Transcript Invertebrates

Invertebrates
JP Keller, Ryan Peterson
Sponges
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Over 9,000 species
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Live mostly in the oceans
and seas
Simplest creature known
to man
Phylum- Porifera
Sponges reproduce both
ways
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Sexually- Sperm and Egg
released into water
Asexually- Budding
Body of a Sponge
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They are not symmetric
They don’t grow from a central point
Their cells are not organized into tissues and organs
Individual cells can grow through a membrane
How a Sponge Eats
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Collar cells pump water through sponge
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One cubic centimeter of sponge can pump 20 liters
of water a day
The collar cells also trap food
The water is filtered to gather tiny animals and
protists for food
Cnidarian- Carnivores
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They have symmetry and are
called true animals
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Also called Eumetazoans
Embryonic stage
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Three different levels of tissue
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Ectoderm- outer body and
nervous system
Mesoderm- skeletons and
muscles
Endoderm- digestive organs
Phylum-Cnidaria, includes
jellyfish, hydra, corals and
anemones
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Other phylum- ctenophore,
includes comb jellies and
delicate marine animals
Radially Symmetric
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Body parts arranged around central point
Stinging cells- Cnidicytes, no other organism has
these, this is where the phylum name comes
from
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Small barbed harpoon, called a nematocyst
Eating and Reproduction
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Food trapped by a Cnidadore is introduced by
endocytosis and it is digested intracellularly
Sexually
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Larvae find a spot to become a polyp
Polyp strobilates
Juveniles become mature
Asexually
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They can either bud like sponges or divide themselves
Body Shape
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Medusa- gelatinous, free floating and umbrella
shaped
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They are the most common
Polyps-cylindrical pipe shaped and normally
attached to rocks
The Evolution of the Body Cavity
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Bilateral symmetry
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Left and right halves are symmetric
Top is called the Dorsal
Bottom- Ventral
Front-Anterior
Back-Posterior
Definite head
Move around head first
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Sensory organs are here to detect food, mates, and possible
danger
Nematodes
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Pseudocoelom- body cavity between the
endoderm and the mesoderm
Many advantages
circulation- allows for quick movement of fluid
 Movement-fluid in body cavity makes body rigid for
muscle driven boy parts
 Organ function- organs can function without muscle
interference
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Key Characteristics
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Mainly parasitic
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Includes tape worms
Only bilaterally
symmetric animals that
don’t have a body cavity
Reproduce sexually
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Occurs through the
exchange of sperm
Other Important Information
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One way gut
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7 animal phyla have a pseudocoelom
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Only one has large amount of species
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Nematodes- round worms
500,000-600,000 species
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Nematode
13,000 named
One spade of dirt- 1 million nematodes
Even More Important Information
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Phylum- platyhelminthes
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20,000 species
Mostly flat worms
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Simplest animal with
organs
No internal body cavity
No circulatory system
Only one opening
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Mouth food enters and
exits
More on Nematodes
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Some can be parasitic, infect humans
Layer of muscle extends the length of body
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Beneath a flexible thick layer of epidermis and cuticle
Muscle pushes against the cuticle and pseudocoelom to move
worm
Mollusks
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Largest phylum except for arthropods
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Body cavity called a Coelom
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Fluid filled cavity in the mesoderm
They have primary induction- one layer interacts
with another
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Over 100,000 species
Physical contact of mesoderm and endoderm
Least advanced because their bodies aren’t
segmented
Other information about the
fascinating mollusk
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They have a circulatory system that move
nutrients, oxygen, and waste
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a circulatory system is a system of vessels that carry
fluids to every part of the body
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The heart(s) power this system
They’re called the most successful land animals
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35,000 terrestrial mollusk species
Physical Characteristics
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Three main body parts
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Visceral mass- central
section that contains
organs
Mantle- heavy fold of
tissues around the visceral
mass
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Gills in aquatic snails
Simple lungs in terrestrial
Every mollusk has a
muscular foot!!
Mollusk Reproduction
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Almost all mollusks reproduce sexually
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There are both male and female mollusks