Glucose is the major energy source in most life forms. For instance, polysaccharides are broken down into their monomers (glycogen phosphorylase removes glucose residues from glycogen). Disaccharides like lactose or sucrose are cleaved into their two component monosaccharides.
The metabolic pathway of glycolysis converts glucose to pyruvate by via a series of intermediate metabolites. Each chemical modification (red box) is performed by a different enzyme. Steps 1 and 3 consume ATP (blue) and steps 7 and 10 produce ATP (yellow). Since steps 6-10 occur twice per glucose molecule, this leads to a net production of ATP.
Glucose is mainly metabolized by a very important ten-step pathway calledglycolysis, the net result of which is to break down one molecule of glucose into two molecules of pyruvate. This also produces a net two molecules ofATP, the energy currency of cells, along with two reducing equivalents of converting NAD+ (nicotinamide adenine dinucleotide:oxidised form) to NADH (nicotinamide adenine dinucleotide:reduced form). This does not require oxygen; if no oxygen is available (or the cell cannot use oxygen), the NAD is restored by converting the pyruvate to lactate (lactic acid) (e.g., in humans) or to ethanol plus carbon dioxide (e.g., in yeast). Other monosaccharides like galactose and fructose can be converted into intermediates of the glycolytic pathway.
In aerobic cells with sufficient oxygen, as in most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two more molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH2 as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thus, oxygen is reduced to water and the original electron acceptors NAD+ and quinone are regenerated. This is why humans breathe in oxygen and breathe out carbon dioxide. The energy released from transferring the electrons from high-energy states in NADH and quinol is conserved first as proton gradient and converted to ATP via ATP synthase. This generates an additional 28 molecules of ATP (24 from the 8 NADH + 4 from the 2 quinols), totaling to 32 molecules of ATP conserved per degraded glucose (two from glycolysis + two from the citrate cycle). It is clear that using oxygen to completely oxidize glucose provides an organism with far more energy than any oxygen-independent metabolic feature, and this is thought to be the reason why complex life appeared only after Earth's atmosphere accumulated large amounts of oxygen.
Main article: Gluconeogenesis
In vertebrates, vigorously contracting skeletal muscles (during weightlifting or sprinting, for example) do not receive enough oxygen to meet the energy demand, and so they shift to anaerobic metabolism, converting glucose to lactate. The liver regenerates the glucose, using a process called gluconeogenesis. This process is not quite the opposite of glycolysis, and actually requires three times the amount of energy gained from glycolysis (six molecules of ATP are used, compared to the two gained in glycolysis). Analogous to the above reactions, the glucose produced can then undergo glycolysis in tissues that need energy, be stored as glycogen (or starch in plants), or be converted to other monosaccharides or joined into di- or oligosaccharides. The combined pathways of glycolysis during exercise, lactate's crossing via the bloodstream to the liver, subsequent gluconeogenesis and release of glucose into the bloodstream is called the Cori cycle.
Relationship to other "molecular-scale" biological sciences
Schematic relationship between biochemistry, genetics, and molecular biology
Researchers in biochemistry use specific techniques native to biochemistry, but increasingly combine these with techniques and ideas developed in the fields of genetics, molecular biology and biophysics. There has never been a hard-line among these disciplines in terms of content and technique. Today, the terms molecular biology and biochemistry are nearly interchangeable. The following figure is a schematic that depicts one possible view of the relationship between the fields:
- Biochemistry is the study of the chemical substances and vital processes occurring in living organisms. Biochemists focus heavily on the role, function, and structure of biomolecules. The study of the chemistry behind biological processes and the synthesis of biologically active molecules are examples of biochemistry.
- Genetics is the study of the effect of genetic differences on organisms. Often this can be inferred by the absence of a normal component (e.g., one gene). The study of "mutants" – organisms with a changed gene that leads to the organism being different with respect to the so-called "wild type" or normal phenotype. Genetic interactions (epistasis) can often confound simple interpretations of such "knock-out" or "knock-in" studies.
- Molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. The central dogma of molecular biology where genetic material is transcribed into RNA and then translated into protein, despite being an oversimplified picture of molecular biology, still provides a good starting point for understanding the field. This picture, however, is undergoing revision in light of emerging novel roles for RNA.
- Chemical biology seeks to develop new tools based on small molecules that allow minimal perturbation of biological systems while providing detailed information about their function. Further, chemical biology employs biological systems to create non-natural hybrids between biomolecules and synthetic devices (for example emptied viral capsidsthat can deliver gene therapy or drug molecules).
6. Тexts on biology in english to high school Listening Solution We classify the organisms to study the diversity effectively and easily hence, it is necessary to arrange various kinds of organisms in an orderly manner.
1. We see microscopic bacteria of the range of few micrometers in size. e.g. Plasmodium, amoeba. They live for a short span of time e.g. blue green algae etc.
2. We have bigger animals like 30 meters long or more e.g. blue whale etc. live for long life.
3. We have even more large organisms as red wood tree of California living for thousands of years.
The Plant Kingdom can be further classified into five divisions. Their key characteristics are given below:
1. Thallophytic:- The plant body is simple thallus type. The plant body is not differentiated into root, stem and leaves. They are commonly known as algae. Examples: Spirogyra, char, Volvo, ulothtrix, etc.
2. Bryophyte:- Plant body is differentiated into stem and leaf like structure. Vascular system is absent, which means there is no specialized tissue for transportation of water, minerals and food. Bryophytes are also known as the amphibians of the plant kingdom, because they need water to complete a part of their life cycle. Examples: Moss, merchant.
3. Pteridophyta:- Plant body is differentiated into root, stem and leaf. Vascular system is present. They do not bear seeds and hence are called cryptogams. Plants of rest of the divisions bear seeds and hence are called phanerogams. Examples: Marisela, ferns, horse tails, etc.
4. Gymnosperms:- They bear seeds. Seeds are naked, i.e. are not covered. The word ‘gyms’ means naked and ‘sperm’ means seed. They are perennial plants. Examples: Pine, cycads, deodar, etc.
5. Angiosperms:- The seeds are covered. The word ‘amigos’ means covered. There is great diversity in species of angiosperm. Angiosperms are also known as flowering plants, because flower is a specialized organ meant for reproduction. Angiosperms are further divided into two groups, viz. monocotyledonous and dicotyledonous.
(a) Monocotyledonous: There is single seed leaf in a seed. A seed leaf is a baby plant. Examples: wheat, rice, maize, etc.
(b) Dicotyledonous: There are two cotyledons in a seed. Examples: Mustard, gram, mango, etc.
Biodiversity refers to all the diverse living organisms like plants, animals and micro-organisms present on earth.
The organisms present in this kingdom are eukaryotic, green autotrophs and multicellular.
First they are differentiated on the basis of the plant body they divided on the basis of vascular systems then again divided them on the basis of occurrence of seed and then furthered divided on the basis of seeds are covered or not.
Ғood It is a biologically known fact that, right since the first living organism breathed for the first time billions of years ago, it needed food to survive and grow. Food is something without which growth, development, and evolution would have been impossible. Every living thing on the face of the earth, irrespective of whether it belongs to the plant or animal kingdom, needs nutrition to survive, grow, and reproduce. All the living organisms on earth are therefore, dependent on each other for survival in some way or the other and that is what we call the ecosystem.
The food chain in nature includes both plants and animals who are a part of it and even the tiniest ecosystem has a food chain for itself.
As mentioned above, without food, there is no survival. Therefore, the answer for why is food important is that, when you consume some mode of food and nutrition, the body functions in a particular manner. Without a catalyst, there is no product that is formed and for all living things like plants, animals, and humans, certainly food is the catalyst. Hence, when you consume food, nutrition is provided to the body for the production of energy and in turn, the body is functional. The food pyramid gives us an idea about its value in our lives and how, in a very pictorial and clear manner. This is a very biological and medical purpose of food as you need it for the cycle of life. Charles Darwin also supported the importance of food through the theory of "survival of the fittest".
Transport in living organisms However, the evolution of more and more complex body structures necessitated the development of proper transport system, and more complex the organisms are the more elaborate transport system they have. The complexity of transport system is related to the size and the metabolic rate of the living organism.
The materials to be transported are taken close to tissues be the transport system so that diffusion can occur efficiently into the cells. The primary function of the transport system is to maintain a link between all cells of the body and the external environment. It transports the nutrients to the points where they are to be used facilitates the elimination of metabolic wastes of each cell and transports surplus substances to the specialized storage tissues or to outside their bodies.
Respiration The way in which organisms obtain energy to power their life processes is called respiration, and this takes place in their cells.
Respiration takes the energy stored in foods (such as glucose) and changes it into a form that can be used by the cell.
Mitochondria are the powerhouses of the cell
- they release all the energy it needs. Glucose enters the mitochondria and combines with oxygen. This process gives off energy in the form of a chemical called ATP. Carbon dioxide and water are the waste products. The term «respiration» means the exchange of gases (oxygen and carbon dioxide) which takes place between the living organism and the environment. One must consider that in higher organisms this exchange takes place at several different levels. An initial exchange must occur between the air in the lungs, from which the oxygen is being continually taken up and into which carbon dioxide is being continually poured, and the external air. This is the process of external respiration.
The composition of the air inside the lungs is different from that of the air which we inhale. The content of alveolar air is very constant, especially the one of carbon dioxide, the partial pressure of which is normally 40 mm of mercury. This constancy is the result of a self-regulating mechanism by which the respiratory activity is governed by the amount of carbon dioxide which has been eliminated from the organism.
The exchange of gases varies according to the size and activity of the organism. In man at rest the absorption of oxygen reaches about 0.25 liter a minute and the elimination of carbon dioxide 0.2 liter. At a time of maximum muscular activity, the consumption of oxygen and the production of carbon dioxide may both exceed 4 liters a minute.In physiology, respiration is defined as the movement of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction.
The physiological definition of respiration should not be confused with the biochemical definition of respiration, which refers to cellular respiration: the metabolic process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and 38ATP (energy). Although physiologic respiration is necessary to sustain cellular respiration and thus life in animals, the processes are distinct: cellular respiration takes place in individual cells of the organism, while physiologic respiration concerns the bulk flow and transport of metabolites between the organism and the external environment.
Isolation In microbiology, the term isolation refers to the separation of a strain from a natural, mixed population of living microbes, as present in the environment, for example in water or soil flora, or from living beings with skin flora, oral flora or gut flora, in order to identify the microbe(s) of interest. Historically, the laboratory techniques of isolation first developed in the field of bacteriology and parasitology (during the 19th century), before those in virology during the 20th century. Methods of microbial isolation have drastically changed over the past 50 years, from a labor perspective with increasing mechanization, and in regard to the technology involved, and hence speed and accuracy.
The laboratory techniques of isolating microbes first developed during the 19th century in the field of bacteriology and parasitology using light microscopy. Proper isolation techniques of virology did not exist prior to the 20th century. The methods of microbial isolation have drastically changed over the past 50 years, from a labor perspective with increasing mechanization, and in regard to the technologies involved, and with it speed and accuracy.
In order to isolate a microbe from a natural, mixed population of living microbes, as present in the environment, for example in water or soil flora, or from living beings with skin flora, oral flora or gut flora, one has to separate it from the mix. This can be achieved in two ways;
Traditionally microbes have been cultured in order to identify the microbe(s) of interest based on its growth characteristics. Depending on the expected density and viability of microbes present in a liquid sample, physical methods to increase the gradient as for example serial dilution or centrifugation may be chosen. In order to isolate organisms in materials with high microbial content, such as sewage, soil or stool, serial dilutions will increase the chance of separating a mixture.
In a liquid medium with few or no expected organisms, from an area that is normally sterile (such as CSF, blood inside the circulatory system) centrifugation, decanting the supernatant and using only the sediment will increase the chance to grow and isolate bacteria or the usually cell-associated viruses.
If one expects or looks for a particularly fastidious organism, the microbiological culture and isolation techniques will have to be geared towards that microbe. For example, a bacterium that dies when exposed to air, can only be isolated if the sample is carried and processed under airless or anaerobic conditions. A bacterium that dies when exposed to room temperature (thermophilic) requires a pre-warmed transport container, and a microbe that dries and dies when carried on a cotton swab will need a viral transport medium before it can be cultured successfully.
More recently, microbes have been isolated without culturing them. Samples are inoculated into microtiter plates or cartridges extracting their particular genetic material (DNA or RNA) which can be used to identifying them.
In all living organisms’ plants and animals, physiological processes are continually taking place in their bodies. In order to sustain life, these processes must be kept going on for which the materials required, must be constantly transported to and from all parts of the body right down to the individual cells. Materials are also to be transported between the cell organism and external environment. In unicellular and simple multicultural organisms, the distribution of materials can be adequately brought about by diffusion and streaming movements of the cytoplasm.
Movement All living things have the ability to move without outside help. This makes them different from non-living things that only move if they are pushed or pulled by something else e.g. a stone that is thrown, a stream that flows, paper blowing about. No outside force has to ‘push-start’ growth of a green shoot towards sunlight or a dog to scratch, or YOU to move…. as you are doing right now! All these things are living, so they move by themselves!
You should be able to: state the difference between movement and locomotion. explain the importance of movement to plants describe the different types of movements in plants distinguish between growth movements in plants and movements in animals.
Movement is rhythmical progression, resulting in a change of pace, posture, position or place. All living organisms show movement of one kind or another. They have the innate ability to move substances from one part of their body to another - called internal movement. Many living organisms also show external movement as well -- they can move various body parts, or move their entire body from place to place, i.e. locomotion.
Find water/soil nutrients, and hold leaves to get maximum sunlight Seek and capture food Obtain support
Protect themselves from damage from: touch/pressure, or sudden temperature change Disperse seeds
Unlike many animals, plant movement is non- locomotor. Movement is confined to specific plant parts (e.g. Stems/roots) and is not always obvious because it is very slow. Plant movements are often related to growth. Tropisms are directional growth responses to an external, unilateral stimulus. Tropic growth movements cannot be reversed! Tropic growth movements are caused by chemicals called auxins that are produced in stem and root tips and cause selective cell growth and elongation which will result in either overall growth or growth curvatures of plant parts affected by the auxins.
Plant movement can also be a non-directional response to a stimulus, called a nastic movement. Plant parts (e.g. leaves and leaf structures, flowers, fruits) respond to touch, light, temperature changes and humidity e.g. by opening/closing/folding or bursting to disperse seeds etc.
Like plants, invertebrate animals such as sea anemones, adult sponges and corals, move body parts only and are non- locomotor. These movements are somewhat like nastic movements in plants since they are temporary and reversible. For example, below left -sea anemones can open/close tentacles. Like plants, many invertebrates move in response to light, moisture, chemicals, temperature changes and, additionally, to magnetic and electrical fields. Their movement differs from that of plants, because the animal’s entire body moves about from place to place = locomotion. Such animals move about with the aid of cilia, flagella, false ‘legs/feet’, hydrostatic pressure against their body wall, or they may have an exoskeleton that enables muscle attachment for locomotion.
If we want to now if an organism is a living animal, we usually observe it or prod it to see if it moves. This is because, in response to stimuli, all animals move various body parts and many can also carry on locomotion. In animals, movement and locomotion usually involves the action of muscles (contractile tissue).
You should be able to: discuss the importance of locomotion in animals. Describe movement in animals. differentiate between growth movements in plants and locomotion in animals.
Locomotion is a common response to all kinds of stimuli. Animals to: move about Escape danger Protect themselves from damage from pressure, pain, or sudden temperature changes Find a mate and to reproduce
Why else would the ability to move about be important to animals? Seek and capture food CHECK •To seek shelter, a suitable habitat/climate; •To avoid competition for food/water, living space etc. Muscles help animals such as dogs, whales, spiders, snakes, worms, flies and humans to move from place to place. Muscles also move body parts and things inside the animal’s body. In fact, no animal could move anything inside or outside of its body if there were no muscles. Without muscles, you wouldn't be alive for very long!
Сoordination And Regulation 1. The Coordination System Coordination systems work together to process information received from stimuli and to produce appropriate responses. Animals have two coordination systems:• the nervous system and• the endocrine system.
2. The Nervous System• The nervous system regulates the body’s activities and responses. It works by means of specialized cells called neurons which transmit information in the form of nerve impulses.
3. Nervous System Responses
4. The Endocrine System• The endocrine system regulates and coordinates the body functions by means of chemical substances called hormones. The endocrine system regulates functions which require maintained responses. These include changes during the metamorphosis of some animals, growth, and the production of milk in mammals.
5. Endocrine System Responses
6. Summary• The coordination system tells the body how to respond to a stimulus. The body can coordinate a response quickly with a nerve impulse or over time as chemicals build up and break down in the blood stream.
Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms
Transcription factors are molecules that control gene expression. They are considered "trans" (as opposed to "cis") because they are not part of the DNA sequence directly adjacent to the gene itself. Generally proteins, they can either decrease or increase expression depending on how they interact with the locus.
Homeotic genes are genes which regulate the development of anatomical structures in various organisms such as insects, mammals, and plants.
Determine the direction of developmental fates of groups of cells in a segment of the embryo.
Include a DNA sequence called the home box that is similar in all homeotic genes.
Programmed cell death is part of a normal process in development, metamorphosis and homeostasis. It is responsible for sculpting away cells that are no longer required in the developmental process or have become ‘life-expired’ and need to be replaced. Examples of this include the removal of tail cells during tadpole/frog metamorphosis; the removal of ‘webbing’ that occurs between digits in human embryo development, and the removal of brain cells that have not ‘linked up’ during development – about half the original number. Many chemotherapy treatments for cancer work by inducing cancer cells to undergo apoptosis.
Reproduction Reproduction (or procreation, breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. There are two forms of reproduction: asexual and sexual.
In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms. The cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically similar or identical copy of itself. The evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sex is that only 50% of organisms reproduce and organisms only pass on 50% of their genes.
Sexual reproduction typically requires the sexual interaction of two specialized organisms, called gametes, which contain half the number of chromosomes of normal cells and are created by meiosis, with typically a male fertilizing a female of the same species to create a fertilized zygote. This produces offspring organisms whose genetic characteristics are derived from those of the two parental organisms.
The process by which cells and organisms produce other cells and organisms of the same kind. Cell reproductionusually involves division of a cell into two identical parts by means of mitosis or into four different parts by meiosis. The reproduction of organisms by the union of male and female reproductive cells (gametes) is
called sexualreproduction. Most multicellular animals reproduce sexually.
Reproduction in which offspring are produced by asingle parent, without the union of reproductive cells, is called asexual reproduction. The fission (splitting) ofbacterial cells is a form of asexual reproduction. Many plants and fungi are
capable of reproducing both sexually andasexually, as are some animals, such as sponges.
Cell Cycle Have you ever watched a caterpillar turn into a butterfly? If so, you’re probably familiar with the idea of a life cycle. Butterflies go through some fairly spectacular life cycle transitions—turning from something that looks like a lowly worm into a glorious creature that floats on the breeze. Other organisms, from humans to plants to bacteria, also have a life cycle: a series of developmental steps that an individual goes through from the time it is born until the time it reproduces.
The cell cycle can be thought of as the life cycle of a cell. In other words, it is the series of growth and development steps a cell undergoes between its “birth”—formation by the division of a mother cell—and reproduction—division to make two new daughter cells.
Stages of the cell cycle
To divide, a cell must complete several important tasks: it must grow, copy its genetic material (DNA), and physically split into two daughter cells. Cells perform these tasks in an organized, predictable series of steps that make up the cell cycle. The cell cycle is a cycle, rather than a linear pathway, because at the end of each go-round, the two daughter cells can start the exact same process over again from the beginning.
In eukaryotic cells, or cells with a nucleus, the stages of the cell cycle are divided into two major phases: interphase and the mitotic (M) phase.
- During interphase, the cell grows and makes a copy of its DNA.
- During the mitotic (M) phase, the cell separates its DNA into two sets and divides its cytoplasm, forming two new cells.
Image of the cell cycle. Interphase is composed of G1 phase (cell growth), followed by S phase (DNA synthesis), followed by G2 phase (cell growth). At the end of interphase comes the mitotic phase, which is made up of mitosis and cytokinesis and leads to the formation of two daughter cells. Mitosis precedes cytokinesis, though the two processes typically overlap somewhat.
Growth And Development The spatial and temporal regulation of interactions between molecules is fundamental to life. Growth & Development is dedicated to understanding how these coordinated interactions lead to cell growth, cell division and the development of living organisms.
Life is more complicated than a binary interaction of two factors and its regulation; various processes need to occur in parallel for a cell to function normally. For this reason, this research area covers a broad range of aspects from signal transduction, gene regulatory networks, cell division and cell cycle control to membrane transport, protein and mRNA transport, in a variety of experimental organisms such as bacteria, yeasts, worms, flies, fish and mammals.
Heredity And Variability Evolution is the process by which organisms change over time. Mutations produce genetic variation in populations, and the environment interacts with this variation to select those individuals best adapted to their surroundings. The best-adapted individuals leave behind more offspring than less well-adapted individuals do. Given enough time, one species may evolve into many others.
The oldest verified sample of DNA has been pulled from soil deep within the permafrost of Siberia. The DNA belonged to grasses, sedges and shrubs estimated to be between 300,000 and 400,000 years old.
The most ancient identified animal genetic material is about 50,000 years old. Although there is evidence of plants and animals dating back hundreds of millions of years, DNA from such specimens has not been identified because it has degraded.
Paleomicrobiology is an emerging field that is devoted to the detection, identification and characterization of microorganisms in ancient remains. Data indicate that host-associated microbial DNA can survive for almost 20,000 years, and environmental bacterial DNA preserved in permafrost samples has been dated to 400,000-600,000 years. In addition to frozen and mummified soft tissues, bone and dental pulp can also be used to search for microbial pathogens. Various techniques, including microscopy and immunodetection, can be used in paleomicrobiology, but most data have been obtained using PCR-based molecular techniques. Infections caused by bacteria, viruses and parasites have all been diagnosed using paleomicrobiological techniques. Additionally, molecular typing of ancient pathogens could help to reconstruct the epidemiology of past epidemics and could feed into current models of emerging infections, therefore contributing to the development of appropriate preventative measures.
Selection Selectionin biology, the preferential survival and reproduction or preferential elimination of individuals with certain genotypes (genetic compositions), by means of natural or artificial controlling factors.
The theory of evolution by natural selection was proposed by Charles Darwin and Alfred Russel Wallace in 1858. They argued that species with useful adaptations to the environment are more likely to survive and produce progeny than are those with less useful adaptations, thereby increasing the frequency with which useful adaptations occur over the generations. The limited resources available in an environment promotes competition in which organisms of the same or different species struggle to survive. In the competition for food, space, and mates that occurs, the less well-adapted individuals must die or fail to reproduce, and those who are better adapted do survive and reproduce. In the absence of competition between organisms, selection may be due to purely environmental factors, such as inclement weather or seasonal variations. (Seenatural selection.)
Artificial selection (or selective breeding) differs from natural selection in that heritable variations in a species are manipulated by humans through controlled breeding. The breeder attempts to isolate and propagate those genotypes that are responsible for a plant or animal’s desired qualities in a suitable environment. These qualities are economically or aesthetically desirable to humans, rather than useful to the organism in its natural environment.
In mass selection, a number of individuals chosen on the basis of appearance are mated; their progeny are further selected for the preferred characteristics, and the process is continued for as many generations as is desired. The choosing of breeding stock on the basis of ancestral reproductive ability and quality is known as pedigree selection. Progeny selection indicates choice of breeding stock on the basis of the performance or testing of their offspring or descendants. Family selection refers to mating of organisms from the same ancestral stock that are not directly related to each other. Pure-line selection involves selecting and breeding progeny from superior organisms for a number of generations until a pure line of organisms with only the desired characteristics has been established.
Darwin also proposed a theory of sexual selection, in which females chose as mates the most attractive males; outstanding males thus helped generate more young than mediocre males.
Evolutionary Development Evolutionary development (evolution of development or informally, evo-devo) is a field of biology that compares the developmental processes of different organisms to determine the ancestral relationship between them, and to discover how developmental processes evolved. It addresses the origin and evolution of embryonic development; how modifications of development and developmental processes lead to the production of novel features, such as the evolution of feathers the role of developmental plasticity in evolution; how ecology impacts development and evolutionary change; and the developmental basis of homoplasy and homology.
Although interest in the relationship between ontogeny and phylogeny extends back to the nineteenth century, the contemporary field of evo-devo has gained impetus from the discovery of genes regulating embryonic development in model. General hypotheses remain hard to test because organisms differ so much in shape and form.
Nevertheless, it now appears that just as evolution tends to create new genes from parts of old genes (molecular economy), evo-devo demonstrates that evolution alters developmental processes to create new and novel structures from the old gene networks (such as bone structures of the jaw deviating to the ossicles of the middle ear) or will conserve (molecular economy) a similar program in a host of organisms such as eye development genes in mollusks, insects, and vertebrates. Initially the major interest has been in the evidence of homology in the cellular and molecular mechanisms that regulate body plan and organ development. However, subsequent approaches include developmental changes associated with speciation.
Organismes And Environment
State Of Ecosystems, Habitats And Species In the past, human interaction with nature, although often having a disruptive effect on nature, often also enriched the quality and variety of the living world and its habitats - e.g. through the creation of artificial landscapes and soil cultivation by local farmers.
Today, however, human pressure on natural environments is greater than before in terms of magnitude and efficiency in disrupting nature and natural landscapes, most notably:
- Intensive agriculture replacing traditional farming; this combined with the subsidies of industrial farming has had an enormous effect on western rural landscapes and continues to be a threat.
- Mass tourism affecting mountains and coasts.
- the policies pursued in the industry, transport and energy sectors having a direct and damaging impact on the coasts, major rivers (dam construction and associated canal building) and mountain landscapes (main road networks).
- The strong focus of forestry management on economic targets primarily causes the decline in biodiversity, soil erosion and other related effects.
Human Impact On The Natural Environment Human impact on the environmentoranthropogenic impact on the environmentincludes impacts onbiophysical environments,biodiversity, and other resources.The termanthropogenicdesignates an effect or object resulting fromhuman activity. The term was first used in the technical sense by Russian geologistAlexey Pavlov, and was first used in English by British ecologistArthur Tansleyin reference to human influences onclimaxplant communities.The atmospheric scientistPaul Crutzenintroduced the term "AAnthropocene" in the mid-1970s.The term is sometimes used in the context ofpollutionemissions that are produced as a result of human activities but applies broadly to all major human impacts on the environment.
The applications of technology often result in unavoidable environmental impacts, which according to the I = PAT equation is measured as resource use or pollution generated per unit GDP. Environmental impacts caused by the application of technology are often perceived as unavoidable for several reasons. First, given that the purpose of many technologies is to exploit, control, or otherwise “improve” upon nature for the perceived benefit of humanity while at the same time the myriad of processes in nature have been optimized and are continually adjusted by evolution, any disturbance of these natural processes by technology is likely to result in negative environmental consequences. Second, the conservation of mass principle and the first law of thermodynamics (i.e., conservation of energy) dictate that whenever material resources or energy are moved around or manipulated by technology, environmental consequences are inescapable. Third, according to the second law of thermodynamics, order can be increased within a system (such as the human economy) only by increasing disorder or entropy outside the system (i.e., the environment). Thus, technologies can create “order” in the human economy (i.e., order as manifested in buildings, factories, transportation networks, communication systems, etc.) only at the expense of increasing “disorder” in the environment. According to a number of studies, increased entropy is likely to be correlated to negative environmental impacts.
Applied integrated sciences
Biochemistry and molecular biology (mcdb) A common concern for the life and composition of the cell brings biologists and chemists together in the field of biochemistry-molecular biology. The vast and complex array of chemical reactions occurring in living matter and the chemical composition of the cell are the primary concerns of the biochemist. Life processes occurring at the molecular level, including the storage and transfer of genetic information and the interactions between cells and the viruses that infect them, are the investigatory concerns of the molecular biologist.