Transcript Cnidarians etc

Cnidarians
Characteristics
• Cnidarian means Thistle
• Referring to the stinging cells (nematocysts) that
all members possess
• All aquatic
• Radial symmetry
• Body has a single opening through which food and
wastes pass
• Has a gastrovascular cavity where digestion
begins
Symmetry
Gastrovascular cavity
Nematocysts
• Some can move around, others are sessile
• Two tissue layers, the ectoderm(outer) and the
endoderm ( inside)
• Simple nervous system and muscle tissue
• Reproduce asexually by budding and sexually by
producing gametes. Cnidarians are
hermaphrodites
Hydra, Jellyfish, Sea anemones, Coral
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Platyhelminthes
Means flat and wide
Simplest animals with bilateral symmetry
Have organs and organ systems
Have an anterior end and so move in a forward
direction
3 tissue layers: endoderm, mesoderm and
ectoderm
Lack a body cavity
Some have a primitive brain and sensory organs
Planarians are free-living, while tape worms and
flukes are parasites
Reproduce sexually and asexually
Planaria, tape worms and flukes
Nematode Worms
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Means thread-like
Commonly called roundworm
Some are free-living and some parasitic
Distinct head and organ systems
Tube within a tube body plan
Has a pseudo coelom (body cavity)
Sexual reproduction
Some species are hermaphrodites
Annelids
• Annelida means ring
• Referring to the body being segmented into
repeating units
• The only group of segmented worms
• They live on land and in water
• They have complete digestion, a closed circulatory
system, a ventral nerve cord, a nephridial
excretory system, and a true body cavity
• Digestion is extracellular ( in special compartment
in the body, not in cells)
• Sexual reproduction, internal fertilization, some
are hermaphrodites
True body cavity
Earthworms, clamworms, leeches
Gross!!!!
• In 1994, a woman's scalp was ripped off
when her hair was yanked into moving
machinery. Doctors performing micro-surgery
at the University of Southern California
reattached the scalp, but one area swelled
with congested blood. They applied leeches,
one at a time for eight days, to suck up
stagnant blood. Eventually new capillaries, or
tiny blood vessels, formed in the scalp
wound, leading to healing circulation.
Mollusca
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Means soft-bodied
unsegmented
Most live in water, a few (slugs) live on land
Most have an internal or external shell
Have a mantle (fold in the body wall that lines the shell)
Muscular foot and/or tentacles
All except bivlaves have a radula and a well-developed
head
• Most have an open circulatory system, some have closed
circulation
• Many respire using gills, slugs use a hole in the side of
their head and breath through their skin
• Gums to bums digestion
Arthropods
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The most successful phylum (106 to 107 species)
Means “jointed foot” but have jointed appendages
Very diverse group
Reproduce sexually, most have separate sexes
Rigid, jointed exoskeleton provides a waterproof protective
armor, a site for muscle attachment, protection from drying
Well developed nervous system
Most have an open circulatory system, breath using gills,
trachea, book lungs
Well developed excretory system ( kidneys)
One way digestive system
Echinoderms
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Means spiny skinned
Most advanced group of invertebrates
Radial symmetry
Digestion is extracellular, one way digestive system
Reproduction is sexual, asexual powers of regeneration
Does not have a centralized nervous system
Has an endoskeleton made of calcium carbonate plates
Water -vascular system with “tube feet”helps catch food,
with movement and gas exchange