The mechanism by which the kidney regulates the glomerular filtration rate is autoregulative. It is carried out by the juxtaglomerular apparatus. Juxtaglomerular apparatus is a microscopic structure located between the vascular pole of the renal corpuscle and the returning distal convoluted tubule of the same nephron.

It plays a role in regulating the renal blood flow and glomerular filtration rate. When there is a fall in the glomerular filtration rate, it activates the juxtaglomerular cells to release renin. This stimulates the glomerular blood flow, thereby bringing the GFR back to normal. Renin brings the GFR back to normal by the activation of the renin-angiotensin mechanism.

• Amphibolic pathway is the one which involves both anabolism and catabolism.
• Krebs cycle is a classic example of amphibolic pathway.
• Krebs cycle involves both the catabolism of carbohydrates and fatty acids and the anabolism of amino acids.
• Fats should be broken into glycerol and fatty acid, and if fatty acids were to be respired they would first be degraded to acetyl CoA and enter the pathway after being converted to PGAL.
• Glycerol enter the pathway after it is converted to PGAL.
• The proteins would be degraded by proteases and the individual amino acids depending on their structure would enter the pathway at some stage within the Krebs cycle.
• Fatty acids would be broken down to acetyl CoA before entering the respiratory pathway when it is used as a substrate.
• But when the organism needs to synthesize fatty acids, acetyl CoA would be withdrawn from the respiratory pathway for it.
• Respiratory pathway can be seen during both breakdown and synthesis of fatty acids.

Phaeophyceae In the members of class-Phaeophyceae, the plant body is usually attached to the substratum by a hold fast and has a stalk called stipe and a leaf like photosynthetic organ called frond.

Loss of water in the liquid state from uninjured parts of plants is known as guttation. It is due to root pressure.
 

The  light intensity, carbon dioxide concentration, and temperature are the three main factors that impact photosynthesis. Greater light intensity leads to higher photosynthesis rates, as does increased carbon dioxide concentration. So in the case of a plant, a higher light intensity means more packets of light called “photons” are hitting the leaves. As you rise from low light intensity to higher light intensity, the rate of photosynthesis will increase because there is more light available to drive the reactions of photosynthesis. At medium temperatures, between 50 and 68 degrees Fahrenheit, or 10 and 20 degrees Celsius, the photosynthetic enzymes work at their optimum levels, so photosynthesis rates gauge high. Depending on the particular plant in question, set the greenhouse thermostat to a temperature within this range for best results.

• Fungi are heterotrophic organisms.
• Fungi are filamentous, with the exception of unicellular yeasts.
• Fungi consist of long, slender thread-like structures called
• The network of hyphae is known as mycelium.
• Some hyphae are continuous tubes filled with multinucleated cytoplasm, these are called coenocytic hyphae and others have septae or cross walls in their hyphae.
• The cell walls of fungi are composed of chitin and polysaccharides.
• Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called
• The fungi that depend on living plants and animals are called
• Fungi can also live as symbionts
• . Example- in association with algae as lichens and with roots of higher plants as

In the taxonomic hierarchy, lower the rank higher is the degree of similarity between the occupants. Order is the assemblage of families, which exhibit a few similar characters. 

Cat belongs to same family Felidae, while rabbit belongs to Leporidae.

The binomial nomenclature was introduced by Carolus Linnaeus in which the genus name and the species epithet  are used for scientific naming of an organism.

The study of plant anatomy helps us to understand the structural adaptations of plants with respect to diverse environmental conditions. It also helps us to distinguish between monocots, dicots, and gymnosperms. Such a study is linked to plant physiology. Hence, it helps in the improvement of food crops. The study of plant-structure allows us to predict the strength of wood. This is useful in utilising it to its potential. The study of various plant fibres such as jute, flax, etc., helps in their commercial exploitation.

The neurons are said to be in resting state when they are not conducting any impulse. In that case, the membrane of the axon is more permeable to potassium ions and impermeable to sodium ions and the negatively charged proteins present in axoplasm. The plasma in the axon contains a high concentration of potassium ions and proteins and low concentration of sodium ions. Whereas the fluid outside the axon contains a high concentration of sodium ions and low concentration of potassium ions. Due to this, a concentration gradient is formed. Active transport of ions occurs across the membrane by the sodium-potassium pump where three ions of sodium are transported outwards and two ions of potassium move into the cell. Because of this, the outer surface of the membrane becomes positively charged while the inner surface is negatively charged. The cell is said to be in a polarised state. The electrical potential difference across the resting plasma membrane is known as resting potential.

When we apply a stimulus at a site on the polarised membrane, the membrane at the site becomes freely permeable to sodium ions. Due to this, sodium ions move into the cell and the outer side of the membrane becomes negatively charged and the inner side becomes positively charged. The membrane is said to be in the depolarised state. The electrical potential difference generated across the plasma membrane at this site is known as action potential or nerve impulse. This area becomes a stimulus for the neighboring area of the membrane which becomes depolarised. The former membrane becomes repolarised due to the movement of sodium ions outside the cell.  This is how impulses are conducted.

Skeletal muscle is composed of muscle fibers which have smaller units called myofibrils. There are three types of proteins make up each myofibril; they are contractile, regulatory and structural proteins.

By contractile proteins, we mean actin (thin filament) and myosin (thick filament). Each actin filament is composed of two helical “F” actin (filamentous actin) and each ‘F’ actin is made up of multiple units of ‘G’ actin. Along with the ‘F’ actin, two filaments of regulatory proteins tropomyosin and troponin at regular intervals are present. During muscle relaxation, troponin covers the binding sites for myosin on actin filaments.

Each myosin is composed of multiple units of meromyosin which has two important parts- a globular head known as heavy meromyosin with a short arm and a tail known as light meromyosin. The head and arms project at regular distance and angle from each other from the surface of myosin filament and are known as the cross arm. The head bears binding sites for ATP and active sites for actin. Let us now try to understand the muscle contraction mechanism.

Mechanism of muscle contraction :

• Mechanism of muscle contraction is explained by sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
• Muscle contraction is initiated by a signal sent by the central nervous system via a motor neuron.
• A motor neuron along with the muscle fibres connected to it constitutes a motor unit.
• The junction between a motor neuron and the sarcolemma of the muscle fibre is called neuromuscular junction or motor-end plate.
• Neurotransmitter releases here which generates an action potential in sarcolemma.
• These causes release of Ca++   into sarcoplasm. 
• These Ca++ binds with troponin, thereby remove masking of active site.
• Myosin head binds to exposed active site on actin to form a cross bridge, utilizing energy from ATP hydrolysis.
• This pulls the actin filament towards the centre of ‘A’ band.
• ‘Z’ lines also pulled inward thereby causing a shortening of sarcomere i.e. contraction.
• ‘I’ band get reduced, whereas the ‘A’ band retain the length.
• During relaxation, the cross bridge between the actin and myosin break.
• Ca++pumped back to sarcoplasmic cisternae.
• Actin filament slide out of ‘A’ band and length of ‘I’ band increases.  This returns the muscle to its original state.
• Repeated muscle contraction causes accumulation of lactic acid, produced from anaerobic breakdown of glycogen leads to muscle fatigue.
• Muscle contains red coloured oxygen storing pigment called myoglobin.
• Muscle with myoglobin called red muscle fibres, they are also contain large number of mitochondria which can utilize large amount of oxygen stored in them for ATP production also called aerobic muscle.
• Some muscles possess very less quantity of myoglobin and less mitochondrion hence called white fibres. Amount of sarcoplasmic reticulum is high in these muscles. They depend on anaerobic process for energy.

Aestivation is the mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl.
There are four main types of aestivation. They are as follows:

1. Valvate aestivation: Sepals or petals in a whorl just touch one another. They do not overlap one another.

2. Twisted aestivation: One margin of the appendage overlaps the margin of the next appendage. Such type of aestivation is seen in lady’s finger, china rose and cotton.

3. Imbricate aestivation: Margins of sepals or petals overlap one another but not in any particular direction. It is seen in Gulmohar and Cassia.
4. Vexillary aestivation: It is also known as Papilionaceous type of aestivation.

There are five petals. The largest petal (called standard) overlaps the two lateral petals (called wings) which further overlap the two smallest anterior petals (called keel).

• Neural tissue exerts the greatest control over the body’s responsiveness to changing conditions.
• Neurons, the unit of neural system are excitable cells and the neuroglial cell which constitute the rest of the neural system protect and support neurons.
• When a neuron is suitably stimulated, an electrical disturbance is generated which swiftly travels along its plasma membrane.
• Arrival of the disturbance at the neuron’s endings, cause stimulation or inhibition of adjacent neurons and other cell.