Introduction to Animal Diversity Lecture 7 Winter 2014
Evolution of Animals 1 Prokaryotes Eukaryotes
Prokaryotes No nucleus Nucleoid region Simple No membrane bound organelles Smaller (1-5 nm) Evolutionarily older Major differences Eukaryotes Nucleus (DNA in a membrane-bound region) Complex Membrane bound organelles Organelle a structure with a specified function w/i a cell Larger (10-100 nm) Evolutionarily younger 2
The Origin of Eukaryotic Cells 3 Evolution of the endomembrane system Remember endomembrane system? See Fig. 25.9
Endosymbiosis 4 Remember endosymbiosis? Mitochondria Formed when early anaerobic eukaryotic cell engulfed an aerobic bacterium Benefits? Plastids Formed when early eukaryotic cell (w/mitochondria) engulfed a photosynthetic cyanobacterium Benefits? See Fig. 25.9
Protist Diversity 5 What is a protist? Eukaryote Unicellular (primarily) Colonial Multicellular (algae seaweed ) Metabolically diverse Photoautotrophs Heterotrophs Mixotrophs combine both
6 Protist Diversity Protista is a paraphyletic grouping Fig. 28.3
Origin of Multicellular Organisms 7 Earliest multicellular fossil ~1.2 bya Cells gather in colonies Cell specialization occurs to divide particular life functions Multicellularity evolved several times independently among eukaryotes
What are animals? 8 Eukaryotes Multicellular Heterotrophic Sexual reproduction (most) Embryonic stage blastula & gastrula Specialized cells, tissues, organs for capturing food, avoiding predation Muscles, nerves, sensory organs
Brief Animal History 9 Common ancestor of living animals ~675-875 mya??? Fig. 32.3
Brief Animal History 10 565-550 mya - First fossils 535-525 mya - Cambrian explosion Large diversification of animals A Wonderful Life by Stephen Jay Gould 360 mya - Vertebrates move to land Fig. 32.5
Animal Phylogeny 11 Fig. 32.10
Body Symmetry Asymmetric (no true symmetry) e.g., sponges Radial symmetry Can be divided into equal but opposite halves by any plane through its central axis Sessile or planktonic 12 Fig. 32.7
Bilateral symmetry Body Symmetry A body form with a central longitudinal plane that divides the body into two equal but opposite halves Must cut on midline Cephalization Sensory organs concentrated in anterior region Benefits? 13 Fig. 32.7
Evolution of true body tissue 14 Tissue: An integrated group of cells with a common function, structure, or both Separated by membranous layer Sponges lack true tissues All other animals - embryo with layered tissue Germ layers Ectoderm Endoderm Mesoderm
Embryonic Development Blastula Hollow ball of cells that marks the end of the cleavage stage Gastrulation Blastula folds inward, producing layers of embryonic tissue Gastrula Stage encompassing the formation of the layers 15 Fig. 32.2
Evolution of true body tissue 16 Diploblasts Ectoderm & endoderm E.g., Cnidarians (jellies, corals) Triploblasts Ectoderm, mesoderm, endoderm Bilateral symmetry Mesoderm forms muscles & most organs between digestive tract and outer covering
Evolution of digestive cavity 17 Digestive cavity Gastrovascular cavity Sac with single opening Acts as both mouth & anus Complete digestive tract (alimentary canal) Two openings, a mouth and an anus Fig. 33.5 Fig. 41.9
Evolution of body cavity 18 Body cavity (coelom) Fluid or air-filled space separating the digestive tract from the outer body wall Functions: Cushions internal organs Organs can move independently of outer body wall Fig. 32.8 True coelom Formed from mesoderm tissue Coelomates
Evolution of body cavities 19 Pseudocoelom Formed from mesoderm & endoderm tissue Pseudocoelomates No body cavity Acoelomates Fig. 32.8
Segmentation & Tagmatization 20 Segmentation Divided into parts, sections Tagmatization Groups of segments become specialized to form specific function for whole body Tagmata (tagma, sing.) Fig. 33.29
Skeletal Systems 21 Endoskeleton Hard supporting element buried within the soft tissue E.g., bones & cartilage (mammals), skeletal fibers of inorganic material or proteins (sponges), ossicles (sea stars)
Skeletal Systems 22 Exoskeleton Hard encasement deposited on an animal s surface E.g., shells (snails, clams), cuticle (crabs, insects)
Animal Development 23 Fig. 33.36 Metamorphosis A dramatic change from the larval form to the adult form of an animal Larva Sexually immature form of an animal that is morphologically distinct from the adult
Protostome Vs. Deuterostome Development 24 Cleavage Spiral Cleavage planes diagonal to vertical axis of embryo Radial Cleavage planes parallel or perpendicular to vertical axis of embryo Tiers of cells aligned directly above the other Determinate Developmental fate of cells determined very early Indeterminate Each cell retains capacity to develop a complete embryo Fig. 32.9
Protostome Vs. Deuterostome Development 25 Coelom formation Gastrula stage Protostome Coelom forms from splits in the mesoderm (schizocoelous) Deuterostome Coelom forms from mesodermal outpocketing in archenteron Fig. 32.9
Protostome Vs. Deuterostome Development 26 Fate of blastopore Blastopore Indentation that during gastrulation leads to the formation of the archenteron Protostome = first mouth Deuterostome = second mouth Fig. 32.9
Animal Phylogeny 27 Fig. 32.10