28 Plasticity Diversity Dec 9

28 Plasticity Diversity Dec 9 - Reminders: Lab Practical -...

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Unformatted text preview: Reminders: Lab Practical - Tomorrow!!!! Lab 2 hrs for exam 4:00 - End of Lab Celebration 4:00 Special TA office hours Special Friday - 10-12 Lab Friday Saturday - 12-2 BLL Atrium Saturday Atrium Lab Notebooks Due AT THE FINAL!! Final Exam - In this room!!! Final Monday Dec 14 11:15 - 1:45 Monday Eat before you come to the exam!!! Sleep the night before the exam! You will remember more! Coloniality, Cont. Three analogies of traits of colonial taxa that make them special: CHIMERAS-makes clonal and colonial animals unlike any other animals. A single "individual" can be composed of multiple genotypes. Which is the "individual"--the body or the genotype? If it fragments - what is the individual? Those BIG questions in biology How does this happen? METHUSELAHS-- can be extremely long-lived (almost infinitely) CHIMERAS--can be of mixed genotypes CHAMELEONS--can change their morphology. These process occur on 2 different scales-(1) that of the component units and (2) at the colony level FUSION of non-identical genotypes. In many groups, siblings, other very close relatives can fuse and form a chimera. Colonial tunicates, sponges, corals Self-non-self recognition system Studied most in tunicates: Partial matching system. Match at a single histocompatibility locus, can fuse. (AC & AB can fuse, share A) Keough 1984 showed that bryozoans will also fuse with their close kin. Fusion of immunologically immature colonies Beyond a certain age, recognize immunological differences. But, at an early age cannot, so fuse. 1 SOMATIC MUTATIONS Mutations in somatic cells (non-gamete cells) transmitted among colony members AND Because colonial animals do not sequester the germ line, these mutations are passed to the gametes that form new offspring Weismann’s doctrine - 1883 Animals sequester germ lines early in development. Only mutations in the germ line are heritable. True for humans and many taxa. Germ tissue sequestered early in development Limits lifetime reproductive potential Mutations in other than the germ line are not transferred Colonial animals (and other taxa of invertebrates) Continually redifferentiate germ cells from somatic tissue. Somatic cell mutations not only persist in individual (chimera) but also become heritable. CHAMELEONPHENOTYPIC PLASTICITY Single GENOTYPE produced multiple PHENOTYPES Specialization of modules Changes in colony in response to environmental changes Construction of modules with new mophrs in response to environmental changes Buss, L. W. 1987. The evolution of individuality. Princeton University, Princeton, NJ. Specialization of modules Specialized zooids, polyps for reproduction, defense E.g., Hydroids Feeding Polyps Polyps for reproduction 2 Changes within the colony Changes Induction of sweeper tentacles in corals, sponge growth form, Induction in spicule density spicule Bryozoans with feeding zooids and others modified for defense Responses to BOTH Physical environment and Biotic environment E.g., Wave or water motion induced responses Sedimentation induced responses Predator induced defenses. Competition induced defenses and offenses Inducible responses also seen in solitary individuals Plastic responses seen in many traits e.g., chemistry, life history, reproduction, behavior Predation by snail, Cyphoma, induces Predation Cyphoma greater chemical responses in gorgonians (simple and complex terpenes, steroids). Some of these steroids). chemicals help the gorgonian fight chemicals fungal diseases (aspergillosis). Bryozoans existing zooids cannot change plasticity seen in new plasticity zooids produced zooids Membranipora membrancea Membranipora Bryozoan Doridella predatory slug = predatory specializes on Membranipora Membranipora Doridella steinbergae 3 no predator - no spines no no predator present spines Spines inhibit slug feeding But - slow water flow near lophopore, But slow lophopore so reduce feeding so So if no slugs, better off without spines Just the smell of the predator will induce spines in new will zooids zooids Sponge colony plasticity - waves and predators Sponge Coral sweeper tentacles Almost every species has something that is plastic ?more interesting now - what is not ?more what plastic and why plastic New zooids make large spines when smell this slug spines inhibit slug feeding other slugs do not induce spines - very specific other Membranipora also produces special zooids Membranipora also stolons - no feeding polypide stolons no polypide use these for spatial competition stolons stop growth of competitors stolons stop reduce competitors size influence reproduction 4 Diversity in Larval Forms Inducible responses also seen in solitary individuals e.g., Snails make different teeth when e.g., eating different foods eating Can be due to different factors physical environment predators competitors etc. In non sessile animals - also have plastic behavior Sand dollar and Urchins Sand High food - short arms, shorter ciliary bands for feeding short bands Low food - long arms, longer ciliary bands for feeding Low long bands Some larvae can change their shape according to the amount of food available. Snail larvae make thicker shells when exposed to predatory crab larvae Barnacle Cthamalus anisopoma Two morphs in the Gulf of California Conic and bent Dawn Vaughn Echinoderm larvae clone at a higher rate when exposed to eau d’ planktivorous rate planktivorous fish, but not fish that do not eat plankton Shape induced by smell of predatory snail Acanthina Snail cannot hold onto Snail bent barnacles to feed bent Bent ones have advantage Chemical cues from predators also induce thicker shells and shape changes that influence thicker predation in a wide range of molluscs molluscs 5 Friday Harbor, WA San Juan Island Pisaster ochraceous Cancer productus Nucella lamellosa Initial and final linear measurements of morphology Predator-specific phenotypes reflect a functional tradeoff SD 9 8 7 6 5 4 3 2 1 0 No. snails eaten/24 h seastar crab SL Behavioral assay – proportion in refuge SW AW thick and rotund thin and elongate Mann-W hitney, P < 0.05 Whitney, Daphnia - common freshwater Daphnia plankton Eaten by fish and predatory insects 6 Inducible Defenses When the SMELL of predators is in the water, Daphnia are born morphologically Daphnia are different different they have a large helmut they helmut Predators have a hard time eating them Presence of predator induces new morphology in prey With predators No No predators predators History and Evolution Of Metazoa Of Burgess Shale Animals have diversified and experienced extinctions for millions of years Questions of the origin of diversity of Life Diversity – numbers of different species (or other taxonomic level) Disparity – numbers of different anatomical/morphological plans Multicellular animals evolved in the Precambrian Neoproterozoic Ediacaran fauna. Soft-bodied Ediacaran-type organisms ranged into the Cambrian period. Soft-bodied fossils are infrequently preserved. Preservation improved with the origin of hard parts. The first animals with shells are called the small shelly fossils. The extinction event at the end of the Permian Period was the worst mass extinction in the history of life. 7 Small Shelly Fossils The small shelly fossils are found at the base of the Cambrian, but are also found in the late Neoproterozoic. Most disappeared by the end of the first stage of the Lower Cambrian. Precambrian animal fossils Precambrian Few mm in size. Many had phosphatic shells. Shells and skeletal remains of primitive molluscs, sponges, and animals of uncertain classification, such as Cloudina, that secreted a calcareous tube. Ediacaria Ediacaria - cannot place in modern phyla Late Precambrian and Early Cambrian shell-bearing fossils from Siberia. Cambrian - first first appearance of animals with animals hard skeletons Why mass explosion? Hypotheses: ?Empty world (ocean)? 1st stocking of oceans ?Organisms and environments ?Organisms qualitatively different? qualitatively Sudden appearance of most modern phyla about 550 mya phyla 550 ?Genomes could change easily? ?Environments full of mutagens? Create novel variation "Cambrian Explosion" What was early life like? How did animal life evolve? Why have some types of animals Why persisted, but others did not? persisted, Burgess Shale Fauna Important fossil formation Soft bodied animals Soft preserved so well internal anatomy, etc. Similar fossils found around world (N. America, China, Greenland, Australia, Poland, Spain, Siberia) China - Chengjian Fauna - earlier than China Chengjian Burgess Shale, animals buried in place 8 Burgess Shale Western Canada Discovered by C.D. Walcott - 1909 Traditional “Cone” of diversity All lineages lead to new diversity Burgess shale fauna support this alternative model - not all lineages model survive, only some Who were these animals? How do we know what they looked like & what they did? Fossils – part & counterpart ! rare presence of soft parts Functional morphology (known from current animals and basic principles of design part and counter part - provide exceptional detail of anatomy Sea Pen Cnidaria Anthozoa Thaumaptilon Choia Choia Ph Porifera Porifera 9 Marella splendens Arthropoda, but own class Canadia Ph Annelida Polychaeta Ph Annelida Canadapsis Perspcaris Waptia Leanchoilia Pikaia - Phylum Chordata Phylum Chordata Aysheaia Onychophora 10 10 Ottoia Ph Priapulida Ottoia Priapulida Hallucigenia - Ph Onychophora? Ph Onychophora Anamalocaris Opabenia - Unknown Phylum Opabenia Amwiksia Haplophrenitis - Mollusca? 11 11 What does the Burgess Shale tell us? Wiwaxia - premollusc? Wiwaxia More Body Plans (phyla) than at present But, most of today’s animals there = Greater Disparity Diversity Greater now = more species Help with Evolutionary Relations of modern taxa Tell us about Ecological roles of taxa Burgess Shale – type faunas also found - Middle Cambrian – North America - Lower Cambrian – North Greenland, Yunnan, People’s Republic of China - Australia, Poland, Spain & Siberia Changjiang Fauna - earlier than Burgess Shale - sediments may be wind blown – animals buried in place – rather than moved due to turbulent transport (slumping) as in Burgess Shale - no evidence of burrowers or bioturbators - shares Many taxa with Burgess Shale ! But some missing 12 12 Cambrian – many more body plans (Phyla) than exist now Why do some persist and some do not? ? Deterministic – “better adapted” “more efficient” ? Random – totally by chance ? Combination of random and deterministic factors? Why so many different types evolved then, and no new phyla now? ? Vacant ecological space ? ? More malleable genomes – fewer interactions and links among genes ? ? Complex developmental programs prohibit it now or complexity per se prevents change ? 13 13 ...
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