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PHYLUM ARTHROPODA

PHYLUM ARTHROPODA

The phylum Arthropoda is the largest and most varied in the animal kingdom. It includes well over one million described species. This represents approximately three-quarters of all known biological organisms, living or extinct. Countless arthropods remain undescribed, and the actual number of living species could be as high as ten million or more. Some of the more well-known arthropods include insects, crustaceans, and spiders. Arthropods are found in virtually every known marine, freshwater, and terrestrial ecosystem, and vary tremendously in their habitats, life histories, and dietary preferences.

Characteristics of Arthropods

All arthropods possess a stiff exoskeleton composed primarily of chitin . In some species, lipids, proteins, and calcium carbonate may also contribute to the exoskeleton. The external skeleton offers organisms protection as well as support for the body. Its walls provide anchors for the attachment of muscles. The exoskeleton is incapable of growth, and is molted repeatedly during the growth of the animal. This process is called ecdysis. Molting allows for rapid growth until the newly secreted exoskeleton hardens.

Arthropod bodies are divided into segments. However, a number of segments are sometimes fused to form integrated body parts known as tagmata. This process of fusion is called tagmosis. The head, thorax, and abdomen are examples of tagmata. Arthropods also have appendages with joints. In early, primitive anthropods, each body segment was associated with a single pair of appendages. However, in most species some appendages have been modified to form other structures, such as mouthparts, antennae, or reproductive organs. 

Some arthropods have highly developed sense organs. Most species have paired compound eyes , and many also have a number of simpler eyes called ocelli. Arthropods have an open circulatory system that consists of a tube that is the heart and an open hemocoel , the coelom of the animal, in which blood pools. Arthropods also have a complete gut with two openings, the mouth and the anus.

Gas exchange in the phylum occurs in various ways. Some species have gills, while others employ tracheae, or book lungs. The tracheal respiratory system consists of external openings called spiracles that are linked to a system of branched tubules which allow respiratory gases to reach internal tissues. Arthropods are characterized by a brain as well as a nerve ring around the area of the pharynx, in the oral cavity. A double nerve cord extends backwards along the ventral surface of the body, and each body segment is associated with its own ganglion, or mass of nerve cells. In most arthropod species, the sexes are separate. Fertilization usually occurs internally, and most species are egg laying. While some species exhibit direct development, in which eggs hatch as miniature versions of adults, other species pass through an immature larval stage and undergo a dramatic metamorphosis before reaching adult form.

Major Groups of Arthropods

Arthropods are divided into four subphyla. These are the Chelicerata, the Crustacea, the Uniramia, and the Trilobita.

Subphylum Chelicerata

 Subphylum Chelicerata comprises a major group within Phylum Arthropoda, including such animals as the arachnids (e.g., spiders and scopions), the extinct eurypterids, and the extant horseshoe crabs that are considered to be living fossils. These arthropods and their ancestral and extinct forms were and are mainly predators. Chelicerates are now predominently terrestrial animals, with most marine chelicerates, including all of the eurypterids, now extinct.

Their name comes from their chelicerae, pointed appendages that grasp food, that differ from the chewing mandibles of most arthropods. Being unable to ingest solid food, most Chelicerata either drink blood or spit or otherwise inject digestive enzymes into their prey, and feed on the fluidized result. Like all arthropods, chelicerates' bodies and appendages are covered with a tough cuticle primarily composed of chitin and proteins that chemically harden. Because this exoskeleton cannot stretch, chelicerates have to molt in order to grow. Thus, they have to molt the old, and await hardening of the new, during which time they have reduced mobility and are otherwise more defenseless.

Subphylum Crustacea

Members of Subphylum Crustacea (the Crustaceans) comprise a large group of arthropods. The group contains familiar popular marine food animals such as lobsters, crabs, shrimp. While mainly found in salt and freshwater environments, there are also terrestrial Crustacea such as woodlice and isopods. Crustaceans have three distinct body parts: head, thorax, and abdomen (also called a pleon). In some, the head and thorax are fused to form a cephalothorax. They have two pairs of antennae on the head, compound eyes, three pairs of mouthparts and a telson. Crustaceans often have a thick carapace on the top (dorsal) side that makes fossilization more likely; crabs and lobsters, for example, have a thicker exoskeleton containing calcium carbonate that is more readily fossilized.

Subphylum Uniramia

Uniramia (uni - one, ramus - branch, i.e. single-branches) is a group within the arthropods. In the past this group included the Onychophora, which are now considered a separate category. The group is currently used in a narrower sense.

Uniramia is one of three subphyla in Arthropoda classification suggested by Sidnie Manton. This classification divided arthropods into a three-phyla polyphyletic group, with phylum Uniramia including the Hexapoda (insects), Myriapoda (centipedes and millipedes) and the Onychophora (velvetworms). The discovery of fossil lobopods, determined to be intermediate between onychophorans and arthropods led to the splintering of the Lobopoda and Onychophora into separate groups. This redefined the Uniramia as strictly "true" arthropods with exoskeletons and jointed appendages. Uniramians have strictly uniramous appendages.

Subphylum Trilobita

The subphylum Trilobita includes only extinct species found in fossil form. The trilobites were a primitive group of marine species that was particularly abundant during the Cambrian (570 million years ago) and Ordovician (505 million years ago) periods. The group became extinct at the end of the Permian (286 million years ago). Trilobites had flattened, oval-shaped bodies. Most were a few inches long, although one species is known to have attained a length of 0.6 meters (2 feet).

 By

Reshma P

VASCULAR BUNDLES

VASCULAR BUNDLES

Plants have two systems for the transportation of substances - using two different types of transport tissue. Xylem transports water and solutes from the roots to the leaves, while phloem transports food from the leaves to the rest of the plant. Transpiration is the process by which water evaporates from the leaves, which results in more water being drawn up from the roots. Plants have adaptations to reduce excessive water loss.

Xylem and phloem

Plants have two transport systems to move food, water and minerals through their roots, stems and leaves. These systems use continuous tubes called xylem and phloem, and together they are known as vascular bundles.

Plant stem

Stem – the xylem and phloem are arranged in bundles near the edge of the stem to resist compression and bending forces.

Plant root

Root - xylem and phloem in the centre of the root to withstand stretching forces.

Xylem

Xylem vessels are involved in the movement of water through a plant - from its roots to its leaves via the stem.

During this process:

1. Water is absorbed from the soil through root hair cells.
2. Water moves by osmosis from root cell to root cell until it reaches the xylem.
3. It is transported through the xylem vessels up the stem to the leaves.
4. It evaporates from the leaves (transpiration).

The xylem tubes are made from dead xylem cells which have the cell walls removed at the end of the cells, forming tubes through which the water and dissolved mineral ions can flow. The rest of the xylem cell has a thick, reinforced cell wall which provides strength.

Phloem

Phloem vessels are involved in translocation. Dissolved sugars, produced during photosynthesis, and other soluble food molecules are moved from the leaves to growing tissues (eg the tips of the roots and shoots) and storage tissues (eg in the roots).

In contrast to xylem, phloem consists of columns of living cells. The cell walls of these cells do not completely break down, but instead form small holes at the ends of the cell. The ends of the cell are referred to as sieve plates. The connection of phloem cells effectively forms a tube which allows dissolved sugars to be transported.

Transpiration

Water on the surface of spongy and palisade cells (inside the leaf) evaporates and then diffuses out of the leaf. This is called transpiration. 

leaf

More water is drawn out of the xylem cells inside the leaf to replace what has been lost. Water molecules have a tendency to stick together – so as water leaves the xylem to enter the leaf, more water is pulled up behind it. This produces a continuous flow of water and dissolved minerals moving up the xylem tube from the roots, up the stem, and into the leaves. This is known as the transpiration stream.

Movement of water through the roots

The movement of water up the xylem means more water must be drawn in through the roots from the soil. To do this, water passes from root cell to root cell by osmosis.

The pathway of water across a root

As water moves into the root hair cell down the concentration gradient, the solution inside the root hair cell becomes more dilute. This means that there is now a concentration gradient between the root hair cell and adjacent root cells, so water moves from the root hair cell and into the adjacent cells by osmosis.
This pattern continues until the water reaches the xylem vessel within the root - where it enters the xylem to replace the water which has been drawn up the stem.

Factors that affect transpiration rate

Light

Transpiration increases in bright light. The stomata open wider to allow more carbon dioxide into the leaf for photosynthesis. More water is therefore able to evaporate. 

Temperature

Transpiration is faster in higher temperatures. Evaporation and diffusion are faster at higher temperatures.

Wind

Transpiration is faster in windy conditions. Water vapour is removed quickly by air movement, speeding up diffusion of more water vapour out of the leaf.

Humidity

Transpiration is slower in humid conditions. Diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air.

Factors that speed up transpiration will also increase the rate of water uptake from the soil. If the loss of water is faster than the rate at which it is being replaced by the roots, then plants can slow down the transpiration rate by closing some of their stomata. This is regulated by guard cells, which lie on either side of a stoma.

Plants can slow down the transpiration rate by closing some of their stomata

If the guard cells are turgid, then they curve forming ‘sausage-shaped’ structures with a hole between them. This is the stoma.
However, if the guard cells are flaccid due to water loss, they shrivel up and come closer together, closing the stoma. This is turn reduces the water loss due to transpiration, and can prevent the plant from wilting.

By

Vinesh S

 

IMMUNOLOGY

IMMUNOLOGY

Anything that causes an immune response is called an antigen. An antigen may be harmless, such as grass pollen, or harmful, such as the flu virus. Disease-causing antigens are called pathogens. The immune system is designed to protect the body from pathogens. 

In humans, the immune system begins to develop in the embryo. The immune system starts with hematopoietic (from Greek, "blood-making") stem cells. These stem cells differentiate into the major players in the immune system (granulocytes, monocytes, and lymphocytes). These stems cells also differentiate into cells in the blood that are not involved in immune function, such as erythrocytes (red blood cells) and megakaryocytes (for blood clotting). Stem cells continue to be produced and differentiate throughout your lifetime. 

Hematopoietic stem cells produce cells in blood and lymph

By the time a baby is born, the immune system is a sophisticated collection of tissues that includes the blood, lymphatic system, thymus, spleen, skin, and mucosa. The immune system is typically divided into two categories--innate and adaptive--although these distinctions are not mutually exclusive. 

Innate immunity

Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. The innate immune response is activated by chemical properties of the antigen.

Adaptive immunity

Adaptive immunity refers to antigen-specific immune response. The adaptive immune response is more complex than the innate. The antigen first must be processed and recognized. Once an antigen has been recognized, the adaptive immune system creates an army of immune cells specifically designed to attack that antigen. Adaptive immunity also includes a "memory" that makes future responses against a specific antigen more efficient.

The cellular system

• T-cells differentiate in the thymus, and have a specific receptor for a fragment of antigen..
• Cytotoxic T-cells contain a surface protein called CD8 and destroy pathogen infected cells, cancer cells, and foreign cells (transplanted organs).
• Helper T-cells contain a surface protein called CD4 and regulate both the cellular and humoral immune systems. This regulation reduces autoimmunity.
• Autoimmune disease- self immunity. Some examples include rheumatic fever, rheumatoid arthritis, ulcerative colitis, myasthenia gravis, etc.

Immunological response 

The graph shows a very important feature of the immune response. When first exposed to antigen "A", we begin to make low levels of antibody in about a week However, a second exposure to antigen "A" produces a much faster response, and several orders of magnitude higher levels of antibody. The ability of antibody to bind antigen also increases dramatically in the secondary response. Injecting a new antigen "B" with "A" shows that a memory or prior exposure is required for the accelerated response. The memory of antigen and the stimulated response is the basis for success in vaccination programs.

The Clonal Selection Theory

• The immune systems produces Billions of kinds of B-cells each making one kind of antibody receptor.
• The presence of antigen leads to the proliferation and differentiation of clones that have antibody capable of binding the antigen. In the diagram the "green" antigen binds to the green antibody on a B-cell. The color code means that only this antibody receptor on the cell binds free antigen.
• The "green" helper T-cell must give a stimulatory signal to allow a particular B-cell to be selected. This step allows a regulation or control of the process.
• The antigen driven selection produces memory cells and plasma cells secreting antibody capable of binding the original selecting antigen with high affinity..
• If antigen appears in the organism a second time, then the memory cells are already present at high levels, and produce a more rapid and much stronger immune response. 

 By

Aparna S M

BIOMOLECULES

BIOMOLECULES

Biomolecules are molecules that occur naturally in living organisms. Biomolecules include macromolecules like proteins, carbohydrates, lipids and nucleic acids. It also includes small molecules like primary and secondary metabolites and natural products. Biomolecules consists mainly of carbon and hydrogen with nitrogen, oxygen, sulphur, and phosphorus. Biomolecules are very large molecules of many atoms, that are covalently bound together. 

CLASSES OF BIOMOLECULES

There are four major classes of biomolecules: 

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

Carbohydrates

Carbohydrates are good source of energy. Carbohydrates (polysaccharides) are long chains of sugars. Monosaccharides are simple sugars that are composed of 3-7 carbon atoms. They have a free aldehyde or ketone group, which acts as reducing agents and are known as reducing sugars. Disaccharides are made of  two monosaccharides. The bonds shared between two monosaccharides is the glycosidic bonds. Monosaccharides and disaccharides are sweet, crystalline and water soluble substances.Polysaccharides are polymers of monosaccharides. They are unsweet, and complex carbohydrates.They are insoluble in water and are not in crystalline form. 

Example: glucose, fructose, sucrose, maltose, starch, cellulose etc.

Lipids

Lipids are composed of long hydrocarbon chains. Lipid molecules hold a large amount of energy and are energy storage molecules. Lipids are generally esters of fatty acids and are building blocks of biological membranes. Most of the lipids have a polar head and non-polar tail. Fatty acids can be unsaturated and saturated fatty acids.

Lipids present in biological membranes are of three classes based on the type of hydrophilic head present:

• Glycolipids are lipids whose head contains oligosaccharides with 1-15 saccharide residues.  
• Phospholipids contain a positively charged head which are linked to the negatively charged phosphate groups. 
• Sterols, whose head contain a steroid ring. Example steroid.

Example of lipids: oils, fats, phospholipids, glycolipids, etc.

Proteins

Proteins are heteropolymers of stings of amino acids. Amino acids are joined together by the peptide bond which is formed in between the carboxyl group and amino group of successive amino acids. Proteins are formed from 20 different amino acids, depending on the number of amino acids and the sequence of amino acids. 

There are four levels of protein structure:

• Primary structure of Protein - Here protein exist as long chain of amino acids arranged in a particular sequence. They are non-functional proteins.
• Secondary structure of protein - The long chain of proteins are folded and arranged in a helix shape, where the amino acids interact by the formation of hydrogen bonds. This structure is called the pleated sheet. Example: silk fibres. 
• Tertiary structure of protein - Long polypeptide chains become more stabilizes by folding and coiling, by the formation of ionic or hydrophobic bonds or disulphide bridges, this results in the tertiary structure of protein.
• Quaternary  structure of protein - When a protein is an assembly of more than one polypeptide or subunits of its own, this is said to be the quaternary structure of protein. Example: Haemoglobin, insulin.

Nucleic Acids

Nucleic acids are organic compounds with heterocyclic rings. Nucleic acids are made of polymer of nucleotides. Nucleotides consists of nitrogenous base, a pentose sugar and a phosphate group. A nucleoside is made of nitrogenous base attached to a pentose sugar. The nitrogenous bases are adenine, guanine, thyamine, cytosine and uracil. Polymerized nucleotides form DNA and RNA which are genetic material. 

FUNCTIONS OF BIOMOLECULES

Carbohydrates provide the body with source of fuel and energy, it aids in proper functioning of our brain, heart and nervous, digestive and immune system. Deficiency of carbohydrates in the diet causes fatigue, poor mental function.

Each protein in the body has specific functions, some proteins provide structural support, help in body movement, and also defense against germs and infections. Proteins can be antibodies, hormonal, enzymes and contractile proteins.

Lipids, the primary purpose of lipids in body is energy storage. Structural membranes are composed of lipids which forms a barrier and controls flow of material in and out of the cell. Lipid hormones, like sterols, help in mediating communication between cells.

Nucleic Acids are the DNA and RNA, they carry genetic information in the cell. They also help in synthesis of proteins, through the process of translation and transcription.

STRUCTURE OF BIOMOLECULES

Structure of biomolecule is intricate folded, three-dimensional structure that is formed by protein, RNA, and DNA. The structure of these molecules are in different forms, primary, secondary, tertiary and quaternary structure. The scaffold for this is provided by the hydrogen bonds within the molecule.

• Primary structure of a biomolecule is the exact specification of its atomic composition and and the chemical bonds connecting the atoms. 
• Secondary structure of the biomolecule is the three-dimensional form of biopolymers, secondary structure is defined by the hydrogen bonds of the biomolecules. 
• Tertiary structure of the biomolecule is the three-dimensional structure,defined by its atomic coordinates, by the formation of hydrogen, ionic or sulphide bonds. 
• Quaternary structure is the arrangement of multiple folds of complex, in a mutli-subunit complex.

By

Bincy mol

KINGDOM MONERA

KINGDOM MONERA

Kingdom Monera - All the organisms of this kingdom are prokaryotes. Complex structure was the basis of classification of organisms, many centuries ago. According to R.H. Whittaker's five kingdom classification all the bacteria were placed under the Kingdom Monera.Monera are considered as the most primitive group of organisms. They include various types of bacteria and blue-green algae.Monerans are most abundant of all organisms, due to their versatility of their habitat.It is estimated that a single drop of water contains 50 billion bacteria.

The Kingdom Monera includes organisms that are single-celled known as bacteria. The microorganisms in Kingdom Monera are considered as the most ancient living forms on earth. The kingdom is divided into two groups Archaebacteria and Eubacteria. All the organisms of this kingdom are prokaryotes. These cells do not have nuclear membrane, the chromosome is a single and circular, they also lack membrane bound cellular organelles. This kingdom includes bacteria, cyanobacteria, mycoplasma etc. They are unicellular organisms and do not have specific mode of nutrition. They can be either aerobic or anaerobic.These organisms have cell wall which is made up of peptidoglycans. The cell organelles are not membrane bound. Cell organelles like endoplasmic reticulum, mitochondria are absent. Reproduction is by spore formation and binary fission.

General characteristics of the kingdom Monera are as follows:  

• They are primitive organisms.
• All organisms of the kingdom are prokaryotes.
• They are present in both living and non-living environment.
• They can survive in harsh and extreme climatic conditions like in hot springs, acidic soils etc.
• They are unicellular organisms.
• Membrane bound nucleus is absent.
• DNA is in double stranded form, suspended in the cytoplasm of the organism,referred as nucleoid.  
• A rigid cell wall is present.
• Membrane bound cellular organelles like mitochondria are absent.
• Habitat - Monerans are found everywhere in hot springs, under ice, in deep ocean floor, in deserts and on or inside the body of plants and animals.
• Nutrition - autotrophs - can prepare their own food, heterotrophs - depend on others for food, saprophytes - feed on dead and decaying matter, parasitic - live on other host cells for survival and cause, symbiotic - in mutual relation with other organisms, commensalism - it is where one organism is benefited and the other is not affected, mutualism - where both the organisms are benefited.
• Respiration - respiration in these organisms vary, they may be obligate aerobes - the organisms must have organisms for survival; obligate anaerobes - the organisms cannot survive in the presence of oxygen; facultative anaerobes - these organisms can survive with or without oxygen. 
• Circulation - is through diffusion. 
• Movement - is with the help of flagella.
• Reproduction is mostly asexual, sexual reproduction is also seen. 

  

Reproduction in BacteriaReproduction in bacteria is mainly by fission.Under unfavourable conditions they reproduce by spores. Sexually bacteria reproduce by a primitive mode of DNA transfer from one bacterium to another i.e., by conjugation, transduction or  transformation. 

Mycoplasma

Mycoplasma are the known to be the smallest living cells. They completely lack cell wall and can survive without oxygen. Most of the mycoplasma are pathogenic in nature in animals and plants. 

Economic Importance of Bacteria

Lactic acid bacteria like Lactobacillus and Lactococcus have been used in fermentation process for thousands of years.
The ability of the bacteria to degrade variety of organic compounds has been used in waste management processing and biorememdiation.In pest control, bacteria can be used in the place of pesticides as these pesticides are regarded environmentally friendly.

Example: Bacillus thuringenesis.
The ability of the bacteria in dividing rapidly and by studies on the bacterial genome, these bacteria can be bio-engineered for the production of  therapeutic proteins like insulin, growth factors and antibodies, etc. 

By

Aswathy.V S 

ECOLOGY

ECOLOGY

Ecology is the study of environmental systems, or as it is sometimes called, the economy of nature. "Environmental" usually means relating to the natural, versus human-made world; the "systems" means that ecology is, by its very nature, not interested in just the components of nature individually but especially in how the parts interact. Ecology is technically an academic discipline, such as mathematics or physics, although in public or media use, it is often used to connote some sort of normative or evaluative issue as in something is “ecologically bad” or is or is not “good for the ecology”. More properly ecology is used only in the sense that it is an academic discipline, no more evaluative than mathematics or physics. When a normative or evaluative term is needed then it is more proper to use the term “environmental”, i.e., environmental quality or “environmentally degrading”. Most professional ecologists are not terribly unhappy when ecology is used in the normative sense, preferring the wider public awareness of environmental issues today compared to the widespread ignorance of three decades ago. 

The subject matter of ecology is normally divided onto four broad categories: physiological ecology, having to do with the response of single species to environmental conditions such as temperature or light; popolation ecology, usually focusing on the abundance and distribution of individual species and the factors that cause such distribution; community ecology, having to do with the number of species found at given location and their interactions; and ecosystems ecology, having to do with the structure and function of the entire suite of microbes, plants, and animals, and their abiotic environment, and how the parts interact to generate the whole. This branch of ecology often focuses on the energy and nutrient flows of ecosystems, and when this approach is combined with computer analysis and simulation we often call it systems ecology. Evolutionary ecology, which may operate at any of these levels but most commonly at the physiological or population level, is a rich and dynamic area of ecology focusing on attempting to understand how natural selection developed the structure and function of the organisms and ecosystems at any of these levels. 

Ecology is usually considered from the perspective of the specific geographic environment that is being studied at the moment: tropical rain forest, temperate grassland, arctic tundra, benthic marine, the entire biosphere, and so on. Thus you might study the population ecology of lions in an African savanna, an ecosystems study of a marine benthic environment, global nutrient budgets, and so on. The subject matter of ecology is the entire natural world, including both the living and the non living parts. Biogeography focuses on the observed distribution of plants and animals and the reasons behind it. More recently ecology has included increasingly the human-dominated world of agriculture, grazing lands for domestic animals, cities, and even industrial parks. Industrial  ecology is a discipline that has recently been developed, especially in Europe, where the objective is to follow the energy and material use throughout the process of, e.g., making an automobile with the objective of attempting to improve the material and energy efficiency of manufacturing. For any of these levels or approaches there are some scientists that focus on theoretical ecology, which attempts to derive or apply theoretical or sometimes mathematical reasons and generalities for what is observed in nature, and empirical ecology, which is concerned principally with measurement. Applied ecology takes what is found from one or both of these approaches and uses it to protect or manage nature in some way. Related to this discipline is conservation biology. Plant ecology, animal ecology, and microbial ecology have obvious foci.

 

There are usually four basic reasons given to study and as to why we might want to understand ecology: first, since all of us live to some degree in a natural or at least partly natural ecosystem, then considerable pleasure can be derived by studying the environment around us. Just as one might learn to appreciate art better through an art history course so too might one appreciate more the nature around us with a better understanding of ecology. Second, human economies are in large part based on the exploitation and management of nature. Applied ecology is used every day in forestry, fisheries, range management, agriculture, and so on to provide us with the food and fiber we need. For example, in Argentina in many circles there is no difference between ecology and agriculture, which is essentially the ecology of crops and pastures. Third, human societies can often be understood very clearly from an ecological perspectives as we study, for example, the population dynamics (demography) of our own species, the food and fossil energy flowing through our society. Fourth, humans appear to be changing aspects of the global environment in many ways. Ecology can be very useful to help us understand what these changes are, what the implications might be for various ecosystems, and how we might intervene in either human economies or in nature to try to mitigate or otherwise alter these changes. There are many professional ecologists, who believe that these apparent changes from human activities have the potential to generate enormous harm to both natural ecosystems and human economies. Understanding, predicting and adapting to these issues could be the most important of all possible issue for humans to deal with. In this case ecology and environmentalism can be the same.

Since ecology by its very nature is an integrative discipline, science students preparing themselves professionally in the field are encouraged to take a broad suite of courses, mostly in the natural sciences and including physics, chemistry, and biology of many sorts but certainly including evolution,  meteorology, hydrology, geography, and so on. Ecologists interested in human ecology are encouraged to take courses and undertake readings in agronomy, demography, human geography, sociology, economics, and so on. Since ecology is so broad there are many things that an ecologist might wish to do and to train for. Today many ecology courses are taught in biology departments, where the focus is often on population or community ecology and also individual species.

Ecology should be more than just a set of ideas and principles that one might learn in a classroom or book but rather more a way of looking at the world which emphasizes the assessment and understanding of how the pieces fit together, how each influences and is influenced by the other pieces and how the whole operates in ways not really predictable from the pieces. When we are lucky we are able to capture these relations in conceptual, mathematical or, increasingly, computer models that allow us some sense of truly understanding the great complexity of nature, including as it is impacted by human activity. This is the goal of most ecologists.

By

Bincy mol

GENETICS

GENETICS

Genetics is the study of genes — what they are, what they do, and how they work. Genes are made up of molecules inside the nucleus of a cell that are strung together in such a way that the sequence carries information: that information determines how living organisms inherit phenotypic traits, (features) determined by the genes they received from their parents and thereby going back through the generations. For example, offspring produced by sexual reproduction usually look similar to each of their parents because they have inherited some of each of their parents' genes. Genetics identifies which features are inherited, and explains how these features pass from generation to generation. In addition to inheritance, genetics studies how genes are turned on and off to control what substances are made in a cell - gene expression; and how a cell divides - mitosis or meiosis.

Some phenotypic traits can be seen, such as eye color while others can only be detected, such as blood type or intelligence. Traits determined by genes can be modified by the animal's surroundings (environment): for example, the general design of a tiger's stripes is inherited, but the specific stripe pattern is determined by the tiger's surroundings. Another example is a person's height: it is determined by both genetics and nutrition.

Genes are made of DNA, which is divided into separate pieces called chromosomes. Humans have 46: 23 pairs, though this number varies between species, for example many primates have 24 pairs. Meiosis creates special cells, sperm in males and eggs in females, which only have 23 chromosomes. These two cells merge into one during the fertilization stage of sexual reproduction, creating a zygote in which a nucleic acid double helix divides, with each single helix occupying one of the daughter cells, resulting in half the normal number of genes. The zygote then divides into four daughter cells by which time genetic recombination has created a new embryo with 23 pairs of chromosomes, half from each parent. Mating and resultant mate choice result in sexual selection. In normal cell division (mitosis) is possible when the double helix separates, and a complement of each separated half is made, resulting in two identical double helices in one cell, with each occupying one of the two new daughter cells created when the cell divides.

Chromosomes all contain four nucleotides, abbreviated C (cytosine), G (guanine), A (adenine), or T (thymine), which line up in a particular sequence and make a long string. There are two strings of nucleotides coiled around one another in each chromosome: a double helix. C on one string is always opposite from G on the other string; A is always opposite T. There are about 3.2 billion nucleotide pairs on all the human chromosomes: this is the human genome. The order of the nucleotides carries genetic information, whose rules are defined by the genetic code, similar to how the order of letters on a page of text carries information. Three nucleotides in a row - a triplet - carry one unit of information: a codon.

The genetic code not only controls inheritance: it also controls gene expression, which occurs when a portion of the double helix is uncoiled, exposing a series of the nucleotides, which are within the interior of the DNA. This series of exposed triplets (codons) carries the information to allow machinery in the cell to "read" the codons on the exposed DNA, which results in the making of RNA  molecules. RNA in turn makes either amino acis or microRNA, which are responsible for all of the structure and function of a living organism; i.e. they determine all the features of the cell and thus the entire individual. Closing the uncoiled segment turns off the gene. 

Heritability means the information in a given gene is not always exactly the same in every individual in that species, so the same gene in different individuals does not give exactly the same instructions. Each unique form of a single gene is called an allale: different forms are collectively called polymorphisms.  As an example, one allele for the gene for hair color and skin cell pigmentation could instruct the body to produce black pigment, producing black hair and pigmented skin; while a different allele of the same gene in a different individual could give garbled instructions that would result in a failure to produce any pigment, giving white hair and no pigmented skin: albinism. Mutations are random changes in genes creating new alleles, which in turn produce new traits, which could help, harm, or have no new effect on the individual's likelihood of survival; thus, mutations are the basis for evolution.  

By

Aparna S M

NUTRITION

NUTRITION

Nutrition is the science that interprets the interaction of nutrients and other substances in food (e.g. phytonutrients, anthocyanins, tannins, etc.) in relation to maintenance, growth, reproduction, health and disease of an organism. It includes food intake, absorption, assimilation, biosynthesis, catabolism and excretion.

The diet of an organism is what it eats, which is largely determined by the availability, the processing and palatability of foods. A healthy diet includes preparation of food and storage methods that preserve nutrients from oxidation, heat or leaching, and that reduce risk of food-born illnesses. 

Registered dietitian nutritionists (RDs or RDNs) are health professionals qualified to provide safe, evidence-based dietary advice which includes a review of what is eaten, a thorough review of nutritional health, and a personalized nutritional treatment plan. They also provide preventive and therapeutic programs at work places, schools and similar institutions. Certified Clinical Nutritionists or CCNs, are trained health professionals who also offer dietary advice on the role of nutrition in chronic disease, including possible prevention or remediation by addressing nutritional deficiencies before resorting to drugs. Government regulation especially in terms of licensing, is currently less universal for the CCN than that of RD or RDN. Another advanced Nutrition Professional is a Certified Nutrition Specialist or CNS. These Board Certified Nutritionists typically specialize in obesity and chronic disease. In order to become board certified, potential CNS candidate must pass an examination, much like Registered Dieticians. This exam covers specific domains within the health sphere including; Clinical Intervention and Human Health.

A poor diet may have an injurious impact on health, causing deficiency diseases such as blindness, anemia, scurvy, preterm birth, stillbirth and cretinism; health-threatening conditions like obesity and metabolic syndrome; and such common chronic systemic diseases as cardiovascular disease, diabetes and osteoporosis. A poor diet can cause the wasting of kwashiorker in acute cases, and the stunting of marasmus in chronic cases of malnutrition. 

Nutrients

Nutrients are thought to be of two types: macro-nutrients which are needed in relatively large amounts, and micro-nutrients which are needed in smaller quantities. A type of carbohydrate, dietary fiber i.e. non-digestible material such as cellulose, is required, for both mechanical and biochemical reasons, although the exact reasons remain unclear. Other micronutrients include antioxidants and phytochemicals, which are said to influence (or protect) some body systems. Their necessity is not as well established as in the case of, for instance, vitamins. Most foods contain a mix of some or all of the nutrient types, together with other substances, such as toxins of various sorts. Some nutrients can be stored internally (e.g., the fat-soluble vitamins), while others are required more or less continuously. Poor health can be caused by a lack of required nutrients or, in extreme cases, too much of a required nutrient. For example, both salt and water (both absolutely required) will cause illness or even death in excessive amounts.

Macronutrients are nutrients that provide calories or energy. Nutrients are substances needed for growth, metabolism, and for other body functions. Since “macro” means large, macronutrients are nutrients needed in large amounts. There are three macronutrients:

• Carbohydrate
• Protein
• Fat

While each of these macronutrients provides calories, the amount of calories that each one provides varies.

Carbohydrate provides 4 calories per gram.
Protein provides 4 calories per gram.
Fat provides 9 calories per gram.

Micronutrients are found naturally in a variety of plant- and animal-based foods. Although they can now be synthesized in the laboratory, a varied diet typically provides all of the vitamins and minerals necessary for human health. In many settings, however, such foods are not available and provide a major threat to the health and development of populations around the globe. Micro-nutrient deficiencies, are the leading cause of mental retardation, preventable blindness, and death during childbirth.

A lack of these important vitamins and minerals also has a profound impact on the body’s immune system. Immune systems weakened by a lack of micronutrients puts children at increased risk of illness.

By

Aswathy. V S