trap the organisms.

• Nepenthes, also called as pitcher plant has its leaves modified into tubular pitcher like structure closed with leaves. These have a network of fibres which entangle the trapped organism and later digest it by secreting hydrolysing enzymes to digest them.
• Venus fly trap feeds on small animals and insects to obtain their nourishment. Its leaves are modified to trap insects. The inner surface of leaves have short, stiff hair. When an insect touches its hairs, the leaves shut in less than a second. These plants especially obtain the nitrogen they require from insects and small animals as the soil on which these plants grow is deficient in nitrogen.
• Bladderwort bear a number of small pear like bladder structures, which act like trapdoors and suck in small insects in less than a second.
• Drosera (commonly known as sundews) have long thin structures called tentacles, which have drops of sticky substance at their ends. The insects sticks to it and is then digested by plant.

c) Saprophytic mode:

The plants which exhibit saprotrophic mode of nutrition are called as saprotrophs. These plants obtain their nutrition from dead and decaying organic matter. Saprotrophs secrete digestive juices onto dead and decaying matter to dissolve it and then absorb nutrients from it.

• Indian pipe which is found on dead and rotting material, inhabits fungus in its roots. These extend their mycelium and secrete enzymes to digest the decaying matter.
• Coral roots are another type of plants exhibiting saprophytic nutrition.

d) Symbiotic mode:

Symbiosis is the phenomenon by which two organisms maintain relationship with each other to be mutually benefitted. In symbiotic mode, organisms develop a special relationship with certain other organisms to obtain nourishment. Organisms involved in this type of relationship are called as Symbionts.

• Rhizobium bacteria and Leguminous plants are symbionts, exhibiting symbiosis. Plants cannot utilise atmospheric nitrogen directly. Hence, leguminous plants establish a symbiotic relationship with bacteria like Rhizobium. Both the organisms of symbiotic relationship are mutually benefited. Leguminous plant provides shelter and nourishment for the bacteria and in turn bacteria fix atmospheric nitrogen to the plant.
• Lichens form a very good example of symbiotic relationship. Lichens are formed by the symbiotic relationship between algae and fungi sharing a single colony. Fungus provides water, nutrients and shelter in the form of network formed by mycelium. Algae synthesises the food for entire colony by the process of photosynthesis. 

 

• Differences between a Parasite and a Saprophyte

PARASITE	SAPROPHYTE
An organism that depends on other organisms for its food and nourishment.	An organism that obtains its nourishment from dead and decaying.
It develops special organs like suckers, hooks or Haustoria to obtain nourishment from the host.	It is capable of secreting some enzymes which can digest complex molecules of into simpler forms.
e.g. Cuscuta (Amarbel), Nephenthes.	e.g. Fungi, Bacteria.

 

CELLS

In biology, cell is the smallest unit of life. They are the building blocks of plants and animals.

There are mainly two types of cell:- Animal cell and Plant cell.

Distinctive features of a Cell

• Cell wall is the outermost rigid covering of the plant cell. It is not present in animal cell.
• Cell membrane or the plasma membrane is the outer lining of the cell inside the cell wall. It protects the cell and controls the passage of substances in and out of the cell.
• Cytosol or cytoplasm is the gel-like matrix inside the cell membrane which constitutes all other cell organelles and carry out all the activities of life process.
• Nucleus is the control center of the cell. It is a membrane bound structure which contains the hereditary material of the cell - the DNA.
• Chloroplast is a plastid with green pigment Chlorophyll. It traps light energy and converts it to chemical energy by the process of photosynthesis. It is not present in animal cell.
• Inside each chloroplast there are sacks of discs called a Thylakoid. They contain chlorophyll and help to absorb light. The stacks of thylakoid are called Grana. These grana are arranged in an aqueous fluid called Stroma.
• Mitochondria carries out cellular respiration and provides energy to the cells.
• Vacuoles are the temporary storage center of the cell. Plant has a big large vacuole whereas animal cell contains small vacuoles.
• Ribosomes are smallest and the most abundant cell organelle. It comprises of RNA and protein. Ribosomes are sites for protein synthesis.

 

INTRESTING FACTS

 

• The earth has more than 80,000 species of edible plants.
• 90 percent of the foods that humans eat, come from just 30 plants.
• 80 percent of the Earth’s original forests have been cleared or destroyed.
• Just 10 percent of the world’s plant-rich areas are protected.
• 68 percent of plants are in danger of going extinct.