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Cladistics
Herpetology 2
| Question | Answer |
|---|---|
| Why is cladistics so popular right now? | Cladistics’ popularity is the result of it being an objective method that produces a phylogeny that is a testable hypothesis about evolutionary history. |
| What is cladistics? | It is a taxonomic method that was developed by Willi Hennig, that recognizes only monophyletic groups which are identified by the presence of shared, derived characters. |
| What kinds of problems does cladistics help us to solve? | It helps us to identify the evolutionary history of various groups of organisms, which allows development of testable predictions about their ecology, geographic distribution, anatomy, physiology, and other biological characteristics. |
| In what way does cladistics differ from older methods? | Cladistics uses only shared, derived characters to identify related taxa. This leads to the recognition of monophyletic taxa only, and avoids both paraphyletic and polyphyletic taxa. |
| What would a "hierarchy of nested groups" look like | This would produce smaller subgroups contained within larger groups |
| Name a shared derived characteristics by which the "dinosaur" group is included in the larger "vertebrate" group? | All vertebrates, including dinosaurs, have a vertebral column. |
| What is each group in an evolutionary tree called?__________; By what is it defined? | These groups are called clades, and they are defined by the presence of shared, derived characters. |
| If cladistics is not a perfect method, why is it used? | It’s biggest strengths are that it is objective and produces phylogenies that are testable hypotheses. If the hypothesized phylogeny is correct, then new data will continue to support the hypothesis and all researchers will produce the same taxonomy. |
| Why is relative geological age not a good indicator of evolutionary relationships? | Speciation does not occur at the same rate in all phylogenetic lineages. Thus, rapid speciation in one lineage would produce many taxonomic levels in the same amount of time that a relatively static lineage would produce few. |
| Which features might we use to determine the evolutionary relationships between living animals? | Any feature that can be objectively identified and is heritable can be a useful cladistics character. This could include anatomical, behavioral, physiological, ecological, geographic, and genetic traits. |
| How many shared derived characters are usually used, in real studies, to show evolutionary relationships? | There are usually many. This may be just a handful; such as when studying anatomical traits of fossils, to many thousands, such as when analyzing nucleotide sequences in DNA. |
| What is the graphic depiction of the evolutionary relationships called? | It is called a cladogram. |
| Which cladogram version is considered the "best" (out of several which could be made for a particular group of organisms)? | The cladogram that is most parsimonious (i.e., requires the fewest evolutionary changes) is considered most likely, and hence best |
| 15. What is a "primitive" feature? Why? What is a better term? What would a cladist call this feature? | Primitive features are those that evolve early in the history of an evolutionary lineage. It would better to call these “ancestral,” although cladists prefer the term “plesiomorphic.” |
| 16. What is an "advanced" feature? Why? What is a better term? What would a cladist call this feature? | Advanced features are those that evolve late in the history of an evolutionary lineage. It would better to call these “derived,” although cladists prefer the term “apomorphic.” |
| What are polyphyletic, monophyletic and paraphyletic groups? Give examples. What does each indicate? | Polyphyletic groups are comprised of multiple evolutionary lineages that do not have a common ancestor within the group. An example would be anapsids if both early amniotes and turtles were included. |
| Monophyletic examples | A monophyletic group is one that includes all descendents of a single common ancestor. An example the the group Amniota. |
| Paraphyletic example | A paraphyletic group includes some of the descendents of a single common ancestor, but not all. Dinosaurs are paraphyletic if birds are not considered to be dinosaurs |
| What is an outgroup? What does one do with an outgroup? | An outgroup is a taxon that is closely related to the group that is being studied, but not included in the group. Traits that are present in the outgroup as well as the group under study are assumed to be plesiomorphic. |
| Paraphyletic | Species in the same group that lack common ancestor |
| Which clades are paraphyletic | Amphibians, reptiles and dinosaurs are paraphyletic |
| Holophyletic | One group with a common ancestor in the group, encompassing all members coming from the common ancestor |
| Who founded cladistics | Willi Hennig |
| Traditional taxonomy only makes sense if | Traditional taxonomy only makes sense if looking at extant species |
| What are the advantages of cladistics | Objective It is a testable hypothesis Reflects real evolutionary relationships |
| How to ID a clade | Use characters (anything identifiable) that are shared or derived Ignore symplesiomorphies (shared and ancestral) |
| What are homoplasies? | Homoplasies are analogous traits which evolve independently in multiple species or lineages. |
| Synapomorphies define | Synapomorphies define clades |
| First basic tenant of phylogenetic systematics | Only shared similarities that are derived are useful in deducing phylogenetic relationships |
| Second basic tenant of phylogenetic systematics | Speciation produces two sister species |
| Third basic tenant of phylogenetic systematics | Speciation is recognizable only if the divergence of two populations is accompanied by the origin of a derived character |
| What is a character | A character can be anything from a gene sequence to morphology to ecology |
| Apomorphic | A derived or modified state relative to the ancestral condition |
| Autapomorphic | a derived state occurring in a single descendant/lineage |
| Synapomorphic | a shared derived state in two or more species |
| Plesiomorphies | the same state as the ancestral species |
| What are the major living clades of lissamphibia | Apoda (caecilians), Anura (frogs), Urodela (salamanders) |
| What are the major clades of living reptiles (amniotes without synapsids) | Lepidosaurs (sphenodontids and squamates) Archosaurs (crocodylians and birds) Turtles (most likely lepidosaurs, possibly archosaur) |
| Vertebrates lived in the | Vertebrates lived in the cambrian |
| Sarcopterygians lived in the | Sarcopterygians lived in the silurian |
| Tetrapods lived in the | Tetrapods lived in the late devonian |
| Amniotes lived in the | Amniotes lived in the carboniferous |
| Synapsides lived in the | Synapsides lived in the permian |
| Mammals, frogs, dinosaurs, sphenoids, and turtles lived in the | Mammals, frogs, dinosaurs, sphenoids, and turtles lived in the triassic |
| birds and squamates lived in the | birds and squamates lived in the jurassic |
| salamanders and snakes lived in the | salamanders and snakes lived in the cretacious |
| Crocodylians lived in the | Crocodylians lived in the cenozoic era |
| What is teleology | the process in heading towards some goal |
| What synapomorphie did most early amphibians have | labyrhinthodont teeth |
| Temnospondyls (1) | Abundant in carboniferous, permian, triassic, part of cretacious. Ancesters to lissamphibia. |
| Temnospondyls (2) what temnospondyls were present in the cretacious | Dendrerpetontidae; Dendrepeton and Balanerpeton, Eryops. All highly terrestrial |
| What was the dominiant amphibian of the permian | Eryops |
| Lepospondyls (1) | Microsaurs; Michrobrachus (aquatic) and Tuditanus (terrestrial) |
| Lepospondyls (2) | Nectrideans; Sauropleura (no horns) and Diplocaulus (horns) |
| Lepospondyls (3) | Aistopods; Aornerpeton (legless lepospondyls) |
| Anatomy of ichthyostega | Retained lateral line, NO otic notch for tympanum, pectoral girdle separated from head, limb attachments move side to side, foot not yet pentadactyl, longer snout and shorter head...not strong enough to be fully supported on land. |
| the way amphibians breath is called | buccal bumping; buccal cavity expands and air is drawn into cavity from outside and lung. Buccal cavity contacts and air is forced out of nostrils and into lungs. |
| What was the earliest fish to have a neck and ankles | tiktaalik, had pectoral girdle separate from skull. |
| Vomeronasal organ | Does not exist in fish, lissamphibians, modern snakes and lizards, pick up volatile and nonvolatile molecules, lost in non terrestrial species. |
| Amniotic eggs | amniotic eggs are NOT waterproof. Can be lain in water or terrestrial if amphibian. |
| Reptilian skin/amphibian skin | Both have keratin and "scales" (caecilians), neither control water loss, loss of glands in reptiles and inclusion of lipids. |
| Skin glands | amphibians have many glands (mucous/granular) and reptiles have few. Femoral pores in lizards and chin glands in turtles. |
| Skin layers | snakes have 7 skin layers, mesos layer has TONS of lipids |
| Reptiles in wet environments | reptiles in wet environments do not have much lipid content in their skin as they live in a well hydrated environment. |
| Testudines (1) | Old phylogeny that had anthracosaurs is a subgroup of ladyrhinthodonts |
| Testudines (2) | Seymouriamorphs and diadectomorphs were the earliest "reptiles", but now neither reptiles or amphibians |
| Testudines (3) | Seymouria=sister taxon to diadectomorphs |
| Testudines (4) | Diadectes: amphibian or reptile? Very early herbivorous tetrapod, late carboniferous, sister group of amiotes |
| Early anthracosaurs | Primarily aquatic, convergent on crocodiles |
| Anapsid | Earliest, had NO temporal fenestrae |
| Diapsid | two fenestrae |
| Synapsid | one fenestrae |
| Euryapsid | one hole high on skull. |
| What is the defining feature between amphibians and reptiles | the defining feature is the amniotic egg |
| What is the defining feature between amphibians and reptiles in the fossil record? | the defining feature is how the jaw attaches to the skull |
| What is an OTU | OTU= operational taxonomic unit |
| What is a clade? | a group of organisms believed to have evolved from a common ancestor |
| What is sister taxa | A sister group or sister taxon is a systematic term from cladistics denoting the closest relatives of a group in a phylogenetic tree. The expression is most easily illustrated by a cladogram: The sister group to A is B |
| What is a holotype | a single type specimen upon which the description and name of a new species is based. |
| What do fossil tetrapods tell us about the transition from water to land? | highly gradual, mostly resulting from some change which led to feeding in shallow waters |
| Why was the amniotic eggs such an important innovation in the evolution of tetrapods | Greater independence to land animals, no longer having to return to water to lay their eggs |
| Explain the difference between evolutionary taxonomy and linnean taxonomy | difference between evolutionary taxonomy and linnean taxonomy. in cladistics, they are grouped according to the relative closeness of their genetic structure. |
| What is an argument for the placement of turtles in the Eureptilia | turtles lack temporal fenestra and the Eureptilia consists of anapsids. |
| Isolethical ova | Small amount of yolk evenly distributed throughout the cell...mammal eggs. |
| Macrolethical | Ova of direct-developing amphibians, very large yolk |
| Growth | growth simply refers to an enlargement of an organism or its component. |
| Earliest synapsid | dimetrodon |
| Diapsids are still a clade? | true |
| Eurysapsids are their own clade | false, clade within diapsids |
| Synapsids include only reptiles | False, still a clade but only amniotes that are not "reptiles" |
| Anapsids are... | polyphyletic AND paraphyletic |
| ___% of all squamates have live young | 20% of all squamates have live young |
| Ichthyosaurs are... | euryapsids |
| Internal fertilization occurs in | All amphibians except for most frogs and a few salamanders |
| Amphibians have what kind of egg? | Amphibians have mesolethical eggs (less yolk in body) |
| Reptiles have what kind of egg? | Reptiles have macrolethical eggs (more yolk in yolk sac) |
| What is the main difference between males and females | females have the large gamete, males have the small gamete |
| Gastrula | embryo after all three skin layers have formed (endo, ecto, meso) |
| Amnion | A thin, tough, membranous sac that encloses the embryo or fetus |
| amphibian eggs have amnion, allantois, and chorion | false |
| Allantois | The allantois is a sac-like structure that grows out of the digestive tract of the embryo. It functions in gas exchange and collects metabolic wastes from the embryo |
| Chorion | The chorion aids in the exchange of gases between the environment and the embryo. |
| What covers amphibian eggs | Amphibian eggs are covered in mucoproteins and mucopolysaccharides |
| What is heterochrony | Heterochrony is a change in the rate and timing of development |
| What is paedomorphois | Slow rate of development (retaining juvenile characteristics until late in life) |
| Features of larvae | all have gills, lack eyelids, and lateral line systems |
| Reptile development | Rate of development and gender is sex determinant |
| How to amphibians hatch | Larvae have a glad on their head (hatching glands) |
| How do reptiles hatch | reptiles have an egg carunkle (keratin) or and egg tooth (bone) |
| What signals metamorphosis | metamorphosis is the result of a surge in thyroid hormones |
| What is growth dependent on | growth is dependent on temperature, food, competition and predation (not necessarily associated with age) |
| Why age? | Age is not an adaption, it is the result from the absence of selection. Senescence is as an effect of reduced selection, not an adaptive result of selection. |
| What type of keratin do amphibians have? | alpha keratin |
| ____% of amphibian glands are mucous glands | 90% of amphibian glands are mucous glands |
| What amphibians have claws | African clawed frogs, xenopus |
| What amphibians have scales | some caecilians have scales |
| How many layers does reptile skin have? | reptiles have 7 layers of skin |
| what type of keratin do reptiles have | alpha AND beta keratin |
| What make up chromatophores | chromatophores are made up of melanophores, irridophores, and xanthophores |
| What is most of the amphibian and reptile brain | the olfactory lobe makes up most of the amphibian and reptile brain |
Created by:
shammar