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Difference between a Parasite and a Saprotrophs: The difference between a parasite and a saprotroph are:

The Plant or animal Organism that grows on the body of another organism and derives nutrition from it is known as a parasite. Parasites are not a disease, but they can spread diseases. Different parasites have different effects. The parasite lives on or in the body of the host. A few examples of parasites are tapeworms, fleas, and barnacles.

The organisms that obtain nutrients from the dead or decaying organic matter are called Saprotroph also called saprophyte or saprobe. Example – Fungi and some bacteria

Why cannot all plants prepare their own food: All plants cannot prepare their own food due to the absence of chlorophyll, which is necessary for photosynthesis, thus the preparation of food cannot be done without chlorophyll.

Mode of nutrition of an Algae :- The mode of nutrition of an algae is autotrophic. They are not aquatic origins but are composed of chlorophyll which is an account of light and air prepares its own food.

Common between a mushroom and a bread mould:-Bread mould and Mushroom are both fungi. They are saprotrophs, i.e. they obtain nutrition from dead and decaying plant or animal matter. Saprotrophs dissolve the dead and decaying matter into a solution form by secreting digestive juices on them and then absorb the soluble nutrition from solution.

Requirements of Photosynthesis:– Photosynthesis requires light energy which is captured by special pigments, most notably chlorophyll. This energy used to create energy – rich carbohydrate molecules (sugar and starch) out of carbon dioxide (CO₂) and water (H₂O).

The process of Photosynthesis in the form of an equation is: – Glucose + Oxygenà Carbon dioxide + water + Energy

Roles of leaves in Photosynthesis:  The leaves of plants capture the sunlight, contains the solar energy which is absorbed by the Chlorophyll. Since the leaves prepare food, it is necessary that the raw materials must reach there. The raw materials required for photosynthesis are carbon dioxide, water and solar energy. The plants absorb carbon dioxide from air, water from soil and energy from the Sun. With these raw materials the leaves prepare their food in the presence of green pigment called chlorophyll. The process of preparing food in the presence of sunlight is called the photosynthesis.

Symbiosis: Symbiosis is the phenomenon by which two organisms maintain relationship with each other to be mutually benefitted. In Symbiotic mode, organism develops a special relationship with certain organism to obtain nourishment. Organisms involved in this type of relationship are called as symbiosis. E.g- Rhizobium bacteria and Leguminous plants are symbiants exhibiting symbiosis.

How are the leaves of the pitcher plant modified to catch insects. : In pitcher plant (nepenthes) the lamins is modified into the pitcher. The rim of pitcher is beautiful color and it is provided with a row of Nectar glands for attracting insects. A pitcher plant has a modified structure which can open and close the mouth of the pitcher. When an insect enters the pitcher, the lid closes and the pitcher secretes digestive juice on it. After digestion of the insect the organic materials including nitrogen from the bodies of the insect are absorbed by the plant. Thus a pitcher plant gets nitrogen by trapping and eating insects.

Heterotrophic nutrition: – is a mode of nutrition  in which organisms depends upon other organisms for food to survive. They can’t make there own food like Green Plants. Heterotrophic organisms have to take in all the organic substances they need to survive.  Different types of Heterotrophic Nutrition are:

• Parasitic Plants : The plants which live on other living plants and obtain their food from them are called parasitic  plants. E.g – Cascuta locally known as Amarbel, has yellow tubular structure which wraps around the stem and branches of the host tree. The roots of cascuta produce haustoris and absorbs readymade food from the tree. Other example is Mistletoe.
• Intivorous Plants: Insectivorous plants are also known as carnivorous plants because they eat insects. The Insectivorous plants lie in the environment deficient in nitrogen. They have special apparatus by which they trap small animals and insects. These are usually green in colour and through the process of photosynthesis they produce their own food like other green plants. E.g. Pitcher plans and venus flytrap are the examples of insectivorous plants.
• Saprophytic plants: Saprophytic plants cannot make their own food as they do not contain chlorophyll. This type of plants obtains food from dead and decaying plants and animals matter. E.g- mushroom and moulds are the examples of saprophytic plants.
• Symbiotic Plants: The lichen symbiosis is an association between fungi and algae which develop into distinct morphologival forms where the algae develop into a phycobiont and the lichen becomes the mycobiont.  E.g- mosses and liverworts.

Why do farmers grow leguminous crops after harvesting of cereals.:  The farmers plant leguminous crops after harvesting cereals to replenish the nitrogen content of the soil. The Leguminous plants contain the symbiotic nitrogen fixing bacteria that live in their root modules. These nitrogen fixing bacteria fix the atmospheric nitrogen into nitrites and nitrates and make them available to the plants for their metabolism.

An ideal example of such bacteria is the Rhizobium sp. They maintain a symbiotic relationship in which the bacteria provides nutrient to the plant and the plant in turn provides food and shelter for the bacteria.

Saprotropes use saprotropes mode of nutrition in which they get nutrition from waste materials. They help in cleaning the environment because they eat the waste substances in the surroundings.