How many lines of symmetry?
Fertilized egg
• Zygote is one diploid cell made by the fusion of the sperm and egg.
• In humans this is internal fertilization within the fallopian tubes.
• Many other organisms have external fertilization where the egg and sperm are both released outside the parent.
blastula
8 cell stage (blastocyst)morula
gastrula
Germ layers
• 3 kinds:– Ectoderm– Mesoderm– Endoderm
– Layers of cells that work together to form specific tissues.
– Sponges (0), cnidarian (2), others (all three)
Body plans: Coelom
If three germ layers, then….
PoriferaSponges
Sessile AdultsMotile Larvae
Assymetry
Very Primitive- “barely” multicellularClassified by hard skeletal spines called spicules
spicules
Investigating sponges
http://www.youtube.com/watch?v=BW05vMziy2o
Sponges spawning
http://www.youtube.com/watch?v=SHJOu9PjKyU
Body of sponge• Osculum: opening at the top• Ostia: openings in the wall of sponge
Cnidaria• Alternation of generations:
Most have both stages in life cycle
• Medusa: motile/sexual/tentacles down/mouth down
• Polyp: sessile/asexual/ mouth up/tentacles up
Characteristics of Cnidaria
• Nematocyst stingers Nerve net (no brain)
• Hydra• Hydra catching food: http://
www.youtube.com/watch?v=Kukv0AtIVdU&feature=related
• Hydra; http://www.youtube.com/watch?v=yqXkaZwiu6s&feature=related
• http://www.youtube.com/watch?v=v9j9iO6Zy4o&feature=PlayList&p=E9E1093124E2F9C9&playnext=1&index=3; jellyfish movement
• http://www.youtube.com/watch?v=M9MMp7QX6e0&feature=PlayList&p=E9E1093124E2F9C9&playnext=1&index=2 polyp stage
Cnidarians
• Portuguese Man-of-War are colonies of four kinds of highly modified polyps: feeding polyps, reproductive polyps, etc..
• Hydra• Hydra catching food:
http://www.youtube.com/watch?v=Kukv0AtIVdU&feature=related
Cnidaria: hydrozoa
Phylum Ctenophora: close relatives to cnidaria but jelly instead of
stingers• Comb jellies
http://www.youtube.com/watch?v=G7WT81ukHZE
Platyhelminthes FLATWORMS
• Tapeworms, Flukes (parasites), free swimming (planaria)
Cephalization
Notice the front end has sensory organs (HEAD?)
Most are parasitic and don’t have cephalization, but platyhelminthes were first to have it.
Characteristics
• Acoelomate/
• No coelom/organs
• Highly branched• Digestive system as
they have no circulatory system
Flatworm videos
• http://www.youtube.com/watch?v=voMKJea91gg free living flatworm
• http://www.youtube.com/watch?v=Ich4Y_K6GuM&feature=PlayList&p=E9E1093124E2F9C9&playnext=1&index=11 planaria eating
• http://www.youtube.com/watch?v=T6pAfQInf2c tapeworm in intestine
Fluke
• All parasitic• Most famous is the Sheep liver fluke that
causes schistosomiasis.• Over 100 million in the world have this
fluke/disease.
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