Download Ch. 27 Invertebrates

Invertebrates!
C-27-1
Invertebrates are organisms that do not have a
backbone!
Phylum Porifera
Sponges - about 9,000 species
Characteristics:
~ asymmetrical
~ lack tissues and organs
~ body wall has 2 cell layers with many pores
~ internal cavity lined with food filtering choanocytes
(collar cells)
~ live in marine water
Filter feeders:
*H2O goes through the pores and the
choanocytes trap the food particles
* H2O leaves the sponge cavity
through the osculum at top
* Choanocytes give the nutrients to
the mesenchyme cells where
amoebocytes carry the nutrients to
other cells and then carry waste from
those cells away
Have simple skeletons:
~ Spongin - flexible protein fibers in most sponges
- makes them soft and squishy!
~ Spicules - needles of silica or CaCO3 embedded in
spongin
- in some sponges; makes them rigid and
tough
- shaped like
Reproduce asexually and sexually:
~ can regenerate if cut up into pieces (asex.)
~ can form gemmules - packages of amoebocytes
encased (asex.)
~ can also release sperm and eggs form the same
sponge! (sexual) but does not fertilize itself
= hermaphroditic
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Phylum Cnidaria
Cnidarians are jellyfish and stinging things!
Characteristics:
~ radially symmetrical
~ gelatinous
~ have distinct tissues
~ bag-like body with 2 cell layers
~ can be marine or freshwater
Class Hydrozoa
~ Most have both polyp and medusa stages in the life
cycle
Hydra - has no medusa stage, only polyp
*reproduces by asexual budding
Portuguese Man-O-War - has both stages…we usually
see the medusa stage
reproduces sexually by releasing sperm and eggs
All Hydrozoans have nematocysts - cells with coiled
barbs that spear food
Class Anthozoa
~ are polyps
~ sea fans, corals, sea anemonies
corals form reefs:
*fringing reef - off beaches
* barrier reef - deeper and farther off shore
* atoll - far out, in form of a ring
Class Scyphozoa
~ Jellyfish!
~ dominant medusa stage
~ only marine
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Phylum Platyhelmenthes
Flatworms!
Characteristics:
~ flat, ribbon-like body
~ no true segments
~ bilateral symmetry
~simplest organisms that have organs
Class Turbellaria
~ most are marine flatworms
~ typically predators, some herbivores or parasites
ex: planaria -
Class Trematoda - flukes
- some are endoparasitic -live on the inside
- some are exoparasitic - live on the outside
Ex: blood flukes - hitches a ride inside snails
(intermediate host) and then the larva infects us (the
final host)
* live in our bladder or intestines
Class Cestoda - tapeworms
- endoparasitic - live in intestines
-make proglottids as they grow
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Phylum Nematoda - Roundworms!
Characteristics:
~ small, , unsegmented worms
~ some are parasitic
~ slender, elongated body
~ simplest org. with a body cavity : pseudocoelomates =
false coelom or body cavity
~ have bodies shaped like pencils sharpened at both
ends
~ are marine or freshwater
ex: Trichinella, Ascaris, Necator, pinworms, Filarial
worms
Ascaris - can live in human intestines; cause respiratory
distress as larvae
Necator - "hookworms" - enter through soles of your
feet
* move through bloodstream into the lungs - get
coughed up and swallowed - live in intestines
Trichinella - in pigs - causes Trichinosis in humans
- get it by eating undercooked pork!
Filarial worms - live in the blood or tissues
- carried by mosquitoes
- can lead to elephantitis in humans
- other types are dog heartworms - can weaken the
heart and eventually kill the animal
Mollusks
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First major group to develop a true coelom
* Can be found in freshwater, marine, or terrestrial
habitats
*All have these characteristics:
~trochophore larvae - larva has cilia which moves the
larva throught the water
~ body cavity - true coelom, usually surrounding the
heart
~ symmetry - bilateral; many have one or more shells
called valves
~ organ systems
*circulatory - 3 chambered heart
- open system (octopuses and squid
have closed systems!)
*respiratory - ciliated gills within the mantle cavity
*digestive - stomach
*excretion - nephridia recover useful molecules
before they are excreted
~ 3-part body plan - 1 -muscular foot
2 - head
3 - visceral mass
3 major Classes:
1.) Class Gastropoda - snails and slugs
* muscular foot
* usually have a hard protective shell
* mostly marine
* eyes on tentacles
* some can be deadly - cone snail
2.) Class Bivalvia - clams, oysters, and scallops
* two-part shell with a hinge
* filter feeders - use siphons to draw water in
* no distinct head
*sexual reproduction - have male and female
organisms
3.) Class Cephalopoda - octopuses and squids
*modified cavity for jet propulsion through water
*have tentacles to capture prey
*very intelligent
*large eyes
*sexual reproduction - male and female animals
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Phylum Annelida
Segmented worms
Characteristics:
~ body cavity - true coelom
~ segmentation into fairly = units…some fused, some
separate
~ organ systems *gut - specialized
*closed circulatory system (pg.669) simple hearts
*many nephridia - collect waste from cells
*exchange O2 through body surfaces
~ bristles - setae = external bristles
- parapodia = fleshy appendages
3 classes:
Class Polychaete - Marine worms!
* have jaws
* well developed head
* antennae
* eyes
* feed by ingesting food (animals) or sediment, some
pump water through bodies or scavenge ocean floor
* have parapodia = fluffy looking - swim, burrow, crawl
* sexual reprod.
Class Oligochaete
Earthworms!
* terrestrial
* eat soil - equivalent to own weight every day!
* no distinct head
* use gizzard to grind soil
* light and touch sensitive organs on body
Class Hirudinae
Leeches!
* no setae or parapodia
* coelom not segmented
*parasitic - live on blood