Major Divisions of Life - FSU Biologybsc2011l/sp_05_doc/annelida_2... · 2005. 2. 15. · Annelida...
Transcript of Major Divisions of Life - FSU Biologybsc2011l/sp_05_doc/annelida_2... · 2005. 2. 15. · Annelida...
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Annelida
Mollusc
aArth
ropoda
Echinoderm
ataChord
ata
Platyh
elmint
hes
Nemato
da
acoe
lom
ate
pseu
doco
elom
ates
eucoelomates
Rotifer
a
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Annelida
Mollusc
aArth
ropoda
Echinoderm
ataChord
ata
Platyh
elmint
hes
Nemato
da
acoe
lom
ates
pseu
doco
elom
ates
eucoelomates
Rotifer
a
protostomes deuterostomes
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blastopore archenteron(primitive gut)
Future anus
mouth
Protostome: blastopore becomes the mouth and the anus forms secondarily
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blastopore archenteron(primitive gut)
Future mouth
anus
Deuterostome: blastopore becomes the anus and the mouth forms secondarily
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Protostome: spiral Cleavage
2 cells 4 cells 8 cells
Blastomeres divide at an oblique angle to one another, so that each lies in the furrow created by the cells beneath them
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Deuterostome: Radial Cleavage
2 cells 4 cells 8 cells
Blastomeres divide in a symmetrical fashion, producing layers of cells directly on top of one another
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Protostome: mosaic Development
4-cell stage
one blastomere is removed
development is arrested
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Deuterostome: regulative Development
4-cell stage
One blastomere is removed
Development continues
each blastomere is capable of regulating its development even when separated from the others
Development continues
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Protosome coelom formation: schizocoely
ectoderm
mesodermendoderm coelom forms from a
split in the mesoderm
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early mesodermal
pouchectoderm
mesodermendoderm coelom forms from an
outpocketing of the archenteron
Deuterostome coelom formation: enterocoely
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Protostome vs Deuterostome
Protostome
• blastopore becomes the mouth
• spiral / determinate cleavage
• mosaic development
• schizocoely
(Annelida, Arthropoda, Mollusca, Bryozoa*)
Deuterostome
• blastopore becomes the anus
• radial / indeterminate cleavage
• regulative development
• enterocoely
(Echinodermata, Chordata)
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Phylum Annelidathe segmented worms
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Annelida Characteristics
Triploblastic
Cephalization
Bilateral Symmetry
Organ level of organization
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Annelida CharacteristicsEucoelomate
Have a “true” body cavity that is completely surrounded by mesoderm
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endodermendoderm
gut
gut gut
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Annelid Characteristicsthe coelom
ectoderm• is a closed, fluid filled cavity that surrounds the gut• the fluid within acts as a circulatory system• mesodermal membranes (mesenteries) suspend organs in the coelom
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Annelida CharacteristicsProtostome development
• blastopore becomes the mouth• spiral / determinate cleavage• mosaic development• schizocoely
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Annelida Characteristics
metameres
pygidium
prostomium
Body Plan
Metamerism:The body is made up of serially repeating, coordinated segments called metameres that are separated from one another by septa.
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septa
Each metamerecontains sets of repeating organs (e.g. gut, blood vessels, nerve cord, excretory organs)
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How areproglottids different from true metameres?
1. Proglottids are not coordinated.
2. Proglottids only contain reproductive organs.
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Annelid Characteristics
• Free living and parasitic species
Feeding and Digestion
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Annelid Characteristics
• complete• regional specialization
Digestive System
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mouth esophagus pharynx cropgizzard
intestine
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Annelida Characteristics
Skeletal System
• fluid in coelom acts as a hydrostatic skeleton
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Annelida CharacteristicsLocomotion
• both longitudinal and circular muscles
• most have setae (chitonous bristles secreted by the epidermis) that aid in locomotion and burrowing
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setae
muscles
epidermis
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• 2 cerebral ganglia• a ventral nerve cord with 2 ganglia per metamere.
• In some species, sensory organs such as eyes, palps, and tentacles have arisen
Annelida CharacteristicsNervous system
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mouthventral nerve cord
cerebral ganglion
segmental nerve
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Annelid Characteristics
Gas exchange
• mainly by diffusion• Some Annelids have specialized structures for gas exchange (e.g. parapodia, gills)
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Annelid Characteristics
Circulatory System• closed circulatory system composed of blood vessels (some of which are contractile and act as “hearts”)• some circulation is also accomplished by the coelomic fluid
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heartssubneuralblood vessel
ventral blood vessel
dorsal blood vessel
subintestinalblood vessel subesophageal
blood vessel
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Annelid Characteristics
• excretion is accomplished by organs called nephridia (singular nephridium)•there are usually 2 nephridia per metamere
Excretion/ osmoregulation
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nephrostomenephridiopores
bladder
tubules and capillaries
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uric acidureaNH3
+
salts
salts
proteinK+, Na+, Cl-water
protein, water, urea, NH3+, Cl-
In nephrostome(from coelomicfluid)
narrow tube
middle tube
wide tube
bladder
water, urea, uric acid, NH3
+, Cl- K+, Na+, (out nephridiopore)
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Annelid Characteristics
• sexual: monoecious or dioecious•Most species have a trochophore larva
Reproduction
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Phylum Annelida
Class PolychaetaClass OligochaetaClass Hirudinea
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Class Polychaeta
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Class Polychaeta
• all marine • this class contains 2/3 of all known Annelids (approx. 10, 000 species)• have a well developed head with specialized sense organs
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Class Polychaeta
• have many setae (chitonous bristles secreted by the epidermis)
(Poly = many, chaeta= setae)
• these setae are arranged in bundles on paddle-like appendages called parapodia
setae
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Class Polychaeta
The parapodia function in gas exchange, locomotion, and feeding.
notopodium
neurodium
aciculamusclessetae
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capillaries
Lateral blood vessels
parapodium
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Class Polychaeta
Tagmatization (tagmosis)• the fusion and specialization of formerly metameric segments
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Class Polychaeta
Many are filter-feeders with specialized structures
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Class Polychaeta
Many are predatory with specialized structures
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Class Polychaeta
Many construct their own homes out of CaCO3 or sand debris and mucous
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Class Polychaeta
Reproduction• usually dioecious• no permanent sex organs; gametes are shed into coelom• fertilization is usually external• indirect development trocophore larvae
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Class PolychaetaEpitoky
epitoke
atoke
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Ecology• Polychaetes often have effective defense strategies:
• some have tubes to hide in • some have vicious jaws• some have modified “stinging” setae
a fireworm
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Ecology
• Some Polychaetes have a mutualistic relationship with their host
• for example, many scalewormsare found near, or in the mouth, of brittlestars, starfish, and sea urchins. • The scaleworm eats its host’s leftovers and with its vicious jaws, it will attack any predator trying to eat it’s host.
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Class Oligochaeta
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Class Oligochaeta
• terrestrial, freshwater and marine•approx 2, 000 species• have few setae (Oligo = few, chaeta = setae)• usually feed on detritus
(decaying organic matter)
• have specialized digestive system to obtain the maximum amount of nutrients out of the detritus (e.g. typhlosole, gizzard, crop…)
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Class Oligochaeta
typhlosole
gut
typhlosole-• infolding of the dorsal side of the intestine• increases surface area for absorption of nutrients
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Class OligochaetaLocomotion
Circular muscle contraction
Longitudinal muscle contraction
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Class OligochaetaReproduction
• usually monoecious• cross-fertilize by
exchanging sperm
clitellum
testis
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Ecology
• Earthworms are essential soil aerators• If all the material ever moved through earthworms was piled up, the heap would rise 30miles , more than 5 times the height of Mount Everest!!• Worm Grunting:
stob
A saw or leaf spring of a pick-up
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Class Hirudinea
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Class Hirudinea
• usually freshwater but there are some marine and terrestrial species• no septa between metameres• no setae• have 2 suckers
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Class Hirudinea
• have an extendable proboscis for feeding
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Class Hirudinea• usually have a fixed number of segments (34)
• each metamere consists of several annuli (think accordion)
1 metamere
annuli
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Class HirudineaLocomotion
Lack septa between metameres, so they are incapable of moving like Oligochaetes.
Instead, they use their anterior and posterior suckers to move.
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Class HirudineaReproduction
• usually monoecious• cross-fertilize by
exchanging sperm
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Ecology• Although some leeches are parasitic blood suckers (can be temporary or permanent), many are predators.