Download Lab 5 - CSUN.edu

Goals
1. Identify which germ layer gives rise to major organs
2. Understand the differences between acoelomates,
pseudocoelomates, & coelomates
Lab 5
3. Identify cross-sections of each category
Pseudocoelomates
&
Lower Coelomates
4. Identify the similarities & differences between the round
worms and segmented worms
5. Identify the similarities & differences between the
different classes of segmented worms
6. Identify the similarities & differences between the
different classes of molluscs
Coeloms- fluid filled cavities
Coeloms- Basic Diagram
• Acoelom
– No cavities
• Pseudocoelom
– Cavity surrounded by
endoderm and mesoderm
• Coelom
– Cavity surrounded by
mesoderm on both sides
• Ectoderm– epidermis (skin), nerves, pigment
• Mesoderm– muscles, blood cells, kidneys, skeleton,
reproductive organs, circulatory system, tendons
ligaments
• Endoderm– digestive system (stomach, liver, etc),
respiratory system, endocrine system (hormonal
glands- thyroid, adrenal, thymus)
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Common Traits of All Phyla Today
Phylum Nematoda
•
Triploblastic
• Pseudocoelom
•
Body cavities
• Long body
•
Organ systems
• Pointed at both ends
•
Complete digestive
system (tube)
• Cuticle
• Dioecious (mostly)
– Mouth and Anus
•
– Two separate sexes
Bilateral symmetry
Ascaris sp.
Nematoda Cross-section
Phylum Rotifera
Endoderm &
Mesoderm
Mesoderm
• Pseudocoelom
• Freshwater
• Corona
Mesoderm
epidermis Ectoderm
Mesoderm
• “Foot” for attachment to
substrate
• Fixed number of body cells
Ascaris sp.
cuticle
Ectoderm
– Cilia around mouth
Endoderm
• Dioecious
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Phylum Annelida– Similarities
Phylum Annelida, Class Polychaeta
• Coelom
• Mostly Marine
• Segmented bodies
• Parapoda (Paired limbs)
with many long setae
• Complete digestive
system
• Closed circulatory system
• Free living or sedentary
(tube worms)
• Setae (chitin bristles)
• Dioecious
Nereis sp.
Phylum Annelida, Class Polychaeta
Phylum Annelida, Class Oligochaeta
Sedentary
•
No parapoda
•
Few setae
•
Monoecious
•
Mostly freshwater or
terrestrial
•
Some marine
Lumbricus sp.
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Earthworm copulation
Lumbriscus Cross-section
Epiderimis Ectoderm
Intestine
Endoderm
Typhlosole Mesoderm
Coelom
Muscle
Mesoderm
Nerve
Ectoderm
From which germ layer is each organ derived?
Phylum Annelida, Class Hirudinea
Phylum Mollusca– Similarities
• Coelomate
• Leeches
• No Setae
• Open circulatory system
• Muscular foot
• Dorsal visceral mass
• Predators or
parasites
• Head
• Mantle
– Protect Gills
– Secretes shell
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Phylum Mollusca, Class Bivalvia
Phylum Mollusca, Class Gastropoda
• Obvious cephalization
• Hinged, Two-part Shell
• Asymmetrical shell
• Wedged shaped foot
(digging)
• Large, flat foot used for
crawling
• No Radula
• Filter feeders
• Terrestrial, marine &
fresh water
• No cephalization
Phylum Mollusca, Class Cephalopoda
Marine
Well developed head
Eyes
Foot modified into
tentacles
• Shell usually reduced or
absent
Evolutionary Relationships
•
•
•
•
Trochophore larvae similar in Annelida & Mollusca
Polychaete (left)
Bivalvia (right)
Shark vs Octopus movie
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