Thursday, April 24, 2008

The Amazing World of Reptiles

By : Brandon Cornett

Reptiles are one of the most diverse groups in the animal kingdom. Their behaviors and physical attributes cover a broad spectrum, which is one of the reasons we humans find them so fascinating.

This article illustrates the amazing diversity found within the animal kingdom. Below, I have compiled what I feel are some of the most interesting facts about reptiles and their behavior.

Interesting Reptile Facts

  • Contrary to popular belief, chameleons do not change their color to blend in with different backgrounds. Chameleons are naturally camouflaged with their su rroundings (most are predominantly green to match their treetop environment). The fact is that chameleons change their color in limited ways, usually by brightening or darkening their skin.

    But these color changes are related to temperature regulation and emotional changes. A frigh tened or angry chameleon, for example, will become extremely bright in color.

  • The skulls of snakes are made up of many small bones that are interconnected i n a flexible fashion. This is entirely different from a human skull, which is one solid piece. This allows snakes to expand their jaws and heads in order to eat prey items larger than their heads. A common garter snake, for example, could swallow a frog more than twice the size of its head. Large constrictors such as the anaconda can expand their jaws to an almost alarming degree!
  • Many people think that reptiles are slimy. But the fact is that reptiles do not have sweat glands like you and I have, so their skin is usually cool and dry. I have several pet snakes for example, and people who touch them for the first time always say the same thing: "Oh wow, they're not slimy at all."

  • The scales of all snakes (and many lizard species) are made of keratin, which is the same substance that makes up the hair and fingernails of humans.

  • Snakes shed their skin in relation to their growth rate. A young snake will shed more often because they typically grow fastest during the first two years of their lives. An older snake will shed less often as its rate of growth slows down.

  • The world's longest snake species is the reticulated python, which can exceed 30 feet (10 meters) in length. While reticulated pythons typically grow longer, the anaconda could be considered the largest snake by overall size and weight. The anaconda is a heavy-bodied snake and can weigh well over 300 pounds.

  • While the reticulated python and anaconda are the largest snakes in general, the king cobra is by far largest of the venomous snakes. It can grow to lengths of more than 18 feet (6 meters) can weigh in excess of 20 pounds.

  • Some species of gecko use their tails as a defensive tool. When attacked, the gecko will wiggle its tail to lure the attacking creature. When the animal bites onto the tail, the gecko can detach the tail and make its escape. In most cases, a new tail will grow in place of the old one.

  • Most snake species lay eggs. But about one-fifth of all snakes bear live young instead. Rattlesnakes and boa constrictors are examples of snakes that bear live young.

  • Many states such as Georgia and Texas still engage in "rattlesnake roundups," in which rattlesnakes are gathered from the wild and slaughtered by the hundreds. These activities are mostly practiced by ignorant rednecks who think that rattlesnakes are somehow evil or malicious. Eventually (one can hope), such practices will be outlawed ... ideally before yet another species of animal goes extinct on this planet.

  • Reptiles are the oldest type of animal on the planet. Turtles, for example, have been on the planet for more than 200 million years, in basically the same form as we see them today. For this reason and many more, reptiles deserve respect from us humans. They do not deserve fear or persecution!

About the Author: Brandon Cornett is the pubisher of Reptile Knowledge, an educational website full of information about lizards, turtles, snakes and other reptiles species .

From :

5 Things You Didn't Know About Sharks

By : Neil Simon

1. Only four types of sharks present a large threat to humans. There are more than 360 species of them, but only the great white, bull, tiger and the oceanic whitetip sharks are known for biting humans. These attacks are provoked more often than not, and sometimes even mistaken! There are a few more species which have attacked humans, but they rarely cause death.

2. Sharks only bite…sometimes! A shark cannot eat several times in a row like we can. Oftentimes a shark will bite something to check if it’s worth eating, much like people checking the back of the box for price and nutrition! If it senses that what it’s biting isn’t worth the digestive time, it releases the person, animal or object and goes off to find better food. Talk about discriminating!

3. Sharks may be afraid of dolphins! We’ve heard tales of dolphins protecting humans from sharks. An experiment was also done by Mythbusters where a mechanical dolphin was placed near a seal cutout and raw bait, while a great white shark was feeding. Instead of going for either target, the shark opted to stay away! He only went for it when the dolphin was removed. Scientists still can’t explain why, so don’t try to rent out a dolphin just yet.

4. Sometimes, sharks don’t need a mate to reproduce. There has been a documented case of a shark giving birth without male contact for three years. The newborn had no parental DNA, which makes it a close copy of its mother! This may be a last resort if there are no males around, but since they can’t evolve because of that, it may cause them to become extinct.

5. Sharks are worshipped as gods! Hawaii, that group of islands out in the Pacific Ocean, has more than its share of sharks. It’s not surprising that they model gods out of these creatures. These gods are said to be able to transform from human to shark at will! Many of them are said to be originally human. A common type of story about these gods goes like this: the shark in human form warns beach-goers about sharks in the water. They ignore him, and are later eaten by the human who warned them, who had turned into a shark. When someone warns you about sharks in the water, follow it!

We humans have not fully unraveled the true workings of the shark. Is it friend or foe? Hopefully these facts will make you appreciate sharks more. What other little tidbits do you know? Share them with us!

About the Author: Neil Simon enjoys traveling a lot either all by himself or with his wife and his (now) grown-up kids.

From :

Wednesday, April 23, 2008

A New Look at Darwinian Sexual Selection

By : MERLE JACOBS Goshen College, Goshen, IN 46526, USA


To explain the origin of the ostentatious plumage of the males of fancy-male bird species and the bright coloration of males of non-avian species, Charles Darwin proposed the theory of sexual selection (1). He argued that the ornate features of males are a consequence of female mate selection based on an abstract aesthetic sense. Darwin likened this process to animal breeders producing fancy-male varieties of pigeons by a process of conscious artificial selection.

Alfred Wallace, Darwin's collaborator and a student of wildlife behavior, suggested an alternative explanation. Male adornment, he noted, was associated with heightened physical activity and he proposed that because of their greater energy the most highly adorned males are able to win out in the competition with rival males (2).

In the 1930s, Julian Huxley (3) and R.W.G. Hingston (4) pointed out that male adornment is itself instrumental in establishing dominance relationships among males. When so employed, adornment actually reduces the physical activity necessary to intimidate rivals.

In the early 1950s, as a graduate student, I examined the process of female choice in studies of the dragonflies Perithemis tenera and Plathemis lydia (5), fruit flies Drosophila melanogaster (6) and other organisms (7). My observations led me to the conclusion that what appeared to be choice of an adorned male by a female was really a mutual attraction of both sexes to a particular type of reproductive site. Thus mate selection required not an aesthetic sense, only an awareness of features characteristic of a suitable breeding site, which might be mirrored in the ornamentation of the male. According to this view, mate selection is related directly to adaptive niche specialization. From this insight, I went on to a career in field and laboratory studies leading to the development of a food-courtship theory of mate selection.

The food-courtship theory

Life on earth is driven by solar energy as found in food molecules in various ecological niches. Organisms compete for these niches. That population most efficient in use of the energy available in a particular niche will be the fittest to survive there. Through natural selection, organisms will tend to become specialized to form isolated populations, each adapted to make the most efficient use of energy available in a particular niche. This process of segregation and specialization of populations is facilitated by employing in the mating process samples of the food available in the preferred niche. In particular cases, the male may display the food to the female or feed it to her in the courtship ceremony.

Among birds, the male may bear permanent representations of specific foods on his plumage. In this case, the female may be attracted to the male because she is attracted to these representations of the territorial foods. This process, bringing together males and females of similar tastes and physiologies, may lead to speciation. Some of the male display features may come to be involved in species identification. Male adornment could have a dual function, repelling rival males as well as attracting females. Clarification of the role of male ornamentation thus presents a huge challenge to investigators.

The food-courtship theory may be applied to the case for mate choice among peafowls Pavo cristatus. The "eyespots" on the tail feathers of the male bear a striking resemblance to blue berries. Thus, according to the food-courtship theory, it is because their plumage bears representations of food that peacocks attract peahens. This is consistent with the finding of Petrie et al. (8) that males with the most "eyespots" on their tail have the greatest mating success. Furthermore, it is not inconsistent with a possible role of the "eyespots" in reproductive competition among males (9). Moreover, this explanation seems more plausible than the suggestion that by selecting mates according to the perfection of their tail-feather "eyespots," peahens are able to identify mates with the greatest "fitness" (10).

Because male bowerbirds place fruit and flower arrangements in their courtyards and paint the walls of their bowers with colored fruit pulp, they are considered to have the most highly developed aesthetic sense among the birds. But according to my observations, it is more plausible to explain the mating behavior of this species in terms of the food-courtship theory.

The male satin bowerbird Ptilinorhynchus violaceus, which has blue plumage and blue eye irises, places blue fruits and flowers (sometimes facsimiles of such blue foods) in his courtyard. He also paints the inner walls of his bower with bluish regurgitated fruit residues. Is it not possible, therefore, that the colored objects in the court represent favorite fruits of the species, and the chewed materials painted on the walls represent such foods hung out to dry in a more permanent form?

In northeastern Australia's Mount Lewis, I studied the satin bowerbird. Early in the day, the male chewed up materials in the courtyard, then immediately regurgitated a viscous substance and applied it with his bill onto the inner walls of his bower. He later occasionally pecked at this as if tasting it. When a female arrived she fed on materials in the male's court. The male then chewed foods in the court while making loud coughing sounds while regurgitating the viscous substance from his beak in the presence of the female. When the female approached him and started to enter his bower, he charged her. She fled, only to return later, and the entire performance was repeated (7).

A published videotape (11), shows both male and female satin bowerbirds pecking at the "painted" walls of the bower within which mating occurs. Bull dog ants swarm over these walls as if finding something edible thereon. The same videotape shows the regent bowerbird, Sericulus chrysocephalis, which has yellow patches on his plumage and yellow eye irises, using yellow fruits much as the satin bowerbird uses blue fruits.

The bowerbird habit of spreading food remnants around the nest may be observed among other birds. It has been reported that among the bird-of-paradise, Parotia lawsii, the male in his court, rubs chalk from a chalk cliff over his display perch. The visiting females eat the chalk, which is rich in calcium (12).

The North American white-breasted nuthatch Sitta carolinensis performs similar food-smearing behavior at the nesting hole. These birds swipe their bills against the bark around their nesting holes while holding food items in their bills. Examination of the bark around the holes reveals parts of insects and spiders (7). Some of these materials are retrieved later and used in mate-feeding or feeding young.

An implication of the food-courtship theory is that the selective pressures associated with food preference, habitat choice, courtship behavior, and male coloration will tend to be mutually reinforcing. This may explain why so many fruit-eating birds bear "florid" or "fruity" plumage. For example, the crested guan Penelope purpurascens of Costa Rica has a red throat pouch, giving the impression that the throat contains a red fruit of the type produced by the palms on which the birds feed. The keel-billed toucan Ramphastos sulfuratus and chestnut mandibled toucan Ramphastos swainsonii feeding on the same fruits have red undertails and bill markings again closely resembling these fruits. The Montezuma oropendolas Psarocolius montezuma feeding on these fruits have red tips on their bills. When the male feeds the female during courtship, it is difficult to know whether he has, or has not, red fruit pulp in his beak (7).

David Snow, an avid student of tropical American birds, was one of the first to link colorful plumage of certain birds with the fruit-eating habit (13). Another such student, Steven Hilty, agrees with Snow's assessment: "By almost any measure, the most colorful tropical birds are usually fruit-eating and nectar-feeding species. These are followed in colorfulness ranking by partly fruit-eating birds, while the legions of dull-colored species are drawn mostly from the ranks of insect-eating birds." (14).

Not only tropical birds, but also those of temperate regions, demonstrate a correlation between colorful plumage and the fruit-eating habit. Among the finch-like birds in the vicinity of my home in Indiana, those bedecked in red are frequently seen eating red berries, such as staghorn sumac Rhus typhina, scarlet elder Sabucus racemosa, and hawthorn Crataegus sp. These birds include the cardinal Richmonena cardinalis, rose-breasted grosbeak "Pheucticus ludovicianus", purple finch Carpodacus purpureus, and house finch Carpodacus mexicanus. On the other hand, black-brown-streaked finch-like birds, such as song sparrows Melospiza melodia are seldom if ever seen feeding on red berries.


(1) Darwin, C.A. 1871. The descent of man and selection in relation to sex. John Murray, London; A.L. Burt Publ., 2nd Ed., 1874, New York.

(2) Wallace, A.R. 1889. Darwinism. 3rd Edn. Macmillan, London.

(3) Huxley, J.S. 1938. Darwin's theory of sexual selection and the data subsumed by it in the light of recent research. American Naturalist 72:416-433.

(4) Hingston, R.W.G. 1933. The meaning of animal colour and adornment. Edward Arnold, London.

(5) Jacobs, M.E. 1955. Studies on territorialism and sexual selection in dragonflies. Ecology 36:566-586.

(6) Jacobs, M.E. 1978. Influence of beta-alanine on mating and territorialism in Drosophila melanogaster. Behavior Genetics 8:487-502.

(7) Jacobs, M.E. 1999. Mr. Darwin misread Miss Peacock's mind: a new look at mate selection in light of lessons from nature. NatureBooks.

(8) Petrie, M., T. Halliday and C. Sanders. 1991. Peahens prefer peacocks with elaborate trains. Animal Behaviour 41:323-331.

(9) Andersson, M. 1994. Sexual selection. Princeton University Press, Princeton, New Jersey.

(10) Zahavi, A. and A. Zahavi. 1997. The handicap principle. Oxford University Press, Oxford and New York.

(11) Kaufman, F. 1997. Bower bird blues. (Videotape) Video Nature Library, Thirteen/WNET (for BBC TV in association with Partridge Films, Executive Producers John Sparks and Michael Rosenberg, Produced by Clive Bromhall, Filmed by Glen Threflo and Neil Bromhall, Written by Barry Paine).

(12) Pruett-Jones, S.G. and M.A. Pruett-Jones. 1988. The use of court objects by Lawes' Parotia. Condor 90:539-545.

(13) Snow, D.W. 1976. The web of adaptation: bird studies in the American tropics. The New York Times Book Co., New York.

(14) Hilty, S. 1994. Birds of tropical America. Chapters Publ. Ltd., Shelburne, Vermont.

About the Author

Merle E. Jacobs is Research Professor Emeritus in Zoology, Goshen College, Goshen, Indiana. His book Mr. Darwin Misread Miss Peacock's Mind: A New Look at Mate Selection in Light of Lessons From Nature was published this year by NatureBooks.

Why do honeybees dance?


Biotechnology and R&D Policy Branch, Agriculture, Fisheries and Forestry Australia, GPO Box 858, Canberra ACT 2601, Australia

dancing bee

Image: Courtesy, Ken Hoare
Editor, South Shropshire Beekeeper

Keywords: Apis mellifera, communication, evolution, foraging, idiothetic movement, Meliponini.

When a honeybee (Apis mellifera L.) returns to the hive after a successful foraging trip, she often performs a "dance," a set of movements that reflects in miniature the details of her trip. The duration and orientation of the movements in the dance depend on the distance from, and the direction of, the bee's latest foraging site relative to the hive.

Professor von Frisch won a Nobel Prize for his studies on this behavior, and in particular for work leading him to conclude that the honeybee's dance communicates information about the location of a food source to hivemates, thereby enabling them to find and exploit the same resource (1). However, there has been persistent debate about this interpretation (2–11) and today it is generally believed that honeybees are guided to suitable foraging sites by odor cues, including those picked up from successful foragers, rather than by locational information contained in the dances of other foragers. If this is correct, the function of the dance, which embodies information without communicating it to other bees, remains unclear.

An explanation is suggested by consideration of the behavior of other species that perform so-called idiothetic movements: movements that reflect in miniature previous large-scale movements (12). For example, the io moth (Automeris io Fabricius) performs movements after flight that contain information about the flight's length (13). Some social stingless bees (Meliponini) also "dance" after foraging. These dances, like those of the honeybee, embody information about the bee's most recent flight, but this information is not used by the other stingless bees. However, the dances do "excite recruits to go out and search" (14). Likewise, africanized honeybees are known to perform dances that contain information about the location of food sources, but the dances do not recruit other bees, because foraging in this subspecies is an individual activity (15). Evidently, therefore, bees and other insects may perform information-laden movements that are not communicative.

Thus, to explain how the function of the honeybee's dance has evolved, I postulate, first, that idiothetic movements evolved in primitive bees, and served to reinforce the memory of locations recently visited. Then, as bees evolved group foraging, they came to rely on odors picked up from successful foragers as a guide to the location of resources. Finally, idiothetic behavior took on the new function of attracting the attention of foragers, making them aware of the odors picked up by successful hivemates. Thus, although the dance of the honeybee contains locational information about food sources, it is not necessary to assume that bee dances convey this information to other bees. However, the dance may communicate the success of a forager's most recent flight and draw attention to the odors associated with the food source

From :

Swimming with lions

By : BRAD COLLIS Melbourne, Victoria, Australia

Keywords: Arctocephalus pusillus, Australian seal lion, Lobodon carcinophagus, Neophoca cinerea

Fur Seal Pup

Fur seal pup (Arctocephalus pusillus).

The changing fortunes of Australia's rare fur seals and sea lions highlight the precarious juggling act required of biologists when they try to protect different species occupying the same habitat.

Over the past few decades marine biologists have managed to pull fur seals back from the brink of extinction, but now have to balance the success of this operation with its possible impact on the equally rare Australian sea lions.

Fur Seal Pup

Australian sea lions (Neophoca cinerea).

Fur seal numbers are increasing at a time when the food supply they share with sea lions - fish and squid - appears to be diminishing and sea lion numbers have mysteriously stalled. Australian sea lions are unique and only found off South Australia and Western Australia and at last count in the mid-1990s totalled a mere 2000.

Fur Seal Pup

Fur seals: they may compete for food with endangered sea lions.

"Small, stationary, populations like this are always the most vulnerable," says wildlife ecologist Dr Peter Shaughnessy, who has been leading a coordinated scientific effort to secure the health of both species."

"So we urgently need to find out why sea lion numbers have levelled off."

"Data collected suggest that too many pups are dying and we don't really know why," says Dr Shaughnessy, a wildlife ecologist with the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

"For example in 1996 at two colonies we found mortality rates of 30 per cent and 55 per cent.

"The following year mortality decreased, but the worry is that we have no idea what's causing these dramatic fluctuations in pup mortality."

Fur Seal Pup

Dr. Peter Shaughnessy with the skull of an antarctic

crab-eater seal (Lobodon carcinophagus).

According to Dr. Shaughnessy, possible causes of death include parasites, such as hookworm, environmental disturbance causing a food shortage for lactating female sea lions, high rates of aggression by adult males, direct human harassment or by entanglement in fishing gear.

But the most worrying possibility is that that sea lions may be facing stronger competition for food from the fur seals, whose numbers have been increasing at an annual rate of around 10 per cent.

"The Australian sea lion is an endemic species that we need to take care of. It's a tourist icon, up there with the koala, and attracts tens of thousands of visitors to the sea lion colonies every year. If we don't find out why their numbers are not increasing, we may face more serious problems later on," he says.

Shaughnessy has now begun a project with officers from National Parks and Wildlife South Australia, to try and learn more about fur seal and sea lion behaviour and movements.

The main distinction between fur seals and sea lions is that fur seals have two layers of hair; an inner fine fur and an outer coarse hair. Sea lions have only one layer, which is why they weren't hunted as much.

In addition to the first-hand surveys which often require Shaughnessy to actually dive into the ocean and swim to rocky outcrops with his waterproof notebook, he and other researchers have begun attaching instruments to some animals to trace their movements, and in particular their feeding habits.

They are also studying the interaction between fur seals, sea lions and the fishing industry, in the hope of reducing the number of marine mammals caught in nets.

"Often the seals caught in nets have been attracted to the area by unwanted fish discarded by trawler crews. It's a big problem, although one answer may be the addition of a steel grid to stop seals being drawn into the bottom of the net with the fish."

The research is a painstaking process of finding the fur seal and sea lion colonies, then counting, weighing and marking the animals to build up a detailed profile of the populations and their well-being.

The fur seal colonies extend from Kangaroo Island to Flinders Island (near Cape Leeuwin) in WA, although 70 per cent of the population is in the central South Australian waters from Kangaroo Island to the southern tip of Eyre Peninsula.

"Like a lot of environmental protection, the work is about building up your knowledge of a species and how it interacts with, or is affected by, human activity. This, hopefully, becomes the basis of wildlife, and national parks, management."

About the Author

Brad Collis runs a freelance writing and editing business, specialising in science, technology and the environment. Aside from 25 years in journalism, he is the author of several books including SNOWY - The Making of Modern Australia, which is the prime reference for the history of Australia's Snowy Mountains Hydro-Electric Scheme, and Fields of Discovery, the history of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia's leading science institution.


Australian fur seal, Actocephalus pusilus

Seal Conservation Society: Australian sea lion, Neophoca cinerea

Monday, April 14, 2008

Characteristics of fish, an introduction

Fish are vertebrate animals, that is, they all have a vertebral column or ‘spine’. There are two main groups of fish, bony fish (Teleosts)

and cartilaginous fish (Elasmobranchs). As the common names imply, the skeletons of teleosts are made of bone while the elasmobranchs have cartilaginous skeletons. The elasmobranchs comprise sharks, rays and dogfish which differ from teleosts in many respects. The teleosts are far more numerous, with a greater diversity of species than the elasmobranchs.

All fish are aquatic and breath by absorbing dissolved oxygen in the water using their gills. The bodies of both teleosts and elasmobranchs are covered with scales but those of elasmobranchs are spiky and project through the skin. This makes the skin feel very rough, like coarse sandpaper. The scales of the teleosts have a flattened, discoid shape and are covered by a thin layer of skin and mucus which probably reduces friction between the body and the surrounding water and makes them very slippery.
The swimming mechanism in both groups is very similar. A series of muscular contractions pass down each side of the fish alternately bending it from side to side and pushing backwards and sideways against the water. The water resistance exerts an opposite sideways and forward force on the fish. The sideways forces cancel each other but the forward force propels the fish forward. In both groups there are variations in this method of propulsion. Skates and rays make undulatory movements in the vertical plane as do flatfish like plaice. Some teleosts, such as the sea horse, propel themselves by undulatory movements of their dorsal fin.

In general, the fins contribute to stability and steering rather than propulsion. The median fins, dorsal and ventral, reduce the sideways thrust of the swimming movements and also reduce the tendency to roll from side to side. The paired fins help to steer the fish upwards or downwards through the water and contribute to turning and braking. The paired fins of elasmobranches are held in rather rigid positions while those of teleosts, with their flexible jointing to the body, are more versatile in their movements and can often be seen moving gently to keep the fish in a steady position.

In the teleosts, there is a swim bladder. An elongated, air-filled sac just below the vertebral column. This air bladder keeps the fish buoyant and prevents it from sinking when it stops swimming. The volume of the air bladder can be adjusted to compensate for changes in pressure at different depths. The elasmobranchs do not have swim bladders and so they start to sink if they stop swimming.

Although water is H2O, aquatic creatures cannot use the oxygen from this. The oxygen they breathe comes from the air which has dissolved in the water. There are four or five pairs of gills situated inside the mouth cavity. In teleosts, they are covered on the outside by a bony plate called the operculum. By movements of the floor of the mouth and operculum, the fish creates, a current of water which passes over its gills. Water is taken in through the mouth and expelled through the operculum in the case of teleosts, and out through separate gill slits in elasmobranchs. The gills are, in effect, finely branched, thin-walled blood vessels which, because of their multiple branches, expose an enormous surface to the water and so facilitate absorption of oxygen and loss of carbon dioxide.

From :

Friday, April 4, 2008

Biological Evolution

By Regina Bailey

What is Evolution?

Biological evolution is defined as any genetic change in a population that is inherited over several generations. These changes may be small or large, noticeable or not so noticeable.

In order for an event to be considered an instance of evolution, changes have to occur on the genetic level of a population and be passed on from one generation to the next.

This means that the genes, or more specifically, the alleles in the population change and are passed on. These changes are noticed in the phenotypes (expressed physical traits that can be seen) of the population.

A change on the genetic level of a population is defined as a small-scale change and is called microevolution.

Biological evolution also includes the idea that all of life is connected and can be traced back to one common ancestor. This is called macroevolution.

What is not Evolution?

Biological evolution is not defined as simply change over time.

Many organisms experience changes over time, such as weight loss or gain. These changes are not considered instances of evolution because they are not genetic changes that can be passed on to the next generation.

Is Evolution a Theory?

Evolution is a scientific theory that was proposed by Charles Darwin. A scientific theory gives explanations and predictions for naturally occurring phenomena based on observations and experimentations. This type of theory attempts to explain how events seen in the natural world work.

The definition of a scientific theory differs from the common meaning of theory, which is defined as a guess or a supposition about a particular process. In contrast, a good scientific theory must be testable, falsifiable, and substantiated by factual evidence.

When it comes to a scientific theory, there is no absolute proof. It's more a case of confirming the reasonability of accepting a theory as a viable explanation for a particular event.

What is Natural Selection?

Natural selection is the process by which biological evolutionary changes take place. Natural selection acts on populations and not individuals. It is based on the following concepts:
  • Individuals in a population have different traits which can be inherited.

  • These individuals produce more young than the environment can support.

  • The individuals in a population that are best suited to their environment will leave more offspring, resulting in a change in the genetic makeup of a population.
The genetic variations that arise in a population happen by chance, but the process of natural selection does not. Natural selection is the result of the interactions between genetic variations in a population and the environment.

The environment determines which variations are more favorable. Individuals that possess traits that are better suited to their environment will survive to produce more offspring than other individuals. More favorable traits are thereby passed on to the population as a whole.

How Does Genetic Variation Occur in a Population?

Genetic variation occurs through sexual reproduction. Due to the fact that environments are unstable, populations that are genetically variable will be able to adapt to changing situations better than those that do not contain genetic variations.

Sexual reproduction allows for genetic variations to occur through genetic recombination.

Recombination occurs during meiosis and provides a way for producing new combinations of alleles on a single chromosome. Independent assortment during meiosis allows for an indefinite number of combinations of genes. (Example of recombination)

Sexual reproduction makes it possible to assemble favorable gene combinations in a population or to remove unfavorable gene combinations from a population. Populations with more favorable genetic combinations will survive in their environment and reproduce more offspring than those with less favorable genetic combinations.

Biological Evolution Versus Creation

The theory of evolution has caused controversy from the time of its introduction until today. The controversy stems from the perception that biological evolution is at odds with religion concerning the need for a divine creator. Evolutionists contend that evolution does not address the issue of whether or not God exists, but attempts to explain how natural processes work.

In doing so however, there is no escaping the fact that evolution contradicts certain aspects of some religious beliefs. For example, the evolutionary account for the existence of life and the biblical account of creation are quite different.

Evolution suggests that all life is connected and can be traced back to one common ancestor. A literal interpretation of biblical creation suggests that life was created by an all powerful, supernatural being (God).

Still others have tried to merge these two concepts by contending that evolution does not exclude the possibility of the existence of God, but merely explains the process by which God created life. This view however, still contradicts a literal interpretation of creation as presented in the bible.

In paring down the issue, a major bone of contention between the two views is the concept of macroevolution. For the most part, evolutionists and creationists agree that microevolution does occur and is visible in nature.

Macroevolution however, refers to the process of evolution that takes place on the level of species, in which one species evolves from another species. This is in stark contrast to the biblical view that God was personally involved in the formation and creation of living organisms.

From :