Roots and tubers are plants yielding starchy roots, tubers, rhizomes, corms and stems. They are used mainly for human food (as such or in the processed form), for animal feed and for manufacturing starch, alcohol and fermented beverages including beer. ... FAO distinguishes among seven primary root and tuber crops. Potato is considered as a stem vegetable because it grows in underground stems, known as stolons. Potato tubers are considered to be thick stems that have the buds sprouting stems and leaves. 

Imbibition is a special type of diffusion that takes place when water is adsorbed by solids-colloids causing an increase in volume. Examples include the absorption of water by seeds and dry wood. If there is no pressure due to imbibition, seedlings would not be able to emerge from soil. Imbibition is the process of water absorption through a solid substance, whereas, osmosis is the process of movement of water from higher concentration to lower concentration through a semi-permeable membrane.

The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. 

The origin of life on Earth is a scientific problem which is not yet solved. There are many ideas, but few clear facts.

Most experts agree that all life today evolved by common descent from a single primitive lifeform. It is not known how this early life form evolved, but scientists think it was a natural process which happened about 3,900 million years ago. This is in accord with the philosophy of naturalism: only natural causes are admitted.

It is not known if metabolism came first or genetics. The main hypothesis which supports genetics first is the RNA world hypothesis, and the one which supports metabolism first is the protein world hypothesis.

A granum (plural grana) is a stack of thylakoid discs. Chloroplasts can have from 10 to 100 grana. Grana are connected by stroma thylakoids, also called intergranal thylakoids or lamellae. Grana thylakoids and stroma thylakoids can be distinguished by their different protein composition. Chlorophyll, the primary pigment used in photosynthesis, reflects green light and absorbs red and blue light most strongly. ... The green pigment chlorophyll is located within the thylakoid membrane, and the space between the thylakoid and the chloroplast membranes is called the stroma

Characteristics of phylum Arthropoda:

(i) Triploblastic, bilaterally symmetrical and metamerically segmented animals.

(ii) Body segments are grouped into two regions - cephalothorax (head and thorax together) and abdomen, or three regions - head, thorax and abdomen. Anterior part of body forms a distinct head, bearing sense organs and brain.

(iii) Exoskeleton of cuticle, containing protein, lipid, chitin and often calcium carbonate is secreted by underlying epidermis and shed (moulted) at intervals.

(iv) Alimentary canal is complete; mouth and **** lie at opposite ends of the body.

(v) Respiration through general body surface, by gills, air tubes (tracheae) or book-lungs.

(vi) True nephridia is absent. Excretion is by coelomoducts, malphigian tubules or green or coxall glands.

(vii) Sexes are usually separate; sexual dimorphism is well marked in several forms.

(viii) Fertilisation is usually internal, oviparous or ovoviviparous and often with metamorphosis.

Chrysophytes are freshwater algae which are generally found in water having low level of calcium.  It contains light harvesting complex like chlorophyll a and c, xanthophylls, beta-carotene, fucoxanthin etc.  Thats why they are photosynthetic and can produce their own food, hence they are chief producers in oceans.

The inclusion bodies are tiny particles found freely suspended and floating within the cytoplasmic matrix. Therefore, also referred to as cytoplasmic inclusions. These cell inclusions are formed with decreasing pH and from the pool of soluble fusion proteins within the cell. They are the elementary bodies, formed during infectious diseases or within the virus-infected cells such as rabies, herpes, measles, etc.

Proteins that speeds up the rate of a chemical reaction in a living organism. An enzyme acts as catalyst for specific chemical reactions, converting a specific set of reactants (called substrates) into specific products. Without enzymes, life as we know it would not exist. Enzymes catalyze nearly all of the chemical reactions that occur in biological systems. Enzymes are generally proteins but also include catalytic DNA and catalytic RNA. Enzymes work by binding to reactant molecules and holding them in such a way that the chemical bond-breaking and bond-forming processes take place more readily. Reaction coordinate diagram showing the course of a reaction with and without a catalyst. With the catalyst, the activation energy is lower than without.

Economic Importance of Gymnosperms:

1. Ornamental value: A number of gymnosperms are grown as ornamental plants, e.g., Cycas, Araucaria, Thuja etc.

2. Food Value:

i. ‘Sago’ starch obtained from pith and cortex of stem of C. revolute, C. rumphi etc.

ii. ‘Seed starch’ obtained from seeds of Cycas rumphii, Dioon edule etc. It is prepared into flour and cooked before eating.

iii. Seeds of Pinus gerardiana (chilgoza) are edible.

iv. ‘Kaffir bread’ prepared from the stem pith of Encephalartos.

v. Young leaves of Cycas cooked as vegetables.

3. Medicinal value:

i. Ephedrine (alkaloid) extracted from Ephedra used in treating asthma, cough, cold, bronchitis etc.

ii. Tincture of Ephedra is a cardiac stimulant.

iii. The juice extracted from young leaves of Cycas revoluta is used for curing blood vomiting and flatulence.

4. Industrial Use:

i. Gum-Cycas gum used as adhesive, antidote for snake bites and using malignant ulcers.

ii. Tannins – Tannins extracted from bark of Araucaria, Pinus, Sequoia etc. used in leather industry.

iii. Canada balsam – It is turpentine obtained from Abies balsamea and used as a mounting medium in biological preparations.

iv. Amber (fossil resin) – obtained from Pinus succinifera. Wood of Pinus is used for doors, poles, beams, railway wagon flooring etc.

v. Plywood prepared from Podocarpus.

vi. Papers like newsprints, writing and printing papers are being prepared from the wood pulp of Pinus, Picea,Abeis, Gnetum etc.

vii. The leaves of cycads are used for preparing baskets, mats, hats, brooms etc.

viii. The fibres obtained from the leaves of Cycas and Macrozamia are used for stuffing pillows and making mattresses.

5. Source of oils:

i. Oils extracted from seeds of C. revoluta, Macrozamia reidlei, Pinus cembra and Cephalotaxus drupacea are used as edible oils.

ii. Red cedar wood oil extracted from the heart wood of Juniperus virginiana is used for cleaning microscopic preparations and for oil immersion lenses.

iii. Oils obtained from Cedrus deodara, Ciyptomeria japonica and Cupressus serm-perivirens are used in preparations of perfumes.

 1) They are sites of cellular respiration.
 2) They uses oxygen to oxidise carbohydrates and fats present in the cell to carbon dioxide and water.Oxidation releases energy,a portion of which is used to form ATP.  Since mitochondria synthesises energy rich compound ATP it is called powerhouse of cell.  ATP is called energy carrier or energy currency of the cell.
 3) Mitochondria are able to make some of their own proteins,so they are regarded as semiautonomous organelles.

Sclerenchyma – These are long, dead cells with a deposit of lignin in their cell wall.  They have no intercellular spaces. They provide strength to the plant and its structures. Sclerenchyma occur around the vascular tissues in stems, in the veins of leaves, and in the covering of seeds and nuts. Sclerenchymatous cells are lignified and elongated dead cells. Fibrous region of the plant is made up of sclerenchymatous tissue, a collection of sclerenchymatous cells.  Fibres and sclereids are two types of sclerenchymatous cells. Sclereids usually shorter than fibres are lignified elongated dead cells.  

Characteristics of Kingdom Plantae:

1. They are multicellular, autotrophic and eukaryotic.
2. They possess cell wall.
3. They are autotrophs and use chlorophyll for photosynthesis.

Classification of plants is done at three levels on the basis of:

1. Presence or absence of well-differentiated body.
2. Presence or absence of vascular tissue.
3. Ability to bear seeds, which could be naked or enclosed in fruits.

The important divisions of Plantae are Thallophyta, Bryophyta, Pteridophyta, Gymnospermae and Angiospermae.

Thallophytes, Bryophytes and Pteridophytes possess inconspicuous reproductive organs and are called Cryptogams. Gymnosperms and Angiosperms are grouped under Phanerogamae, since they possess well-differentiated, seed producing reproductive tissues.

Scavenger fish are bottom feeders that eat debris, dead fish, and algae on the floor of a body of water. Scavengers help keep water clean and are a major asset to the environment in which they live. Other catfish and loach species are scavengers and will hunt around the aquarium floor looking for waste food material. These fish often use sensitive barbels to locate food.