Animals

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  • Animals

    1. 1. Lecture 8: Animals
    2. 2. What is an animal?Multicellular eukaryotesChemoheterotrophs- digest food insidebodySexual reproductionMuscles and nerves
    3. 3. Animal AncestryColonial flagellate hypothesis Ancestor was colony of flagellates in a sphere > cells became specialized > infolding created two layers of cells Supported by fact that many tissues develop this way embryonically Supported by implication that radial symmetry preceeded bilateral symmetry Supported by choanoflagellates- closest protist relative of animals
    4. 4. Colonial Flagellate• This is an illustration of Proterospongia. The cells are embedded in a jelly- like matrix. Whether this is a colonial choanoflagellate or a very simple animal depends upon whom you ask.
    5. 5. Evolution Many kinds arose during Cambrian explosion, happened so fast the origin of many is murky DNA evidence points to the tree we currently use See pg. 312
    6. 6. Terms Used for ClassificationGerm layer: tissue layers found in embryos;develop into different tissue typesEndoderm: Innermost germ layer- gives riseto lining of digestive tract, etc.Ectoderm: Outermost germ layer- gives riseto nervous system and outer integumentMesoderm: Middle germ layer- gives rise tomany organs, muscle, connective tissue
    7. 7. Terms Used for ClassificationRadial symmetry: organized circularlyBilateral symmetry: left- rightsymmetry (like us)Cephalization: localization of brain andsensory organs
    8. 8. Terms Used for ClassificationProtosomes: the first embryonic openingbecomes the mouthDeuterosomes: the first embryonicopening becomes the anusCoelom: Body cavity where the organsare located
    9. 9. Terms Used for ClassificationAcoelomates: do not have a coelomPseudocoelomates: have a partial coelomCoelomates: have a true coelomSegmentation: repetition of body partsalong the length of the body
    10. 10. ClassificationAnimals are classified based on thecharacteristics we just listedWe will now examine different groups
    11. 11. SpongesPhylum PoripheraBase of evolutionary tree of animals - collar cells at poresare basically identical to choanoflagellatesCellular level organization Multicellular, but lack organized tissuesFilter feeders, can filter huge amounts of water per dayCan reproduce both sexually and asexually Asexually: budding Sexually: eggs and sperm released into central cavity
    12. 12. CnidariansPhylum Cnidaria, sea anemones andjellyfishHave radial symmetryHave two germ layers: ecto and endodermCapture prey with tentacles that havestinging cellsHave tissue level of organization
    13. 13. FlatwormsPhylum PlatyhelmenthesBilateral symmetryHave all 3 germ layersAcoelomatesHave cephalization- small brain, eyespots,chemosensitive organsCaptures food by wrapping it up and covering itin mucus, then tearing and sucking up
    14. 14. More flatwormsDigestive tract only has one openingHemaphrodites; sexual reproductionFree living are called planariansParasitic are tapeworms and flukes Have hooks and suckers on mouth to hold onto host tissues Can live for years
    15. 15. RoundwormsPhylum NematodaHave a body cavity- Pseudocoelomates, because notcompletely surrounded by mesodermComplete digestive tract- open on both endsNonsegmentedMany are free living and live in a variety of habitatsand eat a variety of foodMany parasites as well: roundworm, hookworm,Elephantiasis, Trichinosis
    16. 16. Hookworms and theAmerican SouthPeople in the South after the Civil War seen aslazyStudy of people and hygiene habitsTrees instead of latrines usedHookworms! Can travel up to 6’ after beingdeposited- were causing large infectionsJust digging a hole that was 6’ deep solved theproblem
    17. 17. MolluscsPhylum Mollusca, snails, octopuses, scallops, clams,nautilusesHave a coelom, proteosomesHave 3 parts: Visceral mass: contains organs Foot: used for locomotion Mantle: covers the visceral mass- may secrete exoskeleton to form shell Also may have a radula: like a toothy tongue
    18. 18. MolluscsThere are 3 types of molluscs:gastropods,cephalopods, bivalvesGastropods: Conchs, snails, nudibranchs Foot ventrally flattened, muscle contractions pass along the foot to move it Terrestrial snails use the mantle as a lung
    19. 19. MolluscsCephalopods: Octopus, Squid, Nautilus“Head-footed” - the foot is the tentacles aroundthe head Have a beak- use tentacles to seize prey and beak and radula to tear it upComplex nervous and sensory systemsCan move quickly by jetting water out of themantle
    20. 20. MolluscsBivalves: Clams, oysters, scallops,musselsShell has two parts, foot projectsventrally from shellFilter feeders, water enters through asiphon and food adheres to the gills; foodthen moved to the mouth by cillia
    21. 21. AnnelidsPhylum Annelida, wormsHas coelom and are segmented, proteosomesCoelom is filled with fluid; it is divided by septa which makeit more rigid- facilitates movementComplete digestive tract; have crop, gizzard, intestine,accessory glands, etc.Circulatory system to carry bloodHave a brainRemove waste by nephridia- ducts that carry waste to poresin the skin
    22. 22. AnnelidsAgain, 3 main groups: Polychaetes, oligochaetes,leechesDivided by how many setae (=bristles) on eachbody segment- these bristles anchor the worm andhelp it movePolychaetes: have many setae, are predatoryOligochaetes: Have a few- decomposers that live insoil: earthwormsleeches: No setae - have suckers to attach to food
    23. 23. Polychaetes
    24. 24. Oligochaetes Giant earthworm!
    25. 25. Leeches
    26. 26. ArthropodsPhylum Arthropoda: Over one million species! Insects, crustaceans,arachnidsCoelom, segmented, proteosomesHave six characteristics: 1. Jointed appendages- hollow tubes moved by muscles 2. Exoskeleton- made of chitin, rigid and jointed 3. Segmentation- Some repeated, some fused in to head, abdomen and thorax only 4. Well-developed nervous system- Brain and ventral nerve cord, eyes, many other senses 5. Variety of respiratory organs- Gills, book lungs, or trachae, also open circulatory system 6. Metamorphosis- reduces competition of various age classes
    27. 27. ArthropodsCrustaceans: lobsters, crabs, barnacles, shrimpMostly marine, but also freshwater (crayfish) andterrestrial (pillbugs)Head has 5 pairs of appendages: antennae,antennules- sensory, 3 mouthpartsThorax has 5 pairs of walking legs, first is the clawAbdomen has swimmerets- like small paddles andtailHugely important in food chain - krill, etc
    28. 28. ArthropodsArachnids: Spiders, scorpions, ticks, mites,harvestmenSpiders- Have cephalothorax and abdomen, killprey with venom, use silkScorpions- oldest terrestrial arthropods, nocturnalTicks- are parasiticHorseshoe crabs- grouped with arachnids, but veryunique in many ways
    29. 29. ArthropodsInsects: Largest group of animalsHave head, thorax, and abdomenCan have wings- one or two pairsLive in huge variety of environmentsand eat huge variety of food
    30. 30. EchinodermsPhylum Echinodermata: sea stars, sea urchins,sea cucumbersDeuterosomes; bilaterally sym. as larvae butradially sym. as adultNo head, brain or segmentationNo advanced nervous or circulatory systemThese seem so primitive, why discuss them here? They are closely related to Chordates!
    31. 31. ChordatesPhylum Chordata: Fish, amphibians, reptiles, mammalsCoelom, deuterosomes, segmented4 characteristics: 1. Notochord: Dorsal supporting rod 2. Dorsal tubular nerve cord: contains a tube filled with fluid 3. Pharyngeal pouches: in many, seen only in the embryo- become gills in larval amphibians and fish, in humans become auditory tubes, tonsils, thymus and parathyroids 4. Tail: A postanal tail
    32. 32. ChordatesMost chordates are vertebrates, in which thenotochord has been replaced by the vertebrae(backbones) which protect the nerve cord(spinal cord)However, there are a few chordates that areinvertebrates: the Tunicates and theLancelets Marine organisms- sea squirts
    33. 33. VertebratesSeries of evolutionary advances used tocharacterize the verts-See evolutionary tree on pg. 325 for alist of these advances
    34. 34. Here, Fishy, Fishy, FishyJawless fish: the first vertebrates No jaws- they are cylindrical, do not have paired fins- they undulate through the water Two groups today: hagfish and lampreys- they have a circular mouth Jaws are thought to have evolved from the first pair of gill arches
    35. 35. Fish- Sharks!Sharks, rays and skates areCartilaginous fish, they have a skeletonmade of cartilage instead of bonesGreat predators: they can sense electricalcurrents, pressure changes, and have agreat sense of smell
    36. 36. FISHBony fish: most numerous and diverse, two types: Ray-finned: Like trout, perch, etc., very diverse group Have swim bladder to control buoyancy, skin covered by bony scales Respire by having water flow through the mouth over the gills Single circuit circulatory system- Heart pumps blood to gills and then directly to body
    37. 37. FISHLobe-finned: Have fleshy fins Ancestors of amphibians Most have lung- so can breathe air
    38. 38. AmphibiansFrogs, toads, salamanders, ceciliansHave jointed limbs so can walk on land, alsoeyelids to keep eye moist, ears, larynx, larger brainNeed water to reproduceMost have lungs, also respire through skin3 chambered heart, blood from body and lungs issent out to body and lungsMost show metamorphosis
    39. 39. ReptilesDinos, snakes, lizards, turtles, crocs, birdsBody covered in scales3 chambered heartCan reproduce on land without water- amnioteegg- provides embryo with food, water andoxygen, protects it from dryingExcept for birds (and some dinos?) areectothermic- body temp controlled by environment
    40. 40. BirdsReally, birds are reptiles- feathers are justmodified scalesHowever, some differences- egg is hard instead ofleathery, endothermicFlying- many many adaptations to allow flight Hollow bones, front legs are wings4 chambered heartWell-developed brains, good vision
    41. 41. MammalsMammals have mammary glands that produce milk foroffspring, and hairFirst mammals were monotremes and marsupials-monotremes lay eggs, marsupials have pouchPlacental mammals evolved later, but are most diversegroup today Embryo develops inside uterus, maternal blood provides nutrients and oxygen It is the same membranes that do this in the egg that do this in the uterus- what the afterbirth isMammals have big brains and are very active
    42. 42. HumansHumans are Primates- includesmonkeys, apes and humans This does not mean monkeys apes humans Rather, it means that all primates share a common ancestor
    43. 43. PrimatesPrimates primarily adapted to arboreal life-limbs are mobile, have 5 digits, haveopposable thumb and frequently big toeTrend is towards larger and more complexbrainHumans most closely related to Africanapes- chimps, gorillas last common ancestor ~ 7 MYA
    44. 44. HominidsHumans, apes and human-likeancestors are the hominids Can stand erect and walk on two feetWe will discuss some human ancestors
    45. 45. HominidsEarly fossils, around 7 MYA, the timeof the ape- hominid split: Sahelanthropus tchadensis: opening for spine suggests bipedalism, smaller caninesArdipithicus ramidus: 4 MYA, teeth lessapelike, only fragments found so far
    46. 46. HominidsAustralopithecines- group of hominidsthat diversified in Africa about 4 MYA A. afarensis- Lucy- stood upright, bipedal, but small brain (3.18 MYA) One of these species may be the direct ancestor of humans
    47. 47. HominidsHomo habilis- ~2 MYA, larger brain, usedtools, smaller teeth skulls seem to indicate that the speech centers of the brain were enlarged- could probably communicate and co-operate to gather food Co-operation may have led to H. habilis out-competing the Australopithecines
    48. 48. HominidsHomo erectus- 1.9- 0.3 MYA, fossils found inAfrica, but also Asia and Europe Probably several species included in this group Still larger skulls, flatter face, taller Fossils found in many sites- were able to travel long distances First to use fire, made advanced tools
    49. 49. HominidsHomo neandertalensis- 200,000 YO, found inGermany Short, stocky, heavy build, prominent brow Culturally advanced- lived in caves, may have made houses, made many tools Hunted large animals Buried their dead
    50. 50. HominidsCro-Magnons- oldest fossils to bedesignated as our species, Homo sapiens Fossils from France Compound tools, great hunters Had language, lived in groups Had art- cave drawings
    51. 51. HominidsHomo sapiens- how did first humans evolve? We’re not sure- there are two theories: Out of Africa: H. sapiens evolved in Africa, migrated to Europe and Asia and replaced hominids already there Multiregional continuity hypothesis: evolved independently in several regions In the MCH- different regions would be genetically dissimilar, OOA would be more genetically alike Thus far it seems that the OOA is the most supported

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