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Monday, July 20, 2015 Topic: Evolution and biodiversity Title: Classification of biodiversity Keywords: • species • ecological niche • binomial system • generic name • specific name • natural classification Learning Objectives: We are learning…. • What is a species? • How are species named? • What are the principles of classification? • How is classification related to evolution? Starter: Can you name this organism? Monkfish, sea devil, angler, belly-fish, headfish, sea monk, fishing frog and goosefish all refer to the same fish. Confusing, right? Linophryne arborifera Scientists use special systems in order to name organisms and avoid confusion. The name here is the scientific, binomial name of the organism. This name is used universally across the world when referring to this organism. What do we know about classification? Choose the correct keyword from the list below: genus taxonomy ecological niche binomial species artificial classification family phylogeny kingdom natural classification Hybrids – What were they thinking? Or the ‘how to name a really silly looking animal badly’ game Guess the hybrid… Zeedonk Zebra and Donkey In South Africa they are called zonkeys and are fairly common where zebras and donkeys are found in proximity to each other. Like mules, however, they cannot usually breed, due to an odd number of chromosomes disrupting meiosis. Guess the hybrid… Liger Lion and Tiger A Liger looks like a giant lion with diffused stripes. Some male ligers grow sparse manes. Like tigers, but unlike lions, ligers enjoy swimming. Guess the hybrid… Cama Camel and Llama Though born even smaller than a Llama calf, the Cama had the short ears and long tail of a camel, no hump and llama-like cloven hooves rather than the dromedary like pads. The Cama apparently inherited the poor temperament of both parents Guess the hybrid… Zorse Zebra and Horse The zorse is shaped more like a horse than a zebra, but has boldly striped legs and, often, stripes on the body or neck. Like most other interspecies hybrids, it is infertile. Guess the hybrid… Wholphin Whale and Dolphin A wolphin or wholphin is a rare hybrid, formed from a cross between a bottlenose dolphin Tursiops truncatus (mother), and a false killer whale Pseudorca crassidens (father). The wolphin's size, colour and shape are intermediate between the parent species. Named Kekaimalu, she has 66 teeth - intermediate between a bottlenose (88 teeth) and false killer whale (44 teeth). The wolphin proved fertile. Key Points • Animals of the same species have the same number of chromosomes (sections of genetic information) • Different species cannot usually interbreed- but sometimes do to produce a hybrid. • Often the hybrid offspring is infertile – due to the amount of chromosomes it has (odd number) The infertility of hybrids – the mule Horses have 32 pairs of chromosomes (64) while donkeys have only 31 pairs (62). When a male donkey and a female horse mate, they produce a mule (a male horse with a female donkey produces a different creature called a hinny). A mule has 31-paired chromosomes as well as an extra chromosome from its horse mother that is not paired. Many think that this extra non-paired chromosome is what makes the mule infertile. The suggested reason for this is that during meiosis, the extra chromosome would not have a partner to match up with. When the paired chromosomes are split apart into separate haploid gametes, the split would be uneven, creating sterility. In biology there are several definitions of what a species is. Ernst Mayr's definition of species is a common one (Ernst Mayr was one of the 20th century's leading evolutionary biologists). He says that a species is a group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. Ligers do not fit this definition for a number of reasons; • Firstly, Ligers are not natural populations; they are a man-made creation as lions and tigers rarely meet in the wild. • Secondly, ligers are not ‘interbreeding’, they are mostly sterile, although a few cases of a fertile liger have been documented, but the liger didn't have cubs with another liger, it had cubs with a lion, meaning that ligers do not interbreed with other ligers. • And finally they are not reproductively isolated. Ligers do not fit any of the three rules an animal needs to meet to be classified as a species. They are a man-made hybrid, and a weak hybrid at that - they have poor health and fertility problems. Classification Why do we classify organisms? Universal system Avoid confusion when naming organisms Ease of identification of new organisms Easier to study properties of new organisms Classification Phenetics and phylogenetics Phenetics is an artificial classification system based on physical characteristics and observable traits. Phylogenetics takes into account the evolutionary relationship between organisms. List the advantages and disadvantages of the phenetic and phylogenetic classification system. Naming Species • Binomial system: organisms identified by 2 names • Universal; based on Latin or Greek Carl Linnaeus (1707-1778) was a Swedish botanist who laid the foundations for the modern scheme of binomial nomenclature Generic name Denotes the genus the organism belongs to (like a surname) Specific name Denotes the species the organism belongs to (like a first name) Why use a binomial name? If we use common names it doesn’t tell us very much about a species And people can get confused easily The binomial name tells us the Genus and the Species of an organism Thus it allows us to not only see what an organism SPECIFICALLY is it also allows us to see what it is closely related to Rules to follow… • Names are printed in italics (underlined if handwritten) • First letter of generic name (genus) is in capitals • Specific name (species) is in lower case (small letters) • Specific name is written as ‘sp.’ if unknown e.g. Felix sp. • Naming of organisms changes as our knowledge of their evolution, physical features, biochemistry and behaviour increases. Classification domains All organisms are classified into one of three domains and six kingdoms – Domain 1 – Archea Kingdom Archaebacteria (ancient bacteria) Methanogens, halophiles, thermacidophiles Domain 2 - Eubacteria Kingdom Eubacteria (true bacteria) Bacteria and cyanobacteria Domain 3 - Eukarya Kingdom Plantae Kingdom Animalia Kingdom Fungi Kingdom protista red algae and dinoflagellates See page 261 Table 1 for more detail on each domain. Did you know? In 2013, previously unknown bacteria were found living in a deep lake nearly 500m below the ice in Antarctica. These organisms have characteristics unlike archeans and other bacteria. Discoveries like this mean that further changes will have to be made to our current system of classification in the future. You will notice that viruses are not included in the classification of living things. They are not considered to be living because they cannot reproduce independently (they require a host cell). Viruses are usually classified by their protein coat. Taxonomy and classifying eukaryoyes • Taxon – a group within a biological classification • Taxonomy – the study of these groups & their positions in the hierarchy. Domain often appears first, followed by…… • Kingdom The largest group Organisms have radically different body plan • Phylum Diversity within a phylum • Class Organisms have additional features in common • Order Differences are less obvious • Family Written with capital • Genus • Species Specific to each individual King prawn curry or fat greasy sausages? Can you think of another acronym to remember the order? Both domains here would be Eukarya Red Kangaroo: Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Diprotodontia Family: Macropodidae Genus: Macropus Species: M. rufus White Oak tree: Kingdom: Plantae Phylum: Magnoliophyta Class: Magnoliopsida Order: Fagales Family: Fagaceae Genus: Quercus Species: alba Principles of Classification • Taxonomy – the theory & practise of biological classification Artificial Classification: Natural Classification: Divides organisms into features useful at the time (e.g. wings) Is based on evolutionary relationships Classifies species into groups using shared features Arranges groups into hierarchy with no overlap Anatomy and homologous structures – artificial classification Initially, classification systems were based on the appearance of an organism. However, details of anatomy are more relevant than appearance. Example – The limb bone pattern of all the animals with four limbs is the same – Homologous characters We can also look at similarities in organs and their function between species. Natural classification Natural classification systems group together organisms with many of the same characteristics that are predictive, so that by studying the characteristics of an organism it is possible to predict the natural group it belongs to. Natural classification systems also consider homologous structures (like limbs) that indicate an evolutionary relationship. Artificial classification Grouping organisms together because of observable characteristics or behaviour in this way can be problematic (e.g. grouping birds, bats and insects together because they can fly). Hierarchical order Means ‘smaller groups within larger groups’ What is the animal? A dichotomous key is a tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish. Keys consist of a series of choices that lead the user to the correct name of a given item. "Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step. Activity: You are a group of scientists who have been sent to investigate a mysterious, uninhabited Island. On the Island you discover some new insects and make sketches of each one. How could you use a dichotomous key to identify each one? Success Criteria: What I’m looking for….. Using the level ladder… • develop a dichotomous key with yes/no answers to identify each new insect. • Give each new insect a name and explain why you have chosen this name Main: Complete the past paper questions Success Criteria: What I’m looking for….. Complete the past paper questions Plenary: 1. What is a species? 2. How many kingdoms are there? 3. What does; K,O,P,G,S & C stand for and what order should they be in? 4. What does a binomial name tell you? 5. What is meant by a “phylogenetic hierarchy”? 6. What order and family do humans belong to? 7. Which would have most in common : Members of the same order or the same family? Members of the same phylum or Genus? How successful were we this lesson? Learning Objective We were learning….. Keywords: •