Bilaterians (Triploblastic): radially symmetry and bilateral symmetry- Protostomes: develop moth first from the blastopore.1. Arrow worm- Embryologist: deuterostomes: they quickly diverged from lophotrochozoans.- Molecular biologist: protostomes: genetic information Mouth second: deuterostomic traits -> symplesiomorphies: ancestral traits Mouth first: protostomic traits -> Synapomorphy: derived traits but not inherited from a basal common ancestor.2. LophotrochozoansA. Bryozoans and entoprocts- look like choanoflagellates- colonial animal- share nutrients on the colony- usually sexual reproduction- costal area contains amazing density of this organism.B. Platyhelminthes (flatworms)- acoelomates: thick band of cilia.- Flat: lack organs transporting oxygen through body. Surface area contacting the air should be large.- Self-fertilize: hermaphroditic- Can regenerate- used to consider the most basal bilaterians, but DNA indicates it is more derived than we consider.- First cephalized group: true head (actual eye spot): sensory organs.- Has only one opening (gut): can’t eat, digest, and excrete simultaneously.- Absorb food through their body wall.C. Rotifers - Pseudocoelomates- Similar appearance with flat worms- Incredible tiny creature- Complex body, Very well-developed organ, Mouth, anus -> gut- Rotifer corona: organ: circle of cilia, get sweet food into the rotifer- Rotifer named for their locomotion: they propel themselves to waterby beating their cilia. When the cilia are moving in unison, they resemble spoke radiating from a wheel. So they typically spin. - Only water living, but some are dormant and dried: when they get wet from rain, they reactivate. They repeat this process.D. Nemerteans (ribbon worms)- similar to flatworms- acoelomate- complete digestive system with mouth and anus, and circulatory system.- Small species: move by geatin gtheir cilia- Larger species: waving muscle contraction - Proboscis- long feeding appendage inside their body.- Almost entire length of their body- Sharp stylet: paralyzing prey.E. Annelids (segmented worms)- 1st coelomates - Segmentation: repeated unit -> specialization -> different function: reproduction, digestion, excretion, feeding, respiration, locomotion- Segment is divided by septa like fungal hyphae.- Annelids segments are stacks of hollowed rings: each of the rings is organ for excretion or locomotion. - Coelom: hydrostatic skeleton, however because of extra muscle in their body cavity, each segment can expand and contract independently. It allows far more complex and movement. - Anterior segments specialize sensory organs. Some of them can be sensitive to light.- Cerebral ganglia-> brain- Ex) Earthworm (hairless): underground: loss eyes but highly developed sensory system.- Ex) Leeches (hairless): sucking blood, medical usage (secrete anti-coagulant)- Ex) Polychaetes (many hair): - Marine- Active predators- One or more pairs of eyes- One or more pairs of tentacles: Filter food from surrounding water.- May be paraphyletic.F. Mollusks(1) Mollusks body plan- Visceral mass hold organ cluster- Foot: locomotion/ attachment, excrete mucus- Mantle: - Thicken sheet of skin of the dorsal part of body.- secretes shell: protective structure: cover the organ.- covers respiratory organ.(2) Pronounce head: highly level of cephalization, but bivalves have no head or reduced head. Chiton has distinct mouth part at anterior end. (3) Radula- mouth part: microscopic teeth- used to gather food- Bivalves don’t have radula.(4) Mollusk reproduction- Distinguished sex, some are hermaphroditic- Cross-fertilization- Some sea slugs change their sexes- Mostly external fertilization (except gastropods: internal prevent body dry out)(5) Polyplacophora (Chitons)- Marine mollusks that have small oval bodies with eight overlapping dorsal plates: dorsal plates homoplasious to pillbugs.- Herbivorous- Live in shallow water- Most external fertilization and few internal gestation (internal development of embryo)(6) Gastropods- Most terrestrial gastropods use internal fertilization: avoid desiccation- Generally have shells (except slug and nudibranch)- Mostly hermaphroditic- Tentacles on their heads: often have eyes on the tip. - Nudibranch is active predator: have mechanism to turn poison into defense mechanism. Bright color: warning predator that it is not good to eat.(7) Bivalves- Marine/ freshwater- Two lateral shells- Mostly hermaphroditic- Filter feeders- Incurrent siphon: inhale- Excurrent siphon: water - No distinct heads or radula- Foot: aheading to the surface, speadly digging dirt.- External fertilization- Free-swimming larvae- Ex) Scallops, clam, oysters, mussels.(8) Cephalopods- Active predators- Foot has separated arm or tentacles.- Ex) Cuttlefish: 10 arms (8 arms + 2 tentacles)- Ex) Octopus: 8arms- Ex) Nautilus: 80~90 tentacles- Tentacles bite the prey in their strong beaks pull the prey items into their mouth with sharp radula.- Lost their shell but can change color: camouflage and give messageto con-specifics (same species)- Modify their excurrent siphon to control exactly how much water they are storing in their mantle -> jet propulsion- Unique brain, highly develop nervous system, very complex eyes ->Highly intelligent 3. Ecdysozoan: grow by molting; shedding an old skin (exoskeleton)A. Nematodes (roundworms)- Pseudocoelomates- Sister taxa of horsehair worms- Marine, freshwater, plant, animal (hook and pinworm)- Parasite: can be predators -> Specializes on sperm whale placenta.- Hermaphroditic- Molt: covered by thick cuticle-like shell: shed 4 times in their lifetime.- Muscles attached to exoskeleton and internal hydrostatic skeleton.- Ex) Caenorhabditis elegans- Eutely: C. elegans has eutley.o Fixed number of cells: 959 -> model organisms: species that is extensively studied to understand particular biological phenomena. o TransparentB. Water bear (Tardigrades)- Live in sand or water- Can stay dormant in dry season for long period.C. Velvet worms (Onychophorans)- Terrestrial and closely related to arthropods - Soft, segmented & unjointed body- Molt- Cuticle that contains chitins- Internal fertilization- The common ancestor to the arthropods probably looks like velvet worms because it use internal fertilization/ internal gestation of large yolky eggs in order to adjust to be terrestrial.D. Arthropods- Jointed appendages: homopleisious to out arms, because there are many species between jointed insects and us that do not have jointed. It
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