Fish, swim! Birds, fly! - Day 5 - creation.com Published in Creation 28(4):44–47 , 2006 ‘Then God said, “Let the waters teem with swarms of living creatures, and let birds fly above the earth in the open expanse of the heavens.” And God created the great sea monsters, and every living creature that moves, with which the waters swarmed after their kind, and every winged bird after its kind; and God saw that it was good. And God blessed them, saying, “Be fruitful and multiply, and fill the waters in the seas, and let birds multiply on the earth.” And there was evening and there was morning, a fifth day’ Genesis 1:20–23. On the fifth day of Creation Week, the earth was ready to support animal life. God had made water, soil, air, and plants and fruits for food. He had also created the sun to give light and warmth. Now God created Earth’s first inhabitants—the animals that live in the sea and those that fly in the air. Once again He simply commanded them all to come into being, and they did!

All the sea creatures When God spoke, the sea was suddenly teeming with every kind of creature that lives there—tiny ones called krill, small fish like sardines, medium-sized fish like salmon, bigger fish such as marlin and swordfish, and much larger creatures like whales and plesiosaurs. God also made jellyfish and eels, corals and crabs, octopuses and porpoises, and all the others too. Some people say that whales evolved from an animal like a cow or from some other land animal that decided it wanted to start living in the sea and eating seaweed or other sea creatures instead of grass. But why would it do that? There is no convincing evidence to support this idea. And God tells us that He did not make the land animals until Day 6. Did you know that the vast majority of fish don’t eat each other, but eat underwater plant material like seaweed, algae (like green rock slime), and drifting tiny plants called plankton (really phytoplankton).

All the flying creatures Suddenly, too, at God’s command, there were all sorts of flying creatures—birds like parrots, pigeons and poultry; flying insects like butterflies, bees and bugs; as well as bats (which are mammals); and the flying reptiles we call pterosaurs. What a marvellous sight it must have been! What a marvellous sound there must have been when the birds began to sing! God made these creatures with four different types of wings. Birds’ wings are made of feathers; insects’ wings are made of membranes or thin scales; bats’ wings are made of skin stretched over long arm and hand bones; while for pterosaurs’ wings the skin was stretched over a long fourth finger bone. Flight feathers are remarkable features. When a bird raises its wing, the feathers move apart to let the air through and reduce resistance. But on the downstroke the feathers close completely, thus greatly improving lift. Also, a bird can vary the shape of its wings for more efficient take-off, flapping, gliding and landing. People who don’t believe in a Creator have no explanation for the remarkable design features of feathers. Most of them claim that a reptile’s scales changed into feathers.

But no fossil showing a transition from scale to feather has ever been found. God designed bird and human bones for their special functions. Bird bones are much lighter. God cares for all God was pleased when he looked at what He had made on Day 5. Not only did He say it was good, He also blessed the fish and the birds, and commanded them to reproduce—each to make baby animals just like itself. Although God does not love animals in the same way that He loves people, He still notices when a sparrow falls to the ground (Matthew 10:29), and He cares for them. How much more God cares for you and me! ‘After its kind’ The Bible tells us that God made each one of these animals ‘after its kind’. Those people who do not believe that God created say instead that one kind of animal evolved into another kind all by itself. Dinosour did not evolve into birds. God created dinosaurs and birds separately But there is no evidence that one kind of animal ever changed into a different kind. In the beginning, there was no evolutionary struggle for existence, with death and disease over millions of years.

Fish did not arise or come into being from a worm in an ancient pond, and birds did not come from dinosaurs. The Bible says God created all of the birds before He created any of the land animals. If animals made themselves from other animals over long periods of time, we should find millions and millions of fossils of ‘half-way’ animals, but we don’t! The theory of evolution says that sea life came first, then land plants, then land animals, then birds. But God says that He made plants first, then sea life and birds together. God did not use evolution to create over millions of years. God’s unlimited knowledge, wisdom and power are seen much more clearly in His creating everything in a short time than if He had used a long-drawn-out, cruel, evolutionary process. Until Adam sinned by disobeying God, no animal died and no human died. On Day 5, God simply gave the order that there should be living creatures in the sea and in the air, and they came into being. God’s powerful Word was fulfilled exactly the way He said. Why can birds fly and we can’t? People’ bodies have heavy bones and were designed to live on land, not in the air.

God designed birds to fly, but He designed us differently. Birds have light bones which are mostly hollow, with cross-members to give strength. Our bones are heavy and solid because they have to support us when we walk, run and jump. Even a bird’s beak is designed to save weight. It is made of lightweight material called keratin (which is in our hair and in a rhino’s horn); our jaws are made of heavy bone. Birds have strong chest muscles to flap their wings; we don’t. Birds have special lungs with tiny one-way tubes; our lungs don’t. Our lungs get all the oxygen we need for us to run around on the ground, while birds’ lungs are designed to get the extra oxygen that birds use for flight. In the air, birds’ bodies are streamlined to cut wind resistance; our bodies are not shaped for flight. This hasn’t stopped men from trying to fly by jumping off bridges and flapping boards attached to their arms. But it was only last century that men learned how to make and fly airplanes, by observing the birds that God made.

Light and heavy bones; flight or flop Click image to enlarge Aerospaceweb.org | Ask Us - Earliest Flying Creatures Earliest Flying Creatures What was the earliest flying creature on Earth? Was it an animal or an insect? - question from Rod The truth is that no one is absolutely sure how or why flying creatures evolved on Earth, but the ability first appeared among insects. The earliest fossils of winged insects have been found in Scotland and date to the Early Carboniferous Period of about 350 million years ago. These insects lived in an aquatic environment, and the prevailing theory is that they share a common evolutionary history with crustaceans. Fossil of an early dragonfly, one of the first flying insects Flying insects and crustaceans share many features, such as jointed legs and a jointed exoskeleton. Crustaceans live in water and are able to swim by rapidly flapping their jointed legs through the fluid. Many scientists believe that the jointed wings of insects evolved from a pair of jointed legs that allowed the creatures to "swim" through the air much like crustaceans swim through water. The earliest wings were probably little more than flaps that could catch the wind and carry the insects away from predators.

Over succeeding generations, the insects learned that flapping the wings could enable them to move through the air on their own. This evolution culminated in the incredibly fast and maneuverable insects we know today, creatures capable of flying in any direction, turning on a dime, and performing aerobatics a stunt pilot could only dream of. A modern species of dragonfly The earliest flying insects found so far belonged to Order Protodonata. Though now extinct, these creatures were closely related to the present-day Order Odonata to which the dragonfly belongs. Indeed, the first winged insects in the fossil record are very similar in structure to the dragonfly we know today, a creature that has changed little for the past 200 million years. The earliest dragonflies, however, were much larger than modern species. The biggest example ever found had a wingspan of 30 inches (76 cm), or two and a half feet! This early dragonfly was discovered in France and was four times as large as any dragonfly species living today. After insects, the next earliest appearance of flight was an animal closely related to the dinosaurs called the pterosaur.

The pterosaur and pterodactyl are often confused, but the pterodactyl is a particular type of pterosaur that evolved later and was distinguished by its short tail. The first pterosaurs evolved during the Late Triassic Period about 225 million years ago. Though other species of lizards or dinosaurs may have been able to glide, the pterosaur is believed to be the first vertebrate animal to achieve sustained flight with flapping wings. New species of pterosaurs continued to evolve through the Jurassic and Cretaceous Periods, but the creature disappeared 65 million years ago during the mass extinction that wiped out the dinosaurs. Fossil remains of pterosaurs, including a Quetzalcoatlus The first pterosaur fossil was discovered in southern Germany in the ancient remains of a warm shallow sea. Most other fossils have also been found on ancient lakeshores or in marine deposits. Besides Germany, other locations that have produced large numbers of pterosaur fossils include Kazakhstan, Kansas in the central United States, Chile, and northeastern Brazil. Pterosaur fossils have been discovered on every continent including Antarctica.

The largest example ever found was an enormous beast with a wingspan over 50 ft (15 m) across! Named Quetzalcoatlus, this species lived in North America and is believed to be one of the final pterosaurs to develop prior to the mass extinction. Most scientists consider pterosaurs to be related to dinosaurs but not true dinosaurs themselves. Moreover, it is also believed that pterosaurs are not directly related to birds, creatures that evolved separately during the Late Jurassic Period. The earliest known bird was Archaeopteryx that first appeared about 150 million years ago. Fossils of Archaeopteryx have been found in Germany and the United Kingdom. Archaeopteryx fossil and a reconstruction of how it might have looked in life Archaeopteryx had wings and feathers like modern birds, but retained the teeth, long tail, claws, small brain, and heavier bone structure of its more reptilian ancestors. Birds rapidly evolved into forms that closely resemble those of today, and there are currently over 10,000 known species in the world.

The final major class of animal to evolve flight was the bat that first appeared about 55 million years ago during the Eocene epoch, which is part of the Tertiary Period in the Cenozoic Era. It was during this period that mammals became the dominant form of life on Earth. Unlike gliding mammals like the flying squirrel, bats are the only mammals to have evolved sustained flight with flapping wings. Earliest known bat fossil Little fossil evidence of bat evolution has been found, and the earliest known bat fossil Icaronycteris was already a fully evolved flying animal. Early bats did have long tails and several teeth that no longer appear in modern species, but bats have otherwise changed very little since that time. Bat fossils have been found throughout the tropic regions and as far north as Italy and northern California. One of the most important questions scientists have yet to answer is what evolutionary characteristics drove these various creatures towards flight in the first place. It has been suggested that insects evolved wings as a means of escaping predators, but there were few predators on land to threaten insects at the time. Similarly, no one yet knows why pterosaurs or birds developed the ability to fly either, and bats are certainly one of the most bizarre of all mammals.

Regardless, what makes humans even more unique is that we were only able to evolve our ability to fly thanks to our intellect and ability to develop technology to make flight possible. - answer by Jeff Scott , 7 November 2004 Related Topics: What Were the First Animals to Walk on Land? (with pictures) What Were the First Animals to Walk on Land? Last Modified Date: 08 December 2016 Copyright Protected: Adorable animal families that will make you "aww" The first animals to walk on land are unknown. There is evidence that soft-bodied arthropods and slug-like animals visited the land as far back as 510 million years ago, in the Cambrian era, leaving behind mysterious tracks called Climactichnites and Diplichnites. These tracks are mysterious because no fossils have been found of the animals that made them. Some of these trace fossils are as wide as four inches. Perhaps these animals did not actually breathe air, and only slimed along on land for short periods as a way of moving from pond to pond. According to scientific consensus, the first verified land animal was a one-centimeter myriapod.

Present-day examples of myriapods include millipedes and centipedes . This myriapod, discovered in 2003 in Scotland and named Pneumodesmus newmani, is dated to 428 million years ago. Paleontologists can tell it lived on land because its fossil shows it possessed spiracles; holes that insects, spiders, rays, and sharks use for breathing air. Prior to the discovery of newmani, the oldest known air-breathing creature was a spider-like organism from 410 million years ago. Ad The first land-walking animals are often incorrectly cited as Devonian transitional forms called “fishapods” because they are intermediate between fish and true tetrapods . An example is the fish Tikaalik, which lived approximately 375 million years ago, during the Devonian period . It is remarkable that such organisms are so frequently cited as the first land animals when land animals from more than 50 million years before, such as Pneumodesmus newmani, are now widely known. The effect may have something to do with a bias in favor of the more familiar vertebrates over invertebrates.

The earliest land animals probably lived in oxygen-poor shallow pools near land. As the first vascular plants developed, they would have choked the areas around these pools with weeds, making it evolutionarily advantageous to climb over and around them via quick forays onto land areas. The land at that time would have been much more nutrient-rich than the water, as plants colonized the land before animals and left their decaying plant matter everywhere. Bacteria and fungi broke down much of the plant matter but it still would have been appealing to a hungry fish. Around 365 million years ago, some fish (so-called “fishapods”) developed limbs and climbed onto the land. The appearance of the first true trees about 370 million years ago would have helped this along, by depositing more nutrients into the soil and making the environment more habitable. Ad The first animals to live successfully on land were A. reptiles. B. flying reptiles. C. amphibians. D. arthropods. You have new items in your feed. Click to view. Question and answer The first animals to live successfully on land were A. reptiles. B. flying reptiles. C. amphibians. D.

arthropods. D. arthropods The first animals to live successfully on land were A. reptiles. B. flying reptiles. C. amphibians. D. arthropods. Original conversation User: The first animals to live successfully on land were A. reptiles. B. flying reptiles. C. amphibians. D. arthropods. Weegy: D. arthropods scijoe21 |Points 2265| User: The pattern of evolution shown in the finches above is known as A. convergent evolution. B. coevolution. C. mass evolution. D. adaptive radiation. Weegy: c. mass evolution User: Birds evolved from A. insects. B. a common ancestor with reptiles. C. amphibians. D. mammals. Weegy: B. a common ancestor with reptiles. selymi |Points 9496| User: According to this cladogram which organisms share a common ancestor? A. none of them B. lancelet and wolf C. fish and frog D.

all of them Weegy: Please provide the cladogram so that I can help you with the question. Expert answered| may100 |Points 2011| vertebrate notes Animals with a Backbone All Materials ï¿½ Cmassengale The vertebrates comprise a large group of chordates, and are subdivided into seven classes (3 classes of fish, amphibians, reptiles, birds, and mammals). Vertebrates have an internal skeleton of cartilage or bone, with vertebrae surrounding the dorsal nerve cord. Subphylum Vertebrata The subphylum Vertebrata consists of about 43,700 species of animals with backbones. Vertebrates exhibit all three of the chordate characteristics at some point during their lives. The embryonic notochord is replaced by a vertebral column in the adult. The vertebral column is made of individual hard segments (vertebrae) surrounding the dorsal hollow nerve cord. The nerve cord is the one chordate feature present in the adult phase of all vertebrates. The vertebral column, part of a flexible but strong endoskeleton, is evidence that vertebrates are segmented.

The vertebrate skeleton is living tissue (either cartilage or bone) that grows as the animal grows. The endoskeleton and muscles form an organ system that permits rapid and efficient movement. The pectoral and pelvic fins of fishes evolved into jointed appendages that allowed vertebrates to move onto land. The skull, the most anterior component of the main axis of the vertebrate endoskeleton, encases the brain. The high degree of cephalization in vertebrates is accompanied by complex sense organs concentrated in the head region. Eyes developed as outgrowths of the brain. Ears were equilibrium devices in aquatic vertebrates that function as sound-wave receivers in land vertebrates. Vertebrates have a complete digestive system and a large coelom. Their circulatory system is closed, with respiratory pigments contained within blood vessels. Gas exchange is efficiently accomplished by gills, lungs, and in a few cases, moist skin. Kidneys are efficient in excretion of nitrogenous waste and regulation of water. Reproduction is usually sexual with separate sexes. Classification of the Vertebrata The first vertebrates were fishlike. Fishes are aquatic, gill-breathing vertebrates that usually have fins and skin covered with scales.

The larval form of a modern-day lamprey, which looks like a lancelet, may resemble the first vertebrates: it has the three chordate characteristics (like the tunicate larva), as well as a two-chambered heart, a three-part brain, and other internal organs that are like those of vertebrates. Small, jawless, and finless ostracoderms were the earliest vertebrates. They were filter feeders, but probably were also able to move water through their gills by muscular action. Ostracoderms have been found as fossils from the Cambrian through Devonian periods, when the group finally went extinct. Although extant jawless fishes lack protection, many early jawless fishes had large defensive head shields. Class Lampreys These long, eel-like, jawless fish are free-swimming predators on other fish. Lampreys hatch in freshwater and many live their lives entirely in freshwater. Some lampreys migrate to the sea, but must return to freshwater to reproduce. Lampreys have a sucker-like mouth that lacks a jaw.

Lampreys Sea lamprey on lake trout Sea lamprey mouth Class Myrini, Hagfish Members of the class Myxini have a partial cranium (skull), but no vertebrae. Their skeleton is made of of cartilage, as is that of sharks. Hagfish lack jaws, and for this reason used to be classified with the lampreys in a group called the Agnatha ("no jaws") or the Cyclostomata ("round mouth"). Hagfish Fish: Vertebrates With Jaws The fish first appeared during the Cambrian Period. Whether fish first evolved in fresh or salt water is unclear from the fossil record. The jawless fish are the most primitive group, although they were a very important group during the Silurian and Devonian periods. Hagfish and lampreys are the only living members of this class today. They have long, cylindrical bodies with cartilage skeletons and no paired fins. The first jawed fish were the Placoderms, an extinct group of Devonian-aged jawed fishes. Placoderms were armored with heavy plates and had strong jaws and paired pectoral and pelvic fins.

Paired fins allow fish to balance and to maneuver well in water, which facilitate both predation and escape. The fossil is a cast of the placoderm, Bothriolepis . The evolution of jaws is an example of evolutionary modification of existing structures to perform new functions. Jaws are modified gill arches, and allowed the exploitation of new roles in the habitats: predators with powerful jaws. There are two classes of jawed fish: the cartilaginous fish and the bony fish. Steps in the evolution of jaws by modification of gill arches. Class Chondrichthyes: Cartilaginous Fish The class Chondrichthyes contains approximately 850 species of skates, rays, and sharks. They have jaws, lots of teeth, paired fins, and a cartilage endoskeleton. Cartilaginous fish first appeared during the Devonian Period and expanded in diversity during the Carboniferous and Permian before nearly disappearing during the great extinction that occurred near the end of the Permian. A large group of cartilagenous fish still survives today and is an important part of the marine fauna.

These fish have five to seven gill slits on both sides of the pharynx, and lack the gill covers found in bony fish. The chondrichthyian body is covered epidermal placoid (or toothlike) scales. Developmental studies show the teeth of sharks are enlarged scales. The largest sharks are filter feeders, not the predators of Hollywood movies. Basking and whale sharks eat tons of crustaceans (small krills, etc.) filtered from the water. Most sharks are fast-swimming, open-sea predators. The great white shark feeds on dolphins, sea lions and seals (and people sometimes). In other words, anything is WANTS to! Shark and Ray Rays and skates live on the ocean floor; their pectoral fins are enlarged into winglike fins; they swim slowly. Stingrays have a venomous spine. The electric ray family can feed on fish that have been stunned with electric shock of over 300 volts. Sawfish rays have a large anterior "saw" that they use to slash through schools of fish.

Class Osteichthyes, the Bony Fish There are about 20,000 species of bony fish, found both in marine and freshwater, comprising the class Osteichthyes. This class is divided into two groups: the lobe-finned (Sarcopterygii) and ray-finned fish (Actinopterygii). The bony fish have a bony skeleton. Most species in this class are ray-finned with thin, bony rays supporting the fins. A few fishes are lobe-finned and are thought to be related to the ancestors of amphibians. Cross section of a fish Ray-finned Fish (Actinopterygii) The ray-finned fish include familiar species such as tuna, bass, perch, and trout. Ray-finned fish are the most successful and diverse of the vertebrates (more than half of all vertebrate species belong to this group). Thin, bony supports with radiating bones (hence the term ray-finned) hold the fins away from the body. Ray-finned fish obtain their food by filter feeding and by preying on insects and other animals. Their skin is covered by scales formed of bone.

These scales are homologous to our own hair (and the feathers of birds), being derived from the same embryonic tissues. The gills in this group of fish do not open separately and are covered by an operculum. Ray-finned fish have a swim bladder, a gas-filled sac, that regulates buoyancy and depth. Sharks lack this feature, which enables fish to "sleep" without sinking. The swim bladder acts much the way a ballast tank does on a submarine to control buoyancy. Salmon, trout, and eels can migrate from fresh water to salt water, but must adjust kidney and gill function to the tonicity of their environments. In freshwater, the fish is hypotonic relative to its aqueous (watery) environment. Water is constantly flooding into the fish, and must be removed by the fish's excretory system. In seawater, the fish is now hypertonic or isotonic relative to the seawater, requiring conservation of body water. Bony fishes depend on color vision to detect both rivals and mates. Sperm and eggs are released into the water, with not much parental care for the newborn. Most fish have fertilization and embryonic development taking place outside the female's body.

Lobe-finned Fish (Sarcopterygii) This group includes six species of lungfishes and one species of coelacanth that has muscular fins with large, jointed bones attaching the fins to the body. Lobe-finned fish have fleshy fins supported by central bones, homologous to the bones in your arms and legs. These fins underwent modification, becoming the limbs of amphibians and their evolutionary descendants such as lizards, canaries, dinosaurs, and humans. The lungfish are a small group found mostly in freshwater stagnant water or ponds that dry up in Africa, South America, and Australia. Australian lungfish Coelacanths live in deep oceans. They were once considered extinct, although more than 200 have been captured since 1938. Mitochondrial DNA analysis supports the hypothesis that lungfish are probably the closest living relatives of amphibians. Coelacanth, a living fossil. The crossopterygian fish (represented by the marine extant deep-living coelacanth and extinct freshwater forms) are regarded as ancestors of early amphibians.

Extinct crossopterygians had strong fins, lungs, and a streamlined body capable of swimming as well as traveling short distances out of water. Comparison of the skeletons of a crossopterygian lobe-finned fish and an early amphibian. The "Tetrapods" The term "tetrapod" (meaning four-limbed or four-footed) has historically been applied to the land vertebrates (amphibians, reptiles, dinosaurs, birds, and mammals). All other animals from this point have four limbs and are called tetrapods. Most zoologists would accept that the Devonian lobe-finned fishes were ancestral to the amphibians. Animals (both vertebrate as well as many invertebrates such as insects) that live on land use limbs to support the body, especially since air is less buoyant than water. Lobe-finned fishes and early amphibians also had lungs and internal nares to respire air. Two hypotheses have been proposed to explain the evolution of amphibians from lobe-finned fishes. Lobe-finned fishes capable of moving from pond-to-pond had an advantage over those that could not.

The supply of food on land, and the absence of predators, promoted adaptation to land. The first amphibians diversified during Carboniferous Period (commonly known as the Age of Amphibians). Class Amphibia: Animals Move Ashore This class includes 4000 species of animals that spend their larval/juvenile stages in water, and their adult life on land. Amphibians must return to water to mate and lay eggs. Most adults have moist skin that functions in helping their small, inefficient lungs with gas exchange. Frogs, toads, newts, salamanders, and mud puppies are in this transitional group between water and land. Amphibian features not seen in bony fish include: Limbs with girdles of bone that are adapted for walking on land. A tongue that can be used for catching prey as well as sensory input. Eyelids that help keep the eyes moist. Ears adapted for detecting sound waves moving through the thin (as compared to water) medium of the air. A larynx adapted for vocalization. A larger brain than that of fish, and a more developed cerebral cortex.

Skin that is thin, smooth, non-scaly, and contains numerous mucous glands; the skin plays an active role in osmotic balance and respiration. Development of a lung that is permanently used for gas exchange in the adult form, although some amphibians supplement lung function by exchange of gases across a porous (moist) skin. A closed double-loop circulatory system that replaces the single-loop circulatory path of fish. Development of a three-chambered heart that pumps mixed blood before and after it has gone to the lungs. Reproduction involves a return to the water. Ther term "amphibian" refers to two life styles, one in water, the other on land. Amphibians shed eggs into the water where external fertilization occurs, as it does in fish. Generally, amphibian eggs are protected by a coat of jelly but not by a shell. The young hatch into aquatic larvae with gills (tadpoles). Aquatic larvae usually undergo metamorphosis to develop into a terrestrial adult. Amphibians, like fish, are ectothermic; they depend upon external heat to regulate body temperatures. If the environmental temperature becomes too low, ectotherms become inactive.

Salamanders more likely resemble earliest amphibians due to their S-shaped movements. Salamanders practice internal fertilization; males produce a spermatophore that females pick up. Frogs and toads are tailless as adults, with their hind limbs specialized for jumping. Frogs Class Reptilia: Reproducton Without Water This class of 6000 species includes the snakes, lizards, turtles, alligators, and crocodiles. Reptiles that lay eggs lay an egg surrounded by a thick protective shell and a series of internal membranes. Reptiles have internal fertilization: their gametes do not need to be released into water for fertilization to occur. The amniotic egg is a superb adaptation to life on land. While amphibians need to lay their eggs in water, their descendants (reptiles) were not as strongly tied to moist environments and could truly expand into more arid areas. Reptiles were the first land vertebrates to practice internal fertilization through copulation and to lay eggs that are protected by a leathery shell with food and other support for the growing embryo.

The amniote egg contains extra-embryonic membranes that are not part of the embryo and are disposed of after the embryo has developed and hatched. These membranes protect the embryo, remove nitrogenous wastes, and provide the embryo with oxygen, food, and water. The amnion, one of these extra-embryonic membranes, creates a sac that fills with fluid and provides a watery environment in which the embryo develops. The embryo develops in a "pond within the shell". Structure of the amniote egg Evolutionary History of Reptiles Reptiles first evolved during the Carboniferous time and partly displaced amphibians in many environments. The first reptiles (often referred to as the stem reptiles) gave rise to several other lineages, each of which adapted to a different way of life. Reptilian success was due to their terrestrial (amniotic) egg and internal fertilization, as well as their tough leathery skin, more efficient teeth and jaws, and in some, bipedalism (traveling on their hind legs, allowing the forelimbs to grasp prey or food, or become wings).

One group, the Pelycosaurs (fin-backed or sail lizards) are related to therapsids, mammal-like reptiles ancestral to mammals. Other groups returned to aquatic environments. Ichthyosaurs were fishlike (or dolphin-like) free-swimming predators of the Mesozoic seas. The plesiosaurs had a long neck and a body adapted tp swimming though use of flippers (legs that evolutionarily reverted to a flipper-like shape). These free-swimmers also adapted to live birth of their young (since they could not return to the land to lay eggs). Thecodonts were the reptiles that gave rise to most of the reptiles, living and extinct. Pterosaurs were flying reptiles that dominated the Mesozoic skies. They had a keel for attachment of flight muscles and air spaces in bones to reduce weight. Dinosaurs (descended from some thecodonts) and mammal-like reptiles' had their limbs beneath the body providing increased agility and facilitating gigantic size. Lizards have their elbows out (like you do when you do a push-up).

By having their elbows in, dinosaurs and mammals place more of the weight of the body on the long bones instead of the elbows, ankles, and knees. Relationship between limbs and body. Note that reptiles have their upper limbs jutting out from the body, while mammals have their limbs in line with the body, supporting and more easily raising the body mass off the ground. Reptiles dominated the earth for about 170 million years during the Mesozoic Era. The mass extinction of many reptile groups at the close of the Mesozoic (the Cretaceous Period) has been well documented and the subject of many hypotheses. The 1980 hypothesis by Luis and Walter Alvarez and others proposes the impact of a large meteorite at the end of the Cretaceous period caused a catastrophic environmental collapse that led to the extinction of nearly 50% of all species of life on Earth. The survivors, birds and mammals, reaped the spoils and diversified during the Cenozoic Era. Three groups of reptiles remain: turtles, snakes/lizards, and crocodiles/alligators. About 6,000 species of reptiles comprise the Class Reptilia. Most live in tropics or subtropics.

Lizards and snakes live on land, while turtles and alligators live in water for much of their lives. Reptiles have a thick, scaly skin that is keratinized and impermeable to water. This same keratin is a protein found in hair, fingernails, and feathers. Protective skin prevents water loss but requires several molts a year. Reptilian lungs are more developed than those of amphibians. Air moves in and out of the lungs due to the presence of an expandable rib cage in all reptiles except turtles. Most reptiles have a nearly four-chambered heart. The crocodile has a completely four-chambered heart that more fully separates oxygen-rich blood from from deoxygenated or oxygen-poor blood. The well-developed kidneys excrete uric acid; less water is lost in excretion. Reptiles are ectothermic; they require a fraction of the food per body weight of birds and mammals, but are behaviorally adapted to warm their body temperature by sunbathing. Photograph of a lizard (L) and a gavial (R) Snakes and lizards live mainly in the tropics and desert.

Lizards have four clawed legs and are carnivorous; marine iguanas on the Galapagos are adapted to spend time in the sea; frilled lizards have a collar to scare predators, and blind worm lizards live underground. Snakes evolved from lizards and lost their legs as an adaptation to burrowing. Their jaws can readily dislocate to engulf large food. The snake's tongue collects airborne molecules and transfers them to the Jacobson's organ for tasting. Some poisonous snakes have special fangs for injecting their venom. Turtles have a heavy shell fused to the ribs and thoracic vertebrae; they lack teeth but use a sharp beak; sea turtles must leave the ocean to lay eggs onshore. Galapagos tortoises Crocodiles and alligators are largely aquatic, feeding on fishes and other animals. They both have a muscular tail that acts as a paddle to swim and a weapon. The male crocodile bellows to attract mates. In some species the male also protects the eggs and young. The Archosauria: Birds, Dinosaurs, and More Cladistic analyses place the birds, alligators, and dinosaurs in the same clade, the Archosauria (or "ruling reptiles").

This group is a major group of diapsids (vertebrates that have two openings in their skulls) that have single openings in each side of the skull, in front of the eyes (antorbital fenestrae), among other characteristics. This helps to lighten the skull, provides more room for muscles and other tissues, and allows more skull flexibility when eating. Other typical archosaurian characteristics include another opening in the lower jaw (the mandibular fenestra), a high narrow skull with a pointed snout, teeth set in sockets, and a modified ankle joint. The ancestral archosaurs probably originated some 250 million years or so ago, during the late Permian period. Their descendants (such as the dinosaurs) dominated the realm of the terrestrial vertebrates for a most of the Mesozoic Era. The birds and crocodilians are the last living groups of archosaurs. Class Aves: Birds of a Feather The class Aves (birds) contains about 9000 species. Birds evolved from either a dinosaurian or other reptilian group during the Jurassic (or possibly earlier).

The earliest bird fossils, such as the Jurassic Archaeopteryx or Triassic Protavis, display a mosaic of reptilian and bird features (teeth in the bill, a jointed tail, and claws on the wing are reptilian; feathers and hollow bones are bird-like). Archaeopteryx, once considered the first bird.The fossil is from the Solenhoefen Limestone (Jurassic) of Germany The distinguishing feature of birds is feathers: which provide insulation as well as aid in flight. Hummingbird Feather Remember, not all animals that fly have feathers, but all almost every endothermic animal (warm-blooded) has a covering of hair or feathers for insulation. The recent (1999) discovery of a "feathered" dinosaur adds credence to this speculation. The dinosaur could not fly, so of what use would feather be but insulation (or possibly mating). Modern birds appeared during the early Tertiary, and have adapted to all modes of life: flying (condors, eagles, hummingbirds), flightless-running (ostriches, emus), and swimming (penguins). Birds exhibit complex mating rituals as well as social structure (a pecking order!).

Class Mammalia: Got Milk? Class Mammalia contains around 5000 species placed in 26 orders (usually). The three unifying mammalian characteristics are: hair the presence of three middle ear bones the production of milk by mammary glands Milk is a substance rich in fats and proteins. Mammary glands usually occur on the ventral surface of females in rows (when there are more than two glands). Humans and apes have two mammary glands (one right, one left), while other animals can have a dozen or more. All mammals have hair at some point during their life. Mammalian hair is composed of the protein keratin. Hair has several functions: 1) insulation; 2) sensory function (whiskers of a cat); 3) camouflage, a warning system to predators, communication of social information, gender, or threats; and 4) protection as an additional layer or by forming dangerous spines that deter predators. Modifications of the malleus and incus (bones from the jaw in reptiles) work with the stapes to allow mammals to hear sounds after they are transmitted from the outside world to their inner ears by a chain of these three bones.

Mammals first evolved from the mammal-like reptiles during the Triassic period, about the same time as the first dinosaurs. However, mammals were minor players in the world of the Mesozoic, and only diversified and became prominent after the extinction of dinosaurs at the close of the Cretaceous period. Mammals have since occupied all roles once held by dinosaurs and their relatives (flying: bats; swimming: whales, dolphins; large predators: tigers, lions; large herbivores: elephants, rhinos), as well as a new one (thinkers and tool makers: humans). There are 4500 species of living mammals. Mammalian Adaptations Mammals developed several adaptations that help explain their success. Teeth are specialized for cutting, shearing or grinding; thick enamel helps prevent teeth from wearing out. Mammals are capable of rapid locomotion. Brain sizes are larger per pound of body weight than most other animals'. Mammals have more efficient control over their body temperatures than do birds. Hair provides insulation. Mammary glands provide milk to nourish the young.

Mammalian Classification Subclass Prototheria: Order Monotremata: Monotremes (typified by the platypus and echinda) lay eggs that have similar membranes and structure to reptilian eggs. Females burrow in ground and incubates their eggs. Both males and females produce milk to nourish the young There are two families living today and quite a few known from the fossil record of Gondwana. Monotremes are today restricted to Australia and New Guinea. The earliest fossil monotreme is from the early Cretaceous, and younger fossils hint at a formerly more widespread distribution for the group. While their fossil record is scarce, zoologists believe that monotremes probably diverged from other mammals during the Mesozoic. Monotremes have many differences with other mammals and are often placed in a separate group, the subclass Prototheria. They retain many characters of their therapsid ancestors, such as laying eggs, limbs oriented with humerus and femur held lateral to body (more lizard-like), a cloaca, skulls with an almost birdlike appearance, and a lack of teeth in adults. This suggests that monotremes are the sister group to all other mammals.

However, monotremes do have all of the mammalian defining features of the group. Echidna Subclass Metatheria: Marsupials (such as the koala, opossum, and kangaroo) are born while in an embryonic stage and finish development outside the mother's body, often in a pouch. Marsupial young leave the uterus, crawl to the pouch, and attach to the nipple of a mammary gland and continue their development. Marsupials were once widespread, but today are dominant only in Australia, where they underwent adaptive radiation in the absence of placental mammals. The Metatheria contains 272 species classified in several orders. Metatheres diverged from the lineage leading to the eutherian (placental) mammals by the middle of the Cretaceous period in North America. The earliest marsupial fossils resemble North American opossums. Marsupial fossils are found on other northern hemisphere continents, although they seem not to have been prominent elements of those faunas. On the other hand, in South America and Australia, marsupials continued to be dominant faunal elements.

The marsupials of South America began to go extinct in the late Miocene and Early Pliocene (Cenozoic era) when volcanic islands grew together and formed the Isthmus of Panama, allowing North American placental mammals to cross into South America. Australian marsupials remain diverse and dominant native mammals of the fauna. During the Cenozoic Era many marsupials in South America and Australia underwent parallel (or convergent) evolution with placental mammals elsewhere, producing marsupial "wolves", "lions", and saber-toothed marsupial "cats". Red Kangaroo with its joey Koala Tasmanian Devil Subclass Eutheria: There are 4000 described species of placental mammals, a group that includes dogs, cats, and people. The subclass is defined by a true placenta that nourishes and protects the embryos held within the mother's body for an extended gestation period (nearly two years for an elephant, and nine very long months for a human). The eutherian placenta has extraembryonic membranes modified for internal development within the uterus. The chorion is the fetal portion of placenta, while the uterine wall grows the maternal portion.

The placenta exchanges nutrients, oxygen, and wastes between fetal and maternal blood. There are 12 orders of placental mammals. Classification is based on the mode of locomotion and methods of obtaining food. Prominent orders include the bats (order Chiroptera), horses (order Perissodactyla), whales (order Cetacea), mice (order Rodentia), dogs (order Carnivora), and monkeys/apes/humans (order Primates).

Question: What creatures were first to live on land and fly?
Answer: Insects