• Excretion in Plants:

The various methods used by the plants to get rid of their waste products are

(i) The plants get rid of gaseous waste products through stomata in leaves and lenticels in stems.
(ii) They get rid of solid and liquid waste by shedding off leaves, peeling of bark and falling of fruits.
(iii) Secreting gums and resins.
(iv) Plants excrete some waste substances into the soil around them.

The main excretory system in animals is the urinary system. The urinary system is composed of the kidneys, in which urine is produced, ureters, urinary bladder, and the urethra. An initial filtration of the blood is produced in the kidneys. ... In fact, the kidney is made up of many repetitions of this structure.

A cofactor that firmly attaches to the apoenzyme is called prosthetic group.
Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme. Cofactor may be organic or inorganic (metal ions).

Dicot leaf :
(i) It is dorsoventral leaf.
(ii) Stomata found only on lower epidermis.
(iii) Reticulate leaf vena¬tion.
(iv) Mesophyll is differ-entiated into spongy and palisade tissues. e.g., Dicot plants.
Monocot leaf :
1. it is is isobilateral leaf.
2.Stomata found both on lower and upper epidermis.
3.Parallel leaf venation.
4.Mesophyll not divided into spongy and palisade tissues, e.g., Monocot plants.

Mineral Nutrition is defined as the naturally occurring inorganic nutrient found in the soil and food that is essential for the proper functioning of animal and plant body. Minerals are vital elements necessary for the body. Both the plants and animals require minerals essentially. For example, Zinc is necessary for the manufacture of protein and for cell division.

Diffusion: During diffusion, roots grow throughout the profile and use up nutrients directly around the root system and the root hairs. As the concentration of nutrients around the root system drops, nutrients from higher concentrated areas move – or diffuse – toward low concentration areas and toward the roots. Mineral nutrients are absorbed by plants from the soil solution as ions. An ion is the charged particle formed by the removal or addition of electrons to any particular atom or molecule. Ions absorbed by the roots are then loaded into the xylem and transported with water up to the leaves when the plant transpires.

Water potential: Water potential is a fundamental concept to understand water movement. It is denoted by yro. The pure water has the maximum water potential due to its greater kinetic energy. As both are related with the movement of water, water potential is expressed in pressure units such as pascal (Pa).
The water potential of pure water at standard temperatures, which are not under any pressure, is taken to be zero.
Solute potential (ys) and pressure potential (yp) are the two main components that affect water potential.
(a) Solute potential: All solutions have a lower water potential than pure water. The magnitude of this lowering due to dissolution of a solute is called solute potential devoted by p. The more the solute molecules, the lower is the ys.
For a solution at atmospheric pressure
|/W = |/S
(b) Pressure potential : If a pressure greater than atmospheric pressure, is applied to pure water or a solution, its water potential increases. Pressure potential is the pressure which develops in an osmotic system due to osmotic entry or exit of water i from it.
It is expressed by y . Its value is always in positive

Systematics is the science which deals with the diversity of organisms and their comparative and evolutionary relationships based on comparative anatomy, comparative biochemistry and physiology.
Systematics helps in
1. Providing knowledge about the evolutionary tree of life
2. Identification of new organisms

Functioning of nephron:
Filtration of blood takes in Bowman’s capsule from the capillaries of glomerulus. The filterate passes into the tubular part of the nephron. This filterate contains glucose, amino acids, urea, uric acid, salts and a major amount of water. Reabsorption: As the filterate flows along the tubule useful substances such as glucose, amino acids, salts and water are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule. The amount of water reabsorbed depends on the need of the body and also on the amount of wastes to be excreted. The filterate which remained after reabsorption is called urine. Urine contain dissolved nitrogenous waste i.e., urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting dust to carry it to the ureter.

In the 1920s, the German biochemist Otto Warburg (1883-1970) discovered that plants consumed oxygen at a higher rate when they were illuminated. He also found that this increased rate of oxygen consumption inhibited photosynthesis. Stimulation of oxygen consumption by light is now referred to as photorespiration. Photorespiration (also known as the oxidative photosynthetic carbon cycle, or C2 photosynthesis) refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. ... Photorespiration also incurs a direct cost of one ATP and one NAD(P)H.

The important steps muscle contraction:
1. Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron and reach the neuromuscular junction. As a result, neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma.
2. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.
3. Increase in Calcium level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
4. The actin filaments are pulled. As a result, the H-zone reduces. It is at this stage that the contraction of the muscle occurs.
5. After muscle contraction, the myosin head pulls the actin filament and releases ADP along with inorganic phosphate. ATP molecules bind and detach myosin and the cross bridges are broken and decreases the calcium ions contraction. As a result, masking the actin filaments and leading to muscle relaxation.

Exchange of gases takes place between the alveoli of lungs and the surrounding blood capillaries.  The two main gases exchanged are oxygen and carbon-dioxide. Oxygen is absorbed by the blood capillaries from the lungs alveoli by diffusion while carbon-dioxide is absorbed by the lungs alveoli from blood capillaries by diffusion.
Transport of oxygen and carbon-dioxide occurs with the help of respiratory pigment called hemoglobin.
Hemoglobin, the iron containing respiratory pigment is a red colored pigment of blood, which has a very high affinity for oxygen. Hemoglobin though is purple colored but oxy-hemoglobin is of bright red color. Oxygen is transported from lungs to the body cells in the form of oxy-hemoglobin.
Carbon-dioxide is transported from the body cell to the lungs in the forms of carboxy-hemoglobin, carbonic acid, bicarbonates of sodium and potassium.

When the enzyme inhibitor closely resemble the molecular structure of the substrate, the enzyme action is inhibited. This is called competitive inhibition. When the active site is blocked by the inhibitor, the inhibition is said to be non-competitive and no enzyme substrate complex is formed.

Gas bladder or air bladder is a gas filled sac present in fishes. It helps in maintaining buoyancy. Thus, it helps fishes to ascend or descend and stay in the water current.

The counter current mechanism operating inside the kidney is the main adaptation for the conservation of water. There are two counter current mechanisms inside the kidneys. They are Henle’s loop and vasa rectae.
Henle’s loop is a U-shaped part of the nephron. Blood flows in the two limbs of the tube in opposite directions and this gives rise to counter currents. The Vasa recta is an efferent arteriole, which forms a capillary network around the tubules inside the renal medulla. It runs parallel to <st1:place w:st="on">Henley</st1:place>’s loop and is U-shaped. Blood flows in opposite directions in the two limbs of vasa recta. As a result, blood entering the renal medulla in the descending limb comes in close contact with the outgoing blood in the ascending limb.

The human circulatory system is a double circulatory system. It has two separate circuits and blood passes through the heart twice: the pulmonary circuit is between the heart and lungs. the systemic circuit is between the heart and the other organs. Blood gets pumped out of the heart. This blood goes to different organs and then blood again comes back to the heart. All this happens in a very systematic way through the different arteries and veins carrying oxygenated and deoxygenated blood. In double circulation, there are two pathways in which blood flows.

Microtubules and microfilaments are two components in the cytoskeleton. The main difference between microtubules and microfilaments is in their structure and function. Microtubules have a long, hollow cylindrical structure. They are formed by the polymerization of tubulin proteins. The major role of microtubules is to provide mechanical support to the cell, involve in chromosomal segregation and maintain the transport of components inside the cell. On the other hand, microfilaments are helical structures, more strong and flexible compared to microtubules. They are involved in the movement of the cell on a surface. Both microtubules and microfilaments are dynamic structures. Their dynamic nature is regulated by associated proteins with the polymers.

Secondary growth is the formation of secondary tissues from lateral meristems. It increases the diameter of the stem. In woody plants, secondary tissues constitute the bulk of the plant. They take part in providing protection, support and conduction of water and nutrients. Vascular cambium produces secondary xylem (toward the center of the stem or root) and phloem (toward the outside of the stem or root), adding growth to the diameter of the plant. This process produces wood, and builds the sturdy trunks of trees.