Rahat Indori's Classic Shayari

Development of Chick Embryo

Chick development

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Definitions of Biological Concepts

Ampula of Vater

It is broad or swollen end of hepatopancreatic duct which is formed by fusion of pancreatic duct and combined bile duct. The pancreatic duct brings the pancreatic juice from pancreas while common bile duct brings bile from hepatic and cystic duct.


Keystone Species


"A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community".The role that a keystone species plays in its ecosystem is analogous to the role of a keystone in an arch. While the keystone is under the least pressure of any of the stones in an arch, the arch still collapses without it. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measures of biomass or productivity. It has become a very popular concept in conservation biology.

The keystone species concept was coined, in 1969, by the zoologist Robert T. Paine, professor emeritus of the University of Washington, to explain the relationship between Pisaster ochraceus, a species of starfish, and Mytilus californianus, a species of mussel. In his classic 1966 paper, Dr. Robert Paine described such a system in Makah Bay in Washington State. This led to his 1969 paper where he proposed the keystone species concept. The concept has been very popular in conservation, deployed in a range of contexts and mobilized to engender support for conservation.

As was described by Dr. Robert Paine in his classic 1966 paper, some sea stars may prey on sea urchins, mussels, and other shellfish that have no other natural predators. If the sea star is removed from the ecosystem, the mussel population explodes uncontrollably, driving out most other species, while the urchin population annihilates coral reefs.

Similarly, sea otters protect kelp forests from damage by sea urchins. Kelp "roots", called holdfasts, are merely anchors, and not the vast nutrient gathering networks of land plants. Thus the sea urchins only need to eat the roots of the kelp, a tiny fraction of the plant's biomass, to remove it from the ecosystem.

These creatures need not be apex predators. Sea stars are prey for sharks, rays, and sea anemones. Sea otters are prey for orca.

The jaguar, whose numbers in Central and South America have been classified as Near Threatened, acts asa keystone predator by its widely varied diet, helping to balance the mammalian jungle ecosystem with its consumption of 87 different species of prey.

Engineers:

Although the terms 'keystone' and 'engineer' are used interchangeably, the latter is better understood as a subset of keystone species. In North America, the grizzly bear is a keystone species—not as a predator but as ecosystem engineers. They transfer nutrients from the oceanic ecosystem to the forest ecosystem. The first stage of the transfer is performed by salmon, rich in nitrogen, sulfur, carbon, and phosphorus, who swim up rivers, sometimes for hundreds of miles. The bears then capture the salmon and carry them onto dry land, dispersing nutrient-rich feces and partially eaten carcasses. It has been estimated that the bears leave up to half of the salmon they harvest on the forest floor.

The prairie dog is also an ecosystem engineer. Prairie dog burrows provide the nesting areas for Mountain Plovers and Burrowing Owls. Prairie dog tunnel systems also help channel rainwater into the water table to prevent runoff and erosion, and can also serve to change the composition of the soil in a region by increasing aeration and reversing soil compaction that can be a result of cattle grazing. Prairie dogs also trim the vegetation around their colonies, perhaps to remove any cover for predators. Even grazing species such as Plains bison, pronghorn, and Mule deer have shown a proclivity for grazing on the same land used by prairie dogs. It is believed that they prefer the vegetative conditions after prairie dogs have foraged through the area.

Another ecosystem engineering keystone species is the beaver, which transforms its territory from a stream to a pond or swamp.

In the African savanna, the larger herbivores, especially the elephants, shape their environment. The elephants destroy trees, making room for the grass species. Without these animals, much of the savannah would turn into woodland.

Metamorphosis and Paedomorphosis

The series of developmental changes by which a lava or a nymph is transformed into an adult are collectively called as metamorphosis, eg; a tadpole of frog is metamorphophed into a frog. 
In some amphibians eg; Axololte, the larva develops its gonads (sex organs) without metmorphosing the other morphological features, this is called as paedomorphosis.

Metabolism

All the biochemical reactions taking place in a living organism within or outside its cells are collectively termed as metabolism.eg; breakdown of glucose in cytosol (catbolism) and formation of glucose in chloroplasts of plants or algae (anabolism).

Metagenesis

There are some organisms which complete there life cycle in more than on larval forms. this phenomenon is termed as metagenesis. eg; in case of Fasciola hepatica.

Metamorphosis:

The developmental changes by which a larva is trasformed into an adult are collectively termed as metamophosis. For example a tadpole becomes a frog;  glochidium of Fresh water mussel etc.

Mimicry rings

In tropical countries, field research has shown that there are large numbers of species involved in mimicry. 54 species of Heliconius are recognised, with over 700 named colour forms. There are four (or perhaps five) assemblages of butterflies, which include the heliconiines and their mimics. These mimicry rings are called tiger, red, blue and orange for short. Members of each ring tend to roost together at night, fly to similar habitats and at the same time of year. Mimicry rings include both Müllerian and Batesian mimicry.

Oviparity, Viviparity and Ovoviviparity:

The complete development of embryo within the shelled egg which is laid by mother (development of embryo outside the body of mother) as in case of most of the fishes, amphibians, reptiles and birds is called oviparity.
The complete development of embryo within the uterus of mother as in case of mtatherian, like kangaroo, and eutherian mammals, like human is called as viviparity.
The complete development of embryo within the shelled egg, within the body of mother as in case of Duck-billed Platypus Ornithorhynchus aculeata is called as ovoviviparity.

Biology:

 The study of life is called Biology.

Guttation:

 The loss of water from the surface of plant in the form of droplets or liquid state.

Hydathodes:

 Guttation is the loss of water from parts of plants in drops. These water droplets secrete from water of lands called Hydathodes.

Cardiac Cycle:

 The alternating contraction & relaxation of heart is called cardiac cycle.

Blood Pressure:

 Pressure per unit area exerted on the walls of arteries or veins when blood flows through them. The blood pressure of a normal person is 120/80 mmHg where 120 mmHg is the systolic pressure while 80 mmHg is the diastolic pressure.

Immunity:

 The capacity of a body to protect against pathogenic or any other harmful substances when they enter in the body or cause an abrupt effect on body. It is controlled by Immune System of the body.

Electrocardiogram:

It is a device which displays the rhythm of heart beat in the form of graph which is shown on screen called electrocardiogram.

Spleenomegaly:

 Enlargement of spleen is called spleenomegaly.

 Circulatory System:

 A type of system in which the circulatory fluids flows in body and exchange of materials take place. The circulatory fluid can be haemolymph, blood or any other thing.

Transgenic Organism:

 The organism processing a foreign gene in their cells is called transgenic organism.

Polymerase Chain Reaction (PCR):

 PCR is used to produce a large no. of copies of gene of interest within a test tube in short time.

Callus:

 Callus is a group of undifferentiated cells formed at the site of wound or cut either in plants or animals.

Biotechnology:

 The use of biological systems to get product to achieve an end desired by the humans is called biotechnology.

Complementary DNA (c-DNA):

 The DNA produced by reverse transcriptase from an m-RNA is called c-DNA.

Probe:

 Probe is a sequence of DNA nucleotides which is used to identify the required gene present in genomic library.

Cumulus cells:

The cells which remain attached to the egg (ovum) after ovulation are called cumulus cells.

Special Not Disable