Wednesday, 5 April 2017

Pond ecosystem

A small fresh water pond is a classic example of an ecosystem to explain its structure and function. Pond represents a self regulatory fresh water ecosystem.

Abiotic components:
The abiotic components of the pond ecosystem comprise simple inorganic substances such as water, CO2 etc and their compounds and organic substances such as amino acid, humus etc. The quantity of light and temperature is other climatic condition which regulate the functioning of the pond ecosystem.

Biotic componets:
The biotic componenta of a pond ecosystem comprise the producer and variety of consumer- producer (Autotrophs); phytoplanktons(Oscillatoria,Anabaena), Filamentous Algae (spyrogyra), Marginal Algae (Phragmites) and surface plants like Eichhornia are the producers.

1. Macro-consumer:
These represent the animal fauna in the pond ecosystem. Zooplanktons like Paramacium, Daphnia, Cylaps, Insect Larvae are the primary consumers. These primary consumers are eaten by similar fishes and water bodies, which are collectively called secondary Consumers, which in turn is eaten by larger fishes called tertiary consumers.

2.Decomposers:
It A small fresh water pond is a classic example of an ecosystem to explain its structure and function. Pond represents a self regulatory fresh water ecosystem.

Abiotic components:
The abiotic components of the pond ecosystem comprise simple inorganic substances such as water, CO2 etc and their compounds and organic substances such as amino acid, humus etc. The quantity of light and temperature is other climatic condition which regulate the functioning of the pond ecosystem.

Biotic componets:
The biotic componenta of a pond ecosystem comprise the producer and variety of consumer- producer (Autotrophs); phytoplanktons(Oscillatoria,Anabaena), Filamentous Algae (spyrogyra), Marginal Algae (Phragmites) and surface plants like Eichhornia are the producers.

1.Macro-consumer:
These represent the animal fauna in the pond ecosystem. Zooplanktons like Paramacium, Daphnia, Cylaps, Insect Larvae are the primary consumers. These primary consumers are eaten by similar fishes and water bodies, which are collectively called secondary Consumers, which in turn is eaten by larger fishes called tertiary consumers.

2.Decomposers:
It constututes a variety of bacteria and fungi and are specially abundant in the mud water. Their principle functioning is to decompose the extreta of animals and dead bodies of plants and animals a variety of bacteria and fungi and are specially abundant in the mud water. Their principle functioning is to decompose the extreta of animals and dead bodies of plants and animals

Tuesday, 4 April 2017

Darwinism

Charles darwin was a great naturalist. After an intensive study for about 20years, Darwin published his monumental work on the origin of species in the book "Origin of Species"
     The theory is based upon five fundamental facts:
1. Economous fertility
2. Struggle for existence
3. Survival of the fittest
4. Variation and heredity
5. Natural selection

1. Economous fertility:
The living beings have a innate desire of producing their own progeny for contunuity of race and therefore possess amazing fertility. It has been observed that more organism of each kind are produced, that can possibly obtain food and survival. As for example- a rabbit produces 6 yound ones in a litter and 4 litters in a year and the young one staff breeding at the age of a month.

2. Struggle for existence:
The individuals increase enormously in number but the space and food available remain almost constant. Therefore there is always an active position.
          The struggle For existance may be:
A. Intraspecific:
It is the competition among the individuals of a species to gain the upper hand.

B. Interspecific:
It is the competition among the organism of different species living together in the same habitat.

C. Environmental struggle:
The natural forces of environmental conditions such as excess moisture or drought, excessive heat and cold, earthquakes etc

3. Survival of the fittest:
As a result of this everlasting competition among the organisms, the stronger heir survives and the weaker one rooted out. Which also helps in maintaining the balance in the environment.

4. Variation and heredity:
The everlasting competition among the organisms has compelled them to change according to the environmental conditions, so that they can utilize the natural resources and can survive successfully. Therefore it is diffucult to find out two individuals alike.

5. Natural selection:
After observing the above mention facts, Darwin summarised his conclusion under the heading "Natural Selection". The successive generation tend to become better adapted to their environment. These adaptation are preserved and accumulated to establish new species.

Sub divisions of Ecology

Ecology may be studied with particular reference to animals or plants, hence animal ecology and plant ecology. Irrespective of animals or plants under study, nowadays the main divisions of ecology are recognised as Autecology and Synecology.

1. Autecology

Autecology is the study of inter-relationship of different organisms of a species and biotic or abiotic environment. It is also known as species ecology. Autecology deals with the nutrition, growth, reproduction, development, and life history of the individuals of a species in a given environment.

2. Synecology:

It is the study of inter-relationship of different groups of living organisms such as- Populations, biotic communities, and ecosystems. Which is associated together as an unit. It can be differentiated ino population ecology, community ecology and evosystem ecology.

(I) population ecology:
Population ecology is the study of various relationship among the individuals of the same group. It deals with the interaction between populations of different species in a community.

(II) Community ecology:
It deals with the study of living components of a community. Major concern of community ecology are-
a. Causes of diversity
b. Reasons of community located in a particular habitat.
c. Change and interaction among different communities.
d. Nature of interdepence between individuals of different species.

(III) Ecosystem ecology:

It deals with the movements of energy and nutrients among the biotic and abiotic drvelopment of an ecosystem. Ecosystem ecology is the most recent development in ecology.

Monday, 3 April 2017

Transposable genetic material

It was used to be thought that genes have a relatively fixed homologous chromosomes which changes only as a consequence of chromosome re-arrangement resulting from illugumate crossing over between completely homologous short section of DNA. In the late 1940's exeriments with Corn showed that certain genetic elements regularly  jumps to a new location. In such jumping or transposition they often inactive the genes, with which they become attached to heir capacitive to disturb the functioning of other previously characterised genes. Through the use of newly developed recombinant DNA technology and DNA sequence technique the nature of Ecoli transposing elements quickly gets established at the molecular level. These elements were found to be DNA sequence that code for enzymes. Transposition involves both recombination and replication process which frequently generates two daughter copies, one copy remains at the parental site and the other appears at the target site.
           The insertion of transposable elemets invariably disturbs the integrity of their targets, since transposable elemets carry signals for the initiation of RNA synthesis, they sometimes activate previously dominant gene. To summarise this, elements can be defined as small mobile DNA sequences that move around chromosome with near total disgard for holomogy and insertion of these elemenys may produce deletions, inversions, chromosomal fusion and even more complicated re-arrangement.

Types of tranaposable elements.
1. Simple tranaposomes also called as Insertion sequences (I)
2. Complex transposomes known as simply as transposome.

Simple transposmes:

It was discovered about two decades ago that certain spontaneous mutants of Ecoli results from insertion of extraneous DNA (Alien DNA). Such mutants can occur in structural and regulatory genes anywhere in the chromosomes. The extraneous DNA consists of insertion sequences, which occur in chromosomes of bacteria and plasmids. The insertion sequences do not carry any genetic information except that is necessary for transposition. The transpsome gene region is often enclosed by specific terminal DNA sequence. Insertion sequence elements have 800-1200 base pairs devoid of any code for recognisable phenotype characters. Little is known about their insertion in DNA and consequent errors in the transcription. It can be assumed that insertion sequence elements play significant role in orientation and joining of the genetic materials.

Complex transposome:

Complex transposomes are tranaposable elements in which termined sequences encloses additional genetic materials unconnected with transposition. In some complex transposomes such as in 1981, two complex elements enclosed one to several functional bacterial genes, often carrying of its elements at the ends. These are most easily recognised when they carry indentificate gene markers. Transposomes can be integrated into the genome at a no. Of places through not randomly. They can integrae from a plasmid or a transverse phrase, as the transposome contain genes that determines recognisable characters.

Tuesday, 21 March 2017

Male and female cone of pinus

Male cone:
On staminate- strobilus male cone are simple, they form compact and oval structures. They occur singly on the axis of scale leaves of long shoots replacing thereby dwarf shoots. Male cone thus appears morphologically equivalent to dwarf shoots.
     Each cone provided with a short and elongated central axis upon which numerous microsporophylls are arranged spirally, microsporophylls are scaly. Each microsporophyll consists of a short stalk and a leaf-like elongated structure, the apex of which is slightly bent upwards. Two microsporangia are borne on the lower side. A microsporangium is Sessile and oblong in shape. It consists of a wall of several layers of the cell. The development of the microsporangia is of eusporangiate type, each microsporangium contains numerous microspores. The pollen grains are winged and yellow in color when mature each microsporangium dehisces by a longitudinal slip along the long axis. As a result, large number of pollen grains are released forming a cloud which is often called "Shower of Sulphur"
Female cone:
Female cone form true cone-like structures and they are compound in nature. They arise in clusters from one to four, in the axils of scale leaves of the long shoots taking the position of dwarf shoots. At first, they are green in color and gradually become brown red.
      The female cone is a hard woody and dry structure. It consists of a central axis upon which numerous megasporophylls are arranged spirally, megasporophylls are shortly stalked. Each megasporophyll consists of a large ovuliferous scale and a bract scale. Each ovuliferous scale bears two inverted or anatropous megasporangia (ovules). Bractscale and ovuliferous scale are supplied with separate vascular traces, and ovule consists of a massive nucleus, surrounded by an integument consisting of three layers, namely
  1. 1.Outer Fleshy
  2. 2.Middle Stony
  3. 3.Inner Fleshy

Friday, 17 March 2017

Importance of fossil

In fossilised forms, gums of ancient resinous carboniferous trees like pinus, succinifera are found, called amber; which is of great commercial value, as it sometime encloses beautiful fossils of flowers and insects. It is even used in jewellery.

Coal is nothing but a highly compressed fossil originated from the first age of the world forest. Coal forests originated in the Paleozoic era of the carboniferous period.

Diatomite- Diatomaceous earth belonging to algae, is formed of skeletons of billions of di-atoms depositing on the beds of sea. The siliceous empty frustles, which are of great industrial importance.

Even Petroleum may be considered as fossil and are of algal origin, as organisms are responsible for its creation.

Graphite used in lead pencils is a fossil in some sense, as this type of carbon is thought to be organic origin.

Formation of limestone- There are different types of algal limestones in the formation of which specific algae took part due to the precipitation of CaCO3. All such minerals are to be considered as fossils of earlier ages.

Bennettitalean fructification

The genus williamsonia was unisexual and dioceous.it is under bennettitales. Female Flowers are known, and they are borne on short lateral branches, which are also covered with leaf bases and scales. The flower consist of more or less conical fertile portion enclosed by linear hairy bracts and scales. The stalked ovule and  inter seminal scale were arranged in close spiral, around the conical receptacle. The ovule had short stalk that bear the body of the ovule. Male flowers were discovered from the jurassic period. The microsporophylls were bifid, one half was sterile and the other was fertile. The synangia were arranged along the inner surface of the microsporophylls. Eac microsporophyll had a finger like outgrowth arising from its middle.