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BIO 385 INVERTEBRATE ZOOLOGY TOPIC 1 EVOLUTION AND PHYLOGENETIC ANALYSIS I Evolution A Biological Organic Evolution a A genetic change in a population of organisms from one generation to the next 1 Populations not individuals evolve 2 Changes that are not genetic eg cultural environmental are not evolution A Phenotypes are not part of evolution a Physical changes N Charles Darwin A Published quotThe Origin of Speciesquot in 1859 B Darwin39s Principle Contributions a Thoroughly documented the evidence of evolution b Argued for idea of Common Descent that different species can be descended from a common ancestor c Proposed Natural Selection as the mechanism to bring about evolutionary change III Natural Selection A Differential reproductive success with respect to particular characteristics or genotypes a Survival of the ttest 1 Not so much about surviving more about reproducing b Variation among members of a population in characteristics that affect survival or reproduction 1 Those individuals that have characteristics that make them best suited to survive andor reproduce ie are the most t will have greater chance to contribute to the next generation 2 If their traits are heritable this will lead to evolutionary change IV Adaptations A Adaptations a Traits that evolved by natural selection for a particular function B Natural selection is the only evolutionary process that produces adaptations C The speci c adaptations that evolve depend on the kinds of variations that exist in the populations D The source of the variations upon which natural selection acts is mutations which occur randomly V Evolutionary Change A Darwin argued that a Small changes that can accumulate each generation via natural selection can over a long enough time period millions of years accumulate into substantial differences b Similarities between different species inheriting those traits from a common ancestor c Differences between species results from their independent evolutionary histories since they diverged from their common ancestor VI Speciation A Natural selection explains change within a species B How to account for the diversity of species and for common descent C Speciation a Process by which a single ancestral species gives rise to two descendant species VII Modes of Speciation A 2 basic modes of speciation a Allopatric Speciation 1 Two populations of a species become geographically isolated from one another allowing populations to diverge b Sympatric speciation 1 Development of reproductive isolation among subgroups within a single area A Rare in animals VIII EvolutionaryTrees A Repeated sequential speciation events eventually give rise to a branching evolutionary history a Phylogeny B Diagrams illustrating the evolutionary history are called dendograms or phylogenetic trees a Phylogenetic trees are hypotheses 1 They represent our best guess about the actual evolutionary relationships b Phylogenetic trees are usually almost always incomplete 1 Maybe simpli ed to better illustrate patterns 2 Missing allmost extinct species and groups IX Phylogenetic Reconstruction A How do we reconstruct phylogenetic trees a Traditional approach has been to groups species based on the overall similarity 1 Phenetics is strictly quantitative comparing large numbers of traits characters 2 Evolutionary Systematics A Is more subjective with an attempt to use only quotevolutionary Informative ie homologous Charactersquot B Problems with traditional reconstructions based on similarity are a Convergent Evolution 1 Some shared characteristics evolved independently homoplasies thus are not helpful in determining true relationships b Rate of Evolution is not always constant X Reconstructing Trees Cladistics A Cladistics attempts to determine evolutionary lineages by using only synapomorphies a Shared homologous derived traits 1 Homologous A Sharing a common evolutionary origin a Shared traits that can be traced to a common ancestor 2 Homoplastic A Having a similar appearance due to convergent evolution and not shared descent a quot analogous traitsquot 3 Homologous traits can be identi ed A Common underlying structure and position B Shared developmental patterns C Shared transitional forms in fossil record 4 Derived trait or apomorphy A A trait of recent origin relative to taxon in question a Resulting from a more recent evolutionary transition 5 Ancestral trait aka primitive trait or plesiomorphy A A trait that was present in some remote ancestor a The condition prior to an evolutionary transition Xl Cladistics A How do we choose among several possible phylogenies if we cannot be B C XII absolutely certain that 2 traits are homologous a Parsinomy 1 Select the phylogeny that requires the fewest evolutionary transitions To increase our con dence in the accuracy of a phylogenetic hypothesis we try to increase the number of characters being examined Types of characters used in cladistics analysis a Morphological 1 Anatomical and physiological behavioral traits 2 Only type available for fossils 3 Easier to recognize homoplasy 4 Can be timeconsuming to produce data 5 Greater potential for nonindependent traits b Molecular esp DNA Sequences 1 Can get large numbers of characters set fairly quickly 2 Not usually available for fossil organisms 3 Homoplasy is dif cult to avoid A eg A gtT can evolve easily many times 4 Best genesregions on depth of clade being resolved Taxonomy In addition to determining phylogenies we also try to classify organisms a Place them in named categories 1 Taxon pl taxa Taxonomy a Practice of naming and classifying organisms The taxa in which organisms are placed usually re ect their evolutionary relationships to varying degrees Types of Taxa Monophyletic Taxon Clade a A group of organisms with a single common ancestor and all of the descendants of the ancestor Paraphyletic taxon a A group that includes the common ancestor of all members but does not include all descendants of the common ancestor XIV XV XVI POP nl39l39l XV Polyphyletic taxon a A group that does not include the common ancestor of its members based on analogous traits Taxonomy Two taxonomic systems being used a Traditional Linnaean classi cation b Phylogenetic classi cation Linnaean Taxonomy Linnaean classi cation places species in nested categories at speci c ranks levels a Kingdom 1 Phylum A Class a Order 1 Family Genus 0 Species Additional ranks can be inserted a Eg Subphylum Super class etc Criticism of the Linnaean classi cation a Limited number of categories relative to nesting levels in a phylogenetic hierarchy 1 Limits ability to re ect evolutionary relationships b Traditional groups based on grades 1 A level or stage of evolutionary development A Such traditional grades are often paraphyletic and not monophyletic clades c Taxonomic ranks are arbitrary 1 Not biological meaning Phylogenetic Classi cation One speci c proposal referred to a quotPhylo Codequot Recognizes only monophyletic clades Does not allow paraphyletic or polyphyletic taxa Would eliminate taxonomic ranks a Eg phylum clades etc Clades would be given permanent stable de nitions Species would not be assigned to clades directly but instead t in clade based on current phylogenetic hypothesis De ning Clades Clades can be de ned by a Synapomorphies that characterize that clade 1 Clades identi ed by genetic studies may not have any obvious morphological synapomorphies A In cladistics synapomorphy or synapomorphic character state is a trait that is shared quotsymmorphyquot by 2 or more taxa and inferred to have been present in their most recent common ancestor whose own ancestor in turn is inferred to not possess the trait XVIII A XIX 2 Extant clades can often be de ned by multiple traits but pose problems for fossil organisms that contains some but not all of those traits A eg Arthropods de ned by presence ofjointed appendages and compound eyes Clades can be de ned as speci c branches on a phylogenetic tree a quotCrown groupquot clade 1 All descendants of most recent common ancestor of a pair or more of species A Usually de ned by extant species a Eg arthropoda 1 All descendants of common ancestor of insects and spiders This de nition would exclude some extinct groups such as trilobites and dinocaridids Phylogenetic Classi cation Clades can be de ned as speci c branches on a phylogenetic tree a quotTotal Groupquot clade 1 All species more closely related to one speciesgroup than another A Eg Total group Arthropoda de ned as all species more closely related to insects then to velvet worms Onychophorans a This de nition would include extinct forms such as trilobites and dinocaridids Problems with phylogenetic classi cation a Any monophyletic clade can be named 1 Results in an excess number of possible names A Reduced effectiveness of communication b Paraphyletic taxa are often useful for communications about organisms c Clades are de ned based on branches rather than by species being assigned to taxa 1 A species quotclassi cationquot can vary depending on the phylogenetic hypothesis d Methods of de ning clades varies crown vs stem groups 1 A problem with fossil organisms Taxonomic Systems Traditional Linnaean system is more effective for communication about organisms generally a Ranks provide useful markers for taxa likely to be widely known as indicate approximate depth within a phylogeny Phylogenetic classi cation better re ects hypothesized evolutionary relationships a More useful when describing speci c evolutionary relationships Topic 2 Introduction to Animal Body Plans I What is an animal A Kingdome Animalia a Metazoan is one of the 2 kingdoms recognized by Linnaeus B We currently recognize at least 5 other kingdoms a Kingdome Eubacteria 1 Typical bacteria b K Archaea 1 Methaneproducing prokaryotes c K Fungi 1 Fungi 2 Molds 3 Yeasts etc d K Plantae 1 Plants e K Protista 1 Algae 2 Protozoans singlecelled 3 Slime molds 4 Etc Paraphyletic C Kingdom Animalia is characterized by Eukaryotic Multicellular Heterotrophs Typically Ingestive 1 Ingest food and digest it inside a cell or body cavity Lack cell wall Collagen proteins 1 In connective tissue A Provides support in place of cell II What are invertebrates A Kingdom Animalia contains 35 phyla a Invertebrates 1 All animas except member of subphyIum Vertebrata of the Phylum Chordata A Some chordates are considered invertebrates a quotInvertebratesquot is considered paraphertic b Invertebrates represent about 98 of known animal species b Traditionally the animaIIike Protista quotprotozoansquot are studied with the animals III AnimaI Body PIans A Each major group eg phylum of animals has characteristic structural features referred to as a body plan or BaupIan Elmo Q h D a Body plans tend to be evolutionarily conserved change little and tend to constrain the evolution and development of animals canalization b Body plans prescribe the range and types of structures for a particular group of animals and their function IV Basic Features of Body Plans A Body Symmetry a Asymmetric 1 Lacking a plane of symmetry A Lack polarity a Differentiation along an axis b Radial Symmetry 1 Multiple planes of symmetry around a central axis 2 Body essentially cylindrical A Sessile sedentary or drifting pelagic species B Interact with environment equally in all directions c Bilateral Symmetry 1 Single plane of symmetry diving animal into right and left halves A Associated with mobile animals exhibiting unidirectional movement B Cephalization a Having a quotHeadquot b Concentration of sensory and nervous system structures at forward end V Body Size and Complexity A The smallest organisms are composed of a single cell unicellular a Includes most members of Kingdom Protista B Some protozoan form colonies a Aggregations of connected interacting cells 1 Cells exhibit little specialization C Multicellular organisms have specialized cells of different types a Cells do not function independently 1 All animas metazoans exhibit this grade D Simplest multicellular animals do not have wellde ned tissues a Sponges and a few small obscure groups 1 Tissues A Collections of structurally and functionally similar cells that work together E Eumetazoa a All animals except sponges and placozonas have tissuelevel organization 1 Secondarily reduced in a few parasitic forms Vl SurfaceVolume Relationship A Why are cells small a The squarecube law 1 Surface area will increase with the square of length while volume will increase with cube length VllBody Size and Complexity A Why are cells small a Cells requirements for nutrients 02 related to volume but ability to exchange materials with environment is limited by surface area b Larger eukaryotic cells solve problem in part by cell surface structures eg microvilli or shapes that increase surface area relative to volume c Diffusion limits maximum cell size to 100um Larger organisms usually most be muticeuar 1 However diffusion is still an issue for larger muticeuar animals A Diffusion of 02 is only effective across 1mm of Ussue B Most cells must be near or in contact with external environment a Eg Adopt shape that maximizes surface area d Even larger body sizes require complex internal transport systems to deliver nutrients and gasses to the tissues and to remove wastes 1 Lead to development of organs A Structures composed of 2 or more tissues a That work together towards the same function VIII Embryonic Germ Layers A During embryonic development of eumetazoa germ layers embryonic tissue layers develop that give rise to various speci c tissues B All eumetazoa exhibit outer ectoderm that forms the epidermis outer coverings and inner endoderm that forms the oastro dermis lined the gut a Diploblastic animals have only 2 layers 1 Separated by acellular region A Cnidarians and ctenophores C Triploblastic animals have a 3rCI embryonic germ layer a The mesoderm that lies between the ectoderm and endoderm 1 Allows for development of more complex structures and body plans 2 Most animals including all bilateral animals are triploblastic IX Body Cavities A Many triploblastic animals have developed an internal uid lled body cavity a not open to external environment 1 Advantages of having a body cavity A Allows separation between outer body walls and gut a Each can function independently B Circulates substances through body G X Anima A B C Provides space for development of more complex organs D Functions as hydrostatic skeleton Acoelomate a Lacking body cavity Pseudocoelomate a AKA blastocoelomate 1 Usually forms from embryonic blastocoel Coelomate a AKA eucoelomate 1 Derived within mesoderm A Lined by peritoneum Traditionally the presence and type of body cavity was an important characteristic used in classi cation of animals Recent molecular data suggest that body cavities may not be as useful due to convergent evolution and repeated secondary loss of body cavities Acoelomate condition may be derived from coelomate ancestor Body Plans Unicellular colonial forms a Protozoans Multicellular a Animals Metazoans 1 Without true tissues A Sponges placozoans 2 With true tissues A Eumetazoa a Diploblastic 1 Cnidarians ctenophores b Triploblastic 1 Bilaterian animals Acoelomate ltgt Flatworms Pseudocoelomate ltgt Nematods etc Coelomates 0 Everything else gtllt gtllt Topic 3 Reproduction and Development I Reproduction A Asexual Reproduction a Production of new genetically identical individuals via mitosis 1 Includes binary ssion budding b lncludes fragmentation c Parthenogenesis 1 Young develop from unfertilized usually diploid eggs A Some arthropods rotifers B In some species female must mate with male of same or different species in order to ovideposit but sperm never unites with egg C lnvolve many mechanisms to produce diploid eggs B Sexual Reproduction a Production of new genetically distinct individuals 1 lnvolves A Formation of haploid gametes ova sperm via meiosis B Fusion of gametes via fertilization to produce diploid zygote b Practice by majority of animals 1 Costs A Production of males halves rate of population growth 1 B Offspring contain only 5 of parents39 alleles 2 Bene ts A Produce variable offspring a Better chance that some will be welladapted in a changing or variable environment B Prevent accumulation of harmful mutations C Dioecious a gonocho s c 1 Having separate sexes A male female D Monoecious or hermaphrodite a Each individual has both ovaries and testes 1 Simultaneous hermaphroditism A Can produce eggs and sperm at the same time a Usually involves mutual cross fertilization b Selffertilization is rare 2 Protandry A Starts as male later switch to female 3 Protogyny A Starts as female later switch to male E Gametes are produced by gonads a Ovaries and testes F Fertilization can be external or internal a Externalfertilization 1 Broadcast spawners release gametes into water column sperm swim to eggs Often highly synchronized b Internal fertilization without mating 1 Sperm swim to eggs within females A marine vertebrates only G Internal fertilization on land or fresh water usually requires variety of accessory structures ducts storage areas accessory glands and copulatory organs a Direct sperm transfer into females genital opening vial male penis b Hypodermic traumatic fertilization 1 Male injects sperm through female body wall c Indirect transfer via spermatohore H Spermatophore a Sperm lled capsule 1 That may also contain nutrients or other material b Transferred to female in many ways 1 Via copulation 2 Deposited on ground and picked up by female 3 Eg transferred to female by male appendage A chelicerae tentacle etc Animal Development A Animals are muticeuar with specialized tissue except sponges pacozoans mesozoans and organs except aso cnidarians ctenophores B Thus development or ontogeny is process of going from a single unspeciaized egg to a complex muticeuar organism C Understanding development can provide clues about a The origin of animals and muticeuarity b Relationships among major animal taxa III The Egg Ovum A Eggs Ova exhibit polarity a Vegeta Pole 1 Contains higher yolk density associated with formation of digestive tract b Animal Pole 1 Lower yolk density development of various other embryonic structures IV Cleavage A Cleavage refers to cell divisions in early zygote a Holoblastic cleavage 1 Divisions pass through entire egg b Meroblastic cleave 1 Divisions do not pass through all the way A Don39t divide the densely yoked regions B Initial 2 cleavages are always along animalvegetal axis a Cell divisions maybe equal 1 Produce similarized blastomeres A Daughter cells b Orunequal 1 Produce different sized blastomers C Radial cleavage a Divisions are strictly longitudinal and transverse Cells in rows along av axis D Spiral cleavage a Cleavage planes at an angle to longitudinal or transverse axes b Cells are displaced to lay in the furrows between other cells E Also distinguished on basis of potential faces of cells a Determinate cleavage 1 Each cells fate is xed by 1St division A Associated with spiral cleavage a Each cells fate is xed by 1St division 1 Associated with spiral cleavage b Indeterminate cleavage 1 Each cell up to 8cell stage if isolated can develop into complete organism A Associated with radial cleavage V Blastula A Blastula stage is reached when the dividing cells form a usually hollow sphere a Variations including solid mass of cells and disk of cells sitting atop dense yolk mass also possible Vl Gastrulation A Gastrulation is a stage in which tissue layers are formed a Typically involves invagination of part of blastula to form endoderm b Archenteron eventually froms guy c Blastopore becomes opening to digestive tract VllFormation of Mesoderm A Formation of middle layer a In diploblastic species eg cnidarians 2 cell layers separated by gelatinous mostly acellular mesenchyme 1 Mesenchyme may contain various cells and bers dirive from ectoderm b In triploblastic species 3rCI cell layer is true mesoderm with cells derived from endoderm 1 Formation of mesoderm tied to formation of coela body cavities Vlll Formation of Mesoderm and Coelom A Single endoderm cell moves into blastocoel between endoderm and ectoderm and gives rise to mesoderm a This process is associated with spiral cleavage B Endodermal cell moves into blastocoel to form mesoderm a Coelom forms via schizocoely as mesoderm patches endlarge and hollow out C Outpocketing of archenteron endoderm gives rise to mesoderm a Associated with radial cleavage b Coelom forms via enterocoely as pockets of mesoderm form with hollow spaces IX Developmental patterns A All coelomate animas and those that secondarily lost their coelomfal into 2 main lineages each of which is associated with particular development patterns a Protostomes b Deuterostomes Protostomes Deuterostomes Cleavage Spiral amp determinate Radial amp indeterminate Blastopore becomes Mouth Anus Mesoderm from Cell split from endoderm Usually from wall of archenteron Coelom formation Schizocoely Enterocoely CNS nerve cords Ventral Dorsal Larval cilia Compound multiple per Single 1 per cell cell of coelomic cavities Variable Usually 3 pairs Examples Arthropods annelids Echinoderms chordate molluscs etc B True coela probably evolved twice once in the protostomes and one in the deuterostomes C Early development of atworms which lacks coela and pseudocoelmate animals suggest they may be protostomes as well a Coelom may have been lost in this forms b Pseudocoelom may result from retention of embryonic condition X Life cycles A Animals exhibit 2 basic life cycles a Indirect development 1 Free living larva is distinctly different from adult must undergo metamorphosis 2 Larva may be A Planktotrophic a Typically planktonic and feeding or B Lecithotrophic a Depend on large yolk for its nutrients b Direct development 1 Embryos are not freeliving but brooded or contained by parents or encapsulated in egg case 2 Emerge as juvenile that generally resemble the parents 3 Typical of most fresh water and terrestrial invertebrates B What are the advantages and disadvantages of various life cycle strategies a Indirect development of planktotrophic larvae favored when parents are benthic and sessile larvae can disperse to new habitats 1 Often associated with broadcast spawning of large numbers of eggs sperm 2 Common in tropical and coastal areas where conditions are more predictable 3 Typically tend to be quotrselectedquot b Indirect development of lecithotrophic larvae requires greater parental investment to produce larger yollq egg 1 Produce fewer young but offspring have higher survivorship 2 Prevalent in deep see species A Avoid risk of larvae traveling to surface to feed c Direct development involves large yollql costly eggs plus subsequent parental care 1 Often associated with mobile adults that can disperse A no larval dispersal needed 2 Typically found in quotkselectedquot species 3 Primary life cycle of terrestrial species A Gamete spawning delicate larvae not possible internal fertilization needed C Many insects have secondarily evolved indirect development in which protected zygotes encapsulated eggs develop into distinct larval form a Holometabolous development 1 Unlike marine species larva is not dispersal stage XI Parasite Life Cycles A Endosymbiotic parasite must be able to exploit environments outside of host since hosts eventually die a Dispersal usually involves releasing young outside of host b Young must then survive nd new host c Leads to complex life cycles De nitive primary host a Host inon which parasite reaches sexual maturity Intermediate host vector a Host inon which larval forms reside Finding new host is dif cult and mortality of larvae is usually high Compensate by having high reproductive rates as adults and having asexually reproducing larval stages PU WU Topic 4 Animal and Protozoan Structure and Function l Animal Requirements A Animals must meet basic requirements for life a b rhme LO LOCO m Obtain energy and nutrients 1 Acquire digest and metabolize food Eliminate waste products from digestion and metabolism 1 Eg NH3 Obtain 02 and eliminate C02 Distribute nutrients and gasses throughout body Structural support for their bodies Avoid being eaten Reproduce otion A Majority of animals and quotprotozoansquot exhibit mobility at some stage in life B Mobility required to locate food a Larger body sizes gt greater need for food gt more ef cient locomotion C Locomotor systems closely tied to supporting skeletal systems lll Viscosity and locomotion A Viscosity a Resistance of uids air H20 to owing 1 Results from friction turbulence and other uid dynamic effects B Air is much less viscous than water a easier to move through 1 Air provides less support A Tend to fall to ground a Friction with ground must be overcome lV Locomotion in water A In aquatic environments viscosity is more important B For protozoans and small animals viscosity is high relative to inertia and turbulence a Must work hard to overcome viscosity but encounter little turbulence b lnertia is essentially non existent 1 Start and stop instantly C For larger animals inertia and turbulence have much greater effect than viscosity a Friction has relatively less effect on larger animals but must overcome drag turbulence 1 Streamlined shape is important b High inertia means they get to speed slowly but can continue to coast forward after they stop actively swimming 1 Energy spent on overcoming inertia V Locomotion and Support A Types of locomotion a Amoeboid movement b Ciliary and Flagellar movement c Hydrostatic propulsion 1 Muscles acting against hydrostatic skeleton ex body B Amoeboid Movement a Used by several groups of protozoans b Used by certain cells within most animals c Involves formation of pseudopod 1 A temporary extension of cell A As cytoplasm ows into pseudopod the cell creeps in that direction B Mechanism not well understood C Cilia and Flagella a Cell with either occur in nearly every animal phylum and majority of protest phyla b Cilia and agella are extension of cytoplasm c Both have same internal structure and function in same way Vl Cilia and Flagella A lnternal structure composed of 9 pairs of microtubules with projecting dynein arms a Dynein arms cause microtubules to slide past one another thus bending the cilium or agellum Vll Cilia vs Flagella A Cilia a Shorter lt1 wavelength long b Generally in patches with large numbers c Movements highly coordinated B Flagella a Longer may be gt1 wavelength b Usually only a few present c May have hairlike projections increase area d Waves can start at bas or tip VlIICilia A Cilia alternate power and recovery stroke B Beat in coordinated wave pattern IX Flagella A Undulations can start at base push cell or at tip pull cell X Types of locomotion A Many smaller animals rely on cilia for locomotion a Eg rotifers atworms larvae B But most animals use muscles to provide locomotion C Muscles must act against some sort of skeleton a Or else animals will just shorten 1 Hydrostatic skeletons A Less rigid animal changes chape 2 Rigid Skeleton A Animal exes at speci c joints Xl Hydrostatic skeletons A uid lled compartment is surrounded by muscles Muscle pressure applied on one part uid to other parts Contraction of longitudinal muscle causes organism to shorten and thicken Contraction of circular muscles causes organism to get thinner and lengthen Combinations of muscle contraction and relaxation can produce variety of movements Dividing a hydrostatic skeleton up into a number of isolated compartments allows for greater range of movements a Eg segmented worms W009 Tn G Muscle contractions moving in wave pattern peristalsis can be used to move substances through a tube such as the gut or to move the organism through a tube burrowing Xll Rigid Skeletons A 110 Rigid skeletons prevent gross changes in body shape less exibility but a Allow for more precise movements b Allow for more rapid movements c Provide greater support for large bodies and is terrestrial environments d Provide better protection against predators Endoskeletons a Inside the body and usually derived from mesoderm Exoskeletons a Usually outside the body derived from ectoderm 1 Test A Any hard rigid externa covering Both types typically include both organic and inorganic components May have arisen inadvertently as a byproduct of waste mineral build up from certain metabolic processes Articulating skeletons a Have multiple parts that move relative to one another lnarticulate skeletons a Single rigid piece or fused components Chemical components of skeletons are varied but include a Calcite or calcium carbonate CaCO3 and other carbonates are very common b Calcium phosphate and collagen vertebrate c Silica Si02 1 Common mineral only in sand or glass 2 Chitin a polysaccharide combined with certain proteins XlllNutritional Modes A B XIV C Most animals and protozoans are heterotrophic Some protozoans are both heterotrophic and autotrophic a Eg euglena dino agellates Some animas have endosymbiotic algae esp diflagellates a Use carbohydrates produced by photosynthesis as food supplement or primary source of energy 1 Corals giant clams and some anemones hydroids s hydra sponges atworms sea slugs etc Obtaining Nutrients Protozoans and animals can obtain nutrients via extracellular or intracellular digestion a Extracellular Digestion 1 Larger molecules broken down outside of cell A Resulting small molecules transport directly across membrane a Diffusion or active transport B Typical of fungi and some funguslike protists b Intracellular Digestion 1 Larger molecules and food items eg other cells are taken into the cell and digested inside vacuoles A This is typical of most quotprototoansquot B Uptake of larger molecules and substance is via Phagocytosis a Inward pinching of membrane to form food vacuole often involves pseudopods XV Digestive Tracts A Most animals have an internal digestive tract gut into which food enters XVI XVII XVIII XIX A digestion takes place and nutrients are absorbed a Incomplete or blind gut 1 Material enters and exits via single opening A Cnidarians atworms b Complete gut 1 Separate mouth and anus so that food ows in one direction A Allows for regional specialization of digestive tract Feeding Strategies Herbivore a Feeds mostly on plants or algae 1 Grazers feed on plant tissue without consuming whole plant also applied to feeding on sessile animals Carnivore a Feeds mostly on other animals 1 Predation can refer to feeding on any other type of organism but usually used for carnivory Omnivore a Feeds extensively on both plant and animal matter Suspension Feeding Suspension Feeding a Trapping and ltering small food particles from surrounding water 1 Water ows past feeding structures food gets trapped and then carried to mouth 2 Typical food types include bacteria phytoplankton zooplankton and detritus Requires water ow a Water currents b Pumping water through feeding structure c Move feeding structures through water Food particles trapped using a Mucuscovered structures mucus trap 1 Particles stick to mucus and are moved to mouth b Tentacles or tube feet 1 Larger objects are grabbed c Finely branched bristles Deposit Feeding Deposit feeding a Obtain nutrients from sediments and soils 1 Direct deposit feeders consume large amounts of sediments and digest organic material and organisms 2 Selective deposit feeders preferentially select portions with greatest amount of organic matter living or detrious Herbivory Consumption of macroscopic plants sea weeds a Requires ability to bite ad chew through plant matter 1 Hard quotteethquot and strong muscles XX Carnivory A Feeding methods are usually complex and sophisticated XXI XXII XXIII a Steps involved in predation 1 Location of prey A Usually requires welldeveloped sense organs 2 Pursuit A Often but not always 3 Capture of prey 4 Handling prey 5 Ingestion of prey Types of predators Motile stalkers active pursuers a Actively pursue stalk or chase prey Sitandwait predators a Hide until prey wanders past them 1 May build special traps A Eg Spider webs Grazing Predators a Feed on sessile or slowmoving animals Special Feeding Types Substrate Feeders a Live in or on their food source and eat their way through 1 Eg leaf miners carrion feeders endoparasites Fluid feeders a Suck nutrientrich uids from a host 1 Plant sap blood nectar Excretion Elimination of metabolic wastes a C02 from cellular respiration 1 Involves structures used for 02 exchange b Nitrogen from amino acid breakdown 1 Produces ammonia A Ammonia NH3 toxic but soluble a Primary form of metabolic wastes for aquatic invertebrates b Easily diffuses out of body Nitrogen excretion a Terrestrial animals cannot afford to lose the water necessary to eliminate ammonia b Instead convert it to either 1 Urea A Rare among invertebrate 2 Uric acid A Least toxic but costs the most energy to produce excreted as semisolid paste a Land arthropods and snails XXIV Osmoregulation A Excretion of nitrogenous wastes usually closely linked to osmoregulation a Osmoregulation 1 Regulation of water and ion levels in body uids XXV A Most marine invertebrates are isotonic same total concentration of dissolve substance to sea water a This simpli es osmoregulation Freshwater animals are hypertonic much higher concentration of dissolved substances to their environment a Risk loss salts to environment b Problem of excessive water in ux Osmoconformers a Osmolarity of body uids varies with osmolarity of environment 1 Best suited for relatively stable marine environments but also in some brackish eg estuaries intertidal zone species Osmoregulators a Maintain constant internal osmolarity regardless of environment Stenohaline species a Have narrow tolerance limits for environmental salinities 1 Regardless of osmoregulator or osmoconformer Euryhaline species 1 Species can tolerate broad range of salinities A May be osmoregulators or osmoconformers a Typical of species in estuarine or intertidal habitats Excretory Structures