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Christoph Richter

Why are animals studied? they are heterotrophs (they obtain carbon compounds from other organisms) they are consumers (they occupy the upper levels of food chains) we study them to understand and preserve ecosystems animals are a rich species and morphologically diverse (10million-50million species of animals) humans depend on wild and domesticated animals for food, transportation and power to understand human biology (drug testing and biomedical research done on mice, rats and primates) Characteristics of animals animals are the only one on tree of life with muscular tissue and nervous tissue reproduce both sexually and asexually (no alternation of generations) diploid adults, the only haploid cells are gametes produced during sexual reproduction Morphology of Animals 34 phyla Body plan 1. Number of tissue layers found in embryo diploblasts (two-buds) : animals whose embryos have 2 types of layer tissues [germ layers are called ectoderm(outer skin =gives rise to simple muscle) and endoderm(inner skin = gives rise to reproductive tissues)] e.g. cnidarians and ctenophorans triploblasts (three-buds) : animals whose embryos have 3 types of layer tissues [germ layers are: ectoderm (gives rise to skin and nervous system ) mesoderm (gives rise to circulatory system, muscle, and internal structures), endoderm (inner skin, gives rise to lining of digestive tract)]. All triploblastic animals have bilateral symmetry except for Echinodermata (radial symmetry involved independently of diploblastic groups. Larva is bilaterally symmetrical however adult echinoderm is radially symmetric) *embryo layers are organized in layers called germ layers 2. body symmetry and degree of cephalization (formation of head region) asymmetry: no planes of symmetry (e.g. sponges) radial symmetry: 2 planes of symmetry, animals usually float in water/attached to a substrate (e.g. jellyfish) bilateral symmetry: 1 plane of symmetry, triggered cephalization (evolution of head or anterior region) - enabled direct movement and hun ting (e.g. lizard) 3. fluid-filled body cavity diploblasts dont have a coelom (fluid-filled cavity, has mesoderm on both inner and outer side of fluid-filled cavity) triploblasts that dont havea coelom= acoelmates (no cavity-form) triploblasts that possess a coelom = coelomates coelom forming between endoderm and mesoderm layers in embryo = pseudocoelom ("false-hollow", has mesoderm on outer side of fluid-filled cavity) *coelom acts as a hydrostatic skeleton which allows movement even without fins/limbs *by providing hydrostatic skeletons, evolution of coelom gave bilaterally symmetric organisms the ability to move 4. how do the events in embryo development proceed except for "adult" echinoderms (radially symmetric, diploblasts), all coelomates are triploblastic and bilaterally symmetrical. Cleavage: series of mitotic divisions that occur in theabsense of growth protostomes: spiral cleavage deuterostomes: radial cleavage Gastrulation: cell movements that form three embryonic tissue layers (begins when cells move into the centre of embryo for both protostomes and deuterostomes) Protostomes Deuterostomes Cleavage (zygote undergoes rapid Spiral (helical arrangement Radial (mitotic spindles orient divisions, forming mass of cells) of cells) parallel/perpedicular to the main axes of cells, cells stack up on one another Gastrulation (mass of cells formed Pore becomes mouth Pore becomes anus by cleavage is reaggrangedto form gut and embryonic tissue layers) Coelom formation (body cavity Mesoderm splits to form Mesoderm pockets pinch off of gut to form coelom lined with mesoderm develops) coelom End achieved: bilaterally symmetrical body that contains a cavity lined with mesoderm Tube-within-a-Tube Design 99% of animals today are bilaterally symmetrical, triploblasts with coeloms which either follow protostome patterns of development or deuterostome's. inner tube= gut, outer tube = body wall. Mesoderm in between forms muscles and organs. Features that give rise to tube-within-a-tube body plan: triploblasts, bilateral symmetry, coelom Extras: Choanoflagellates = closest living relatives of animals both are sessile (attached to a substrate), Sponges are multicellular Ponifera (sponges) = most basal animal phylum paraphyletic and represent independent lineages Choanocytes= Sponge-feeding cells that trap and ingest food particles Diploblasts are at the base of the tree means = endoderm and ectoderm were the first tissues to evolve and radial symmetry evolved before bilateral Acoelomorpha= most ancient bilateral symmetrical group, no coelom (animal bodies evolved from simpler to complex) Platyhelminthes (Protostome ~ Lophochotrozoan) = no coelom, ancestors had a coelom Change from coelom -> pseudocoelom occured in nematodes and rotifera Segmentation evolved independently in annelids, arthropods, molluscs and vertebrates atleast 3 times Vertebrates : monophyletic, presence of skull and backbone Invertebrates: paraphyletic (includes some but not all of the descendants of a common ancestor) Therefore, triploblasty, bilateral symmetry, coeloms, prostostome and deurterostome development all evolved once. Protostomes 1) Ecdysozoa : grow by moulting (shedding their external skeleton and expanding their bodies) 2) Lophotrochozoa: grow by extending the size of their skeletons WHAT THEMES OCCURED IN DIVERSIFICATION OF ANIMALS? What triggered the diversification of species with each lineage? the evolution of innovative methods for feeding and moving Feeding The structure of an animal's mouthparts correlates with its method of feeding 1) Suspension Feeders/Filter Feeders: capture food by filtering out or concentrating particles suspended in water or air. 2) Deposit feeders eat their way through a substrate. They digest organic matter in the soil. (food: soil-dwelling bacteria, archaea, protists and fungi). Most common deposit feeders=echinoderms (sea cucumbers) 3) Fluid Feeders: suck liquids e.g. butterflies, blowflies 4)Mass Feeders: take chunks of food e.g. horses, snails (feeding structure radula functions like a rasp/file) What do animals eat? Herbivores: eat plants/algae Carnivores: feed on animals Omnivores: eat both plants and animals Detritivores: eat dead organic matter Predators/Parasites: harvest nutrients from causing death Movement Movement has 3 functions: 1) finding food 2) finding mates 3) escaping from predators Structures that provide movement: 1) cilia 2) flagella 3) muscles that attach to hard skeleton/compress a hydrostatic skeleton 4) Hydrostatic skeleton (usually for wormlike bodies) 5) Limb: important in ecdysozoans and vertebrates Homology: similarity in traits due to inheritance from a common ancestor. Traditionally joint and unjoint limbs were not homologous. Some appendages evolved independetly of oneanother. Different genes are responsible for each major type of appendage. Gene: Distal- less (Dll) = "grow appendage out this way. Dll (homologous Distal-less gene) = involved in the development of homologous limbs Therefore limbs and appendages are both homologous. Idea is that a simple appendage evolved early in the history of bilateria, evolution by natural selection produced the diversity of limbs, antennae and wings. Reproduction and Life Cycles Asexual reproduction (via mitosis) Sexual reproduction (via meiosis and fusion of gametes) - fertilization may be internal/external Metamorphosis (change-form): change from a junevile to an adult body type o Holometabolous (whole change): junevile is called a larva which looks different from the adult, pupation causes the pupa's body to be transformed into a new, adult form o Hemimetabolous (half-change): junevile is called a nymph and looks like a miniature of the adult form viviparous (live-bearing): embryos are kept inside thebody, mammals give birth to the live young oviparous (egg-bearing): species deposit fertilized eggs ovoviviparous (egg-live-bearing): female retains eggs inside her body, embryo is nourished by yolk inside the egg then birth to live young is given *Go over PONIFERA (sponges, paraphyletic), CNIDARIA (no coelom, diploblasts), CTENOPHORA, ACOELOMORPHA (no coelom, bilateral symmetry) Animals Prostome Deuterostome Ponifera Lophotrochozoa Echinodermata Cnidaria  rotifera Hemichordata Cternophora  platyhelminthes Chordata Acoelomorpha  annelida  mollusca Ecdysozoa  nematoda  arthropoda  Onychophora  Tardigrada Protostomes = monophyletic group There are two major monophyletic groups of bilaterally symmetrical, triploblastic, coelomate animals: Protostomes and Deuterostomees Protostomes: spiral cleavage, pore forms the mouth, mesoderm splits to form coelom Two monophyletic groups of Protostomes: lophotrochozoa and ecdysozoa Lophotrochozoan [molluscs, annelids, flatworms (platyhelminthes)] 14 phyla grow by additions to body locophore ("tuft-bearer"): feeding structure functionsin suspension feeding, beating of cilia = water current that sweeps food into tentacles which is then ingested in mouth trochophore (wheel-bearer): type of larva common tomarine molluscs and annelids has a ring of cilia around its middle. Ecdysozoan (ecdysis = to slit out/escape) [nematoda, arthropods] grow by moulting (shedding an exoskeleton/external covering and coming out of its cuticle [if its soft] or exoskeleton [if its hard]) Hypothesis explaining growth my moulting: growth by moulting was required once tough outer cuticles/thick exoskeletons evolved for protection from predators. animals dont move/eat and hide during intermoult period since its easier for predators to attack individuals not protected by exoskeleton WHAT THEMES OCCURED IN DIVERSIFICATION OF PROTOSTOMES ? Body plans All protostomes are triploblasts with bilateral symmetry but radical changes occured in the coelom formation After coelom evolved, reversion to an acoelomate body plan occurred. Pseudocoelom arose independently in rotifera and ecdysozoans. (Nematoda have a prominent pseudocoelom). In wormlike phyla, coelom is well-developed but in morphologically diverse and complex phyla (arthropoda, mullusca) coelom is reduced. (arthropod and mullusc coeloms are vistigialtraits) Arthropod Body Plan: segmented bodies, tagma (head+thorax+abdomen), joint limbs, CaCO3/chitin made exoskeleton, homocoel (blood-hollow, provides space for internal organs andcirculation of fluids and functionsas a hydrostatic skeleton) Molluscan Body Plan: foot, viceral mass, mantle (covers viceral mass, may/may not secret calcium carbonate shell). Coelom's functions are replaced by viceral mass and the muscular foot. Fluid enclosed by the viceral mass and the muscular foot functions as the hydrostatic skeleton Proboscis: extended structure for suspension feeding in worms, it forms a gutter leading to the mouth  Spoon worms: food particles trapped in mucus by proboscis and moved to mouth by cilia  Penis worms: sit and wait predators, turn its throat inside out, grab the prey (annelida) and retract the structure to take in the food  Ribbon worms: active predators, move around ocean floor, extend out proboscis Adaptation: any trait that increases the fitness of an individual Adaptations for Water to Land Transition (transition occured multiple times in protostomes) 1) exchange gases 2) avoid drying out to solve this problem, round worms and earth worms live in wet soils or moist env, arthropods and molluscs have a watertight exoskeleton /shell that minimizes water loss and respiratory structures in their body that close to minimize water loss Green plants moved from freshwater -> land just once Fungi moved from aquatics -> land (just once/several times? not sure) Only one lineage among deuterostomes moved onto land The ability to live in terrestrials evolved independently in arthropods(atleast twice), molluscs, roundworms and annelids Adaptations for feeding suspension / deposit feeders, liquid suckers, food-mass feeders, exploit detritus, prey on/parasitize algae, plants and other animals diversity in food = due to diversity in mouthparts arthropods: most diverse mouthparts, limbs play a role in getting food (e.g. krills use their legs to sweep food into their mouth via suspension feeding Adaptations for moving variation in movement n protostomes depends on twofeatures 1) presence/absence of limbs: allowed protostomes to move in a variety of ways  wing: to fly  waves of muscle contractions: allow to glide across a surface as these waves sweep down the muscular foot  jet propulsion: cavity surrounded by mantle fills with water, mantle muscles con/tract, stream o
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