The term meristem was given by Carl Wilhelm von Nägeli. Meristematic tissue contains undifferentiated cells which are the building blocks of the specialized plant structures.

Meristematic tissues contain living cells with varied shapes. They possess a large nucleus devoid of the vacuole. The cells have no intercellular space. The zone where these cells exist is known as meristem.

The cells of the meristematic tissue divide actively to form specialized structures such as buds of leaves and flowers, tips of roots and shoots, etc. These cells help to increase the length and girth of the plant.

Dehydration happens when your body doesn't have as much water as it needs. Without enough, your body can't function properly. You can have mild, moderate, or severe dehydration depending on how much fluid is missing from your body.

  Soil contains minerals such as Iron, Zinc, Nitrogen compounds, etc. that are all essential to sustaining life.
It also holds water and makes it available for plants to use.
Soil also contains ores from which we can extract metals such as iron, copper, gold, and aluminum.

The plants which obtain their nutrients from other plants are called parasitic plants.

For example – Dodder or cuscuta

• Plants take up carbon-dioxide from the atmosphere through the tiny pores known as stomata present on thesurface of the leaves and surrounded by ‘guard cells’.
• The process of photosynthesis releases oxygen in the atmosphere during the synthesis of food.
• Plants absorb the water and minerals from the soil with the help of deep penetrated roots inside the soil and transport them to the leaves of the plants where synthesis of food takes place.
• The green pigment present in leaves known as chlorophyll helps the leaves of plant to capture the sunlight that act as the source of energy to carry out the process.
• After this the chlorophyll holding the cells of leaves in the presence of sunlight, carbon dioxide and water to produce carbohydrates in the leaves and is stored in the plants in the form of energy.

• Amoeba is a microscopic single-celled organism found in pond water which has a cell membrane, a round, dense nucleus and many bubble like vacuoles.
• The shape of amoeba is variable.
• It has tiny finger like projections called pseudopodia or false feet for movement and capture of food.
• It eats tiny organisms by spreading out its pseudopodia around its food particle and then engulfing it.
• The food gets trapped inside food vacuole, into which digestive juices are secreted and convert them into simpler substances.
• The digested food is then absorbed which is required for growth, maintenance and multiplication.
• The undigested food is expelled out by vacuole.

Plants, algae and few bacteria are said to be autotrophic as they are able to prepare their own food, with the help of sunlight, air, and water. Conversely animals like cow, dog, lion, horse, etc. are said to be heterotrophic as they cannot prepare their own food and depends directly or indirectly on others for their nutrition.

Some plants cannot produce their own food and must obtain their nutrition from outside sources—these plants are heterotrophic. This may occur with plants that are parasitic or saprophytic. Some plants are mutualistic symbionts, epiphytes, or insectivorous.

Plant Parasites

A parasitic plant depends on its host for survival. Some parasitic plants have no leaves. An example of this is the dodder which has a weak, cylindrical stem that coils around the host and forms suckers. From these suckers, cells invade the host stem and grow to connect with the vascular bundles of the host. The parasitic plant obtains water and nutrients through these connections. 

Saprophytes

A saprophyte is a plant that does not have chlorophyll and gets its food from dead matter, similar to bacteria and fungi (note that fungi are often called saprophytes, which is incorrect, because fungi are not plants). Plants like these use enzymes to convert organic food materials into simpler forms from which they can absorb nutrients. 

A symbiont is a plant in a symbiotic relationship, with special adaptations such as mycorrhizae or nodule formation. Fungi also form symbiotic associations with cyanobacteria and green algae (called lichens). Lichens can sometimes be seen as colorful growths on the surface of rocks and trees. The algal partner (phycobiont) makes food autotrophically, some of which it shares with the fungus; the fungal partner (mycobiont) absorbs water and minerals from the environment, which are made available to the green alga. If one partner was separated from the other, they would both die.

Nutrition losses can happen due to the following reasons also.

• Leaching
• Denitrification
• Volatilization
• Crop removal
• Soil erosion and runoff  etc.,

The process by which plants make their own food in the presence of sunlight, carbon-dioxide present in air, water, minerals and chlorophyll present in leaves is termed as photosynthesis.

• Plants absorb the water and minerals from the soil with the help of deep penetrated roots inside the soil and transport them to the leaves of the plants where synthesis of food takes place.
• The green pigment present in leaves known as chlorophyll helps the leaves of plant to capture the sunlight that act as the source of energy to carry out the process.
• After this the chlorophyll holding the cells of leaves in the presence of sunlight, carbon dioxide and water to produce carbohydrates in the leaves and is stored in the plants in the form of energy.

• Absorption is the process by which digested food passes through the blood vessels in the wall of intestine.
• The inner wall of small intestine has finger like projections called villi which increases the surface area for absorption of food.

Symbiosis is the combination of two Greek words ‘Sym’ means ‘with’ and ‘biosis’ means ‘living’, which means living together. In symbiosis or mutualism two different types of organisms live and work together for their mutual benefit from each other. They share shelter and nutrients, e.g. Lichens. Lichens are composite organisms composed of fungus and alga. Fungus is a saprophyte and alga is an autotroph. The Fungus supplies water and minerals to the cells of the alga while the alga supplies food; prepared by photosynthesis.

Step I:  The first step is the removal of the fleece of the sheep along with a thin layer of skin. This process is termed as shearing. The hair provides woollen fibres that are then processed to obtain woollen yarn.

Step II: The sheared fleece is systematically washed in tanks in order to remove the grease, dust and dirt. This is known as scouring.

Step III: The scoured hair is then sorted and sent to a factory where hair of different textures are separated or sorted.

Step IV:  Here the small fluffy fibres, called burrs, are separated from the hair and the hair is scoured again and dried. The wool is then ready to be drawn into fibres.

Step V: The fibres are dyed into various vibrant colours because the natural colour of the fleece is black, brown or white.

Step VI: The fibres are then straightened, combed and finally rolled into yarn. The longer fibres are made into wool for sweaters whereas the shorter fibres are spun and woven into woollen cloth.

Adult house flies feed where they find decaying matter, sugar, or flower nectar. They feed on honeydew left by aphids or other bugs. Adult houseflies never have chewing mouthparts. They use saliva to change solids to liquids. Sponge-like mouthparts pick up semi-liquid foods, such as feces and decaying matter.

Fly larvae feed on moist organic matter. They need to store away a great deal of protein so as adults they have energy to search for food, find a mate, and produce eggs. They have sharp, curved “mouth hooks” used to scrape and cut solid food before flooding it with digestive enzymes.

Grass eating animals are called ruminant animals. Example – cow. They have special stomach to digest cellulose present in the grass. Their stomach is large and is divided into four compartments.

1. Rumen:
2. Omasum 
3. Abomasum
4. Reticulum

   Rumen is the first and the biggest compartment of a cow’s stomach. It contains cellulose digesting bacteria. When a cow eats grass as food, it does not chew it completely but swallow it and gets stored in the rumen. The bacteria present in the rumen start to digest cellulose and gets partially digested. The partially digested food/grass in the rumen of a cow is called cud. After some time, the cud is brought back into the mouth and is chewed thoroughly. That is why, a cow moves its jaws from side to side and chew continuously even when it is not eating grass.

   The process by which the cud is brought back from the stomach to the mouth of the animal and chewed again is called rumination. The animals which chew the cud are called ruminants. When the cud is thoroughly chewed in the mouth of the cow, it is swallowed and goes into the other compartments of the cow’s stomach and then into the small intestine for complete digestion and absorption.  

The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms. 

Turmeric: Turmeric is also used as natural indicator. Turmeric is of yellow colour. Turmeric paper turns into red when it is dipped into basic solution. Turmeric paper does not change its colour with acid.

Turmeric: Turmeric is also used as natural indicator. Turmeric is of yellow colour. Turmeric paper turns into red when it is dipped into basic solution. Turmeric paper does not change its colour with acid.

The slightly digested food reaches the stomach through oesophagus for further digestion where it is broken down into smaller pieces. The inner lining of the stomach secretes gastric juice which includes mucus, hydrochloric acid and digestive juices. Mucus protects the lining of the stomach from hydrochloric acid. Hydrochloric acid makes the medium in the stomach acidic to facilitate the digestion of proteins. The digestive juices break down the protein into simpler substances. Then the partially digested food goes into the small intestine.

The small intestine is a very long and narrow tube where complete digestion of food takes place. It receives secretions of liver, pancreas and its own walls. Liver secretes liquid called bile which helps in the digestion of fats and converts them into small droplets. Pancreas secretes pancreatic juice which breaks down fats into fatty acids and glycerol. Pancreatic juice also breaks down carbohydrates and proteins into simpler forms. The intestinal juice secreted by the walls of small intestine breaks down the carbohydrates into glucose, proteins into amino acids. Thus, the food gets completely digested in small intestine.