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Animal diversity 2 - Animalswithout a coelomKey concepts• Simple animals may be
evolutionarily successful, havediverse life styles and behavior!
• Basic biology ofPorifera/ Cnidaria/Platyhelminthes/ Nematoda
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Mapping body plan characterson the tree
PORIFERA
CNIDARIAPLATYHELM
INTHESNEM
ATODA
PROTOSTOMESDEUTEROSTOMESARTHROPODA
ANNELIDA
MOLLUSCA
ECHINODERMATA
CHORDATA
PROTISTAMULTICELLULARITYEXTRACELLULAR DIGESTION
TISSUES
RADIAL SYMM
ETRY
BILATERAL SYMMETRY
MOUTH AND ANUS
MO
UTH AND ANUS TRUE COELOM
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Today: phyla without a true coelom
PORIFERA
CNIDARIAPLATYHELM
INTHESNEM
ATODA
PROTOSTOMESDEUTEROSTOMESARTHROPODA
ANNELIDA
MOLLUSCA
ECHINODERMATA
CHORDATA
PROTISTAMULTICELLULARITYEXTRACELLULAR DIGESTION
TISSUES
RADIAL SYMM
ETRY
BILATERAL SYMMETRY
MOUTH AND ANUS
MO
UTH AND ANUS TRUE COELOM
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Diversity of Sponges
A. Body plan -cells inextracellularmatrix, tubestructurewith flow ofwaterbringingfood to cells
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B. FeedingIf choanocytes specialized forfeeding, how are other cell typesnourished?
via another cell type- amoeboid cellsthat movethroughout thesponge, collectingand furtherdigesting materialfrom choanocytes,then passing it onto other cells...
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Diversity of SpongesC. ReproductionAsexual - branches may ‘pinch’ off and
regenerateSexual - most are hermaphroditesHermaphrodite - single individual produces
both male and female gametes
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Diversity of SpongesSperm are produced
from modifiedchoanocytes, releasedinto the environment
A ‘smoking sponge’releasing sperm
Choanocytes of othersponges ‘capturesperm’ in intracellularcapsules, thentransform intomigrating amoeboidcells, carry sperm to anegg! 7
Diversity of Sponges
The zygote (fertilizedegg) givesrise to swimminglarva -with choanocytes onoutside formovement
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Diversity of SpongesC. ReproductionLarva eventually settles, gives rise to
mature sponge
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Diversity of CnidariaTwo basic body formsThe polyp and the medusa - a
sedentary and mobile form
Polyp Medusa
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Many cnidarians have both forms in theirlife cycle, in others, one formpredominates
Which form predominates in jellyfish? Insea anenomes? In coral?
Polyp Medusa
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Diversity of CnidariaFeedingAdaptations for feeding and defense
- nematocysts - organelles thatfunction like miniature harpoons
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NematocystsTrigger senses ‘foreign’ chemical profile
a trigger
b ‘harpoon’
‘Harpoon’ released - can pierce a crab shellReleases toxin - some specieshave toxins fatal to humans
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Diversity of CnidariaWhat do cnidarians use their
nematocysts for?Capturing preyDefense against predatorsDefending territories (video
segment)
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Diversity of Cnidaria:Corals inparticular…Corals - polyp-form cnidarians, live in large
colonies, and secrete calcium carbonate
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Corals in particular…Corals - polyp-form cnidarians, live in
large colonies, and secrete calciumcarbonate
When old polyps die, new ones build ontop
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Diversity of CnidariaA coral reef is millions of coral
skeletons with living ones on theperiphery
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Coral polypswithzooxanthellae
Corals in particularWhere are the autotrophs in the coral reef
community? Corals live in shallow, clear,nutrient-poor water...
Corals get much of their energy fromphotosynthesizing plant-like protists -“zooxanthellae” that live within theircells
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Diversity of CnidariaZooxanthellae are dinoflagellates that have
developed a mutualism with coralsMutualism; interaction between species in
which both partners benefit
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Corals in particularEnvironmental threats
to the coral -zooxanthelleinteraction
Ocean pollution - lightcan’t penetratecloudy waters
“Coral bleaching-”corals lose theirzooxanthellae - arecent seriousproblem
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Coral bleaching: What causes it?Various factors, pollution, UV
irradiation, and most importantly,heat
Because of global warming, somepredictions that coral reefcommunities may be extinct within50 years
But there’s somehope the coralsare ahead of us insolving this problem
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Coral bleaching: The “adaptivebleaching hypothesis”
Bleaching can be adaptive ifcorals give upzooxanthellae adapted toold environment and pickup new ones, with forexample, increased heattolerance
Some evidence for this butstill controversial
And it’s a high risk strategy -corals have a limitedamount of time to reaquirezooxanthellae beforethey’re dead
Dead coral beingcolonized by algae 22
Diversity of Cnidaria
ReproductionAsexual reproduction - budding off
from polypsSexual reproduction - fertilized eggs
give rise to mobile, planktonicforms
Plankton - small ocean organismsthat drift with water movement
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Flatworms (Platyhelminthes) andRoundworms (Nematoda)
PORIFERA
CNIDARIAPLATYHELM
INTHESNEM
ATODA
PROTOSTOMESDEUTEROSTOMESARTHROPODA
ANNELIDA
MOLLUSCA
ECHINODERMATA
CHORDATA
PROTISTAMULTICELLULARITYEXTRACELLULAR DIGESTION
TISSUES
RADIAL SYMM
ETRY
BILATERAL SYMMETRY
MOUTH AND ANUS
MO
UTH AND ANUS TRUE COELOM
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PlatyhelminthesBody planNo body cavityIn most mouth but no anusLack circulatory, respiratory
system, absorb O2 throughbody wall
Movement?slowly, through muscle
contraction and/or beat cilia in slime trail!
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PlatyhelminthesFeedingSome free-living, many parasitesi. Some of the parasites with complex life
cycles: several different forms and morethan one host
Human liver flukemust passthrough two otherhosts to completelife cycle
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PlatyhelminthesExample of a human platyhelminthes
parasite: Schistosoma
1) Parasiteeggs shedin humanwaste,gets intowater
2) Eggs hatch, infect snails
3) Snails shedswimming stage
4) Burrowinto humanskin, infectorgans,reproduce 27
The platyhelminth parasiteSchistosomaHumans (where parasite reproduces)
thedefinitive hostSnails the intermediate host 1) Parasite
eggs shedin humanwaste,gets intowater
2) Eggs hatch, infect snails
3) Snails shedswimming stage
4) Burrowinto humanskin, infectorgans,reproduce 28
The platyhelminth parasite,Schistosoma
- causes schistosomiasis- found throughout tropical Asia, sub-
Saharan Africa, mid-East and LatinAmerica
- 200 million people infected, chronicinfection damages the liver, intestines,lungs, 20 million develop ‘severeconsequences’
- What changes could help reducedisease transmission?
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Platyhelminthes
Reproduction- some asexual - e.g. can cut
Planaria in two
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- sexual, most hermaphrodites - two hermaphrodites lie next to each other, each donates sperm to the other’s egg sac
Body planFeeding
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Nematoda - roundwormsBody plan- very simple - “a tube within a tube”
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Nematoda - roundwormsBody planHave a pseudocoelom for body
cavity
Have a one-way digestive system: amouth and an anus
Mesoderm linesthe body wall butdoesn’t surroundthe gut
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Nematoda - roundworms20K species, range in length
from 0.3 mm to 8 m (in whaleplacenta *)
* What was it doing there?
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Nematoda - roundworms
FeedingMany free living decomposers
andparasites of almost everything -
plants and animals
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Nematoda - roundwormsFeedingMany free living decomposers
andparasites of everything - plants
and animals
Example - Trichinella35
On cooking pork...Trichinella, a roundworm parasite of
mammals, including rodents, pigs andhumans
Pigs get infected from eating uncookedmeat scraps or from rodentcontamination, humans from eatingundercooked pork
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On cooking pork...
• Short-term symptoms - abominal pain,vomiting, fatigue and fever
• Then, headaches, fever, aching jointsand muscles
• Later most symptoms subside - chronicinfection
•Trichinella worms lay eggs in intestine,young larvae travel through arteries andencyst in muscles - can live for years
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On cooking pork...Trichinosis not very common any moreIn 1940, 16% of US human population
infectedIn 1970, 4%In 1991-1996, average of 38 cases per yearWhy the improvement?No raw meat fed to hogs, rodent control,
stringent inspections, and freezing andthorough cooking of pork more common
Still a concern with wild game, esp. bearmeat
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What about Wilbur?
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Nematoda - roundwormsWhen parasites are our allies- the use of insect-parasitic
nematodes for control of pests
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Nematoda - roundwormsNematode parasites sometimes have
mutualistic bacterial associatesInsect-parasitic nematodes release
bacteria in the host, the bacteria killthe host
Some of thesebacteria areluminescent!
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Nematodes that cause riverblindness, elephantiasis in humansalso have mutualist bacteria
Just recently led to new therapies with antibiotics
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Nematoda - roundwormsReproductionSexual - some species have
both sexes, some arehermaphrodites
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Nematoda - roundworms
ReproductionThe record for reproductive output?Ascaris the parasitic roundworm,
produces 100,000 - 200,000 eggsper day!
Assuming population isn’t growing,what does this say about mortalityof immature stages?
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