BIOL 111 Lecture Notes - Lecture 11: Trematoda, Sea Anemone, Retract
5 Jul 2018
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BIOLOGY 111 LECTURE 11
CHNIDARIANS AND PLATYHELMINTHES (embryonic and development and
symmetry)
What is the advantage of having a nervous system?
Haploid multicellular stage is not a characteristic of animals, diploid is dominant
*Most animals undergo unique embryonic development patterns*
Embryonic Development
Zygote multicellular organism (2N)
Diploid cell resulting from union of two haploid gametes 1st cell of next generation
Embryo – young animal or plant while it is still contained within a protected structure
(ex; egg)
Two Major Processes occurring during embryonic devolpment:
LOOK AT SLIDE
Cleavage –
Zygote – 2 cell stage – 8 cell stage – Morula (solid ball) – blastula (hollow ball) –
gastrula (pinching in at one end, outer layer of cells and outer), late gastrula phase
Ex: Sea Urchin (early gastrula on the outside of te gastrula with the blastospore) on the
inner there is an extracellular matrix
Germ Cells:
Ectoderm “outer skin” – give rise to the nervous system
Endoderm: “inner skin” – lining of the digestive system and respiratory system
Mesoderm “middle skin” – skeletal system, muscles, heart, stomach
LOOK AT SLIDE
Archenteron “old gut” – extracellular digestion, secrete enzymes into this space and
absorb nutrients across their cell walls, give rise to tissues, more complex
body/organization, larger particles that can digest over a longer period
Hole in the embryo – blastospore – give rise to the anus or the mouth
Chnidarians – blind gut (waste excreted) – diplontic (2 germ layers) – radial symmetry
Platyhelmenthis (Flatworms) – triploplastic (3 germ layers) – bilateral symmetry,
concentrated sense organs to create a centralized nervous system
Types of Symmetry:
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1. Asymmetrical: no axis that equally divides the organism in half (ex: some
sponges)
2. Radial Symmetry: along a single plane, there are multiple angles in where you
can cut this organism in half (ex: sea anemone, cnidarians) slide pic
3. Bilateral Symmetry: single axis that divides the organism into equal halves, you
cut from the eyes (ex: frog)
Fun Fact: Sea Star is radial symmetric!! (chordate), adults are radial, the seastar
larvae is bilateral
Chnidaria:
-Jellyfish, sea anemones, corals, hydrozoans
-11 000 species
-Mostly marine
-Microscopic to many metres
-Carnivorous
-SLIDE
Generalized Body Plan:
Mesoglea – gelatinous material, collagen and porteoglycans, gastrodermis,
epidermis (from ectoderm), diploplastic, mouth from blastospores, gastrovascular cavity
Body Forms: polyp and medusa phase:
Polyp: small polyp that form branches and create cloned organisms (asexual)
Hermphroditic, LOOK AT SLIDE FOR LIFE CYCLE
How do Chnidarians obtain energy:
-Chnidocytes: coiled trigger that stings you with posion, used to capture their
prey with venom and stick to prey
-Extracellular digestion in gastrovascular cavity
-Symbiotic algae
Simple Nervous System:
-Sensory information can come in any direction
-Little to no integration or processing of signals
find more resources at oneclass.com
find more resources at oneclass.com
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