Biogeography. A cladogram by the Field Museum of Science Cladogram Crocodilia. HS/Biology Science Unit: 06 Lesson: 01

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1 Biogeography HS/Biology Biogeography is a branch of geography that studies the past and present distribution of the world's many species, organisms, and ecosystems. It is usually considered to be a part of physical geography as it often relates to the examination of the physical environment and how it affects species and shapes their distribution across geographic gradients of the following: altitude elevation isolation habitat area As such, biogeography includes the study of the world's biomes and taxonomy - the naming of species. In addition, biogeography has strong ties to biology, ecology, evolution studies, climatology, and soil science. The field of biogeography is concerned with the distribution of species in relation both to geography and to other species. Biogeography comprises two disciplines: historical biogeography, which is concerned with the origins and evolutionary histories of species on a long time scale, and ecological biogeography, which deals with the current interactions of species with their environments and each other on a much shorter time scale. Historical biogeographers depend heavily on evidence from other disciplines. Fossil records: provide a large part of the information needed to determine distributions and past interactions Molecular biology: furnished historical biogeographers with molecular clocks, metabolic molecules whose change over time help track the relatedness of species Historical biogeographers also make use of a tool called an area cladogram. This diagram is made by taking a taxonomic tree, which shows various species and their relatedness, and replacing the species names with the geographic location in which those species are found. This new tree allows scientists to determine how the differences in environments have affected the evolutionary history of different species of common origin. A cladogram by the Field Museum of Cladogram Crocodilia 2011, TESCCC 10/05/11 page 1 of 1

2 Homologies Biology HS/ Evolutionary theory predicts that related organisms will share similarities that are derived from common ancestors. Similar characteristics due to relatedness are known as homologies. Homologies can be revealed by comparing the anatomies of different living things, looking at cellular similarities and differences, studying embryological development, and studying vestigial structures within individual organisms. A vestigial structure is a degenerated or imperfectly developed organ or structure that has little or no utility. Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs, as different as a bat's wing, a seal's flipper, a cat's paw and a human hand, have a common underlying structure of bones and muscles. Owen reasoned that there must be a common structural plan for all vertebrates, as well as for each class of vertebrates. Comparative Anatomy whale human dog bird 2011, TESCCC 10/05/11 page 1 of 2

3 Biology HS/ Homologous traits of organisms are due to sharing a common ancestor, and such traits often have similar embryological origins and development. This is different than analogous traits (similarities between organisms that were not present in the last common ancestor of the taxa being considered but rather evolved separately). An example of analogous traits would be the wings of bats and birds, which evolved separately but both of which evolved from the vertebrate forelimb. Therefore, they have similar early embryology. Comparative Embryology tortoise chick human Whether or not a trait is homologous depends on both the taxonomic and anatomical level at which the trait is examined. For example, the bird and bat wing are homologous as forearms in tetrapods. However, they are not homologous as wings because the organ served as a forearm (not a wing) in the last common ancestor of tetrapods. By definition, any homologous trait defines a clade. A clade is a taxonomic group of organisms classified together on the basis of homologous features traced to a common ancestor. 2011, TESCCC 10/05/11 page 2 of 2

4 Morphologies HS/Biology Morphology is broadly defined as the study of animal form. It is a field that helps us understand animal diversity and animal history. For centuries, scientists have been interested in how animals are put together and how the parts work together to make functioning organisms that can run, fly, swim, eat, and survive. Early scientific efforts focused on descriptive methods in which scientists dissected specimens and described the musculoskeletal and other body systems with words and detailed drawings. As new techniques were developed, scientists began to specialize along the lines of various subdisciplines, including functional morphology and ecological morphology. Morphologists moved beyond what had started as a purely descriptive science and began to ask and answer more complex questions. Functional morphology emphasizes the mechanics of a particular structure how it works. For example, a functional morphologist might examine the pattern of musculoskeletal activity involved in an activity such as running. Using techniques, such as high-speed video, X-ray video, force-platform measurements, and EMGs (electromyographs, or recordings of electrical activity in muscles), the scientist can determine a joint's range of motion, the duration and intensity of muscle activity, and the order in which the muscles activate to produce a pattern of movement. Functional morphologists are often interested in the performance limits of a particular system. They ask questions such as: How much force can the human jaw produce? How fast can a lizard sprint on an inclined surface? How much weight can a thigh bone stand before it breaks? Ecological morphology (also called "ecomorphology") considers the structure of an organism in the context of its habitat and ecological role. Ecological morphologists are more interested in how structures are actually used in nature than in the limits to which structures can be pushed in an artificial laboratory setting. Ecological morphologists distinguish between a structure's biological role and its function. Therefore, they usually spend some time familiarizing themselves with the habits and natural surroundings. Sheen, Judy P. "Morphology." Animal s Retrieved October 05, 2011 from Encyclopedia.com: , TESCCC 10/05/11 page 1 of 2

5 HS/Biology Darwin's finches are a classic example of species diversification by natural selection. Although we don t know the basis for their development, the differences in beak morphology are associated with a variety of ecological niches. Cactus-eating finch Warbler-like finch Insect-eating finch Ground finch Plant-eating finch Woodpecker-like finch Galapagos Islands The Galapagos Islands are 972 km west of Ecuador. Ecuador 2011, TESCCC 10/05/11 page 2 of 2

6 Molecular Data HS/Biology In general, the molecular study of evolution can be divided into three primary areas: 1. Determining the extent and causes of genetic variation in natural populations. 2. Researching molecular processes that influence evolutionary events. 3. Constructing phylogenies (or evolutionary trees) for various groups of organisms. Molecular evolution (sometimes called chemical evolution) is in part a process of evolution at the scale of DNA, RNA, and proteins. Evolution of DNA was hypothesized by Miller and Urey in (for more information: Protobionts are systems that are considered to have possibly been the precursors to prokaryotic cells. RNA can act as an enzyme to assemble new RNA molecules on an RNA template. Molecular data is genetic. Evolution is the result of genetic change over time and anatomical, physiological, and other traits often have a genetic basis, but the relation between the genes and the trait can be quite complex. Molecular data, however, has a pretty clear genetic basis that is easier to interpret. Molecular data research can be used with all organisms. Whereas, early research often focused on traits that were confined to a certain group of organisms (for example, human blood type), molecular data can be gathered from all living organisms. Molecular data can provide access to a huge amount of genetic variation. Through molecular research methods, an enormous amount of data can be accessed. Entire genomes can be sequenced, providing large pools of genetic information about the organisms. Molecular data allows the comparison of all organisms. Attempting to understand the evolutionary history of distantly related organisms is often difficult, as they have few characteristics in common. However, all organisms seem to have some molecular traits in common. These common traits, such as ribosomal RNA sequences and some fundamental proteins, make comparing distantly related organisms a lot easier. Molecular data can be quantified. Sequence data is precise, accurate, and quantifiable, which improves the ability to objectively study evolutionary relationships between organisms. 2011, TESCCC 10/05/11 page 1 of 2

7 HS/Biology Molecular data often provide information about the evolutionary process. Important clues about the process of evolution can be gathered from molecular data. A mutation, for example, can be traced back through time, revealing its origin. Steenbok Evolutionary Tree 2011, TESCCC 10/05/11 page 2 of 2

8 Embryological Data HS/Biology Evidence for evolution can also be seen by comparing the embryos of different animals. Embryo Stage Fetal Stage Newborn Stage In the picture above, the first row (left to right) shows the embryo for a tortoise, a chick, and a human. There is similarity between the three embryos. The embryo is the name of the structure from the early hours after fertilization until the point where the organs are fully formed. After the embryonic stage, comes the fetal stage. The fetuses of the three animals are shown in the second row. Notice that the fetuses now appear different from one another. In the bottom row, we see the newborn stage of the tortoise, the chick, and the human. At this point, we can observe how extremely different the newborns are from each other. Early embryos of tortoises, chicks, and humans all display fishlike structures, including arched blood vessels and gill slits. In fish, these gill slits develop into gills, while in animals, such as humans, the gill slits never become functional. The similarities of these embryos demonstrate that certain developmental processes remain constant during the evolution of animals. The similarities show that in the process of evolution, pre-existing structures were adapted to serve new functions. The similarities (or parallels) in embryonic structures are accounted for through evolution. 2011, TESCCC 10/05/11 page 1 of 1

9 Complexities of the Cell (endosymbiosis) HS/Biology The hypothesized process by which prokaryotes gave rise to the first eukaryotic cells is known as endosymbiosis and ranks among the most important of evolutionary milestones. Chloroplasts in plants and mitochondrion in other eukaryotes are believed to have evolved through a form of endosymbiosis. There are many variations of the theory, regarding what organism(s) engulfed what other organism(s), as well as how many times it occurred and when across geological time. There is compelling evidence that mitochondria and chloroplasts were once primitive bacterial cells. This evidence is described in the endosymbiotic theory. How did this theory get its name? Symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other, it's called endosymbiosis. The endosymbiotic theory describes how a large host cell and ingested bacteria could easily become dependent on one another for survival, resulting in a permanent relationship. Over millions of years of evolution, mitochondria and chloroplasts have become more specialized, and today they cannot live outside the cell. One theory holds that the mitochodrion evolved from small heterotrophic prokaryotes that were engulfed by a larger eukaryotic cell. The heterotrophic prokaryote used cellular respiration to intake oxygen and convert organic molecules to energy. The prokaryotic cells that were too small to be digested continued to live inside the host Eukaryotic, eventually becoming dependent on the host cell for organic molecules and inorganic compounds. Conversely, the host cell would have acquired, by the addition of the aerobic function, an increased output of ATP for cellular activities, leading an improved selective advantage. Under this theory, the prokaryotes that gave rise to all eukaryotes were probably from the domain Archaea, both because several key characteristics and DNA comparisons suggest that Archaeans are more closely related to the eukaryotes than are eubacteria. This is the so-called serial endosymbiosis theory (a sequence of endosymbiotic events) of a monophyletic origin of the mitochondrion from a eubacterial ancestor. That fact that mitochondria have their own DNA, RNA, and ribosomes supports the endosymbiosis theory. The existence of the amoeba, a eukaryotic organism that lacks mitochondria and therefore requires a symbiotic relationship with an aerobic bacterium, also supports this theory. 2011, TESCCC 10/05/11 page 1 of 2

10 HS/Biology Endosymbiotic Theory 2011, TESCCC 10/05/11 page 2 of 2

11 The Fossil Record HS/Biology Fossils are the preserved remnants or impressions left by organisms that lived in the past. The fossil record provides snapshots of the past that, when pieced together, illustrates a view of evolutionary change over the past four billion years. The picture may be unclear in places, and may have missing information, but fossil evidence clearly shows that life is old and has changed over time. Today, we may take fossils for granted, but we continue to learn from them. Each new fossil contains additional clues that increase our understanding of life s history and help us to answer questions about their evolutionary story. First, a working definition of the fossil record is needed. We will use an overarching definition: all fossils known to science. The fossil record is not complete, but more information is added daily. Sedimentary rocks form from layers of sand and silt that are carried by rivers to seas and swamps, where the minerals settle to the bottom along with the remains of organisms. As deposits pile up, they compress older sediments below them into layers called strata. The fossil record is the ordered array in which fossils appear within sedimentary rock strata. These rocks record the passing of geological time. Fossils can be used to construct phylogenies (evolutionary histories), only if we can determine their ages. The fossil record is a substantial, but incomplete, chronicle of evolutionary change. The majority of living things were not captured as fossils upon their death. Even if fossils were formed, later geological processes destroyed many of them. The likelihood of an organism becoming fossilized is poor, and even less likely is that more than a small portion of tissues will become fossilized. If death is the primary prerequisite for fossil formation, then the second prerequisite is the prevention of decay. Typically, an organism that has died will become the nutritional source for another organism. The transformation of an individual deceased organism into a fossil is rare. Only a fraction of existing fossils have been discovered. We find more fossils of certain types than others. This means the fossil record is biased in favor of species that existed for a long time, were abundant and widespread, and had hard shells or skeletons that fossilized readily. It is important to note the rarity of fossils in the context that for any particular organism that once existed, the probability that it is now a part of the fossil record is extremely small. This is because: 1) Fossil formation is a rare event. 2) Fossil survival is a rare event 3) An exceedingly tiny fraction of surviving fossils will ever be able to be found, even though the crust of the earth is filled with them. We can envision that, as the ancient Earth s crust cooled, a time was eventually reached when rain from a dense atmosphere containing all the water was not immediately evaporated. Once begun, hard rains fell and fell for countless millions of years, finally filling the ocean basins. With the first rainfall, the processes of erosion and dissolution began, wearing away the then barren Earth s crust and ultimately filling the ocean basins with not only water, but also the dissolved elements needed for life in its most primitive forms to appear in the primeval seas. 2011, TESCCC 10/05/11 page 1 of 2

12 HS/Biology The rain caused the seas, and the seas began wearing the land away, forming the sediments needed to cover and preserve the traces of living organisms known as fossils. The formation and transport of sediments might be compared to a never ending snow storm. Relentlessly, the sediments have been carried by the rainwater; down by force of gravity. Sometimes the sediment particles were light and sparse and other times more like a blizzard. The sediments were also a relentless force grinding away everything in their path. We now know that geological time is full of orogeny (Greek for "mountain generating") events that are the result of plate tectonics. These events have pushed up huge mountain ranges, on the land or in the seas, many of which have been mostly or completely worn away (example: the Appalachian Orogeny). Mountains that were miles high have been ground down to remnants of former greatness, testimony to the scale and power of the rain and the sediments. 2011, TESCCC 10/05/11 page 2 of 2