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Lecture 12

BIOLOGY 1M03 Lecture 12: 12-Phylogenies and Trees of life

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Ben Evans

Bio 1M03 February 2, 2016 Phylogenies and Trees of life Biological innovation Can Trigger Adaptive Radiations - Zero time is splitting point - Opening up opportunities in environments - Explore niches - Allow species to exploit Cichlid Fish Underwent Multiple Adaptive Radiations - Cichlids are a family teleost fishes that include approximately 3000 species about 10% of extant teleost diversity - Great Lakes of Tanganyika Malawi and Victoria have around 250-800 species in each lake - Adaptations for feeding - Variations in social behavior - Size - Morphology - Cichlid dishes have a functionally decoupled set of jaws- oral and pharyngeal - Frees up jaws to independently specialize in food collection and processing - Exploit new niches - The fish have a huge number of species per lake - Collection and processing of food makes it easier due to the two jaws - Example of a morphological adaption that allows to exploit opportunities Biological Innovation as a Trigger - The evolution of many other key innovations allow ancestors to rapidly diversify - Live in new areas exploit new food sources and move in new ways - Examples include multicellularity, shells, exoskeletons, limbs - Insects - Flowers - Throat jaws - Feathers Ecological Opportunity as a Trigger - One trigger of adaptive radiations is ecological opportunity meaning the availability of new types of resources - Some species vary in characteristics - Larger locations have more species and diversity Anolis Lizards - These ecotypes evolved independently and repeatedly on the large islands of the Caribbean - The same adaptive radiation of Anolis has occurred on different islands, starting from different types of colonists - Derived from ancestors that colonized the islands of the Caribbean and were faced with a new environment in terms of niches - The lizards managed to diversify on multiple islands - They evolved independently on each island - Each ecotype is independent from the island - Body is related to ecological role - Vary in leg length, tail length and the regions in which they inhabit most - These ecotypes independently and repeatedly on each island - Ancestor may have been different on each island - The descendant lineages all diversified and matched the ecotype defined by where they spend most their time - Natural selection favored the diversification of different ecotypes - Alternative explanation is that they evolved once and dispersed but then the relationships would’ve been different - All the big lizards would’ve been related but that’s not the case Fanged Frogs - Comparison to Philippines - Multiple sympatric ecotypes that re-evolved in different places - Variation in modes of reproduction - Variation in body size - Sexually dimorphic characteristic - Expectations based on island biogeography, in general islands that are larger, there are more species - Platymantis lays eggs on land (adaptation that allows them to not need water) - 3 types of frogs, based on size (large, medium, small) - The difference between expectations (adaptive vs. dispersal) - Different ecotypes are sympatric in diff parts of Sulawesi - Variation in modes of reproduction and body size - Multiple sympatric ecotypes that re-evolved in different places. Extinction - Mass extinctions are periods with extreme levels of biodiversity loss - The background rate of extinction refers to the level of extinction during periods when mass extinctions are not occurring - The big five - Background extinctions typically occur when normal environmental change, emerging diseases or competition reduced certain populations to zero - Mass extinction result from extraordinary, sudden and temporary changes in the environment, they cause extinction randomly with respect to individuals fitness under normal circumstances - Speciation exceeds extinction, then there is a narrowing due to mass extinction events - Large traintion is after each exticntion - Abrupt changes in communities What Killed the Dinosaurs? - The impact hypothesis proposes that a meteorite struck Earth 65 mya and caused the extinction of an estimated 60-80% of the multicellular species alive, including dinosaurs - Evidence: iridium, shocked quartz, and microtektites found in rock layers and a huge crater off Mexico’s Yucatan peninsula all dated to approximately 65 mya Differential Survival - Some evolutionary lineages were better able than others to withstand the environment change brought on by the meteorite impact - For example, among vertebrae’s, the dinosaurs, pterosaurs (flying reptiles) and large marine reptiles perished, while the mammals, crocodilians, amp
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