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Bio1130 Final ultimate key word list

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Jon Houseman

Biology Key Words- Exam Organizing the Living World Adaptive radiation - Diversification of a species or single ancestral type into several forms that are each adaptively specialized to a specific environmental niche. To radiate means to spread outward, it refers to one or a few species which diversify ("spread out") and generate multiple daughter species. The most common situations which result in adaptive radiation occur following mass extinctions, or when species move into new, unoccupied regions. Darwin Finches When Charles Darwin was in the Galapagos Islands, one of the first things he noticed is the variety of finches that existed on each of the islands. All in all, there were many different species of finch which differed in beak shape and overall size. This is adaptive radiation and natural selection at work. These finches, better known as 'Darwin's Finches' illustrated adaptive radiation. This is where species all deriving from a common ancestor have over time successfully adapted to their environment via natural selection. Previously, the finches occupied the South American mainland, but somehow managed to occupy the Galapagos islands, over 600 miles away. They occupied an ecological niche with little competition. As the population began to flourish in these advantageous conditions, intraspecific competition became a factor, and resources on the islands were squeezed and could not sustain the population of the finches for long. - Due to the mechanisms of natural selection, and changes in the gene pool, the finches became more adapted to the environment, illustrated by the diagram below. As competition grew, the finches managed to find new ecological niches that would present less competition and allow them, and their genome to be continued. As indicated by the diagram above, the finches adapted to take advantage of the various food sources available on the island, which were being used by other species. Over the long term, the original finch species may have disappeared, but by diversifying, would stand a better chance of survival. All in all, the finches had adapted to their environment via natural selection, which in turn, has allowed the species to survive in the longer term, the prime directive of any species. Advanced characters – similarities between organisms that were not in the last common ancestor of the taxa being considered but rather evolved separately. (Similarity of function and superficial resemblance of structures that have different origins.) For example, the wings of a fly, a moth, and a bird are analogous because they developed independently as adaptations to a common function—flying. The presence of the analogous structure, in this case the wing, does not reflect evolutionary closeness among the organisms that possess it. Another important example would be the development of a camera-type eye in both mollusks and vertebrates. This example of analogous structures is especially useful because one of most common claims made by religious creationists is that something as complex as an eye couldn't possibly have evolved naturally - they insist that the only viable explanation is a supernatural designer (which is always their god, though they rarely admit this outright). The fact that eyes in different species are analogous structures proves not only that the eye could evolve naturally, but that it in fact evolved several times, independently, and in slightly different ways. The same is true of other analogous structures as well, and this is because certain functions (like being able to see) are just so useful that it's inevitable they will evolve eventually. No supernatural beings, whether gods or not, are necessary to explain or understand how eyes evolved multiple times. Apomorphy – A derived characteristic of a clade, or derived state is a characteristic believed to have evolved within the tree. For example, all tetrapods have four limbs; thus, having four limbs is an apomorphy for vertebrates but a plesiomorphy for tetrapods. Jaws for example, would be an apormophy described in the cladogram above. Autoapomorphy, In cladistics, an autapomorphy is a distinctive anatomical feature, known as a derived trait, that is unique to a given terminal group. That is, it is found only in one member of a clade, but not found in any others or outgroup taxa, not even those most closely related to the group (which may be a species, family or in general any clade). It can therefore be considered an apomorphy in relation to a single taxon Binomen, The combination of two names, the first being a generic name and the second a specific name, that together constitute the scientific name of a species. Example Canis lupus wolf Both names are typed in italics, but only the generic name is capitalised. Camera eye, Described in advanced characters Character convergence, process whereby two relatively evolved species interact so that one converges toward the other with respect to one or more traits. Character polarity, Character polarity is the issue of the evolutionary history of a character: given two character states, which we call a and a' , we need to know whether a evolved from a' ' or the other way round. Discerning character polarity is a fundamental task of phylogeny. Character reversal, The re-establishment of an ancestral character state through the loss of an evolutionary novelty (apomorphy). For example, winged insects (Pterygota) evolved from a wingless ancestor; however, some pterygote lineages have subsequently lost their wings, e.g., fleas, lice, some grasshoppers and beetles. Cladistics, Cladistics emerged in the 1950s and 1960s when some researchers criticized the inherent lack of clarity in classifications based on two distinct phenomena, branching evolution and morphological divergence. After all, how can we tell why two groups are classified in the same higher taxon? Sometimes they have shared a recent common ancestor (e.g., lizards and snakes), but other times they have not (e.g., lizards and crocodilians). To minimize such confusion, many systematists followed the philosophical and analytical lead of Willi Hennig, a German entomologist who wrote Phylogenetic Systematics, published in 1966. Hennig and his followers argued that classifications should be based solely on evolutionary relationships. Cladistics produces phylogenetic hypotheses and classifications that reflect only the branching pattern of evolution. Cladistics ignores morphological divergence. Cladists group together species that share derived characters. Cladists argue that mammals form a monophyletic lineage, a clade , because they have a unique set of derived characters, including hair, mammary glands, reduction of bones in the lower jaw, and a four- chambered heart. The ancestral characters found in mammals, such as an internal skeleton, a vertebral column, and four legs, do not distinguish them from other tetrapod vertebrates, so these traits are excluded from analysis. Phylogenetic trees produced by cladists (cladograms ) illustrate the hypothesized sequence of evolutionary branchings, with a hypothetical ancestor at each branching point (Figure 19.13b). Cladograms portray strictly monophyletic groups and are usually constructed using the principle of parsimony. Once a researcher identifies derived, homologous characters, constructing a cladogram is straightforward Cladogram, Clade, A cladogram is a tree-like diagram showing evolutionary relationships. Any two branch tips sharing the same immediate node are most closely related. All taxa that can be traced directly to one node (that is they are "upstream of a node") are said to be members of a monophyletic group.A cladogram is a diagram much like a family tree showing the phylogenic tree of different species and demonstrating where they evolved from common ancestors. Once taxonomists based cladograms on physical, easily-observed characteristics; today, they can use more reliable information like genetic and biochemical analysis to determine the relationships between different species.Each branch on a cladogram is referred to as a "clade" and can have two or more arms. Taxa sharing arms branching from the same clade are referred to as "sister groups" or "sister taxa." Synapomorphies are characteristics shared by the taxa branching from the same clade, but not shared by taxa on other branches – for instance, vertebrates share certain synapomorphies that are not shared by invertebrates.The two basic principles behind assembly of a cladogram are that the process from ancestor to descendant should be shown as simply as possible in the tree; and the taxonomic categories applied to the branches in a clade should be monophyletic, or cover an ancestor and all its descendants. Cladograms should not be seen as evolutionary fact, but only as a possible path for speciation. Classical taxonomy, The oldest form of taxonomy is what is now called classical taxonomy and it is concerned primarily with the description, naming, and classification of organisms based on their morphological characteristics. An adaptation of classical taxonomy is now taking into account molecular and biochemical (chemosystematics) data that is now available. Classification, A classification is an arrangement of organisms into hierarchical groups that reflect their relatedness. Most systematists want classifications to mirror phylogenetic history and, thus, the adaptive radiation (evolutionary history) of the group of organisms in question. Common ancestor, an ancestor that two or more descendants have in common. Biological evolution also includes the idea that all of life is connected and can be traced back to one common ancestor. Convergent evolution, Henning, Convergent evolution represents a phenomenon when two distinct species with differing ancestries evolve to display similar physical features. Environmental circumstances that require similar developmental or structural alterations for the purposes of adaptation can lead to convergent evolution even though the species differ in descent. These adaptation similarities that arise as a result of the same selective pressures can be misleading to scientists studying the natural evolution of a species. For example, the wings of all flying animals are very similar because the same laws of aerodynamics apply. These laws determine the specific criteria that govern the shape for a wing, the size of the wing, or the movements required for flight. All these characteristics are irrespective of the animal involved or the physical location. In various species of plants, which share the same pollinato Dendrogram, is a tree diagram frequently used to illustrate the arrangement of the clusters produced by hierarchical clustering. Dendrograms are often used in computational biology to illustrate the clustering of genes or samples. For a clustering example, suppose this data is to be clustered using Euclidean distance as the distance metric. Derived characters, Among a given group of organisms, the shared derived characters are generally the less common characters. The evolutionary interpretation is that these characters of organisms are more recently evolved. They are contrasted with primitive characters. Shared derived characters should have the same structure and function. Derived characters are present members of 1 group of the line but not in the common ancestor. Fro Example: comparing fish & mammals. fish have scales and mammals have hair. so having hair is a derived character for mammals because only the mammals have ancestors with hair. Dichotomy, A dichotomy is a split into two parts which are considered to be either contradictory or mutually exclusive. For example, the colors black and white represent a classic dichotomy: either something is black, or it is white, with no room for overlap or alternatives. Dichotomies are used in a number of ways and in an assortment of fields, from philosophy to biology, and learning to think about dichotomies can be important. It is also a good idea to learn to identify a false dichotomy; a dichotomy which is not, in other words, a true dichotomy Divergent evolution, Divergent evolution occurs when a group from a specific population develops into a new species. In order to adapt to various environmental conditions, the two groups develop into distinct species due to differences in the demands driven by the environmental circumstances. A good example of how divergent evolution occurs is in comparing how a human foot evolved to be very different from a monkey's foot, despite their common primate ancestry. It is speculated that a new species (humans) developed because there was no longer was a need for swinging from trees. Upright walking on the ground required alterations in the foot for better speed and balance. These differing traits soon became characteristics that evolved to permit movement on the ground. Although humans and monkeys are genetically similar, their natural habitat required different physical traits to evolve for survival. Evolutionary taxonomy, Evolutionary taxonomy can be considered a mixture of phenetics and cladistics. It classifies organisms partly according to their evolutionary branching pattern and partly according to the overall morphological similarity. Evolutionary taxonomy is basically the method used by the early evolutionary taxonomists and is also called classical taxonomy. Folk taxonomy, A folk taxonomy is a vernacular naming system, and can be contrasted with scientific taxonomy. Folk taxonomies are generated from social knowledge and are used in everyday speech. Anthropologists have observed that taxonomies are generally embedded in local cultural and social systems, and serve various social functions. Fungi, Fungi are heterotrophic eukaryotes that obtain carbon by breaking down organic molecules synthesized by other organisms. Although all fungi are heterotrophs, fungi can be divided into two broad groups based on how they obtain carbon. If a fungus obtains carbon from nonliving material, it is a saprotroph . Fungi that decompose dead plant and animal tissues, for example, are saprotrophs. If a fungus obtains carbon from living organisms, it is a symbiont . Symbiosis is the living together of two (or sometimes more) organisms for extended periods; symbiotic relationships range along a continuum from parasitism , in which one organism benefits at the expense of the other, to mutualism , in which both organisms benefit. Although we often think of fungi as decomposers, fully half of all identified fungi live as symbionts with another organism. Hierarchical, Arranged in a hierarchy, in which the items are represented as being "above," "below," or "at the same level as" one another. Abstractly, a hierarchy is simply an ordered set or an acyclic graph. Homologous, Having the same typical structure and position. In Biology homologous may refer to two anatomical structures or behavioral traits within different organisms which originated from a structure or trait of their common ancestral organism. The structures or traits in their current forms may not necessarily perform the same functions in each organism, nor perform the functions it did in the common ancestor. An example: the wing of a bat, the fin of a whale and the arm of a man are homologous structures. Homology, A homology is a character shared between species that was also present in their common ancestor. This can be contrasted with homoplasy, which is a convergent character shared between species but not present in their common ancestor. Homologies are divided into derived homologies and ancestral homologies: a derived homology is one that is unique to a particular group of species (and their ancestor) and an ancestral homology is one that is found in the ancestor of a group of species and some, but not necessarily all, of its descendants. The word homology has also been used in other senses. For example, before the theory of evolution was developed, homology referred to deep similarities of characters between species, as opposed to more superficial similarities called homoplasies. Homoplasy, A homoplasy is a character shared by a set of species but not present in their common ancestor. A good example is the evolution of the eye which has originated independently in many different species. When this happens it is sometimes called a convergence. Homoplasies can be compared with homologies, which are characters shared by a set of species and are present in their common ancestor. Figure: the wings of birds and bats are homoplasies. They are structurally different: the bird wing is supported by digit number 2, the bat wing by digits 2-5. KISS principle, KISS is an acronym for the design principle "Keep it simple, Stupid!". Other variations include "keep it short and simple" or "keep it simple and straightforward". The KISS principle states that simplicity should be a key goal in design, and that unnecessary complexity should be avoided. Linnaeus, The practice of naming and classifying organisms originated with the Swedish naturalist Carl von Linné (1707–1778), better known by his Latinized name, Carolus Linnaeus . A professor at the University of Uppsala, he developed the basic system of naming and classifying organisms still in use today. Linnaeus described and named thousands of species on the basis of their similarities and differences. Keeping track of so many species was no easy task, so he devised a taxonomic hierarchy for arranging organisms into ever more inclusive categories (Figure 19.8). A family is a group of genera that closely resemble one another. Similar families are grouped into orders , similar orders into classes, similar classes into phyla (singular, phylum ), and similar phyla into kingdoms . Finally, all life on Earth is classified into three domains (see Chapter 3). The organisms included within any category of the taxonomic hierarchy comprise a taxon (plural, taxa). Woodpeckers, for example, are a taxon (Picidae) at the family level, and pine trees are a taxon (Pinus) at the genus level. Mechanical taxonomy, Key Term Main Points Monophyletic -group organisms that includes single ancestral species and all descendants -taxon or group organisms -most common in creation of cladograms Natural taxonomy -uses evolutionary principles of similarities to classify things -used by Darwin to create his cladogram -also known as evolutionary taxonomy Node -place on phylogenetic tree where group organisms extend off -found between two branches -can have one or more organisms grouped together Out group -has all major characteristics -used as comparison point -found on separate branch than all other organisms Paraphyletic -group organisms that includes ancestral species -includes some but not all descendants -don’t want on phylogenetic tree Parsimony -also known as KISS principle -simplest way to organize organisms -in making phylogenetic tree, grouping that requires smallest number evolutionary changes Phenetic (numeric) taxonomy -uses numbers and measurements to show underlying genetics -no stability cause could use different numbers -usually used for plants Phylogenetic taxonomy -created by Hemming to get rid of bias -looks at changes in shared traits -use traits that are primitive and advanced -also known as cladistics Phylogenetic tree -branching diagram -depicts evolutionary relationships of groups of organisms -Hemming’s attempt to get away from all problems -also known as cladogram Phylogeny -evolutionary history of groups of organisms -connections between all groups organisms as understood by ancestor/descendant relationships -relationships can be monophyletic, polyphyletic or paraphyletic Plesiomorphy -an ancestral or primitive character -features shared more widely than in a group of interest -character state present in both out group and ancestors Polyphyletic -group organisms belong to different evolutionary lineages and don’t share recent common ancestor -2 organisms look similar so must be related but turns out they aren’t -convergent evolution plays a role Polytomy -section of a phylogeny in which evolutionary relationships can’t be fully resolved to dichotomies -in phylogenetic tree represented as node which has more than 2 immediate descending branches -means many temporal based branches Primitive characters -attributes of which all members of group possess -also known as plesiomorphies -when shared between groups called symplesiomorphies Sister group -also known as out group -has all major characteristics -used as comparison point Symplesiomorphy -shared primitive characters that are shared between groups -not evidence that groups are related -character inherited from ancestors older than last common ancestor Synapomorphy -derived characters shared between groups -derived character originated in groups last common ancestor -can be used as evidence that groups are related Systematics -a branch of biology -study of the diversity of life and its evolutionary relationships -rule used is evolutionary related Taxon -name designating a group of organisms included within category of Linnaean taxonomic hierarchy -usually a taxon is given a name and rank -a good taxon reflects evolutionary relationships Taxonomy -science of classification of organisms into ordered system that indicates natural relationships -when apply rules to collection in which organize things (eg. Linnaeus = morphology) -uses taxa (taxons) Triassic, Jurassic and Cretaceous Periods Key Term Main points Amniote animals -group of tetrapod vertebrates -have a terrestrially adapted egg -include mammals, reptiles and birds Anapsid -member of the group of amniote vertebrates -have no temporal arches and no spaces on sides of skull -includes turtles Angiosperm -seed producing plants -also are flowering plants which are the most diverse group of land plants -more highly evolved than algae, mosses, fungi and fern Anther -pollen-bearing part of stamen in flower -terminal part of stamen -place where the pollen grains are produced Bird hipped dinosaurs -type of dinosaur classified by pelvis bone -have hip structure similar to that of birds -did not lead to birds Carpel -reproductive organ of flower -houses an ovule and its associated structures -leaflike seed-bearing structure Cartilagenous fish -skeleton made of cartilage rather than bone -includes sharks and rays -vertebrates -also known as Chondrichthyes Cephalopods -category of molluscs -includes octopus and squids -live in marine environment -have two well-developed eyes for hunting Co-evolution -can occur at multiple levels of biology -change of biological object triggered by change of related object -each thing involved exerts selective pressure on the other Cretaceous -period with relatively warm climate -ended with one of the largest mass extinctions -was after the Jurassic period -there were new groups of mammals, birds and flowering plants that appeared Diapsids -member of a group within amniote vertebrates -has skull with two temporal arches -includes lizards, snakes, crocodiles and birds Double fertilization -characteristic feature of sexual reproduction in flowering plants -process involves joining of one female gametophyte(embryo sac) with two male gametes(sperm) -complex fertilization mechanism that has evolved in flowering plants, angiosperms th End Triassic extinction -4 ranked in severity of the 5 mass extinctions -allowed dinosaurs to become dominant land animals -affected a lot of marine and land life Endosperm • Tissues derived from that 3n cell. They nourish the embryo and, in monocots, the seedling, until its leaves form and photosynthesis has begun. Embryo-nourishing endosperm forms only in flowering plants, and its evolution coincided with a reduction in the size of the female gametophyte. • Endosperm offers an advantage over female gametophyte tissue as a nutrient source for embryos because its development is tied to that of the embryo: if no embryo forms, the plant does not commit resources to endosperm. • And if an angiosperm embryo is aborted, which can happen if environmental conditions become unfavourable for embryo development (e.g., in the case of drought), endosperm development also ceases, saving the plant energy and resources. • Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. Extinct • A species is said to be extinct when there are no living representatives known on Earth. • Mass extinctions occurred at the end of the Ordovician and the beginning of the Devonian, at the end of the Devonian, at the end of the Permian, at the end of the Triassic, and at the end of the Cretaceous. • The Permian extinction was the most severe, and more than 85% of the species alive at that time disappeared forever, including the trilobites, many amphibians, and the trees of the coal swamp forests. • CausesAsteroid impact, Marine anoxia, Sea level changes, Elevated Carbon dioxide( Flood Basalts, Volcanoes, Gas hydrates) Extant • refers to taxa, such as species, genera, and families that is quite ancient but still in existence Fruit • Fruits have two functions: they protect seeds, and they aid seed dispersal in specific environments. • Fruits begin to develop after ovules are fertilized. The fruit wall, called the pericarp, develops from the ovary wall and can have several layers. Hormones in pollen grains provide the initial stimulus that turns on the genetic machinery leading to fruit development; additional signals come from hormones produced by the developing seeds. • A major defining feature is the nature of the pericarp, which may be fleshy (peaches) or dry (hazelnut). A fruit also is classified according to the number of ovaries or flowers from which it develops. Simple fruits, such as peaches and tomatoes develop from a single ovary, and in many of them, at least one layer of the pericarp is fleshy and juicy. Jurassic • formed in the second period of the Mesozoic era, between the Triassic and Cretaceous periods, lasting for 55 million years during which dinosaurs and ammonites flourished • The supercontinent begins to rotate, but the different components of the huge mass rotated at different rates and then in different directions, forming rift valleys. This was North America drifting westward, opening the Gulf of Mexico, and forming the central Atlantic. Jurassic period (206 - 144 Ma) 200 Ma - Pangaea starts to break apart 150 Ma - Birds K/T (K/P) boundary, • Geologists' shorthand for the boundary between the rocks of the Cretaceous and the Tertiary periods 65 million years ago. It coincides with the end of the extinction of the dinosaurs and in many places is marked by a layer of clay or rock enriched in the element iridium. Extinction of the dinosaurs at the K-T boundary and deposition of the iridium layer are thought to be the result of either impact of an asteroid or comet that crashed into the Yucatán Peninsula, perhaps combined with a period of intense volcanism on the continent of India. Keratin • Ectoderm cells synthesize mainly keratin, a different protein. • Keratin is a component of surface structures such as skin, hair, feathers, scales, and horns. • In response to induction by the optic vesicle, genes of ectoderm cells coding for crystalline are activated, but genes coding for keratin are not. • Some epithelial cells, particularly in the epidermis of vertebrates, contain a network of fibres of keratin, a family of tough proteins. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble and form strong unmineralized tissues • Keratin forms the scales of fish and reptiles (including the shells of turtles), the feathers of birds, and the hair, claws, hooves, horns, and fingernails of mammals. • First, waterproof skin: keratin and lipids in the cells make skin relatively impermeable to water. Megasporangium, • Produces megaspores • Are the comparable "female" structures on these plants, associated with the flower carpel and the megasporangial cone. • megasporangium is surrounded by extra layers of sporophyte tissue, which would add additional protection for gametes and embryos, • Surrounded by layers of sporophyte tissue called the integument. The integument and structures within (megasporangium, megaspore) are the ovule. Megaspore • One of the two types of haploid spores produced by a heterosporous plant • A plant spore that develops into a female gametophyte; usually larger than a microspore. • Inside the cell mass, a diploid megasporocyte (also called a megaspore mother cell) divides by meiosis, forming four haploid megaspores. In most plants, three of these megaspores disintegrate. The remaining megaspore enlarges and develops into the female gametophyte Mesozoic • The Mesozoic Era is a period from about 250 million years ago to about 67 million years ago. • Era featured the dramatic rifting of the supercontinent Pangaea. Pangaea gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. This created the passive continental margin that characterizes most of the Atlantic coastline. • The Mesozoic was a time of tectonic, climatic and evolutionary activity. The continents gradually shifted from a state of connectedness into their present configuration; the drifting provided for speciation and other important evolutionary developments. • The climate was exceptionally warm throughout the period, also playing an important role in the evolution and diversification of new animal species. Changing earth highlights Triassic period (248 - 206 Ma) 220 Ma - Mammals, dinosaurs, crocodiles 215 Ma - Flying reptiles 206 Ma - Late Triassic extinction Jurassic period (206 - 144 Ma) 200 Ma - Pangaea starts to break apart 150 Ma - Birds Cretaceous period (144 - 65 Ma) 130 Ma - Flowering plants 65 Ma - Tropical climate extends to Polar Regions, end Cretaceous extinction Microsporangium • Microsporangia are the structures on the stamens of flowers called anthers, and the pollen-producing structures on the microsporophyll’s of male conifer cones or cycad cones. • Microspores of gymnosperms (and other seed plants) are not dispersed. Instead, they are retained inside microsporangia and are enveloped in additional layers of sporophyte tissue. • As in other heterosporous plants, each microspore produces a male gametophyte, which develops inside the microspore wall. Microspore • A plant spore from which a male gametophyte develops; usually smaller than a megaspore. • In seed plants the microspore gives rise to the pollen grains, and the megaspores are formed within the developing seed • The spores that give rise to male gametophytes are produced in anthers. The pollen sacs inside each anther hold diploid microsporocytes (microspore mother cells); each microsporocyte produces four small haploid microspores by meiosis. Inside the spore wall, each microspore divides again, this time by mitosis. The result is an immature, haploid male gametophyte—a pollen grain. Mollusc, • The mollusc is a soft-bodied, usually shelled INVERTEBRATE belonging to one of the largest animal phyla (Mollusca) with some 100 000 living and about 35 000 FOSSIL species. • Molluscs are found on land and in salt and fresh water, and include SNAILS, ABALONE, CLAMS, MUSSELS, octopuses and squid. • The group is characterized by a muscular foot on which the animals creep; a calcareous shell secreted by the underlying fleshy mantle; and a feeding structure, the radula, consisting of a membrane, bearing sharp cusps, thrusting out from the mouth (found in all major groups except Bivalvia). Nectar, • A sweet liquid secreted by flowers of various plants, consumed by pollinators, such as hummingbirds and insects, and gathered by bees for making honey. • Produced either by the flowers, in which it attracts pollinating animals, or by extrafloral nectarines, which provide a nutrient source to animal mutualists providing anti-herbivore protection. • It is produced in glands called nectarines. Common nectar-consuming pollinators include bees, butterflies and moths, hummingbirds and bats. Ornithischia • The largely herbivorous ornithischian dinosaurs had large, chunky bodies. This lineage included armoured or plated dinosaurs (Ankylosaurus and Stegosaurus), duck- billed dinosaurs (Hadrosaurus), horned dinosaurs (Styracosaurus), and some with remarkably thick skulls (Pachycephalosaurus). • The ornithischian pubis bone points downward and toward the tail (backwards), parallel with the ischium, with a forward-pointing process to support the abdomen. This makes a four-pronged pelvic structure. In contrast to this, the saurischian pubis points downward and toward the head (forwards), as in ancestral lizard types • They were more numerous than the saurischians. They were prey animals for the theropods and were smaller than the sauropods. Oviparous • Amniotes that reproduces by laying an enclosed egg on land • The animals lay eggs, whereas viviparous and ovoviviparous animals bear live young. The eggs of oviparous animals contain all of the nutrients necessary for development of the embryo outside the mother's body. • This is the reproductive method of most fish, amphibians, reptiles, all birds, the monotremes, and most insects and arachnids. Birds and most invertebrates including snails are oviparous Ovule • The lower part of a carpel is the ovary, where inside it contains one or more ovules, in which an egg develops and fertilization takes place. • A seed is a mature ovule. In many flowers that have more than one carpel, the carpels fuse into a single, common ovary containing multiple ovules. • Meanwhile, in the ovary of a flower, one or more dome-shaped masses form on the inner wall. Each mass becomes an ovule, which will develop into a seed after fertilization, if all goes well. • Only one ovule forms in the carpel of some flowers, such as the cherry. A numerous amount form in the carpels of other flowers. At one end, the ovule has a small opening, called the micropyle. Pangea, • About 250 million years ago, Earth's landmasses coalesced into a single supercontinent that existed during the Paleozoic and Mesozoic eras. • Later continental drift separated Pangea into a northern continent, Laurasia, and a southern continent, Gondwana. Laurasia and Gondwana subsequently broke into the continents we know today • The rifting that took place between North America and Africa produced multiple failed rifts. One rift resulted in a new ocean, the North Atlantic Ocean. The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The South Atlantic did not open until the Cretaceous. Laurasia started to rotate clockwise and moved northward with North America to the north, and Eurasia to the south. The clockwise motion of Laurasia also led to the closing of the Tethys Ocean. Meanwhile, on the other side of Africa, new rifts were also forming along the adjacent margins of east Africa, Antarctica and Madagascar that would lead to the formation of the south-western Indian Ocean that would also open up in the Cretaceous. The second major phase in the break-up of Pangaea began in the Early Cretaceous (150–140 Ma), when the minor supercontinent of Gondwana separated into multiple continents (Africa, South America, India, Antarctica, and Australia). Placoid scale, • Tough scales that cover the skin of elasmobranchs (sharks and rays). • Like our teeth, placoid scales have an inner core of pulp (made up of connective tissues, blood vessels, and nerves), which is covered by a layer of dentine (hard calcareous material). This dentine is covered by enamel-like vitrodentine. • Even though placoid scales are similar to the scales of bony fish, they are really modified teeth and are covered with hard enamel. • Placoid scales are packed tightly together and grow with their tips facing backwards. This gives the fish's skin a rough feel. The function of these scales is for protection against predators, although in some sharks, they may also have a hydrodynamic function. • Scales in bony fish grow as the fish gets larger, but placoid scales stop growing after they reach a certain size, and then more scales are added as the fish grows. Plesiosaurs • Group of marine reptiles that were Mesozoic diapsid reptiles that lived in the ocean, but breathed air. • Plesiosaurs appeared at the start of the Jurassic Period and thrived until the K-T extinction, at the end of the Cretaceous Period. The animal was less fish-like in form than the ichthyosaurs, but was still adapted for life in the oceans. • Cruised slowly below the surface of the water, using their long flexible neck to move their head into position to snap up unwary fish or cephalopods. • Their four-flippered swimming adaptation may have given them exceptional manoeuvrability, so that they could swiftly rotate their bodies as an aid to catching prey. There were two kinds of plesiosaurs: • Plesiosaurids, which had long snake-like necks with tiny heads and a large physical frame. • Pliosauroids, which had large heads with strong jaws. They had short necks and consumed larger sea creatures. Pollen, • The male gametophyte of a seed plant. • Pollen grains have a hard coat that protects the sperm cells during the process of their movement between the stamens to the pistil of flowering plants or from the male cone to the female cone of coniferous plants. • When pollen lands on a compatible pistil of flowering plants, it germinates and produces a pollen tube that transfers the sperm to the ovule of a receptive ovary. Pollen tube, • This male gametophyte consists of three cells—two sperm cells plus a third cell that will form a pollen tube. When pollen lands on a stigma, this tube grows through the tissues of a carpel and carries the sperm cells to the ovary. • A mature male gametophyte consists of the pollen tube and sperm cells—the male gametes. • The walls of pollen grains are tough enough to protect the male gametophyte during the somewhat precarious journey from anther to stigma. • These walls are so distinctive that the family to which a plant belongs usually can be identified from pollen alone—based on the size and wall sculpturing of the grains, as well as the number of pores in the wall. • Because they withstand decay, pollen grains fossilize well and can provide revealing clues about the evolution of seed plants, as well as help biologists reconstruct ancient plant communities and determine how climates have changed over time. Pollination, • The transfer of pollen to a flower's reproductive parts by air currents or on the bodies of animal pollinators. • The process by which plants produce seeds—which have the potential to give rise to new individuals—begins with pollination, when pollen grains make contact with the stigma of a flower. • Pollination and fertilization can take place only if the pollen and stigma are compatible. For example, if pollen from one species lands on a stigma from another, chemical incompatibilities usually prevent pollen tubes from developing. Pterosaurs, • Pterosaurs , now extinct, were flying predators of the Jurassic and Cretaceous and included the largest vertebrate
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