Mutagens can be classified into two broad categories :

Physical Mutagens : Radiations are the most important physical mutagens. These are of two types.

• Ionizing Radiations :  These include X-rays, gamma-rays, alpha-rays and beta-rays. These cause breaks in chromosomes and cells show abnormal cell division.
• Non-Ionizing Radiations : These include UV rays. They have longer wavelengths but lower energy, and thus are insufficient to induce ionization. Thymine dimer formation is the major effect.

Chemical Mutagens : Large numbers of chemical mutagens exists. These are more harmful. Usually divided into two groups

• Mutagenic to both replicating and non replicating DNA - Nitrous Acid
• Mutagenic to Replicating DNA - Acridine Dyes, Base Analogues

Procedures, methods and information that are useful in identification and classification of organisms are called taxonomical aids .

Taxonomical Aids are of the following types. :

• Herbarium : It is a collection of dried, pressed and preserved plants. This is usually done on sheets for reference.Standard size is 41cm*29cm.The largest herbarium of the world is at Kew.
• Botanical Gardens : It is a collection of living plants maintained for reference.Largest botanical garden is in Moscow.
• Zoological Parks : Eenclosed areas where animals are kept in open enclosures instead of cages.Useful for exsitu conservation through acaptive breeding of endangered animals.
• Museums : A place used for storage,preservation and exhibition of objects of natural history,art and objects of natural antiquities.  Provides information about local flora and fauna but also other areas.
• Keys : Itis used in identification of organisms based upon similarities and dissimilarities.It is a dichotomic table of alternate characters known as couplet, each character of couplet is known as lead.Keys are unique for each category.

Hello Aspirant!

You may know that Commensalism (+0) is a type of ecological Host-Parasite interaction (between two organisms) where the parasite species derives nutrition, shelter, protection, locomotion etc. from the host species. And here, the parasite species is benefitted while the host species is neither benefitted nor harmed.

Some common examples of Commensalism are :-
1. Goby fishes live on the body surface of other marine animals. They change colour to blend in with the host, thus gaining protection against predators.
2. Burdock plants produce spiny seeds that cling to the fur of animals or human clothings. The plant relies on this method for dispersion of seeds during its reproductive season, while the animals are unaffected.
3.The small suckerfish (or Remora) is a member of the ray-finned fishes. The remora forms a commensal association with large marine organisms, like turtles, whales and sharks. Its specially-designed suckers attach to the fins of the host organism and thus it attains benefit of transportation and protection from predators. It also utilizes the leftover of sharks for feeding, without causing any harm to the host.
4.Barnacles are the organisms which are unable to move on their own as they lack well developed locomotory organs . So, during the larval stage, they stick to other organisms such as whales or they attach themselves to shells, ships, and rocks. They grow and develop on these surfaces without causing any negative affect to the host. Barnacles feed on plankton and other food materials during the movement of whales.They do not feed on blood or flesh. Therefore, they cause no harm to the whale. This way, they get benefit in transportation (or locomotion) and nutrition.
5. The emperor shrimp attaches itself to sea cucumbers where they get benefit in transportation and protection from predators without energy expenditure . The shrimp get off the host cucumber for feeding and then attaches to another host when it wants to move to a different place. As the emperor shrimp is small and light, it does not cause any harm to the sea cucumber.
6. Monarch butterflies derive certain toxins during their larval stage from milkweed hosts, which make them distasteful to predatory birds.These toxins are not poisonous to the butterfly larvae but its consumption is harmful for the vertebrates. Milkweeds are not carnivorous plants. They do not affect the growth and development of the butterfly larvae. So, in this way, the butterflies acquire protection against its predators without harming its host milkweed species.
7. Tree frogs get protection against its predators by cryptically hiding on the surface of the bark of trees. Due to similarity in colour of the frogs and tree trunk, its predator cannot differentiate and navigate the frog.

I hope you find this answer helpful.

Hello Aspirant,

Basically there are two dating methods

• Absolute Dating- used to determine a precise age of a rock or fossil through radiometric dating  methods. This uses radioactive minerals that occur in rocks and fossils almost like a geological clock. It’s often much easier to date volcanic rocks than the fossils themselves or the sedimentary rocks they are found in.
• Relative Dating- Most of the time this fossil dating technique  is used to determine the used age. Using relative dating the fossil is compared to something for which an age is already known.

I hope it helps

Thank you

Hello Student,

Here are the names of all the theories and the scientists

Theories for Origin of Life

1. Big Bang Theory - Abbe Lemaitre

2. Nebular Theory - Kant and Laplace

Classical Theories

1. Theory of Special Creation - Father Suarez

2. Theory of Spontaneous creation/Abiogenesis -Aristotle and Pluto were great supporters of this theory.

3. Cosmozoic Theory/Theory of Panspermia - Richter

4. Theory of Biogenesis - Louis Pasteur

5. Theory of Catastrophism - Cuvier

6. Theory of Chemical Origin/Oparin Haldane Theory/Modern Theory -Oparin and Haldane(They proposed their theories seperately but now it is studied collectively)

Hope this helps

Hello Student,

Gastric gland are of many types each having their own role and found in different positions within the stomach.

The different glands and their distribution is as follows :

1) Cardiac Part : Mucous Neck Cells are present here which secrete mucous.

2)Fundic/Gastric part : Four Types of Cells are found here

1. Peptic/Zymogenic/Chief/Central Cells : Secrete proenzymes pepsinogen and prorennin. Smaal amount of gastric lipase is also produced.
2. Oxyntic/Parietal cells : Secrete HCL and Castle's Intrinsic factor required for vit B12 absorption.
3. Mucous Neck Cells : Secrete alkaline mucous.
4. Argentaffin/Enterochromaffin/Kultchitsky Cells : Secrete vasoconstrictor serotonin and vasodilator histamine.

3)Pyloric part :

1. Mucous Neck cells : Secrete mucous
2. G Cells : Secrete Gastric which i ncreases gastric motility and stimulates gastric juice secretion by gastric glans.

Hello,

Water soluble vitamins are opposite to fat soluble vitamins as they are not stored in the body . It absorbs what it needs and then release them through urine . As they cannot be stored they are needed by the body continuously . Some of the water soluble vitamins are :

Vitamin C

Vitamin B1

Vitamin B2

Vitamin B3

Vitamin B12

Hello Student ,

The composition of living tissue/biomolecules can be studied by chemical analysis. The stepwise procedure is as follows

1. Living tissue is taken and grinded in trichloroacetic acid.
2. Then the mixture is strained with a cheese cloth
3. Filtrate and Retentate are obtained after straining.
4. Filtrate contains the acid solube pool - Mol Wt of biomolecules- 18-1800 Daltons . These are biomicromolecules.
5. Retentate contains Acid Insoluble pool - Mol Wt of biomolecules - >800 D. These are biomarcomolecules.

Note : Lipids are absent in biomicromolecular pool due to their non polar nature. They associate and form larger compounds.

Hello Student ,

The various feeding mechanism found in living organism are as follows :

Feeding in Liquid Feeders/ Fluid Feeders

1. Diffusion - Absorption through general body surface
2. Pinocytosis - Ingestion of liquid food through invagination by surface of the body .
3. Blood Sucking

Feeding in Microphagous Animals/ Filter Feeders

1. Food is suspended in water and they have filtering devices  for feeding.

Hope this helps .

Hi,
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