Waste products created after metabolic activity are toxic for the body. They can harm all vital functions so their removal is necessary from the body.

Skull is also known as brain box. The main role of skull is to give protection to brain. Apart from this the human skull is positioned in a way which makes it easy for humans to stand erect. This type of position is called Frankfurt plane.

Pectoral girdle provides fulcrum to forelimbs.

In leaves of herbs, when transpiration is nil during night, root pressure results in collection of water droplets on leaves. This phenomenon is called guttation

The glands, which are asbsent in male are ovaries and which are absent in female are tests.

Somatostatin inhibits the secretion of growth hormone from anterior lobe of pituitary gland.

The floral formula of the described flower is represented as:

Actinomorphic flowers are represented by the symbol . ­
A bisexual flower is indicated by.
The calyx contains five united sepals which can be represented as K₍₅₎.
The corolla consists of five free petals and it represented as C₅.
The androecium consists of five free stamens and is represented by A₅.
The gynoecium consists of a superior ovary with two united carpels and axile placentations, which can be represented as 

Freshwater bony fishes  Labeo, rohita, Catla catla, Cirrhina mrigala, Cyprio corpio.
Marine bony fishes Hilsa, Harpodon, Stromateus

Cycas have coralloid root in which nitrogen-fixing cyanobacteria is present

Correlated characters are those common features, which are used in delimitation of a taxon above the rank of species.

The number and kinds of organisms are never constant at a place, as development and reproduction keep the number changing. This is influenced by season and availability of resources, e.g., number of mosquitoes is very large in warm and humid weather, whereas in extreme summer or winter, they can be seen rarely.

All organisms from the prokaryotes to the most complex eukaryotes can sense and respond to their environment.
The human have five sense organs, which help them to sense their environment.These are eyes, ears, nose, tongue and skin.

Osteoporosis is the condition in which the bone mass is decreased. This leads to general weakening of bones. Even a minor slip can result in fractures if a person is suffering from osteoporosis.
Women are at greater risk of suffering from osteoporosis because of several reasons. During child bearing major part of calcium from their body is utilized in formation of the skeleton of the foetus. Additionally during lactation there is further depletion of the calcium reserve of the body because of milk formation. A calcium rich diet can help prevent the progression of osteoporosis. Milk and eggs are good source of calcium. During pregnancy oral calcium supplement is also given to prevent osteoporosis.

Comparison of different transport mechanisms

Parasites on Human Body
1. Taenia solium (Tape worm) Platyhelminthes.
2. Fasciola hepatica (Blood worm) Platyhelminthes.
3. Ascaris lumbricoides (Round worm) Aschelminthes.
4. Wuchereria bancrofti (Filarial worm) Aschelminthes.
5. Ancyclostoma (Hook worm) Aschelminthes.

(i) No, actually he was not able to differentiate colours.
(ii) In human, colours vision results from the activity of cone cells of different colours are produced by various combination of these cones and their pigments.
(iii) the daylight vision and colour vision are functions of cones cells of retina.
(iv) The teacher showed his concerns about hid student.

A person lying in coma is not conscious of its surrounding environment. Thus, he/she is not capable of responding to the external environmental stimuli. The person is supported by machines for various functions of the body. The person is otherwise brain dead. Some of these patients never come back to normal life. They can neither be called living nor non-living or dead.

The functioning of the kidneys is efficiently monitored and regulated by hormonal feedback mechanisms involving the hypothalamus, JGA and to a certain extent, the heart.
i) Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. An excessive loss of fluid from the body can activate these receptors which stimulate the hypothalamus to release antidiuretic hormone (ADH)or vasopressin from the neurohypophysis. ADH facilitates water reabsorption from latter parts of the tubule, thereby preventing diuresis.
ii) An increase in body fluid volum can switch off the osmoreceptors and suppress the ADH release to complete the feedback. ADH can also affect the kidney function by its constrictory effects on blood vessels. This causes an increase in blood pressure. An increase in blood pressure can increase the glomerular blood flow and thereby the GFR.
iii) The JGA plays a complex regulatory role. A fall in glomerular blood flow/ glomerular blood pressure/GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensin II, being a powerful vasoconstrictor, increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the adrenal cortex to release Aldosterone. Aldosterone causes reabsorption of Na' and water from the distal parts of the tubule. This also leads to an increase in blood pressure and GFR. This complex mechanism is generally known as the Renin-Angiotensin mechanism.
iv) An increase in blood flow to the atria of the heart can cause the release of Atrial Natriuretic Factor (ANF).ANF can cause vasodilation (dilation of blood vessels) and thereby decrease the blood pressure. ANF mechanism, therefore, acts as a check on the rennin angiotensin mechanism.

There are millions of species on this planet.The largest phylum Arthropoda alone comprises of millions of species. To study all of them properly we need some system for categorizing them, based on some common characteristics.
Apart from that think of the differences in language and you will find different names for the same species in different languages.In the absence of a system of nomenclature it would have been difficult to share scientific knowledge among the scientists of different nations.
To make things easier and systematic the need for classification was felt.Earlier attempts by people like Aristotle segregated living beings into plants and animals.This was good point to start with, but there are certain living beings which do not fit in either of plants or animals.So a three kingdom classification was devised.The three kingdom classification was used for some time.But as none of the scientific theory is permanent so further discoveries led to creation of a five kingdom classification.The five kingdom classification is the most accepted system of classification.

Taxonomical Aids help scientists keep a record and study common and uncommon characteristics of animals and plants. This study helps them to decide about the correct place of a species in the given taxonomical category.
Herbarium :
Collected plant species are dried for preservation. The place where they are kept as collection is known as herbarium.
Botanical Gardens :
Here live plants are reared for ready reference. Through live plants botanists can study certain features, like mode of reproduction, pattern of pollination, etc.
Museums :
Dead animal specimens are preserved in museums. Extinct species, like Dodo are kept in certain museum and act as good reference source.
Zoological Parks :
They are helpful in studying live specimens of animal species. Certain ferocious animals are easier to study in zoological parks.
Keys :
Keys are pairs of contrasting characters, out of which either of the characters is carried forward across generations and another is discarded to gain better adaptability. These keys are good tool to understand how complex organisms evolved from simpler organisms.
Manuals and Records :
Manuals and records show historical data about flora and fauna of a particular geographical location.

The endocrine glands and hormones that are responsible for maintaining calcium homeostasis, are thyroid and parathyroid glands and their associated hormones an calcitonin and Parathyroid Hormone (PTH).
(i) Parathyroid glands are the glands developed from the endoderm of the embryo The cells of parathyroid glands are of two types, i.e., chief cells and oxyphil cells. Thr chief cells of the parathyroid glands secrete parathyroid hormone (PTH).
This hormone (PTH) is involved in regulating calcium and phosphate balance betweer the blood and other tissue. It mobilises the release of calcium into the blood from bones. PTH increases calcium reabsorption by the body organs like intestine anc kidneys.
(ii) Thyroid gland is the largest endocrine gland located anterior to the thyroid cartilage o. the larynx in the neck. This gland plays a vital role in maintaining calcium homeostasis It releases thyroculcitonin hormone produced by the parafollicular cells, also called 'C cells.
This hormone is secreted when the calcium level in blood gets high. It is a 32 aminc acid peptide hormone that lowers the calcium level by suppressing release of catciurr ions from the bones. Thus, calcitonin has an action opposite to that of the parathyroic hormone on calcium homeostasis.

Two groupings, i.e., the ABO and Rh^- are widely used all over the world. ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce immune response) on the RBCs, i.e., A and B. Similarly, the plasma of different individuals contain two natural antibodies (proteins produced in response to antigens).
Blood Groups and Donor Compatibility

From the above-mentioned table, it is evident that group 'O' blood can be donated to persons with any other blood group and hence 'O' group individuals are called 'universal donors'. Persons with 'AB' group can accept blood from persons with AB as well as the other groups of blood. Therefore, such persons are called 'universal recipients'.

The continuous process of breakdown and synthesis of biomolecules through chemical reactions occurring in the living cells is called metabolism.
(i) Each of the metabolic reaction results in a transformation of biomolecules.
(ii) Most of these metabolic reactions do not occur in isolation but are always linked with some other reactions.
(iii) In these reactions, the metabolisms are converted into another metabolite in a series of linked reactions called metabolic pathways.
(iv) Each metabolite has a define rate and direction during the flow through a metabolic pathways called the dynamic state.
In living systems, metabolism involves two following types of pathways
(i) The anabolic pathways is called biosynthetic pathway. It leads to a more complex structure from a simpler structure, e.g., the pathway involving the conversion of acetic acid into cholesterol. These pathways consume energy.
(ii) The catabolic pathways leads to simpler structure from a complex structure, e.g., the pathways involving conversion of glucose into lactic acid in our skeletal muscles. This pathway leads to the release of energy, e.g., energy is liberated when glucose is degrated to lactic acid in our skeletal muscles.

Differences between poly and medusa are

A living thing has multiple levels of organisation. Each lavel of organisation has its own properties, which are not found in its constituents.
Examples of three tissues supporting the statements are
(i) Cardiac Muscle Tissue : It is contractile tissue present only in heart. Cell junctions fuse the plasma membrane of cardiac muscle cells and make them stick together. When one cell receives a signal to contract. It means a single cell cannot contract, while there are some fusion points, which allow the cells to contract as a unit.
(ii)  Blood : It is a fluid connective tissue. The individual components of blood, i.e., RBCs, WBCs and platelets have different properties but as a unit they make the blood, a tissue serving many functions.
(iii)  Bone : It is a hard connective tissue that forms the framework of the body. The individual cells inside the bone do not have this property.