CHORDATA: dorsal, hollow nerve cord
CRANIATES: have a skull (hagfish)
VERTEBRATES: have a backbone (lampreys)
GNATHOSTOMES: have jaws (extinct)
CHONDRICHTHYANS: cartilage skeleton (sharks and rays)
OSTEICHTHYANS: bony skeleton (fishes)
TETRAPODS: four feet (amphibians: frogs, salamanders)
AMNIOTES: have a yolk egg (reptiles: turtles, snakes, crocodiles, birds)
MAMMALS: have hair and produce milk (marsupials, etc)
Chordates have a notochord and a dorsal, hollow nerve cord. They are not quite invertebrates, but are more closely related to vertebrates than to invertebrates. A notochord (primitive vertebral column) is a long, flexible rod located between the digestive tube and the nerve cord. It provides skeletal support throughout most of the length of the back. It differs from vertebrates in that it is not jointed; the notochord in humans is reduced to discs sandwiched between the vertebrae, known intervertebral discs. A dorsal, hollow nerve cord (spinal cord) is unique to chordates. Other animals have solid nerve cords. The nerve cord of a chordate embryo develops into the central nervous system including the brain and spinal cord. Rather than a fully developed brain, chordates have only a slightly swollen tip at the anterior end of their dorsal nerve cord.
Craniates are chordates that have a skull. One example is the hagfish, which have a skull made out of cartilage, but they lack jaws and vertebrae. They swim in a snake like fashion by using their muscles. Hagfish have a small brain, eyes, ears, and a nasal opening that connects with the phalanx. They also have tooth like formations made out of protein in their mouth. All species are marine, and measure up to 60 cm in length. Most are bottom dwelling scavengers that feed on worms or sick or dead fish. A hagfish has rows of slime glands that secrete a slime to repulse other scavengers. When a hagfish is attacked, it can produce several liters of slime in less than a minute. This slime coats the gills of an attacking fish, forcing it to retreat or suffocate. Scientists are investigating the properties of hagfish slime in hopes of producing it as a space-filling gel which can be used to stop bleeding during surgery.
Vertebrates are craniates that have a backbone. They have a more complex nervous system and a more elaborate skeleton, and have become active predators.
In most vertebrates, the vertebrae enclose the spinal cord. Aquatic vertebrates also acquired dorsal, ventral, and anal fins which provide thrust and steering control during swimming. They also adapted more efficient gas exchange systems in their gills.
Lampreys differ from fishes in that they lack jaws and they lack paired fins. They represent the oldest of the vertebrates. Most are parasites that feed by clamping their round, jawless mouth onto the flank of a live fish. They then use their rasping tong to penetrate the skin of the fish and ingest the fish's blood. Their skeleton mostly consists of cartilage. Collectively, jawless fish are referred to as agnathans (“no jaw”). Hagfish are also agnathans.
Gnathostomes (“jaw mouth”) are vertebrates that have jaws. A jaw is a hinged structure that, with help of the teeth, enables gnathostomes to grip food firmly and slice it up. Their forebrain is enlarged compared to that of other craniates, which allows them enhanced senses of smell and vision. Running the length of each side of the body in aquatic gnathostomes is the lateral line system, a row of microscopic organs sensitive to vibrations in the surrounding water. Additionally, they have a mineralized endoskeleton. All of the vertebrates that we will discuss are descents of this clade; the species that are only gnathostomes are all extinct.
Chondrichthyans have a skeleton and that is predominately cartilage, impregnated with calcium. Examples include sharks and rays. They are the biggest and most successful vertebrate predators in the ocean.
Sharks have hinged jaws, vertebrae, a flexible skeleton made of cartilage, and a lateral line system. A lateral line system is a row of sensory organs running along each side that are sensitive to changes in water pressure and can detect vibrations caused by animals swimming nearby. They have a streamlined body and are swift swimmers, but they do not maneuver very well. Powerful movements of the trunk and tailfin propel them forward. The dorsal fins function mainly as stabilizers. They do not have a swim bladder. A swim bladder is a gas-filled sac that can help keep a fish afloat. Instead, the shark gets buoyancy by storing a large amount of oil in its huge liver, the animal is still denser than water, and if it stops swimming it sinks. Continual swimming also ensures that water flows into the shark’s mouth and out through the gills, where gas exchange occurs. However, some sharks spend a good deal of time resting on the seafloor. When resting, they use muscles of their jaw to pass water over the gills.
The largest sharks and rays are suspension feeders that consume plankton (algae). Most sharks, however, are carnivores that swallow their prey whole or use their powerful jaws and sharp teeth to tear flesh from animals too large to swallow in one piece. Sharks have several rows of teeth that gradually move to the front of the mouth as old teeth are lost.
Acute senses are adaptations that go along with the active, carnivorous lifestyle of sharks. Sharks have sharp vision but cannot distinguish colors. The nostrils of sharks function only for smelling, not for breathing. Sharks also have a pair of regions in the skin of their head that can detect electric fields generated by muscle contractions of nearby animals. Like other aquatic vertebrates, sharks have no eardrums to transmit sound waves. Sound reaches a shark through water, and the animal's entire body transmits the sound to the hearing organs of the inner ear.
Rays are closely related to sharks, but they have adapted a very different lifestyle. Most rays are flattened bottom-dwellers that feed by using their jaws to crush mollusks and crustaceans. They use their greatly enlarged pectoral fins like water wings to propel themselves through the water. The tail of many rays is whip-like and in some species, have poisonous barbs that function in defense. Sharks and rays are severely threatened with overfishing. In 2003, sharks in the Northwest Atlantic declined 75% in 15 years.
Osteichthyan means “bony fish”. They have a bony skeleton made out of calcium phosphate. Informally, we call these “fish”. They breathe by drawing water over four or five pairs of gills located in chambers covered by a protective bony flap called the operculum.
Most fish control their buoyancy with an air sac known as a swim bladder. Movement of gases from the blood to the swim bladder increases buoyancy, making the animal rise. This skin is often covered by flattened, bony scales that differ in structure and function from the tooth-like scales of sharks. Glands in the skin secrete a slimy mucus over the skin to reduce drag during swimming. Like sharks, boney fish have a lateral line system. There are two main types of fishes: Ray-finned and lobe-fins.
Ray-finned fishes have an operculum, a lateral line system, a swim bladder, and flattened scales covering the skin, but they do not have a flexible skeleton made of cartilage. Nearly all of the osteichthyans we are familiar with are among the ray-finned fishes. Examples include bass, trout, perks, tuna, and herring. The fins are modified for maneuvering, defense, and other functions. Ray-finned fishes originated in fresh water and spread to the seas. Some species have returned to fresh water at some point in their evolution. Some of them, including salmon and trout, replay their evolutionary round-trip from freshwater to sea water and back to fresh water during their lifecycle. Ray-finned fishes serve as a major source of protein for humans. However, industrial-scale fishing operations now threaten some of the world's biggest fisheries with collapse. Ray- finned fishes also face other pressures from humans, such as the diversion of rivers by dams.
The key derived characteristic of lobe-finned fish is a series of rod-shaped bones in their fins surrounded by a thick layer of muscle in their pectoral and pelvic fins. During their evolution, they lived in brackish waters where they probably used their lobed fins to swim and “walk” underwater across the bottom. Today only two main types of lobe-fins survive. One is called the coelacanths, which shifted to the ocean. Scientists once thought that coelacanths had become extinct 75 million years ago, but in 1938, fishermen caught a living coelacanth in the western Indian Ocean. A second species has been discovered in Indonesia. Another lineage of living lobe-fin is a lung fish which are found in the southern hemisphere. They are found only in fresh water stagnant ponds and swamps. They have gills as well as lungs; they surface to pull air into their lungs. They also have gills for additional gas exchange. When ponds shrink during the dry season; they burrow into the mud and wait for conditions to improve.
Fish: the Good News and the Bad News
Fish is a good source of protein and, unlike fatty meat products it’s not high in saturated fat. It’s also a good source of omega-3 fatty acids, which benefit heart health. The American Heart Association recommends eating fish at least twice a week. However, some types of fish may contain high levels of mercury and other environmental contaminants. Levels of these substances are generally highest in older, larger, predatory fish and marine mammals.
Fish with the highest levels of mercury are shark, swordfish, golden bass or golden snapper, and king mackerel. These fish should be avoided by pregnant and nursing women and by young children.
Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish. Albacore ("white") tuna has more mercury than canned light tuna; you may eat up to 6 ounces (one average meal) of albacore tuna per week. Fish sticks and "fast-food" sandwiches are commonly made from fish that are low in mercury.
Tetrapods (“four feet”) are gnathostomes that have limbs and feet which evolved from the fins of lobe-fin fish. Once tetrapods moved onto land, they eventually took on many new forms, from leaping frogs to flying eagles.
The limbs can support their weight on land and their feet allow them to walk. They do not have gills slits. The ears are adapted to the detection of airborne sounds. Some species developed wings, while others, such as whales, retained the shape of a fish. The first tetrapods to evolve were amphibians, represented by salamanders (with tails), frogs (tail-less), and caecilians (legless).
Most salamanders that live on land walk with a side to side bending of the body. Adult frogs use their powerful hind legs to hop along the terrain. A frog nabs insects by flicking out its long, sticky tongue, which is attached to the front of the mouth. Frogs display a great variety of adaptations that help them avoid being eaten by larger predators. Their skin glands secrete distasteful or even poisonous mucus. Many poisonous species have bright coloration, which predators apparently associated with danger. Other frogs have color patterns that camouflage. Caecilians are legless and nearly blind, and superficially they resembled earthworms. They inhabit tropical areas and burrow in moist forest soil.
Amphibians were the first terrestrial vertebrates. Most amphibian life cycles include a metamorphosis, and larval amphibians have a lateral line system resembling that in fishes. Amphibian means “two lives”. The larval stage of a frog, called a tadpole, is an aquatic herbivore with a long tail. Larval amphibians have a lateral line system like bony fishes and sharks. The tadpole initially lacks legs and swims by its tail. During the metamorphosis that leads to the second life, the tadpole develops legs, lungs, a pair of external eardrums, and a digestive system adapted to a carnivorous diet. At the same time, the gills disappear. The young frog crawls onto shore and becomes a terrestrial hunter. Lungs and appendages for support did NOT evolve first in amphibians. Lungs evolved from the swim bladders of fish, and appendages evolved from their fins.
Most amphibians are found in damp habitats such as swamps and rain forests. Even those that are adapted to drier habitats spend much of their time in burrows or under moist leaves, where the humidity is high. Amphibians generally rely heavily on their moist skin for gas exchange with the environment.
They usually lay their eggs in water. Fertilization is external and most amphibians; the male grasps the female and spills his sperm over the eggs as the female sheds them. Adults display various types of parental care. Depending on the species, either males or females may house eggs on their back, in their mouths, or even in their stomach. Some species make nests, and others abandon their eggs in water or in moist environments on land.
Many amphibians exhibit complex and diverse social behaviors, especially during their breeding seasons. Frogs are usually quiet, but the males of many species vocalize to defend their breeding territory or to attract females.
Over the past 25 years, there has been a rapid decline in amphibian populations throughout the world. There appears to be several causes, including habitat degradation, fungal pathogens, and acid rain. One difference between an amphibian and a reptile is that amphibians do not have an amniotic egg.
Amniotes have an amniotic (yolk) egg, such as reptiles (including birds). An amniotic egg is one that contains specialized membranes that protect the embryo. They function in gas exchange, waste storage, and the transfer of storage nutrients to the embryo. The amnion is the layer that contains fluid and acts as a shock absorber. In contrast to the shell-less eggs of amphibians, the amniotic eggs of most reptiles and some mammals have a shell. The shells of bird eggs are made of breakable calcium carbonate, while the shells of many reptile eggs are leathery and flexible. The shell significantly slows dehydration of the egg in the air, an adaptation that allowed amniotes to occupy a wider range of terrestrial habitats than amphibians. Most mammals don’t have a shell, and the embryo develops within the mother. Amniotes also acquired other adaptations to terrestrial life, including less permeable skin and the ability to use the rib cage to ventilate the lungs. They also walk with a more elevated stance.
Reptiles include snakes, lizards, turtles, crocodiles, and birds. Reptiles have scales, amniotic eggs, and waterproof skin, but no lateral line system in larvae. Unlike amphibians, reptiles have scales that contain the protein keratin. Scales create a waterproof area that helps prevent dehydration in dry air. Scales prevent reptiles from breathing through their skin like amphibians; most reptiles rely on their lungs alone for gas exchange. Turtles are the exception to this rule; many turtles also use the moist surfaces of their skin for gas exchange.
The adaptation of an amniotic egg allowed reptiles to complete their life cycles on land. Most reptiles lay shelled eggs on land. Fertilization must occur internally, before the shell is secreted. Many species of snakes and lizards are viviparous; their amniotic membranes form a placenta that enables the embryo to obtain nutrients from its mother.
Many reptiles are sometimes said to be “cold-blooded” because they do not is their metabolism to control their body temperature. However, they do regulate their body temperature by using behavioral adaptations. For example, many lizards bask in the sun when the air is cool and seek the shade when the air is too warm. A more accurate description of these reptiles is to say they are ectothermic. By heating their bodies directly with solar energy rather than through metabolic breakdown of food, an ectothermic reptile can survive on less than 10% of the food required by a mammal of the same size. Ectothermic animals include frogs, lizards, turtles, and alligators.
A snake is a scaly, limbless, elongate reptile. Snakes descended from an extinct lizard-like ancestor that was venomous. All snakes are carnivorous. Some snakes have a venomous bite, which they use to kill their prey before eating it. Other snakes kill their prey by constriction. Still others swallow their prey whole and alive. A snake smells by using its forked tongue to collect airborne particles then passing them to an organ in their mouth to examine them. The term poisonous snake is false - poison is inhaled or ingested whereas venom is injected. Snake venom is used in biotechnology to rapidly stop excessive bleeding during vascular surgery and major trauma.
Lizards normally possess four legs, external ear openings and movable eyelids. They can range in size from a few centimeters (geckos) to nearly three meters (Komodo Dragons).
Turtles are the most distinctive group of reptiles alive today. All turtles had a box like shell made of upper and lower shields that are fused to the vertebrae. In most species, the shell is hard, providing excellent defense against predators. The earliest turtles could not retract their heads into their shell; mechanisms for doing so evolved independently in two separate branches of turtles. The side-necked turtles fold their neck horizontally, while the vertical-neck turtles fold their neck vertically.
Some turtles have adapted to deserts, and others live almost entirely in ponds and rivers. Still others have returned to the sea. Sea turtles have a reduced shell and enlarged forelimbs that function as flippers. They are the largest living turtles and can weigh over 1500 kg. Sea turtles feed on sponges and jellyfish and dive as deep as 60 m. They are endangered by fishing boats that accidentally catch them in their nets, as well as by the humans’ development of the beaches where turtles lay their eggs.
Alligators and Crocodiles
Alligators and crocodiles are collectively called crocodilians. They are confined to the warmer regions of the world. Alligators in the United States have made a strong comeback after spending years on the endangered species list. Unlike crocodiles, alligators have a more narrow nose, are less aggressive, and they take care of their young after they are hatched.
Birds are in the same category as reptiles; they evolved from dinosaurs when they developed hollow bones, then some feathers, then flight feathers, then two toes in front and two in back. Although they are reptiles, their reptilian anatomy has undergone adaptations that are weight saving modifications to make flying more efficient. Adaptations for flight include the absence of teeth, very short tail bones, large breast muscles, efficient lungs, lack of a urinary bladder, an extremely high rate of metabolism, and the females of most species only have one ovary. The skull is especially light and the bones are hollow, although a bird skeleton as a whole is no lighter in relation to body weight than the skeleton of a mammal of similar size.
Birds also have relatively large brains and possibly the best vision of all vertebrates. Although most birds are fabulous flyers, some birds are flightless. Birds generally display very complex behaviors, particularly during breeding season, when they engage in elaborate courtship rituals. Fertilization is internal and the amniotic egg of birds has a hard outer shell. Male and female frequently share responsibility for the incubation and care of the young.
Although their general body form is similar, different species can be distinguished by their body profile, flying style, behavior, feather colors, beak shape, and foot structure.
Mammals evolved from reptiles. Mammals have hair and have mammary glands which produce milk. All mammalian mothers nurse their young with milk, a balanced diet rich in fats, sugars, proteins, minerals, and vitamins. Hair and a fat layer under the skin help to retain the body heat. Like birds, mammals are endothermic, and most have a high metabolic rate. This is supported by an efficient respiratory system with a diaphragm and efficient circulatory system, including a four-chambered heart. Live births are not limited to mammals (some reptiles have live births), and some mammals lay eggs.
Mammals generally have a larger brain than other vertebrates of equivalent size. A relatively long duration of parental care extends the time for offspring to learn important survival skills by observing their parents.
Mammals are endothermic (warm-blooded). They use heat generated by metabolism to maintain a warm, steady body temperature. Differentiation of teeth is another important mammalian trait. The teeth of mammals come in a variety of sizes and shapes adapted for chewing many types of food. Humans, for example, have teeth modified for shearing and for crushing and grinding. The three major groups of mammals are the monotremes, marsupials, and eutherians.
Monotremes are found only in Australia and New Guinea and are represented by the platypus and spiny anteater. Like all mammals, monotremes have hair and produce milk, but they lay eggs and they lack nipples; the baby sucks milk from the mother’s fur.
Examples are opossums, kangaroos, and koalas. A marsupial is born very early in its development and completes its development while nursing in a maternal pouch called a marsupium. A red kangaroo is about the size of a honey bee at its birth, just 33 days after fertilization. Its hind legs are merely buds, but it's forelegs are strong enough for it to crawl from the exit of its mother's reproductive tract to a pouch that opens to the front of her body, a journey that lasts a few minutes.
Australia has not been in contact with another continent for about 65 million years. Most marsupials evolved after South America and Australia broke off from the other landmasses. That is why kangaroos and koalas are only found in Australia. Australia’s native species face serious challenges from introduced, alien species.
Eutherians (placental mammals)
Eutherians are commonly called placental mammals because their placentas are more complex than those of marsupials and they have a longer period of pregnancy. Eutherians complete their embryonic development within the uterus. The major order of eutherians we will discuss is the Primates.
This order includes the lemurs, the tarsiers, the monkeys, and the apes. Humans are members of the ape group. Most primates have hands and feet adapted for grasping, and their digits have flat nails instead of claws. Additionally, the fingers have skin ridges (fingerprints). Primates have a larger brain than other mammals, and short jaws, giving them a flat face. They have forward-looking eyes that are close together on the front of the face. Primates also have relatively well-developed parental care and complex social behavior.
The earliest primates were probably tree dwellers, and many of the characteristics of primates are adaptation to the demands of living in trees. All modern primates, except humans, have a big toe that is widely separated from the other toes, enabling them to grasp branches with their feet. All primates have a thumb that is relatively mobile and separate from the fingers, but only monkeys, apes, and humans have a fully opposable thumb; that is, they can touch the tip of all four fingers with the fingerprint surface of the thumb of the same hand. In humans, a distinctive bone structure at the base of the thumb allows it to be used for more precise manipulation. Having two eyes facing forward causes and overlapping of visual fields, which enhances depth perception.
There are three main groups of living primates: the lemurs of Madagascar, the tarsiers of South East Asia, and the anthropoids, which include monkeys, apes, and humans. After South America and Africa a drifted apart, South America is called the New World and Africa and Asia are called the Old World. New World monkeys and Old World monkeys underwent separate adaptive evolutions. All species of New World monkeys live in trees, have prehensile tails, and nostrils that open to the sides. Old World monkeys include ground dwelling as well as tree-dwelling species, lack a prehensile tail, and their nostrils open downward. Most monkeys in both groups are active during the day and usually live in bands held together by social behavior.
The other group of anthropoids, the hominoids, consists of primates informally called the apes. This group includes gibbons, orangutans, gorillas, chimpanzees, and humans. Hominoids have relatively long arms, short legs, no tail, and a larger brain in proportion to their body size than other primates.
“Homo sapiens” (wise or rational man) is the genus and species for humans. Humans are the only living members of the Homo genus. A number of characteristics distinguish humans from other hominoids. Humans have a much larger brain, and are capable of written language, symbolic thought, and they can manufacture and use complex tools. Humans also have reduced jawbones and jaw muscles and a shorter digestive tract. Humans are 99% genetically identical to chimpanzees, but that 1% translates into a large number of differences in a genetic sequence that contains 3 billion genes.
The characteristics of humans have been reconsidered recently; a gorilla named Coco demonstrated knowledge and use of sign language. An African gray parrot named Alex has also demonstrated an understanding of spoken vocabulary, and not just mimicry. And many species of mammals make their own tools to obtain food, however they are not complex tools that humans make.
Other Orders of Eutherians (not on the exam)
Xenarthra: sloths, anteaters, armadillos
Carnivora: dogs, wolves, bears, cats, weasels, otters, seals, walruses
Artiodactyls: sheep, pigs, cattle, deer, giraffes
Cetaceans: whales, dolphins, porpoises
Rodentia: squirrels, beavers, rats, porcupines, mice
Perissodactyla: horses, zebras, rhinoceroses
ANIMAL FORM AND FUNCTION
Structure Fits Function in the Animal Body
Anatomy is the study of an organism's structures; physiology is the study of the function of an organism's structures. The structure of an organism fits its adaptive function. For instance, a gecko’s anatomy includes tiny hairs on its feet that allow it to climb vertical walls; a physiologist would study the functioning of these hairs in order to understand how they work.
Another example is the flight apparatus of birds. Feathers give the wing its broad shape without adding much weight to the body. They remain dry because they are lightly coated with oil, and they also trap air, which provides insulation that helps a bird to maintain its high body temperature and metabolism. The function of feathers results from their unique structure. Feathers consist entirely of nonliving material, mainly the protein keratin. A flight feather has a hollow shaft that provides a central support with minimum weight. Small flat rods called barbs extend from both sides of the shaft. Still finer rods called barbules extend from the sides of the barbs. Each barbule has tiny hooks that interlock with adjacent barbules. This gives a feather a particular shape and rigidity that support flight. When a bird preens, it draws its feathers through its beak, hooking the barbules back together like zipping up a zipper.
The muscles and bones in a bird wing also show the relationship between structure and function. Muscles provide power, and the bones provide support for flight. The flight muscles are situated on the breast and around the base of the wings, keeping most of the weight off the wings and helping maintain the birds balance in flight.
The bones in a bird wing are similar to those in a human arm, but the number of the bones is fewer. The bird wing only has three fingers, and only the middle one has a complete set of bones. This adaptation helps make the wing lighter but less flexible than a human hand. This reduced flexibility stabilizes the wing and helps it function as a unit in flight.
Animal Structure Has a Hierarchy
Just as there is a progression from atoms to molecules to cells, the progression continues within an animal. Cells connect with other cells of similar function in and coordinate themselves, making up a tissue. For instance, cardiac muscle cells are branched and can communicate with each other. A tissue is a group of similar cells that perform a specific function, for instance, cardiac tissue. An organ is a group of tissues that work together to perform a specific task, for example, the heart. An organ system consists of multiple organs that together perform a vital bodily function, for instance, the circulatory system consists of the heart and blood vessels. An organism contains a number of organ systems, each specialized for certain functions and all functioning together as a coordinated unit. For example, the pelican’s circulatory system cannot function without the oxygen supplied by the respiratory system and nutrients supplied by the digestive system. And it takes the coordination of muscle and bone systems to enable the bird to fly.
Digestive System: ingests and breaks down food to be absorbed.
Respiratory System: exchanges gases with the environment, supplies blood with oxygen
Circulatory System: delivers oxygen into the body cells
Immune System: Defends the body against infections
Lymphatic System: filters and cleans the fluid that leaks out from blood vessels.
Excretory System: removes waste products
Endocrine System: secretes hormones that regulate body activities
Nervous System: coordinates body activities
Integumentary System: protects against injury, infection, temperature, and dryness
Skeletal System: supports the body and protects internal organs
Muscular System: produces movement of the body, maintains posture
Reproductive System: produces gametes and sex hormones.
PROBLEMS WITH THE THEORY OF EVOLUTION
According to the theory of evolution, humans evolved from apes, which evolved from protozoa. The theory also states that the carnivores: dogs (canines), cats (felines), and bears (Ursidae) evolved from Miacidae (miacids), a weasle-like animal. Here is a link for Miacidae:
That means that at some point, this weasel gave birth to a cat, another gave birth to a dog, and another gave birth to a bear, forming each family of the carnivores.
Current DNA research is shedding doubt on that aspect of the Theory of Evolution. There is no evidence that genes increase in complexity over time. DNA only decays over time. There is also no evidence that one family of organisms can give rise to another family (megaevolution). The only changes we have evidence of is one species giving rise to a subspecies (microevolution). The theory of evolution states that megaevolution has occurred, but there is no evidence that this is even possible. There are almost no intermediate life forms in the fossil record, either. During the Cambrian Era "explosion", many new orders of animals suddenly appeared in the fossil record, with no fossil intermediates. Evolution cannot explain that.
Here are several papers I wrote during my PhD in Biology at Loma Linda University:
Microevolution is when there is a relatively small evolutionary change within a species. Speciation is evolution of a new species. These differ from megaevolution, which is when huge evolutionary changes occur, producing new families and genera (categories above the species level) of organisms on the earth.
Even within the same species, there are differences in size, color, behavior, and other characteristics. This genetic variation occurs because of mutations or recombination in the genome. Mutations can occur by exposure to radiation, chemicals, or factors within the cell. If the mutation is not lethal, the new gene sequence is passed to the next generation.
Recombination is a natural occurrence when the genes of a male are mixed with the genes of a female during sexual reproduction. Mutations and recombination are random processes: the cause of the mutation is not related to the need of the animal. The exception to this might be in cases where breeding selection is intentional. For instance, if a mate is selected by the animal itself or by a breeder, the desirable characteristics are encouraged to proliferate. In this way, humans can selectively breed flowers that are more scented, fruits that are larger, and horses that are faster. Humans can likewise select for characteristics that we find esthetic in domestic animals, but which would not likely favor survival in the wild. Such examples include chickens with 12-foot long feathers, tumbling flight of show pigeons (a nervous disorder), and the short legs of dachshunds.
Natural selection when those individuals with characteristics best adapted to their environment have the best chance of surviving and successfully reproducing. Wolves in Alaska can only catch the caribou which are sick, slow, or not alert. Even a very young caribou can outrun a wolf. Therefore, the wolf keeps the caribou strong, because the weak ones are eliminated from reproducing.
There is usually an excess of offspring produced by an organism since so many of them die before reproducing. The ones with genetic variations that make them more successful are the ones that pass on these genes. Although there is plenty of evidence of natural selection, it is highly debatable that genetic mutation and recombination can induce enough change in the genome bring about macroevolution. If mammals evolved from reptiles as Darwin’s theory suggests, it would require major changes in the genome to account for anatomical and physiological differences, including structures and the endocrine control mechanisms for the development and birth of live young, milk glands to nourish them, a larger and more complex brain, and an ability to maintain a higher metabolism and warm-blooded condition. If one genetically evolved creature appeared, it would still have to be able to mate with another one like it and produce viable offspring.
Thus, natural selection is evident in nature, but it does not support the theory that humans and other complex organisms evolved from a single ancestor.
The Fossil Problem
Darwin's most formidable opponents were not clergymen, but fossil experts. There are very few intermediate links between kingdoms, families, etc. in the fossil record. Darwin's theory predicted that fossil transitionals would be found, and that most of the fossil record would be transitional types of organisms. However, the links between the discontinuous groups that once existed have vanished because they couldn't adapt. Darwin's explanation was that the fossil record is in perfect, and he admitted that he had no satisfactory answers.
Continual, gradual extinctions are a necessary consequence of the assumption that ancestor species are constantly being supplanted by better adapted descendants. However, in the case of a global catastrophe, survival is not related to fitness; it occurs entirely at random. Darwinism could therefore be tested not only by searching for transitional species, but also by studying the pattern of extinctions to measure the importance of catastrophes. Darwinism suggests that that macro-evolution is gradual. Yet most species appear in the fossil record looking pretty much the same as when they disappear, and new species arise suddenly, already fully formed in the fossil record.
To account for rapid change and speciation, people are studying random mutations in the regulatory genes. Species do not seem to change much in the fossil record because the population as a whole is not changing. The important evolutionary changes occur only among peripheral isolates. Darwinists explain the sudden appearance of a new species on a gap in the fossil record. Why is it that Darwinists evolution always happened in such a manner as to escape detection? Darwinism as a scientific hypothesis should be confirmed or falsified by fossil evidence.
The greatest problem with the fossil record for Darwinism is the Cambrian explosion of 600 million years ago. Nearly all the animals first appear in the rocks of this period, without a trace of evolutionary ancestors. The general picture of animal history is therefore a burst of general body plans followed by extinction. No new phyla evolved thereafter. Darwin admitted that this is a problem with his theory.
My proposed modifications to the theory of evolution
1. Origin and direction of evolutionary change
There is no evidence to support Darwin’s claim that microevolution and speciation will result in megaevolution. The high point of complexity was at the beginning. Organisms were designed with genetic variability for adaptation. After exposure to radiation or chemicals, mutations arose, and natural selection weeded out those changes which were not suitable for life and reproduction.
2. Loss of genetic information
Loss of genetic information occurred later, such as loss of sight by cave creatures and loss of flight by some birds. Parasitic organisms also developed later. Just because certain species of birds that are less specialized (plain color, simple courtship, crude nest) does not mean they are ancestors of those who are more specialized.
3. Natural selection
Many organisms today are less complex and less adaptable than they were at the beginning of life on earth. Birds that are highly specialized are less adaptable. If random mutations and natural selection improve the ability to adapt, newer species should be more adaptable to their environment, not less so.
4. Evolutionary rate
Evolutionary change only occurs within limits. Evolution rate in naturalism would take a long time. Proponents of the Intelligent Design theory say that all the major taxa were in existence in the beginning but that a process of diversification began. This change comes from a sorting of genetic potential that was created in the beginning.
5. Regulatory genes and Heterochrony in evolution
Changes in regulatory genes during embryological development control activation of structural genes. Intelligent Design proponents do not think that these processes could account for new body plants, but they could explain how a significant amount of change could occur rapidly within a family.
Standard evolutionary scientific viewpoint
Fix, Alan G. Migration and Colonization in Human Microevolution (Cambridge Studies in Biological and Evolutionary Anthropology) Cambridge University Press; New Ed edition (September 8, 2005). Fix uses computer simulations to study migration as a microevolutionary process to the understanding of longer term global patterns of human diversification.
Non-Standard evolutionary scientific viewpoint
Lamarck's Signature : How Retrogenes Are Changing Darwin's Natural Selection Paradigm by Edward J. Steele (Author), Robyn A. Lindley (Author), Robert V. Blanden (Author) Basic Books (December 1, 1999). This book provides evidence that Lamarck’s ideas have credibility regarding inheritance of acquired characteristics; it provides evidence that aspects of acquired immunities developed by parents in their own lifetime can be passed on to their offspring.
Vestigial Organs Are Fully Functional: A History and Evaluation of the Vestigial Organ Origins Concept Creation Research Society Books (December 1990) by Jerry Bergman (Author). This book provides evidence that all of the supposedly functionless organs touted by Darwinists do in fact have functions, as would be expected if organisms were in fact designed; "Junk DNA" is now being discovered to play important functional roles.
Standard evolutionary scientific viewpoint
The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life by Xian-Guang Hou (Author), Richard J. Aldridge (Author), Jan Bergstrom (Author), David J. Siveter (Author), Derek J. Siveter (Author), Xiang-Hong Feng (Author) Wiley (December 19, 2003). Mainly intended for professional palaeontologists, this illustrated guide details the amazing fossils, 525 million years old, from algae to chordates.
Icons of Evolution: Science or Myth? Why Much of What We Teach About Evolution is Wrong by Jonathan Wells (Author) Regnery Publishing, Inc.; 1 edition (January 2002). Intelligent design maintains that we can infer from evidence in nature that some features of the universe and living things are better explained by an intelligent cause than by unguided processes as Darwin states.
Microevolution and speciation could produce a lot of biological change in a much shorter time than most scientists think because of the effect of regulatory “jumping genes”.
Regulatory genes are already fully encoded within the genome of all biological organisms. As soon as an organism comes into existence, it brings with it a fully-prepared DNA sequence. A regulatory gene regulates the expression of other genes or controls the rate at which other genes make products. For instance, some regulatory genes encode for repressor proteins that will prevent RNA polymerase from transcribing RNA. Inducer proteins inactivate repressor proteins and allow the RNA transcription to proceed. Much of what is now termed “junk” DNA may have regulatory functions that we do not understand. According to our textbook, recent studies suggest that the percent of the genome that is non-coding is directly proportional to the structural complexity of the organism, implying that is has a function in generating that complexity. Although these regulatory genes are present at conception, they are not necessarily turned on.
However, regulatory genes can be activated quickly according to environmental demands. When an amphibian spends some of its time in the water and then the water source begins to dry up, it may become necessary for some adaptations to occur to enable its offspring to require less time in the water, or no time at all. Likewise, when the temperature or food sources change, an organism (and its offspring) must quickly adapt to these new circumstances. Such changes probably only occur within the species, genus or family of an organism. For genes to combine into a much more complex organism (especially one from another Kingdom) is not as likely.
Thus, regulatory genes can account for many biological changes in a short period of time. Recent studies on embryological hearts in mice1 have shown that regulatory genes can be invoked under laboratory-stimulated conditions, resulting in a change in the genome that can be quantitatively assayed. Spontaneous mutations are not expected to account for such changes because in such conditions, adaptations are needed immediately and must result in a selective advantage for the organism, or they will be eliminated from the population.
1. Identification of biological themes in microarray data from a mouse heart development time series using GeneSifter ™
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