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….

Porifera Sponges Sessile Adults Motile Larvae Assymetry Very Primitive- “barely” multicellular Classified by hard skeletal spines called spicules

spicules

Investigating sponges Sponges spawning

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: ?v=Kukv0AtIVdU&feature=relat ed ?v=Kukv0AtIVdU&feature=relat ed Hydra; ?v=yqXkaZwiu6s&feature=relat ed ?v=yqXkaZwiu6s&feature=relat ed

Zy4o&feature=PlayList&p=E9E E 2F9C9&playnext=1&index=3; jellyfish movementhttp:// Zy4o&feature=PlayList&p=E9E E 2F9C9&playnext=1&index=3 p7QX6e0&feature=PlayList&p=E9E E2F9C9&playnext=1&index=2 polyp stagehttp:// p7QX6e0&feature=PlayList&p=E9E E2F9C9&playnext=1&index=2

Cnidarians

Portuguese Man-of-War are colonies of four kinds of highly modified polyps: feeding polyps, reproductive polyps, etc.. Hydra Hydra catching food: ?v=Kukv0AtIVdU&feature=relat ed ?v=Kukv0AtIVdU&feature=relat ed Cnidaria: hydrozoa

Phylum Ctenophora: close relatives to cnidaria but jelly instead of stingers Comb jellies

PlatyhelminthesFLATWORMS 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 a91gg free living flatwormhttp:// a91gg K6GuM&feature=PlayList&p=E9E E2F9C9&playnext=1&index=11 planaria eatinghttp:// K6GuM&feature=PlayList&p=E9E E2F9C9&playnext=1&index=11 nf2c tapeworm in intestinehttp:// nf2c

Fluke All parasitic Most famous is the Sheep liver fluke that causes schistosomiasis. Over 100 million in the world have this fluke/disease.