Geol30_08_Lecture_14b

Geol30_08_Lecture_14b - 2/21/2008 Geology 30 History of...

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Unformatted text preview: 2/21/2008 Geology 30 History of Life -- Lecture #14 -Paleozoic Marine Life 02/21/08 -- Outline Today's lecture -From last time: Explaining the Cambrian Explosion Evolutionary steps leading to complex multicellularity Major animals groups, their characteristics, & fossil record 1 2/21/2008 Contingency (Lect. 13) An event that may occur; a possibility Current events are contingent (~dependent) upon past events Changes in the past have lasting repercussions in the future Mass extinctions give opportunities for new groups to become dominant But perhaps even more important... The Cambrian may have been an particularly important time for a specific body plan to survive and/or become dominant Morphological disparity vs. diversity Disparity = degree of `differentness' differentness Note: distinct from Diversity ~ species richness High morphological disparity = things look really different from each other e.g., eg vs. Low diversity High disparity High diversity Low disparity morphology morphology 2 2/21/2008 Adaptive radiation (Lect. 13) Within a few tens of millions of years, animals diversify at the phylum, class, and order l h l l d d level l A large-scale adaptive radiation largeadaptive Most phyla had few only species This phenomenon is unique (but adaptive radiations are not) What b t th Wh t about these new phyla? h l ? Kingdom Phylum Class Order Family Genus Species S.J. Gould's implications The important role of contingency: contingency: Most Cambrian `phyla' phyla went extinct ! A good adaptive body plan is important, BUT... Probably somewhat random...who got "axed" & who didn't Crown groups morphology If you `replayed the tape' you'd get `replayed tape' you d get... A different world; e.g. if *Yunnanozoan got axed, would there be vertebrates? ? Would there be us?! * Or another early chordate Early g p groups Note: the many different lineages at the base 3 2/21/2008 Current view: early phylogenetic view: groupings are less important crown Focus on stem groups and crown groups, groups, not naming numerous phyla RIP Many taxa we see in the Early Cambrian are stem groups Stem groups can have their own distinct autapomorphies, in addition to the synapomorphies they share with crown groups stem RIP RIP The Cambrian Conundrum* Conundrum* (*Conundrum: a difficult or paradoxical problem/issue) 4 2/21/2008 Cambrian radiation (review) Many modern phyla of animals appeared in the Early Cambrian Many included taxa that evolved skeletons Not a uniform radiation (throughout the Cambrian) Lowermost: mostly simple skeletal fossils Tommotoian fauna Larger animals: some belong to phyla that have survived to the present Within a few tens of millions of years, animals diversify at the phylum, class, and order level = adaptive radiation (more on this in a bit) Cambrian conundrum Huge amount of diversification i a very short amount of H t f di ifi ti in h t t f geologic time! Some animals seem to appear out of nowhere e.g., when we first see trilobites, they are differentiated and distributed globally Where are the intermediates? Note: Note focus here is on animals 5 2/21/2008 Cambrian conundrum, cont. Possible Solutions: a) There is a hidden history of animal evolution Many early animals not preservable (i.e., no hard parts) b) The fossil record tells it like it is Animals underwent a spectacular diversification in the first ~20 Ma of the Cambrian ~20 A "biomineralization" event? Does it appear that animals radiate simply because they evolved hard parts? parts? Answer: Answer: No Skeletal fossils tell us that independent evolution of hard parts was part of the Cambrian explosion BUT.... Trace fossils tell us that something more than that happened Increasing complexity can be re-assembled in the refossil record Animals were becoming more complex--even without hard parts Other groups were also diversifying (e.g. protists, algae) 6 2/21/2008 Ecological pressures? Cause: evolution of predators? p E.g., Anomalocaris (below, top of image) Early mineralized fossils have drill-holes drill Explains hard parts (protection) Cloudina with drill holes Cambrian conundrum, revisited Solutions: Both solutions are in the realm of possibility (and perhaps it's a bit of both) a) There is a hidden history of animal evolution Early animals not preservable Some are, some perhaps are not b) The fossil record tells it like it is Animals underwent a spectacular diversification in the first ~20 Ma of the Cambrian ~20 Pressure to diversify from predation BuildBuild-up of oxygen (allows multicellular organisms to get enough oxygen to all their cells) Possible genetic factors (e.g., evolution of developmental genes) More detailed info in the textbook: pp. 59-63 7 2/21/2008 Cambrian conundrum, revisited Solutions: Both solutions are in the realm of possibility (and perhaps it's a bit of both) a) There is a hidden history of animal evolution Early animals not preservable Some are, some perhaps are not b) The fossil record tells it like it is Animals underwent a spectacular diversification in the first ~20 Ma of the Cambrian ~20 Pressure to diversify from predation BuildBuild-up of oxygen (allows multicellular organisms to get enough oxygen to all their cells) Possible genetic factors (e.g., evolution of developmental genes) More detailed info in the textbook: pp. 59-63 Animals, their Characteristics, and their Early Fossil Record 8 2/21/2008 Sponges Cnidaria ~ radial symmetry Broad outline of Animal Phylogeny BILATERIA bilateral symmetry Is this depicted in the fossil record? tissues ANIMALS multicellularity Chart of (approximate) first appearances of metazoans PreC PreC = Precambrian Cambrian, Ordovician, Silurian, ... You should know metazoan gro ps meta oan groups indicated here Note: disregard red/yellow coloring (or grayscale shading) of the various groups http://www.ucmp.berkeley.edu/phyla/metazoafr.html Ediacaran 9 2/21/2008 Sponges Cnidaria radial symmetry Outline of Animal Phylogeny BILATERIA bilateral symmetry tissues ANIMALS multicellularity What leads to this?... Building cellular complexity (Lect. 12) 12) Protists ~ unicellular eukaryotes 10 2/21/2008 Multicellularity Several levels of organization: organization: 1. Colonies with no integration or differentiation of cells Archaea, bacteria, & some protists 2. Colonies with cell integration and differentiation photosynthesis Communication between cells nitrogen fixation Cell specialization p Cyanobacteria & some protists The cyanobacterium, Anabaena Multicellularity, cont. 3. Macroscopic structures with coordinated cell differentiation "Complex multicellularity" only in eukaryotes evolved >5 times! ... Multicellular organisms Animals, fungi, green algae, red algae, brown algae Animals A i l are particularly complex: 30-40 cell t ti l l l 30ll types; vertebrates >200 cell types! 11 2/21/2008 Protists metazoans (multicellular organisms) The protist (left) is independent and mobile Uses flagella for locomotion The sponge cell (right) is but one from a multicellular organism Similar structure and function, but the cell is anchored in the body of the sponge Figure 4.1: a protist and a sponge cell A colony of attached protists A group of sponge cells = choanocyte Figure 4.2 Porifera (Sponges) choanocytes Body plan: asymmetric or radially symmetric Water flows through pores (ostium) in sides Flagella draws food into the sponge Choanocytes filter water Water exits through large openings (osculum) 12 2/21/2008 Porifera (Sponges) Skeleton composed of Silica (SiO2) spicules spicules Carbonate (CaCO3) spicules or layered Spongin (protein) fibers But no true tissues! ... Simplified Metazoan Phylogeny Echinodermata water vascular system pentameral symm. (adults) Hemichordata Cephalochordata (incl. lancelets) 3-part body Craniates (incl. vertebrates) well developed head (skull, brain, eyes, nose, ears, etc.) tunicates (sea squirts) Cnidaria jellyfish sea jellyfish, anemones, corals, et al. 3-part larval coelom CHORDATA muscle segmentation annelids ("worms") notochord segmentation molluscs (clams, snails, et al.) nematocysts (stinging cells) DEUTEROSTOMES acoelomate flatworms bryozoans pharyngeal slits mouth not from blastopore lophophore brachiopods nematodes arthropods segmented g exoskeleton "sponges" choanoflagellates coelom molting outer cuticle mouth from blastopore tissue BILATERIA EUMETAZOA through gut (separate anus) organs cephalization METAZOA multicellularity 13 2/21/2008 Sponges Cnidaria stinging cells ~ radial symmetry Broad outline of Animal Phylogeny BILATERIA bilateral symmetry EUMETAZOA tissues ANIMALS ~ METAZOA multicellularity Eumetazoans General characteristics Symmetry (radial, bilateral, etc.) Nervous system Digestive cavity Muscle cells Synapomorphy to remember: Tissue (aggregations of similar cells organized to perform a specific function) f ifi f ti ) Examples: muscle, nerve, epidermal, and connective 14 2/21/2008 Simplified Metazoan Phylogeny Echinodermata water vascular system pentameral symm. (adults) Hemichordata Cephalochordata (incl. lancelets) 3-part body Craniates (incl. vertebrates) well developed head (skull, brain, eyes, nose, ears, etc.) tunicates (sea squirts) Cnidaria jellyfish sea jellyfish, anemones, corals, et al. 3-part larval coelom CHORDATA muscle segmentation annelids ("worms") notochord segmentation molluscs (clams, snails, et al.) nematocysts (stinging cells) DEUTEROSTOMES acoelomate flatworms bryozoans pharyngeal slits mouth not from blastopore lophophore brachiopods nematodes arthropods segmented g exoskeleton "sponges" choanoflagellates coelom molting outer cuticle mouth from blastopore tissue BILATERIA EUMETAZOA through gut (separate anus) organs cephalization METAZOA multicellularity Chart of (approximate) first appearances of metazoans Cnidarians Jellyfish Corals Sea anemone Portuguese manmanofof-war (not much of a fossil record) Ediacaran http://www.ucmp.berkeley.edu/phyla/metazoafr.html 15 2/21/2008 Ediacaran `discs' (Lect. 13) ? Stem group cnidaria (= jellyfish, corals, anemones) "Stranded jellyfish?" Cnidarians Synapomorphy Stinging structures g g (nematocysts) nematocysts) Body plan Radially symmetric Two body forms: polyps and medusae (upside down from each other) Tentacles polyp l medusa http://en.wikipedia.org/wiki/Imag e:Anemone.bristol.750pix.jpg 16 2/21/2008 Corals Corals - good fossil record (?Mid-Cambrian to Present) MidRugose solitary or colonial radial septa extinct by end-Paleozoic end- Tabulate always colonial no radial septa extinct by end-Paleozoic end- Corals, cont. Scleractinians major reef builders today solitary or colonial Triassic to present Many have symbiotic relationships with algae 17 2/21/2008 Simplified Metazoan Phylogeny Echinodermata water vascular system pentameral symm. (adults) Hemichordata Cephalochordata (incl. lancelets) 3-part body Craniates (incl. vertebrates) well developed head (skull, brain, eyes, nose, ears, etc.) tunicates (sea squirts) Cnidaria jellyfish sea jellyfish, anemones, corals, et al. 3-part larval coelom CHORDATA muscle segmentation annelids ("worms") notochord segmentation molluscs (clams, snails, et al.) nematocysts (stinging cells) DEUTEROSTOMES acoelomate flatworms bryozoans pharyngeal slits mouth not from blastopore lophophore brachiopods nematodes arthropods segmented g exoskeleton "sponges" choanoflagellates coelom molting outer cuticle mouth from blastopore tissue BILATERIA EUMETAZOA through gut (separate anus) organs cephalization METAZOA multicellularity Bilateria Characters 1. Bilateral symmetry 2. Cephalization (a brain--or at brain--or least a concentration of nerves) 3. Coelom: fluid-filled body cavity, Coelom: fluidin which organs are suspended anus 4. A through-gut throughCoelomates mouth gut 18 2/21/2008 Protostomes and Deuterostomes Distinguished by their embryonic development Deuterostomes: the first Deuterostomes: opening (the blastopore) becomes the anus *Protostomes: the blastopore *Protostomes: becomes the mouth Blastopore = an ope g in hallow astopo e a opening a o body of cells (i.e., in the developing zygote) * Note: the term protostome has fallen out of favor with paleontologists--even paleontologists--even though the term is often seen in texts 19 2/21/2008 Simplified Metazoan Phylogeny Echinodermata water vascular system pentameral symm. (adults) Hemichordata Cephalochordata (incl. lancelets) 3-part body Craniates (incl. vertebrates) well developed head (skull, brain, eyes, nose, ears, etc.) tunicates (sea squirts) Cnidaria jellyfish sea jellyfish, anemones, corals, et al. 3-part larval coelom CHORDATA muscle segmentation annelids ("worms") notochord segmentation molluscs (clams, snails, et al.) nematocysts (stinging cells) DEUTEROSTOMES acoelomate flatworms bryozoans pharyngeal slits mouth not from blastopore lophophore brachiopods nematodes arthropods segmented g exoskeleton "sponges" choanoflagellates coelom mouth from blastopore tissue molting outer cuticle BILATERIA EUMETAZOA through gut (separate anus) organs cephalization "PROTOSTOMES" METAZOA multicellularity Chart of (approximate) first appearances of metazoans Molluscs Snails Clams Octopi Squid Nautiloids Ammonoids (extinct) ( i ) Ediacaran http://www.ucmp.berkeley.edu/phyla/metazoafr.html 20 2/21/2008 Simplified Metazoan Phylogeny Echinodermata water vascular system pentameral symm. (adults) Hemichordata Cephalochordata (incl. lancelets) 3-part body Craniates (incl. vertebrates) well developed head (skull, brain, eyes, nose, ears, etc.) tunicates (sea squirts) Cnidaria jellyfish sea jellyfish, anemones, corals, et al. 3-part larval coelom CHORDATA muscle segmentation annelids ("worms") notochord segmentation molluscs (clams, snails, et al.) nematocysts (stinging cells) DEUTEROSTOMES acoelomate flatworms bryozoans pharyngeal slits mouth not from blastopore lophophore brachiopods nematodes arthropods segmented g exoskeleton "sponges" choanoflagellates coelom molting outer cuticle mouth from blastopore tissue BILATERIA EUMETAZOA through gut (separate anus) organs cephalization METAZOA multicellularity Question: can you tell from this cladogram if bryozoans preceded molluscs ? snail Molluscs Characteristics: Carbonate shell (sometime internal) Radula (rasping feeding device) Typically have a soft, un-segmented body unand a protective calcareous shell Many have a fantastic fossil record--why? record--why? Also includes organisms with a high degree of cephalization (e.g. octopi, squid) centralization of neural and sensory organs in the head http://bio.fsu.edu/~bsc2011l/mollusca_images_sum_04/bivalvia/ 21 2/21/2008 Chart of (approximate) first appearances of metazoans Brachiopods Articulates Inarticulates Ediacaran http://www.ucmp.berkeley.edu/phyla/metazoafr.html Simplified Metazoan Phylogeny Echinodermata water vascular system pentameral symm. (adults) Hemichordata Cephalochordata (incl. lancelets) 3-part body Craniates (incl. vertebrates) well developed head (skull, brain, eyes, nose, ears, etc.) tunicates (sea squirts) Cnidaria jellyfish sea jellyfish, anemones, corals, et al. 3-part larval coelom CHORDATA muscle segmentation annelids ("worms") notochord segmentation molluscs (clams, snails, et al.) nematocysts (stinging cells) DEUTEROSTOMES acoelomate flatworms bryozoans pharyngeal slits mouth not from blastopore lophophore brachiopods nematodes arthropods segmented g exoskeleton "sponges" choanoflagellates coelom molting outer cuticle mouth from blastopore tissue BILATERIA EUMETAZOA through gut (separate anus) organs cephalization METAZOA multicellularity 22 2/21/2008 Brachiopods An articulate brachiopod Look like clams but different planes of symmetry t Often anchored to the ocean floor Like bryozoans, they have a lophophore (a tentacular feeding organ, used to filter feed) Two kinds Articulate hinged to prevent slipping Inarticulate held together by muscles Major players in the Paleozoic But rare and inconspicuous today Inarticulate brachiopods 23 ...
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