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Distinguish between biological and phylogenetic species and identify the limitations of each definition. Identify an example of an interspecific hybrid that does not produce fertile offspring.
Explain what is meant by a phylogenetic tree. Distinguish between monophyletic, polyphyletic, and paraphyletic taxa in phylogenetic trees. Explain what is meant by a clade and describe the basis of classifying organisms using cladistics. Identify the assumptions of cladistics including shared common ancestry, bifurcation branching , and parsimony.
Interpret cladograms to infer the evolutionary relatedness between groups of organisms. Understand the basis of DNA barcoding and molecular phylogenetics. Analyse data from molecular sequences to infer species evolutionary relatedness. Describe the applications of this molecular information. Explain how species can be classified according to their interactions with other species, e. Define: ecosystem. Using examples, explain that ecosystems are composed of varied habitats from the very small microhabitats to the much larger ecoregions.
Interpret data to classify and name an ecosystem. Use the process of stratified sampling to collect and anlyse primary biotic and abiotic field data to classify an ecosystem. Key Idea: The classification of biodiversity into groups, or taxa, is constantly being updated in light of new information. Various classification systems exist, each based on different methods and with different advantages and disadvantages. As with all science, taxonomic approaches are constantly changing as new information is discovered.
Early classification systems were based on physical appearance. The increasing use of molecular analysis as a taxonomic tool has since led to the reclassification of many taxa, including birds, reptiles, many plants, and primates. Recognising three domains of life, based on genetic analyses, is an early example of this. Increasing use of molecular tools has provided new insights into how we group organisms.
Whittaker The five kingdom system places all prokaryotes in one kingdom, with protists, fungi, plants, and animals being the other four. The data supported the hypothesis of three major evolutionary lineages and gave rise to a modified six kingdom classification. Domain Bacteria Lack a distinct nucleus and cell organelles. Includes well-known pathogens, many harmless and beneficial species, and the cyanobacteria photosynthetic bacteria containing the pigments chlorophyll a and phycocyanin.
Domain Archaea Methanococcus jannaschii was the first archaean genome to be sequenced. The sequencing identified many genes unique to Archaea and provided strong evidence for three evolutionary lineages. Although archaeans may resemble bacteria, they posses several metabolic pathways that are more similar to eukaryotes.
Other aspects of their structure and metabolism, such their membrane lipids and respiratory pathways, are unique. Although once regarded as organisms of extreme environments, such as volcanic springs, archaeans are now known to be widespread, including in the ocean and soil. Domain Eukarya Complex cell structure with organelles and nucleus.
The three domain classification recognises the diversity and different evolutionary paths of the unicellular eukaryotes formerly Protista , which have little in common with each other. The fungi, animals, and plants form the remaining lineages. Based on the Linnaean system after Linnaeaus. Organisms are grouped into taxonomic ranks levels on the basis of similarities in physical features morphology. The scheme is hierarchical. A group within a taxonomic rank is called a taxon pl.
Species are named using binomial nomenclature by genus and species italicised. One difficulty with traditional taxonomy is that ranks are not equivalent for different types of organisms. Historically, this resulted in many newly discovered organisms in the New World being misclassified into Old World taxa.
Phylogenetic classification ties names to clades, so it is often called cladistic. A clade is taxonomic group that consists of an ancestor and all its descendants they are monophyletic. The characteristics used for assigning organisms to a clade can be morphological or molecular DNA or proteins. Molecular data is useful because species that appear similar can be easily distinguished.
Phylogenetic classification schemes do not rely on taxonomic rank in the same way as traditional schemes. Using cladistics, many of the taxa with which we are familiar such as reptiles do not exist because they do not meet the classification criteria they are not monophyletic. However, some familiar taxa, e. The rodent clade below corresponds to the order Rodentia. The example below shows how as we move through the taxonomic ranks, the organisms we are grouping become more exclusive based on the characteristics of the group.
In this case, we are looking at the classification of the plains mouse Pseudomys australis. Kingdom: Animalia. Using the example of the three domains system, explain how the use of molecular data e. DNA sequencing has led to a more accurate representation of the diversity of life on Earth:. The best classification schemes attempt to reflect the true evolutionary history of a species its phylogeny. Traditional and phylogenetic schemes are like this. These groupings are do not necessarily reflect evolutionary history although they may do so.
Classification by mode of reproduction Note that there is great variation in the reproductive strategies of eukaryotes. Only a few examples are given. Classification by life history strategy Organisms can be grouped according to how they allocate their resources to growth and reproduction. Compare and contrast the basic features of traditional and phylogenetic classifications.
In your answer, identify some of the advantages and drawbacks of each system:. Defining groups of organisms and evaluating their ancestry using morphological features alone can be problematic because similarities in structure may not necessarily be the result of shared ancestry. This problem can be overcome by only considering the shared derived characteristics, i. Tracing the evolution of derived character states is the basis of cladistics and more accurately identifies the evolutionary history of a taxon.
The ancestry of birds below illustrates this. Although birds are commonly regarded as a single taxon in traditional classification schemes and in modern terms they are birds are simply the last in the lineage of theropod dinosaurs dinosaurs characterised by hollow bones and three-toed limbs. Recent analysis of the protein structure of fossil collagen from fossils puts birds and theropod dinosaurs firmly in the same taxon.
Why do you think classifications based on molecular evidence provide a more likely phylogeny than one based on appearance alone:. Key Idea: How we define species has implications for classification but also for conservation. There are two ways by which we can define species. The first is based on the ability to successfully interbreed a biological species and the second is based on shared evolutionary.
Both methods of defining species have their merits and their problems. However we define a species, being able to recognise the true diversity of organisms has implications for conservation because you cannot protect what you cannot recognise. Horses and donkeys are true species despite the fact that they can produce viable offspring.
A mule is the hybrid offspring of a male donkey and female horse, but mules are sterile infertile. Red wolves, grey wolves, Mexican wolves, and coyotes are all capable of interbreeding to produce fertile hybrids. The taxonomic status of the red wolf is debated as its original lineage was as a grey wold-coyote hybrid.
Red and Mexican wolves are very rare and now extinct in the wild. These animals are highly territorial, but they ignore members of the other jackal species and no interbreeding takes place.
A species is defined as the smallest group of organisms that all share a derived character state. The derived characters are identified by colours. Although the primitive character unites all 4 species, the branching of the tree is based on characters derived from the ancestral ones.
These may be morphological, especially for higher taxonomic ranks, or biochemical e. DNA differences. Under the phylogenetic species model, there are no subspecies.
Either a population is a phylogenetic species or it is not taxonomically distinguishable. Species B and C are related to species A as they share three of four characters with it. However they only share two characters with each other.
True sparrows all belong to the genus Passer. There are a large number of species distinguished by size, song, and plumage. Many populations are not good biological species because they hybridise freely to produce fertile offspring.
Many birds are like this and may be best described using the phylogenetic species model. Tree sparrows P. Remember that all sexually reproducing organisms are genetically variable, so scientists must determine what level of variation is acceptable within a species before a new species classification is made. If such boundaries were not set, every molecular variation observed would result in the classification of a new species.
Molecular studies have been important in identifying cryptic species, i. The African bush elephant and the African forest elephant were once considered subspecies, but recent genetic analysis has confirmed they are separate species, which diverged from each other million years ago. Analysis of morphological differences, including skull anatomy, supports this.
The finding has been important in making sure populations of both species are conserved. Suggest how genetic techniques could be used to determine the likely phylogeny of several related phylogenetic species:. Traditionally, phylogenetic trees have been constructed based on similarities in appearance morphology , but increasingly molecular comparisons are used, especially to distinguish closely related taxa.
Molecular phylogenetics can reveal differences not seen in morphological comparisons, and have resulted in the revision of some morphological phylogenies where organisms could not be separated on appearance. Phylogenetic trees are often constructed based on cladistic criteria below. Key Idea: Phylogenetic trees represent possible evolutionary relationships among organisms.
They can be constructed based on appearance or molecular data. Phylogenetics is the study of the evolutionary history of organisms or groups of organisms. These relationships are often shown as a diagram called a phylogenetic tree. A phylogenetic tree represents a likely hypothesis of the evolutionary relationships among biological taxa sing. A taxon may consist of an individual species or it may be a. Phylogenetic trees represent possible evolutionary histories, and there are many different ways they can be drawn right.
Depending on how the tree is constructed, some represent evolutionary time through the length of the branches lines. Phylogenetic trees based on cladistics cladograms do not represent evolutionary time. Cladistic analysis groups species according to their most recent common ancestor on the basis of shared derived characteristics. All other characters are ignored.
It excludes both paraphyletic and polyphyletic groups right. It is important to understand these terms when constructing cladograms and to also understand that the terms are relative to whereever you start in the phylogenetic tree i.
Taxon 3 is paraphyletic. The traditional grouping of reptiles is paraphyletic because it does not include birds. Taxon 2 is polyphyletic as it includes organisms with different ancestors. One problem with this approach is that a strictly cladistic classification could theoretically have an impractically large number of taxonomic levels and may be incompatible with a Linnaean system.
Taxon 1 is monophyletic as all the organisms are related to species B the common ancestor. All the descendants of the first reptiles form a monophyletic group. Why might phylogenetic trees based on molecular differences be preferred over phylogenies based on appearance? Increasingly, cladistic methods rely on molecular data e.
DNA sequences to determine phylogenies. Highly conserved DNA sequences are used because changes are likely to signal a significant evolutionary divergence. Cladograms may not always agree completely with phylogenies constructed using traditional methods but similarities in the trees indicate that the proposed relationships are likely to be correct. Key Idea: Cladograms are phylogenetic trees constructed on the basis of shared derived characteristics.
A cladogram is a phylogenetic tree constructed using a taxonomic tool called cladistics. Cladistics groups organisms on the basis of their shared derived characters features arising in an ancestor and shared by all its descendants and ignores features that are not the result of shared ancestry.
A clade, or branch on the tree, includes a common. When constructing cladograms, shared derived characters are used to separate the clades branches on the tree. Using ancestral characters those that arise in a species that is ancestral to more than one group would result in distantly related organisms being grouped together and would not help to determine the evolutionary relationships within a clade. Whether or not a character is derived depends on the taxonomic level being considered.
For example, a backbone is an ancestral character for mammals, but a derived character for vertebrates. Production of milk is a derived character shared by all mammals but no other taxa. The backbone in a mammal, e. However, the production of milk from mammary glands is a derived character, shared by all mammals but no other taxa. Several different cladograms can be constructed from the same data. To determine the most likely relationships, the rule of parsimony is used.
Parsimony assumes that the tree with the simplest explanation the least number of evolutionary events is most likely to show the correct evolutionary relationship. A table listing the features for comparison allows us to identify where we should make branches in the cladogram. An outgroup one which is known to have no or little relationship to the other organisms is used as a basis for comparison. The table right lists features shared by selected taxa.
The outgroup jawless fish shares just one feature vertebral column , so it gives a reference for comparison and the first branch of the cladogram. As the number of taxa in the table increases, the number of possible trees that could be drawn increases exponentially. A possible cladogram for the data in the table is shown on the right.
Its construction assumed that six evolutionary events took place labelled as blue bars on the cladogram. If other cladograms were constructed, but involved more evolutionary events, the one shown would be assumed to be correct because it is the most parsimonious.
Parsimony can lead to some confusion. Some evolutionary events have occurred multiple times. An example is the evolution of the four chambered heart, which occurred separately in both birds and mammals. The use of fossil evidence and DNA analysis can help to solve problems like this. Two possible phylogenetic trees constructed from the same character table are shown below. The numbers next to a blue bar represent an evolutionary event. Use the shapes below to construct a cladogram that shows their phylogenetic relationships hint: A is the outgroup.
Key Idea: A table of selected characteristics can be organised systematically as a matrix and used to construct a cladogram. Selected characters for cladogram assembly 1. Viviparity live bearing 2. Males with flask organ 3. Orbit without bony front wall 4. Tail length 5. Body depth 6. Body size 7. Length of dorsal fin base 8. Eye diameter 9 Males with anal crescent 10 Pectoral bone with process Length of dorsal sheath Body mostly darkish Flanks with large black bars.
Surfperches are viviparous live bearing and the females give birth to relatively well developed young. Some of the characters below, left relate to adaptations of the male for internal fertilisation. Others relate to deterring or detecting predators. In the matrix, characters are assigned a 0 or 1 depending on whether they represent the ancestral 0 or derived 1 state.
This coding is common in cladistics because it allows the data to be analysed by computer. This activity provides the taxa and character matrix for 11 genera of marine fishes in the family of surfperches. The outgroup given is a representative of a sister family of rudderfishes zebra-perch sea chub , which are not live-bearing.
Your task is to create the most parsimonious cladogram from the matrix of character states provided. To help you, we have organised the matrix with genera having the smallest blocks of derived character states 1 at the top following the outgroup representative.
Use a separate sheet of graph paper, working from left to right to assemble your cladogram. Identify the origin of derived character states with horizontal bars, as shown in the previous activity.
CLUE: You should end up with 15 steps. Two derived character states arise twice independently. Staple your cladogram to this page. In the cladogram you have constructed for the surfperches, two characters have evolved twice independently: a Identify these two characters:. It has many applications including in cladistics and in DNA barcoding.
The advent of rapid throughput DNA sequencing and the analysis of biological data using computers bioinformatics has given rise to a new field of science called molecular. Molecular phylogenetics uses computers to compare and align different DNA sequences to produce the maximum number of matches. The number of matches and unique DNA bases can be used to produce phylogenetic trees. New standards such as DNA barcoding that use particular sequences of DNA have produced a vast amount of data that can be used in molecular phylogenetics.
The sequence of DNA that is chosen for analysis depends on the type of organism e. This information can then be applied wherever species-specific knowledge is important.
Applications include evolutionary biology, conservation, detection of invasive species, dietary analysis to help describe food webs , and food safety. DNA barcoding and molecular phylogenetics work on the assumption each species DNA is different but that the more closely related species are, the more similar their DNA will be.
Conserved genes found throughout the range of organisms being studied are assumed to evolve gain mutations at a constant rate, thus differences between the genes reflect differences between species. The language of classification and evolutionary relationships can be confusing and many terms are used somewhat interchangeably.
To help you, refer to the definitions below:. Many different trees may be proposed for any one taxon. Taxa must be monophyletic. Phylogenetic classifications are essentially cladistic whereas traditional classifications may not be. Using molecular phylogenetics Differences in DNA can be used to build phylogenetic trees. The sequences are similar but have some differences. Additionally the sequences need to be correctly aligned before they can be useful.
If you study 6 and 7 carefully, you will see the sequences are very similar but fail to align perfectly. Do a rough analysis of the sequences above. Can you identify two groups that the sequences fall into? A computer program can to be used to align and then analyse the phylogeny of the DNA quickly. There are many online programs to do this.
One of the simplest to use is Phylogeny. In the large box, you need to copy in the DNA sequences above as per the screen shot right. You can find these sequences in the Weblinks below or type them in manually. Make sure the formatting is correct as in the screen shot. This may take a minute or so. Why is using a conserved gene such as cytochrome oxidase useful when producing DNA barcodes for species?
Key Idea: Every species interacts with others. The interactions usually, but not always, benefit at least one of the species. Species interact with other species. The nature and outcome of these interactions structures communities and leads to interdependence. Interactions range from those that are beneficial to all parties, to those where only one species. In a relationship involving exploitation, one party benefits at the expense of another.
Sometimes, neither party benefits from the interaction. Such interactions include amensalism below or competition, a relationship in which two parties which may be the same or different species directly or indirectly contest the same resource e. Examples: Tick bird on zebra removes parasites and alerts zebra to danger, while tick bird gains access to food. Flowering plants and their insect pollinators have a mutualistic relationship. Flowers are pollinated and the insect gains food below.
Examples: Remora are fish with special sucker organs to attach to other marine animals such as sharks or turtles. The remora saves energy by hitching a ride on the other animal, and the shark or turtle is unharmed.
One species incidentally harms the second species but does not obtain any benefit from the interaction. Examples: Algal blooms can lead to the death of fish and other aquatic organisms by depleting the water of oxygen or producing toxins. However, the algae do not benefit from the deaths of the fish. Examples: Lion preying on wildebeest or praying mantis below consuming insect prey.
The adaptations of predators and prey are the result of their close ecological relationship throughout their evolution: predators have adaptations to capture prey and prey have adaptations to avoid capture.
The parasite lives in or on the host, taking usually all its nutrition from it. The host is harmed but usually not killed. Some plants e. They photosynthesise but rob the host plant of nutrients and water.
The honeyeaters are a diverse family of small to medium-sized nectar-feeding birds common in Australia. Many Australian plant species, including proteas and myrtles, are pollinated by honeyeaters. Examples of interactions between different species are illustrated below. For each example, identify the type of interaction, and explain how each species in the relationship is affected. The squat anemone shrimp, also known as the sexy shrimp, lives among the tentacles of sea anemones, where it gains protection and scavenges scraps of food from the anemone.
Dingoes will kill and scavenge a range of species. In groups of two or more, they can attack and kill large animals, such as kangaroos, but will also scavenge carrion, such as this dingo with a fish on Fraser Island. The Australian paralysis tick, Ixodes holocyclus, lives attached to the skin of mammalian hosts, commonly bandicoots, koalas, possums, and kangaroos, where it sucks body fluids and causes irritation.
Large herbivores expose insects in the vegetation as they graze. The cattle egret, which is widespread in tropical and subtropical regions, follows the herbivores as they graze, feeding on the disturbed insects when the herbivore moves away. Key Idea: An ecosystem is a community of living organisms and the abiotic components of their environment, interacting as a system. Ecosystems include varied habitats.
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