Summary of development of frog

Summary of development of frog:

 

1-      Egg + zygote = fertilization

2-      Zygote = rapid division of cells

3-      Meurola= formation of blastocells

4-      Blastolla= gestrolation

5-      Gestrolla= elongation of embryo and formation of neural tubes 

6-      Neurolla= development of tails and gills

7-      Tadepol= metamorphosis -->  adult frog

 

The Hardy- Weinberg theorem of population:

The Hardy- Weinberg theorem:

In 1908, English mathematician Godfrey H. Hardy and German physician Wilhelm Weinberg independently derived a mathematical model describing what happens to the relative frequency of alleles in a sexually reproducing population over time. Their combined ideas became known as the Hardy-Weinberg Theorem. It states that the mixing of alleles at meiosis and their subsequent recombination do not alter the relative frequencies of the alleles in future generations, if certain assumptions  are met. Stated another way, if certain assumptions are  met, evolution will not occur because the relative allelic frequencies will not change from generation to generation, even though the specific mixes of alleles in individuals may vary.

The assumptions of he Theorem are:

1-      Population size must be large. Large size ensures that gene frequency will not change by chance alone.

2-      Individuals cannot migrate into or out of the population. Migration may introduce new alleles into the gene pool or add or delete copies of existing alleles.

3-      Mutations must not occur. If they do, mutational equilibrium must exist. Mutational equilibrium exists when mutation from the wild type allel to a mutant forn is balanced by the mutation from the mutant form back to the wild type. In either case, no new genes are introduced into the population from the sources.

4-      Sexual reproduction within the population must be random. Every individuals must have and equal chance of mating with any other individuals in the population. If this condition is not fulfilled then some individuals are more likely too reproduced than others, and natural selection may occur.

These assumptions must be met if allelic frequencies are not changing that is if evolution is not occurring. Clearly, these assumptions are restrictive and few, if any real population meet them. This mean that most population are evolving.The Hard-Weinberg Theorem does provide a useful theoretical frame work for examining changes in allelic frequencies in population.

CONCEPT OF EVOLUTION

CONCEPT OF EVOLUTION

Main aspects for assignment on concept of evolution are

→ Theories of evolution

→ Homologue and analogue

→ Evidances of evolution

→ Hardy Weinberg Theorm

→ Fossil and fossilization

→Types of frog and their geological scale

°THEORIES OF EVOLUTIONt:

“The formation of complex organisms from simple one ,with the passage of time is known as the process of evolution”

Many scientists made many hypothesis for the concept of evolution,some historical aspects about evolution are given below

1-ARISTOTLE (322-384)B.C

He described concepts of change in living organisms over time.

2-Georges-Louis Buffon(1707-1788)

He spent many years studying comparative anatomy. His observations of structural variations in particular organs of related animals convinced him that change must have occurred during the history of life on earth. Buffon attributed change in organisms to the action of the environment. He believed in a special creation of species and considered change as being degenerate. For example, he described apes as degenerate humans.

3-Eramus Darwin(1731-1802)

A Physician and the grandfather of Charles Darwin, was intensely interested in questions of origin and change. He believed in the common ancestry of all organisms.

4- Jean Baptiste Lamarck (1744-1892)       

He was a distinguished French zoologist. His contributions to zoology include important studies of animal classification. Lamarck published a set of invertebrate zoology books. His theory was based on a widely accepted theory of inheritance that organisms develop new organs, or modify existing organs. Lamarck believed that “ need “ was dictated by environmental change and that change involved movement toward perfection. The idea that change in a species is directed by need logically led Lamarck to the conclusion that species could not become extinct, they simply  evolved into different species.

Lamarck illustrated his ideas of change with the often-quoted example of giraffe. He contended that ancestral giraffes had short necks, much like those of any other mammal. Straining to reach higher branches during browsing resulted in their acquiring higher shoulders and longer necks. These modifications, produced in one generation, were passed on to the next generation. Lamarck published his theory in 1802 and included it in one of his invertebrate zoology books, Philosophie Zoo (1809). He defended his ideas in spite of intense social criticism.

Lamarck’s acceptance of a theory of inheritance that we now know is not correct led him to erroneous conclusions about how evolution occurs. There is no evidence that changes in the environment can initiate changes in organisms that can be passed on to future generations. Instead, change originates in the process of gamete formation.

Homology and Analogy:

Structures and processes of organisms may be alike. There are two reasons for similarities, and both cases provide evidence of evolution. Resemblance may occur when two unrelated organisms adapt to similar conditions. For example, adaption for flight have produced flat, gliding surfaces in the wings of birds and insects. These similarities indicate that independent evolution in these two groups of animals to exploit a common aerial environment. The evolution of superficially similar structures in unrelated organisms is called convergent evolution, and the similar structures are said to be analogous.

Resemblances may also occur because two organisms share a common ancestry. Structures and processes in two kinds of organisms that are derived from common ancestry are said to be homologous. Homology can involve aspects of an organism’s structure, and these homologies are studied in the discipline called comparative anatomy. Homology can also involve aspects of animal development and function and homologous processes are studied using techniques of molecular biology.

Evidences of evolution:

Biogeography:

It was the geographical distribution of species---- biogeography---- that first suggested the idea of evolution to Darwin. Islands have many species of plants and neighboring island. Consider armadillos, the armored mammals that live only in America. The evolutionary view of biogeography predicts that contemporary armadillos record confirms that such ancestors existed.

The Fossil Record:

The succession of fossil forms is a strong evidences in favour of evolution. It provides a visual record in a complete series showing the evolution of an organism. For instance, evidence from biochemistry, molecular biology and cell biology places prokaryotes as the ancestors of all life and predicts and bacteria should precede all eukaryotic life in the fossil record. Indeed, the oldest known fossils are prokaryotes.

Comparative Anatomy:

Anatomical similarities between species grouped in the same taxonomic category bring another support  to the theory of the Descent with modification. For example, the same skeletal elements make up the forelimbs of human, cats, whales, bats, and all other mammals, although these appendages have very different functions. The basic similarity of these forelimbs is the consequence of the descent of all mammals from the common ancestor. The arms, wings, flippers, and forelegs of different mammals are variations on a common anatomical theme that has been modified for divergent functions. Similarities in characteristics resulting from common ancestry is known as homology, and such anatomical signs of evolution are called homologous structures. Common anatomy supports that evolution is a remodeling process in which ancestral structures that functioned in one capacity become modified as they take on new functions. The flower parts of a flowering plant are homologous. They are considered to have evolved from leaves to form sepals, petals, stamens and carpels.

The oldest homologous structures are vestigial organs, rudimentary structures of marginal, if any use to the organism. Vestigial organs are historical remnants of structures that had important functions in ancestors but are no longer essential presently.

Comparative Embroyology:

Closely related organisms go through similar stages in their embryonic development. For example, all vertebrate embryos go through a stage in which they have gill pouches on the slides of their throats. At embryonic stage of development, similarities between fishes, frogs, snakes, birds, humans, and all other vertebrates are much more apparent than differences. As development progresses, the various vertebrates diverge more and more, taking on the distinctive characteristics of their classes.

Molecular biology:

Evolutionary relationships among species are reflected in their DNA and proteins--- in their genes and gene products. If two species have genes and copied from a common ancestor. For example, a common genetic code brings evidence that all life is related. Molecular biology thus provided strong evidence in support of evolution as the basis for the unity and diversity of life.

References: 

                        Stephen A. Miller and John P. Harley 8th edition 

Amaltas plant with their mature seeds

Amaltos plant in 1st figure and second figure contains the mature seeds of this plant (Casia fistula)

List of wild animals

               Crow                                       Corvus bennetti    (Australiain crow)
               Lizard                                      Central bearded dragon, Pogona vitticeps
               Chinkara deer                           Gazella gazelle
               Jackal                                      Canis aureus
               Rabbit                                     Oryctologus  coniculus  
               Porcupine                                Hystrix indica
               African lion                              Panthera leo
               Wild boar                                 Sus scrafa
               Mongoose                               Helogale parvula
               Cobra Snack                           Ophiophagus hannah          
               Fox                                         Vulpus vulpus      
               House sparrow                         Passer domesticus
               Rat                                          Rattus norvigicus
               Jungle cat                                 Fellis chaus
               Parrot                                      Psittacus erithacus (African Grey Parrot )
               Green Pigeon                           Columba livia
               Crocodile                                Crocodylus talusens
               Dolphin                                   Delphinus delphis
               Black bear                               Selenarctos thibetanus
               Leopard (tiger)                        Panthera pardus

CARBOHYDRATES

                                             CARBOHYDRATES:

More than half of all the organic carbon on planet Earth in stored in just two carbohydrates molecules-Starch and cellulose. Both are the polymers of the sugar monomer, glucose.

The only different between them is the manner in which the glucose units are joined together.

When the word ‘’carbohydrate’’ was coined, it originally referred to compounds of the general formula Can (H2O2)n, However, only the simple sugars, or mono-saccharides, fit this formula exactly.

ü Monosaccharaides: Structure and Stereochemistry:-

A Monosaccharaides can be a poly hydroxyl aldehyde (aldose) or a poly hydroxyl ketone (ketoses). The simplest Monosaccharaides contain three carbon atoms are called trioses (tri meaning three). Glyceraldehyde is the aldose with three carbon (an aldose triose), and di hydroxyl acetone is the ketose with three carbon atoms (a keto triose).

Six-carbon sugars are the most abundant in nature, but to five-carbon sugars, ribose and

deoxyribose occur in the structures of RNA and DNA, respectively. Four-carbon and seven-carbon sugars play roles in photosynthesis and other metabolic pathways.

Ø Cyclic Structures: Anomers

Sugars, especially those with five and six carbons atoms, normally exist as cyclic molecules rather than as the open-chain forms. They cy-citation takes place as a result of interaction between for functional groups on distant carbons such as C-1 and C-5 to form a cyclic hemiacetal (in aldohexoses). Another possibility in interaction beyween C-2 and C-5 to form a cyclic hemiketal (in ketohexoses). In either case, the carbonyl carbon becomes a new chiral center called the enomeric carbon. The cyclic sugar can take either of tow different forms, designated a and B, and are called anomers of each other.

ü Oligosaccharides:

Oligomers of sugars frequently occur as disaccharides, form by linking tow monosaccharide’s units by glycosides’ bonds. They are sucrose, lactose and maltose.

Sucrose is the common table sugar extracted from sugarcane and sugar beets. The Monosaccharaides units that make up sucrose are a-D glucose and B-D-fructose. Glucose (an aldohexoses) is a pyranose, and fructose (a ketohexoses) is a furanose. The a C-1 carbon of the glucose is linked to the B C-2 carbon of the fructose in a glycosidic linkage that has the notation Ab (1-2). Sucrose is not a reducing sugar because both anomeric groups.

Lactose is disaccharides made up of B-D-galactose and D-glucose, Galactose is the C-4 epimer of glucose. In other words, the only difference between glucose and galactose is inversion of configuration at C-4.

ü Polysaccharides:

Polysaccharides that occur in organisms are usually composed of a very few types monosaccharide components. A polymer that consists of only one type of monosaccharide is a homopolysaccharide. Glucose is the most common monomer. Cellulose and chitin are polysaccharides with B-glycosidic linkages and are structural materials. Starch and glycogen, also polysaccharides, have a-glycosidic linkages, and serve as carbohydrates storage polymers in plants and animals, respectively.

·        Chitin:

Polysaccharides that is similar to cellulose in both structure and function is chitin, which is also a linear homopolysaccharides with all the residues linked in B (1-4) glycosides’ bonds. Chitin differs from cellulose in the nature of the monosaccharide unit; in cellulose the monomer is B-D-glucose, and in chitin the monomer is N-acetyl-B-D-glucosamine.

·        Glycoproteins:

Glycoproteins contain carbohydrates residues in addition on the polypeptide chain, some of the most important example of glycoproteins are involved in the immune response; for example, antibodies.

The structures of proteins determine Their Functions

Ø The structures of proteins determine Their Functions:

·        Levels of Structure in Proteins:

Biologically active proteins are polymers consisting of amino acids linked by covalent peptide bonds. Many different conformations (three-dimensional structures) are possible for a molecule as large as a protein. Of these many structures, one or, at most. A few have biological activity; these are called the native conformations. Many proteins have no obvious regular repeating structure. As a consequence, these proteins as are frequently described as having large segments of “random structure” (also referred to as random coil). The term random is really a misnomer, since the same nonrepeating structures found in the native conformation of all molecules of a given proteins, and this conformation is needed for its proper function. Because proteins are complex, they are defined in terms of four levels of structure.

v  Primary Structure:-

                                        Primary structure is the order in which the amino acids are covalently linked together, The peptide Leo-Glee-Thru-Val-Argo-Asp-His (recall that the N-terminal amino acids is listed first) has a different primary structure from the peptide Val-His-Asp-Leo-Argo-Thru, even though both have the same number and kinds of amino acids. Note that the order of amino acids can be written on one line. The primary structure is the one-dimensional first step in specifying the three- dimensional structure of protein.

Two three- dimensional aspects of a single Polypeptide chain, called the secondary and tertiary structure, can be considered separately. Secondary structure is the arrangement in space of the atoms in the peptide Backbone. The a-helix and B-pleated sheet arrangements are tow different types of secondary structure. Secondary structures have repetitive interactions resulting from hydrogen bonding between the amide N-H and the carbonyl groups of the peptide backbone. In my proteins, the folding of parts of the chain can occur independently of the folding of other parts. Such independently folded portions of proteins are referred to as domains or super-secondary structure.

v Tertiary Structure:-

                                        Tertiary structure includes the three- dimensional arrangement of all the atoms in the proteins, including those in the side chains and in any prosthetic groups (groups of atoms other than amino acids).

A protein is consisting of multiple polypeptide chains called subunits. The arrangements of subunits respect to one another are the quaternary structure. Interaction between subunits is mediated by monovalent interactions, such as hydrogen bonds, electrostatic attractions, and hydrophobic interactions.

v Quaternary Structure of Proteins:

Each chain is called a subunit. The number of chains can range from tow to more than a dozen, and the chains may be identical of different. Commonly occurring examples are dimmers, timers, and tetramers, consisting of two, three, and four polypeptide chains, respectively. The generic term for such a molecule, made up of a small number of subunits, is oligomer.

o   Hemoglobin:

Hemoglobin is a tetramer, consisting of four polypeptide chains, tow a-chains and tow B-chains (Figure 4.20). The overall structure of hemoglobin is A2B2 in Greek letter notation. Both the a-and B-chains of hemoglobin are very similar to the myoglobin chain. The a-chain is 141 residues long, and the B-chain is 146 residues long; for comparison, the myoglobin chain is 153 residues long. Manu of the amino acids of the a-chain the B-chain and myoglobin are homologous; that is, the same amino acid residues are in the same positions. The heme group is the same in myoglobin and hemoglobin.

o   Myoglobin: An Example of protein structure:-

                                                                                                Myoglobin was the first protein for which the complete tertiary structure was determined by X-ray crystallography. The complete myoglobin consists of a single polypeptide chain of 153 amino acid residues and includes a prosthetic group, the heme group, which also occurs in hemoglobin. The myoglobin molecule (Including a heme group) has a compact structure, with the interior atoms very close to each other. This structure provides examples of many of the force responsible for the three-dimensional shapes of proteins. In myoglobin, three are eight a-helical regions and no B-pleated sheet regions.

Structure and function of liver with special reference to detoxification

               Structure and function of liver with special                                          reference to detoxification

·      What is liver?

ü The liver is the largest internal organ of body.  

ü The body’s second largest organ after the skin.

·      It has four lobes and is surrounded by a capsule of fibrous connective tissue called Glisson’s capsule.                         Location of liver in human body.

The liver is located in the upper right-hand portion of the abdominal cavity, beneath the diaphragm, and on top of the stomach, right kidney, and intestines.

·      Morphology of liver.

ü Shaped like a cone.

ü Liver is a dark reddish-brown organ.

ü Weighs about 3 pounds.

ü It doesn't pulsate.

ü it doesn't move much, only passively, and you don't ordinarily see it secreting anything.

Here is a diagram of liver.

STRUCTURE OF LIVER

The liver holds about one pint (13 percent) of the body's blood supply at any given moment. The liver consists of two main lobes, both of which are made up of thousands of lobules. These lobules are connected to small ducts that connect with larger ducts to ultimately form the hepatic duct. The hepatic duct transports the bile produced by the liver cells to the gallbladder and duodenum (the first part of the small intestine).

·      Over activity of liver.

 When considering a cleansing program. When the liver is over-stressed all other organs start to dysfunction. It is constantly working to break down not only the environmental and external toxins that invade our body though breathing and eating, but also those produced during normal metabolic processes in the body (internal toxins). Many common symptoms such as headaches, mental confusion, muscle pain, fatigue, poor coordination, nerve problems, skin irritations and emotional imbalances can be a result of over exposure to toxins. If liver function can be improved the entire body will benefit.

FUNCTIONS OF LIVER

The liver has a number of important functions, some of the main ones being:

1-Detoxification of potentially toxic chemicals from both inside and outside of the body including drugs, alcohol and toxins from intestinal microbes. Accomplished with antioxidant nutrients and enzymes such as glutathione. The liver detoxifies these harmful substances by a complex series of chemical reactions. The role of these various enzyme activities in the liver is to convert fat soluble toxins into water soluble substances that can be excreted in the urine or the bile depending on the particular characteristics of the end product.

1.   Storage of sugar as 'glycogen' and regulation of blood sugar levels.

2.  Production and storage of proteins as well as the regulation of many substances involved in protein metabolism.

3.  Production of bile which aids in the digestion of fats.

4.    Production of blood proteins, clotting factors and                    red blood cells (erythrocytes).

5.     Regulation of a number of hormones.

6.    Neutralization of 'free-radicals' by antioxidants.          free radicals are highly reactive oxygen molecules that can damage tissues.

    7.  Storage of vitamins, mainly iron, copper, B12, vitamins A, D, E and K

     8.  It plays an important role in digestion (breaking nutrients down)

    9.  Involved with assimilation (building up body tissues).

    10.  Red blood cells, which are responsible for carrying oxygen around the body, are recycled in the liver. 

DETOXIFICATION

Detoxification is the process of clearing toxins from the body or neutralizing or transforming them, and clearing excess mucus and congestion. Many of these toxins come from our diet, drug use, and environmental exposure, both acute and chronic.

Detoxification process:

 The liver is one of the four major organs that eliminate toxins from the body. The other three organs involved are the kidneys, intestinal tract and skin. The liver detoxifies harmful substances whether they come from internal sources such as burning sugars, fats, protein, or from external sources like medications, drugs, hormone enhancers, food additives, preservatives, food colorings, sweeteners, and flavor enhancers, chemicals used in agriculture, alcohols, volatile organic compounds, fumes, air pollution and many other factors. Many of the toxins that enter the body are fat soluble which means they dissolve only in fatty or oily solutions and not it water. They all must travel through the body and the first step in the detoxification process they will encounter is the liver. The liver has to convert fat soluble toxins into water soluble substances that can be excreted from the body.

 The liver plays several roles in detoxification: it filters the blood to remove large toxins, synthesizes and gets rid of bile full of cholesterol and other fat-soluble toxins, and the live enzymatically eliminates unwanted chemicals. The enzymatic process to dispose of toxins occurs in two phases: phase 1 (Oxidations) and phase 2 (Conjugation). Phase 1 neutralizes the toxin or changes the toxic chemical to form activated intermediates which will then be neutralized by phase 2 of the enzyme system. This pathway converts a toxic chemical into a less harmful chemical and is achieved by oxidation, reduction and hydrolysis reactions. During this process, free radicals are produced and if there are too many it can damage the liver cells. With the help of antioxidant, it reduces the damage caused by free radicals. One important antioxidant for neutralizing the free radicals produced in phase 1 is glutathione (GHS) is oxidized to glutathione disulfide (GSSG). This antioxidant is required for one of the key phase 2 processes. When so many free radicals are produced from phase 1, the glutathione stops producing oxidative stress or liver damage. The toxins are then transformed into activated intermediates; therefore the rate at which phase 1 produces activated intermediates must be balanced by the rate at which phase 2 finishes their processing. Phase 2 is called the conjugation pathway because the liver cells add another substance such as cysteine, glycine, or a sulphur molecule to a toxic chemical to make it less harmful. As a result it makes the toxin water-soluble so that it may then be excreted from the body via watery fluids such as bile or urine. 

 Ø Urea cycle : The metabolic pathways in the production of urea are termed as urea termed as urea cycle. Two ammonia and one carbon dioxide molecules are shunted into the to generate one molecule of urea.

One ammonia molecule combine with carbon dioxide and already available precursor from previous cycle ornithine to form citruline, subsequently another ammonia is combines to form arginine. The arginine is split by arginase. The arginine  is split by arginase to form urea and the precursor orthinine for next cycle. 

Mitochondria & Golgi bodies

THE ORIGIN OF MITOCONDRIAL PROTEINS:

A typical eukaryotic cell contains roughly 10`000 different proteins, of which about 10% are in the mitochondria. Because mitochondria synthesize only a dozen proteins, they must import 99% of their proteins from the cytoplasm. In the transfer of such proteins to the mitochondria the proteins need to be located in of four positions:

In the inter membrane space, on the outside of the inner membrane, on the matrix side of the inner membrane and in the matrix.

Most proteins imported into the mitochondria are synthesized with a cleavable N-terminal targeting sequence.

THE ROLE OF GOLGI APPARATUS:

The role of Golgi apparatus is highly specialized for a variety of functions including protein glycosylation and subsequent transport of glycoproteins to their final destinations. Three compartments have been identified in the Golgi apparatus; these are termed cis, medial and Trans. Each compartment is involved in a different stage of protein processing. The last station is named the trans-Golgi network (TGN), which plays a pivotal role in directing proteins to their appropriate cellular destination.