The sequential events in the heart which are repeated cyclically is called cardiac cycle and it consists of systole (contraction) and diastole (relaxation) of both the atria and ventricles. The duration of a cardiac cycle is 0.8 seconds. Periods of cardiac cycle are atrial systole (0.1 second), ventricular systole (0.3 second) and complete cardiac diastole (0.4 second).

The definition of metagenesis is the reproduction cycle of an organism that alternates between sexual and asexual generations. An example of metagenesis is the reproduction cycle of a cnidarian.

The cnidarians exhibit alternation of generations in which one generation is the Polyp form while the other is the Medusa form 

Working of Human blood circulatory system takes place in the steps below:

(i) When the muscles of all the four chambers are relaxed, the pulmonary vein brings the oxygenated blood from the lungs in the left atrium of the heart.

(ii) When the left atrium contracts, the oxygenated blood is pushed into the left ventricle through valve V₁.

(iii) When the left ventricle contracts, the oxygenated blood enters the main artery called aorta from which it goes to the different body organs through small branches called arterioles and capillaries.

(iv) The main artery carries the blood to all the organs of the body head, arms etc except the lungs. The oxygenated blood gives off oxygen, digested food and dissolved materials to the body cells. The carbon dioxide produced in the cells enters the blood. The deoxygenated blood enters main vein called vena cava which carried it to the right atrium of the heart.

(v) When the right atrium contracts, the deoxygenated blood enters right ventricle through valve V₂.

(vi) When the right ventricle contracts, the deoxygenated blood enters the lungs through pulmonary artery and releases carbon dioxide and absorbs fresh oxygen from air. The blood becomes oxygenated again and is sent to the left atrium of heart by pulmonary vein for circulation in the body. This whole process is repeated continuously.

Satiety is defined as the state of inhibition over further eating that follows the end of an eating episode and arises from the consequences of food ingestion. Satiety is the feeling of fullness and the suppression of hunger for a period of time after a meal. • The feeling of satiety occurs due to a number of bodily signals that begin when a food or drink is consumed and continue as it enters the gut and is digested and absorbed. •

WBCs are irregular in shape, but have a nucleus and an outer buffer coat. 120 days. There is only one type of RBCs found in the blood. There are various types of WBCs with distinct functions in the blood:neutrophils, T lymphocytes, B lymphocytes (plasma cell) monocytes (macrophage), eosinophils, basophils.

Tracheid consists of a single elongated cell with pointed ends and a secondary, cellulosic wall thickened with lignin (a chemical binding substance) containing numerous pits but having no perforations in the primary cell wall.

A prions  is an infectious agent composed of protein in a misfolded form. Prions propagate by transmitting a misfolded protein amyloid fold, in which the protein polymerises into an aggregate consisting of tightly packed  state. When a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated, prion form; the prion acts as a template to guide the misfolding of more proteins into prion form. These newly formed prions can then go on to convert more proteins themselves; this triggers a chain reaction that produces large amounts of the prion form. All known prions induce the formation of an beta sheets. Amyloid aggregates are fibrils, growing at their ends, and replicating when breakage causes two growing ends to become four growing ends. The

Hemostasis involves three basic steps: vascular spasm, the formation of a platelet plug, and coagulation, in which clotting factors promote the formation of a fibrin clot. Fibrinolysis is the process in which a clot is degraded in a healing vessel. Anticoagulants are substances that oppose coagulation.

The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen. In the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water. The electron transport chain occurs across the inner mitochondrial membrane. Its main function is to build an electrochemical gradient across the inner membrane using protons. The ETC pumps hydrogen ions out of the matrix of the mitochondria and into the intermembrane space.

Water is passively transported into the roots and then into the xylem. 2-The forces of cohesion and adhesion cause the water molecules to form a column in the xylem. 3- Water moves from the xylem into the mesophyll cells, evaporates from their surfaces and leaves the plant by diffusion through the stomata. Osmosis is the movement of water across membranes that allow water to move freely but that control the movement of dissolved substances, such as mineral ions.

Poultry farming is done to raise domestic fowl for egg production and chicken meat. Therefore, improved poultry breeds are developed and farmed to produce layers for eggs and broilers for meat by cross-breeding programmes.

The cross-breeding programmes between Indian (indigenous, for example, Aseel) and foreign (exotic, for example, Leghorn) breeds for variety improvement are focused on to develop new varieties for the following desirable traits—

1. Number and quality of chicks.
2. Dwarf broiler parent for commercial chick production.
3. Summer adaptation capacity/tolerance to high temperature.
4. Low maintenance requirements;
5. Reduction in the size of the egg-laying bird with ability to utilize more fibrous cheaper diets formulated using agricultural by-products.

Chickens are raised up to 6-7 weeks in the poultry farm. They are fed with vitamin rich supplementary feed for good growth rate and better feed efficiency.

The mechanism of ATP synthesis appears to be as follows. During the transfer of hydrogen atoms from FMNH2 or FADH2 to oxygen, protons (H+ ions) are pumped across the crista from the inside of the mitochondrion to the outside. This complex forms a specific proton pore in the membrane. Depending on the type of organism, cells transfer energy and generate ATP by photophosphorylation, substrate-level phosphorylation, and/or oxidative phosphorylation. Phosphorylation refers to the attachment of a phosphate group to a molecule.

In plants, ATP synthase is also present in chloroplasts (CF1FO-ATP synthase). The enzyme is integrated into thylakoid membrane; the CF1-part sticks into stroma, where dark reactions of photosynthesis (also called the light-independent reactions or the Calvin cycle) and ATP synthesis take place. The mechanism of ATP synthesis appears to be as follows. During the transfer of hydrogen atoms from FMNH2 or FADH2 to oxygen, protons (H+ ions) are pumped across the crista from the inside of the mitochondrion to the outside. ... Attached to the crista is a complex enzyme (ATP synthetase) that binds ATP, ADP, and Pi.

The monocot stem has scattered vascular bundles and their arrangement is conjoint and closed. Moreover, water containing-cavities are present within the vascular bundles.
In a monocot stem, each vascular bundle is surrounded by a sclerenchymatous bundle sheath and parenchymatous ground tissue.

In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme). The induced-fit theory assumes that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible. The induced fit model describes the formation of the E-S complex as a result of the interaction between the substrate and a flexible active site. The substrate produces changes in the conformation on the enzyme aligning properly the groups in the enzyme. It allows better binding and catalytic effects.