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Protostomes include:
phyla annelida, mollusca, arthropoda
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Deuterostomes include:
phyla echinodermata, chordata
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Both protostomes and deuterostomes share this body plan:
- eucoelomate
- triploblastic
- bilaterally symmetrical
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Protostome
Fate of the blastopore
becomes the mouth
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Deuterostome
Fate of the blastopore
becomes the anus
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Protostome
Division cleavage
spiral cleavage
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Deuterostome
Division cleavage
radial cleavage
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Protostome
Cell differentiation cleavage
- determinate cleavage - the developmental fate of each cell determined early on
- if a zygote is split, it will become two halves of an embryo; the blastomeres will give rise to two different parts of the body
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Deuterostome
Cell differentiation cleavage
- indeterminate cleavage - fates of the blastomeres do not become fixed until later on in development
- can create identical twins from one fertilized egg
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Protostome
Coelom formation
- schizocoelom
- solid masses of mesoderm form near the blastopore; these masses split open, forming a fluid-filled body cavity
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Deuterostome
Coelom formation
- enterocoelom
- masses of mesodermal cells bud off of the wall of the archenteron to form the enterocoelom
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Phylum Annelida
body plan characteristics
- triploblastic, eucoelomate, bilaterally symmetrical
- cephalization
- protostome
- segmentation; metamerism
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metamerism
- serial repetition of compartments
- metameres - the identical body compartments, along with their appendages
- an important evolutionary attribute becasue it allowed specialization of body parts
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digestive systems (annelids)
- extracellular digestion
- typhlosole - ridgelike fold of the side of the intestine into the lumen; increases surface area
- chloragogue cells function in storing carbohydrates and lipids, and maybe excretion
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osmoregulatory/excretory systems (annelids)
- posses metanephridia - tubules that open at two ends (one to outside, one to coelom)
- filtrate is collected via the nephrostome and eliminated outside via the nephridiophore
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protonephridia vs. metanephridia
- protonephridia - no opening on the inside of the body; flame cells in the protonephridium causes the filtrate to move outward; essentially osmoregulatory organs (flatworms, rotifers, roundworms)
- metanephridia - larger, more complex structures that often function in both excretion and osmoregulation; 2 openings
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circulatory and respiratory systems (annelids)
- closed circulatory system; allow for more efficient and rapid transport of blood
- leeches are exception with an open circulatory system - blood is found in blood-filled sinuses or cavities
- gas exchange is through diffusion across body wall
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nervous systems (annelids)
- monoecious or dioecious
- fertilization is external, occurring in the water column or inside a cocoon
- larvae of marine species are called trochophores, which metamorphose into adults
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muscular systems (annelids)
circular and longitudinal bands of muscle present
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integumentary and skeletal systems (annelids)
- epidermis produces the cuticle
- muscles are able to affect locomotion and digestion by contracting against the fluid filled coelom (acts as hydrostatic skeleton)
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parapodium
- serve as locomotion and breathing apparatuses in annelids
- acicula - connected to body wall muscles; help the parapodia move
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Phylum Mollusca
body plan characteristics
- triploblastic
- eucoelomate
- bilaterally symmetrical
- cephalization (with exception of bivalves)
- protostomes
- 4 distinct body parts present - foot, mantle, shell, visceral mass
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4 distinct body parts in molluscs
- muscular foot
- calcareous shell (secreted by mantle)
- mantle - part of the skin, adapted to prevent excessive water loss
- visceral mass - contains the digestive and reproductive systems
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integumentary and skeletal systems (molluscs)
- calcareous shell
- a ciliated epidermis creates a thin cuticle (composed of the protein conchin)
- three layers of smooth muscle - outer circular layer, diagonal layer, inner longitudinal layer
- hydrostatic skeleton
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muscular systems and locomotion (molluscs)
- large muscular foot
- glide through a layer of mucus (produced by the epidermis) by ciliary action
- muscular contractions that sweep along the bottom of the foot
- cephalopods and some bivalves can use jet propulsion by expelling water out of the mantle cavity
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digestive systems (molluscs)
- extracellular digestion
- complete tract
- radiula - chitinous ribbon of teeth that scrapes food off of substrates
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osmoregulatory/excretory systems (molluscs)
- large metanephridia (like the annelids)
- eliminate mostly ammonia; some land snails can convert ammonia to uric acid
- osmoconformers or osmoregulators
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osmoconformer
- body fluids are iso-osmotic to seawater
- includes some marine molluscs and most previous observed phyla
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osmoregulators
- body fluids remain hyperosmotic compared to their environments
- ability to regulate many ions
- includes many aquatic molluscs and land snails
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circulatory systems (molluscs)
- open circulatory system with a large hemocoel (blood filled cavity)
- cephalopods - closed circulatory system with one systemic heart and auxiliary branchial hearts
- includes forms of hemoglobin
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nervous systems (molluscs)
- brain and one or more ventral nerve cords
- sensory receptors (light, chemical, current) are foundi n various places of the body
- unidirectional movement of action potentials (like annelids, flatworms)
- advancements in nervous system sturcutre and function allow annelids and molluscs to be capable of more complex behaviors, compared to flatworms and cnidarians
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respiratory systems (molluscs)
- gills for gas exchange
- gastropods may have secondarily evolved a lung
- respiratory pigments (hemoglobin) present
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reproductive systems (molluscs)
- monoecious or dioecious, internal or external fertilization, depending on species
- may have free-swimming trochophore larva, which develops into other larval stages before settling and metamorphosing into adults
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immune systems (molluscs)
- exhibit a non-specific immunity against potential invading microorganisms
- integument is primary barrier to pathogens
- internal wandering amebocytes that phagocytize foreign cells and particles
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gas exchange (molluscs)
- bivalves - walls (lamellae) have a series of ridges (gill filaments); water flows past the gill filaments due to the activity of the numverous cilia along the filaments
- pulmonate gastropods - mantle makes an interior fold called the lung
- gas exchange also occurs across the skin, esp on the mantle
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Phylum Arthropoda
body plan characteristics
- tirploblastic
- eucoelomate; coelom is reduced to a body cavity called the hemocoel
- bilaterally symmetrical
- cephalization
- protostomes
- segmented; segments form tagmata
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tagmata
- segments that are fused together
- regional formation of body parts that are specialized and highly adaptive; tagmata are involved in locomotion (thorax), sensation and feeding (head), or visceral activities of reproduction, excretion, and digestion (abdomen)
- arachnids (chelicerata) - two tagmata; cephalothorax and abdomen
- crustaceans - two tagmata; cephalothorax and abdomen
- uniramians include centipedes, millipedes, insects
- centipedes, millipeds - two tagmata; head and body
- insects - three tagmata; head, thorax, abdomen
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muscular systems (arthropods)
- jointed appendages that are made of segments called podomeres
- have specialized functions
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integumentary and skeletal systems (arthropods)
- exoskeleton composed of the polysaccharide chitin
- protects the animal against disease, predators, dessication, provides sites for muscle attachment
- periotic ecdyses (molts) allows the animal to grow larger
- produced by the epidermis
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digestive systems (arthropods)
- extracellular digestion occurs within the lumen of the gut
- complete tract
- mechanical digestion, storage, chemical digestion, and nutrient absorption occur in sequential sections
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osmoregulatory/excretory systems (arthropods)
- well-developed
- either green antennal glands or Malpighian tubes
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green (antennal) glands
- crayfish
- type of neprhidium that excretes large amounts of ammonia and water
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Malpighian tubes
- terrestrial arthropods
- dump nitrogenous wastes and water into the gut; reabsorb water
- uric acid is crystalized and eliminated
- not a type of nephridium; it is closed on one end
- because of the relative insolubility and savings from decreasing water loss, arthorpods have much more successfully colonized land
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circulatory and respiratory systems (arthropods)
- open circulatory system with tubular heart and blood vessels; hemolymph
- gills (aquatic insects and crustaceans)
- trachea (most insects) - series of tubes that run throughout the body; oxygen diffuses
- book lungs (spiders)
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nervous systems (arthopods)
- anterior brain
- paired central nerve cord
- lateral nerve for appendages, etc.
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reproductive systems (arthropods)
- dioecious; internal fertilization
- metamorphosis is hallmark
- in many insect species, the larval stages are adpated for a different habitat than the adult
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immune systems (arthropods)
- like annelids and molluscs
- non-specific immunity consisting of exoskeleton and wandering amebocytes
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gradual metamorphosis
- egg - nymph - adult
- nymphs are similar to adults
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complete metamorphosis
- egg - larvae - pupae - adult
- dramatic change in body plan occurs
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Phylum Echinodermata
body plan characteristics
- deuterostome
- all marine
- sessile
- radially symmetrical as adults, bilaterally symmetrical as larvae
- triploblastic
- no segmentation
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integumentary systems (echinoderms)
- dermal endoskeleton made of a series of calcareous plates (ossicles) and spines
- some classes have pincer-like pedicellariae on their outer surface that prevent small organisms from from settling on the body surface (asteroidea, holothuroidea, crinoidea)
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skeletal systems (echinoderms)
- a part of the coelom forms a series of water-filled canals and cavities collectively called the water vascular system
- acts as a hydrostatic skeleton
- helps move tube feet used in prety capture and locomotion
- brittle stars do not have suckers on their tube feet
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digestive systems (echinoderms)
- extracellular digestion
- complete tract (except for brittle stars, lost their intestines and anus)
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excretory, respiratory, circulatory systems (echinoderms)
- not extensive
- metabolic wastes (primarily ammonia) diffuse directly across the body wall
- finter-like extensions off the epidermis called dermal branchiae serve as sites for respiratory gas exchange
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nervous systems (echinoderms)
- do not exhibit cephalization
- nerve net (analogous to cnidarians)
- sensory systems are reduced
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reproductive systems (echinoderms)
- dioecious
- external fertilization
- larvae are planktonic organisms that feed inthe open waters
- most echinoderm larvae metamorphose into sessile adults
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immune systems (echinoderms)
possess wandering phagocytic cells
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