Why fossils are important to scientists

They even have tiny back limbs. Although the front limbs of these fossil animals are in some ways similar to legs, in other ways they also show strong similarities to the fins of modern whales. Subdisciplines of Paleontology The field of paleontology has many subdisciplines. A subdiscipline is a specialized field of study within a broader subject or discipline. In the case of paleontology, subdisciplines can focus on a specific fossil type or a specific aspect of the globe, such as its climate.

Vertebrate Paleontology One important subdiscipline is vertebrate paleontology , the study of fossils of animals with backbones. Vertebrate paleontologists have discovered and reconstructed the skeletons of dinosaurs, turtles, cats, and many other animals to show how they lived and their evolutionary history. Using fossil evidence, vertebrate paleontologists deduced that pterosaurs, a group of flying reptiles, could fly by flapping their wings, as opposed to just gliding.

Reconstructed skeletons of pterosaurs have hollow and light bones like modern birds. One type of pterosaur , Quetzalcoatlus , is considered one of the largest flying creatures in history.

It had a wingspan of 11 meters 36 feet. Paleontologists have competing theories about if and how Quetzalcoatlus flew. Some paleontologists argue it was too heavy to fly at all.

Others maintain it could distribute its weight well enough to soar slowly. Still other scientists say Quetzalcoatlus was muscular enough to fly quickly over short distances. These theories demonstrate how vertebrate paleontologists can interpret fossil evidence differently.

Invertebrate Paleontology Invertebrate paleontologists examine the fossils of animals without backbones—mollusks, corals, arthropods like crabs and shrimp, echinoderms like sand dollars and sea stars, sponges, and worms.

Unlike vertebrates, invertebrates do not have bones—they do leave behind evidence of their existence in the form of fossilized shells and exoskeletons, impressions of their soft body parts, and tracks from their movement along the ground or ocean floor. Invertebrate fossils are especially important to the study and reconstruction of prehistoric aquatic environments.

For example, large communities of million-year-old invertebrate marine fossils found in the deserts of Nevada, in the United States, tell us that certain areas of the state were covered by water during that period of time. Paleobotany Paleobotanists study the fossils of ancient plants. These fossils can be impressions of plants left on rock surfaces, or they can be parts of the plants themselves, such as leaves and seeds, that have been preserved by rock material. These fossils help us understand the evolution and diversity of plants, in addition to being a key part of the reconstruction of ancient environments and climates, subdisciplines known as paleoecology the study of ancient environments and paleoclimatology the study of ancient climates.

At a small site in the Patagonia region of Argentina, paleobotanists discovered the fossils of more than plant species that date back about 52 million years. The Patagonia leaf fossils may disprove this theory. Some plant fossils are found in hard lumps called coal balls.

Coal, a fossil fuel , is formed from the remains of decomposed plants. Coal balls are also formed from the plant remains of forests and swamps, but these materials did not turn into coal. They slowly petrified, or were replaced by rock. Coal balls, found in or near coal deposits, preserve evidence of the different plants that formed the coal, making them important for studying ancient environments, and for understanding a major energy source.

Micropaleontology Micropaleontology is the study of fossils of microscopic organisms, such as protists, algae , tiny crustaceans, and pollen. Micropaleontologists use powerful electron microscopes to study microfossils that are generally smaller than four millimeters 0.

Microfossil species tend to be short-lived and abundant where they are found, which makes them helpful for identifying rock layers that are the same age, a process known as biostratigraphy. The chemical makeup of some microfossils can be used to learn about the environment when the organism was alive, making them important for paleoclimatology.

Shells accumulate on the ocean floor after the organisms die. Because the organisms draw the elements for their shells from the ocean water around them, the composition of the shells reflects the current composition of the ocean.

By chemically analyzing the shells, paleontologists can determine the amount of oxygen, carbon, and other life-sustaining nutrients in the ocean when the shells developed. They can then compare shells from one period of time to another, or from one geographic area to another.

Differences in the chemical composition of the ocean can be good indicators of differences in climate. Micropaleontologists often study the oldest fossils on Earth. The oldest fossils are of cyanobacteria , sometimes called blue-green algae or pond scum. Cyanobacteria grew in shallow oceans when Earth was still cooling, billions of years ago.

Fossils formed by cyanobacteria are called stromatolites. The oldest fossils on Earth are stromatolites discovered in western Australia that are 3. History of Paleontology Throughout human history, fossils have been used, studied, and understood in different ways.

Early civilizations used fossils for decorative or religious purposes, but did not always understand where they came from. Although some ancient Greek and Roman scientists recognized that fossils were the remains of life forms, many early scholars believed fossils were evidence of mythological creatures such as dragons. From the Middle Ages until the early s, fossils were widely regarded as works of the devil or of a higher power.

Many people believed the remains had special curative or destructive powers. Many scholars also believed that fossils were remains left by Noah's flood and other disasters documented in the Hebrew holy book. Some ancient scientists did understand what fossils were, and were able to formulate complex hypotheses based on fossil evidence. Greek biologist Xenophanes discovered seashells on land, and deduced that the land was once a seafloor.

Remarkably, Chinese scientist Shen Kuo was able to use fossilized bamboo to form a theory of climate change. The formal science of paleontology—fossil collection and description—began in the s, a period of time known as the Age of Enlightenment. Scientists began to describe and map rock formations and classify fossils. Geologists discovered that rock layers were the product of long periods of sediment buildup, rather than the result of single events or catastrophes.

Once a fossil is removed from the ground it cannot be put back, so paleontologists strive to record as much information as possible regarding the context of each fossil. Without such detailed context information, our knowledge of ancient life and landscapes would be greatly reduced and precise connections between parks and other fossil sites would be much more difficult.

The fossil record of the national parks includes billions of individual fossils spanning more than a billion years of earth's history. Some fossils are common. Others are one-of-a-kind or found nowhere else on the planet. Florissant Fossil Beds National Monument Colorado contains the only fossilized redwood trio on earth.

The most common fossil fish at Fossil Butte National Monument Wyoming , Knightia eocaena a herring , is the state fossil of Wyoming and perhaps the most abundant articulated vertebrate fossil in the world. Waco Mammoth National Monument Texas represents the largest known concentration of mammoths dying from the same event in North America and the nation's first and only recorded evidence of a nursery herd of Columbian mammoths. It is a spectacularly fossiliferous million year old reef.

As a result, hybrid or mosaic structures can evolve that exhibit partial homologies. For example, certain compound leaves of flowering plants are partially homologous both to leaves and shoots because they combine some traits of leaves and some of shoots. Homologous sequences are considered paralogous if they were separated by a gene duplication event; if a gene in an organism is duplicated to occupy two different positions in the same genome, then the two copies are paralogous.

A set of sequences that are paralogous are called paralogs of each other. Paralogs typically have the same or similar function, but sometimes do not. It is considered that due to lack of the original selective pressure upon one copy of the duplicated gene, this copy is free to mutate and acquire new functions.

Homology vs. This is because they are similar characteristically and even functionally, but evolved from different ancestral roots. Paralogous genes often belong to the same species, but not always. For example, the hemoglobin gene of humans and the myoglobin gene of chimpanzees are considered paralogs.

This is a common problem in bioinformatics; when genomes of different species have been sequenced and homologous genes have been found, one can not immediately conclude that these genes have the same or similar function, as they could be paralogs whose function has diverged. The opposite of homologous structures are analogous structures, which are physically similar structures between two taxa that evolved separately rather than being present in the last common ancestor.

Bat wings and bird wings evolved independently and are considered analogous structures. Genetically, a bat wing and a bird wing have very little in common; the last common ancestor of bats and birds did not have wings like either bats or birds. Wings evolved independently in each lineage after diverging from ancestors with forelimbs that were not used as wings terrestrial mammals and theropod dinosaurs, respectively.

It is important to distinguish between different hierarchical levels of homology in order to make informative biological comparisons.

In the above example, the bird and bat wings are analogous as wings, but homologous as forelimbs because the organ served as a forearm not a wing in the last common ancestor of tetrapods. Analogy is different than homology. Although analogous characteristics are superficially similar, they are not homologous because they are phylogenetically independent.

Analogy is commonly also referred to as homoplasy. Convergent evolution occurs in different species that have evolved similar traits independently of each other. Sometimes, similar phenotypes evolve independently in distantly related species.

For example, flight has evolved in both bats and insects, and they both have wings, which are adaptations to flight. However, the wings of bats and insects have evolved from very different original structures. This phenomenon is called convergent evolution, where similar traits evolve independently in species that do not share a recent common ancestry.

Convergent evolution describes the independent evolution of similar features in species of different lineages. The two species came to the same function, flying, but did so separately from each other. Both sharks and dolphins have similar body forms, yet are only distantly related: sharks are fish and dolphins are mammals.

Such similarities are a result of both populations being exposed to the same selective pressures. Within both groups, changes that aid swimming have been favored. Thus, over time, they developed similar appearances morphology , even though they are not closely related.

One of the most well-known examples of convergent evolution is the camera eye of cephalopods e. Their last common ancestor had at most a very simple photoreceptive spot, but a range of processes led to the progressive refinement of this structure to the advanced camera eye. Eye evolution : Vertebrates and octopi developed the camera eye independently.

In the vertebrate version the nerve fibers pass in front of the retina, and there is a blind spot 4 where the nerves pass through the retina. This means that octopi do not have a blind spot. Convergent evolution is similar to, but distinguishable from, the phenomenon of parallel evolution.

Parallel evolution occurs when two independent but similar species evolve in the same direction and thus independently acquire similar characteristics; for example, gliding frogs have evolved in parallel from multiple types of tree frog. Traits arising through convergent evolution are analogous structures, in contrast to homologous structures, which have a common origin, but not necessarily similar function.

The British anatomist Richard Owen was the first scientist to recognize the fundamental difference between analogies and homologies. Bat and pterosaur wings are an example of analogous structures, while the bat wing is homologous to human and other mammal forearms, sharing an ancestral state despite serving different functions.

The opposite of convergent evolution is divergent evolution, whereby related species evolve different traits. On a molecular level, this can happen due to random mutation unrelated to adaptive changes. Some organisms possess structures with no apparent function which appear to be residual parts from a past ancestor. For example, some snakes have pelvic bones despite having no legs because they descended from reptiles that did have legs.

Another example of a structure with no function is the human vermiform appendix. These unused structures without function are called vestigial structures.

Other examples of vestigial structures are wings which may have other functions on flightless birds like the ostrich, leaves on some cacti, traces of pelvic bones in whales, and the sightless eyes of cave animals.

Vestigial appendix : In humans the vermiform appendix is a vestigial structure; it has lost much of its ancestral function. There are also several reflexes and behaviors that are considered to be vestigial. The arrector pili muscle, which is a band of smooth muscle that connects the hair follicle to connective tissue, contracts and creates the goose bumps on skin.

Vestigial structures are often homologous to structures that function normally in other species. Therefore, vestigial structures can be considered evidence for evolution, the process by which beneficial heritable traits arise in populations over an extended period of time. The existence of vestigial traits can be attributed to changes in the environment and behavior patterns of the organism in question. In some cases the structure becomes detrimental to the organism.

Whale Skeleton : The pelvic bones in whales are also a good example of vestigial evolution whales evolved from four-legged land mammals and secondarily lost their hind legs. Letter c in the picture indicates the undeveloped hind legs of a baleen whale.

If there are no selection pressures actively lowering the fitness of the individual, the trait will persist in future generations unless the trait is eliminated through genetic drift or other random events.

Although in many cases the vestigial structure is of no direct harm, all structures require extra energy in terms of development, maintenance, and weight and are also a risk in terms of disease e. The vestigial versions of a structure can be compared to the original version of the structure in other species in order to determine the homology of the structure. Homologous structures indicate common ancestry with those organisms that have a functional version of the structure.

Vestigial traits can still be considered adaptations because an adaptation is often defined as a trait that has been favored by natural selection. Adaptations, therefore, need not be adaptive, as long as they were at some point. The biological distribution of species is based on the movement of tectonic plates over a period of time. Biogeography is the study of the geographic distribution of living things and the abiotic factors that affect their distribution. Abiotic factors, such as temperature and rainfall, vary based on latitude and elevation, primarily.

As these abiotic factors change, the composition of plant and animal communities also changes. Ecologists who study biogeography examine patterns of species distribution. No species exists everywhere; for example, the Venus flytrap is endemic to a small area in North and South Carolina. An endemic species is one which is naturally found only in a specific geographic area that is usually restricted in size.

Other species are generalists: species which live in a wide variety of geographic areas; the raccoon, for example, is native to most of North and Central America. Since species distribution patterns are based on biotic and abiotic factors and their influences during the very long periods of time required for species evolution, early studies of biogeography were closely linked to the emergence of evolutionary thinking in the eighteenth century.

Some of the most distinctive assemblages of plants and animals occur in regions that have been physically separated for millions of years by geographic barriers. If you read these pages you should get a pretty good idea of what a fossil is.

Introducing the basics What can fossils tell us? How do fossils form? Different types of fossils Find out more about fossils by visiting Invertebrate I.