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Diversity of Life in the Sea • It would be virtually impossible to consider the breadth of organisms in the sea without some sort of classification system Diversity of Life in the Sea • Fortunately, there is a unifying concept that helps make this bewildering diversity of life comprehensible: EVOLUTION! • Evolution describes the genetic changes in a population over time • Organisms are adapted to their environment; a good fit (but not perfect!) Natural Selection and Adaptation • Evolution is descent with modification • Evolution occurs because individual organisms have genetic differences in their ability to find food, mates, avoid being eaten, in their metabolism and in countless other attributes • The best adapted individuals – those most successful at meeting the challenges of the environment – produce more offspring (on average) than those not so well-adapted. Natural Selection • Natural selection is the process by which favorable, inherited traits become more numerous in successive generations of a population of reproducing organisms • Over time, natural selection leads to species that are well adapted (highly evolved) to their environments • Populations either adapt to environmental changes or become extinct The Principles of Natural Selection • Struggle for existence/Competition – More offspring are produced than can be supported by resources King Penguin Rookery © Momatiuk - Eastcott/Corbis The Principles of Natural Selection • Variation – Some individuals, due to heredity or mutation, possess characteristics which make them better adapted to their environment The Principles of Natural Selection • Inheritance of Traits – Best-suited organisms will survive to produce more individuals that share same adaptation 1Population with varied inherited traits 2 Elimination of individuals with certain traits 3 Reproduction of survivors Certain individuals with a distinct, inherited characteristic will be selected against, while others with a (different) distinct, inherited trait will survive Classifying Living Things • The adaptation of various populations to different environments has produced a fantastic variety of life forms • In order to properly study these organisms, it is necessary to classify them • Must first identify what a “species” is exactly What defines a species? • Biological species concept: – A species consists of a population whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot interbreed with other such groups – Species are based on their ability to interbreed; not on physical similarities! Biological Species Concept • All domesticated dogs are the same species because they can interbreed; a subspecies of the gray wolf, Canis lupus Taxonomy • Taxonomy is the practice and science of classification • Taxonomy uses taxonomic units, or taxon • A taxon is a taxonomic unit at any level; for example, Mammalia is a taxon at the Class level • Domain Kingdom Phylum Class Order Family Genus Species Domain Kingdom Phylum Subphylum Class Order Family Diversification Genus Species Scientific names • Organisms are typically identified by 2 names; the name of their genus and their species = scientific name • No two organisms can have the same scientific name and this name is the same everywhere in the world! • Written as Genus species Orcinus orca Taxonomy • Scientific names are descriptive • May describe unique characteristic, region where species is found, etc. • Ex. Humpback whale Megaptera novaeangliae = “long-winged New Englander” • Common names can be deceiving!!! – “dolphin” – “bear” Phylogenetics • Many hierarchies are being re-examined based on the results of molecular analysis (DNA, RNA) • Binomial taxonomy does not take into account evolutionary relationships • Enter phylogeny and systematics… • Reconstructs evolutionary relationships by grouping organisms by their relatedness Phylogeny and Systematics • Systematics is the reconstruction and study of evolutionary relationships • Phylogeny – an evolutionary tree; species grouped by how long they’ve shared a common ancestor • Evidence for determining these relationships must come from body structure*, reproduction, embryological and larval development, and molecular characteristics *homologous structures Homologous structures http://www.edwardtbabinski.us/mpm/mpm_whale_limb.html Phylogenetic Tree: The Tree of Life • Domain Archaea • Domain Bacteria • Domain Eukarya You Are Here No nucleus Have a nucleus