Bio 201 F07 True lect 13 post - Animal diversity what's the...

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Animal diversity - what’s the point? Understand the major biodiversity you see in the world – Adaptations Apply insights we have learned from evolutionary theory History of life on earth Roles of organisms in larger systems • Communities • Ecosystems Understand human effects on the environment
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Evolution of Eukarya: Origins of multicellularity Multicellularity evolved multiple times in the tree of life; but only once in animals.
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Advantages of multicellularity Larger size Specialization of cells for different function
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Major groups of organisms (e.g. phyla, classes, orders, families) differ in major traits For example, the number of segments How do these traits arise? – They must arrive from variation within species – But most novel (“weird”) traits probably cannot survive They would be maladaptive – However, at some times in the past, probably extremely rarely, some novel traits were advantageous, and gave rise to new taxa that persisted Reminder: Domain Kingdom Phylum Class Order Family Genus Species
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Variation in mammalian vertebral number Red boxes indicate variation within species. • This is an example of variation in segment number - a major trait separating animal forms (“higher” taxonomic groups such as Classes, Orders, Families) • This variation is tolerated in these species (presumably does not affect fitness). • In the past, this type of variation within species led to the differences in body plan between major groups we see today Sacral and caudal vertebrae are fused in humans
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How do novel traits arise? Do they arise suddenly ( one step) or gradually (many steps) – This depends in large part on the number of genes involved We can only study this in living organisms – Try to gain insights about how new body plans evolved in the past
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As we “march through the taxa”… Think about how new morphological forms might arise – Genetic variation – Natural selection -> adaptation – Novel environments / environmental change
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  • Fall '08
  • Haltiwanger
  • Cambrian Explosion, Burgess Shale, Burgess Shale Fauna, Ancestral Colonial choanoflagellate, Cambrian Explosion Burgess

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