Simple Invertebrates
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Transcript of Simple Invertebrates
Phylum Platyhelminthes(Flatworms)
More complex than sponges and cnidarians. Organisms with long, flat body. Clearly defined head with mouth. Some have senses, a few even have eyespots. Some move freely. Live in ponds, streams, or in a host! Many are parasites
Characteristics:
Simplest of all worms 1 body opening Flat bodies
Hermaphrodites
Most flatworms are parasites
Reproduce- Asexually-
regeneration & fission
Sexually Cellular Level-
Organs 3 tissue layers
Endoderm Mesoderm Ectoderm
Planarians:
Triangular head with eyespots that sense light
Parasites
Feed on dead plant & animal matter
Reproduce asexually- Regeneration
Digestive system- Mouth Pharynx intestine
Tapeworms:
Long, flat ribbons
Parasites
Live in bodies of humans & animals
head has hooks that attach to the host
can grow up to
18 feet long!
Liver fluke:
Parasite
Live in the liver or blood of an animal host
Animal hosts: Snails Fish Humans
Humans can get liver fluke by eating raw or uncooked fish that contains the parasite.
Preventions?
Phylum: Nematoda (Roundworms)
Another step up the ladder! Live on land or in the water Some even have a simple nervous system. Some have a digestive system that runs through
the entire body -- with two openings, one for food to enter and one for wastes to leave.
Most are parasites. Some are harmless microscopic critters that live
in the soil.
Characteristics:
Examples: hookworm, heartworm, pinworm, Trichinella
Described as a “tube within a tube” First animals with a complete
digestive system two body openings: mouth & anus
Trichinella Parasite Lives in the muscle tissue of pigs Live and reproduce in the intestine of
the host.
Prevention? The disease is called Trichinosis
Hookworm:
Parasite Live in small intestine
where it enters the bloodstream
From the bloodstream it enters the lungs, coughed up, then swallowed and enters the digestive system.
Hookworm eggs are passed in the feces of an infected person.
Hookworm infection is mainly acquired by walking barefoot on contaminated soil.
Prevention?
Heartworm:
Parasite Enters the blood of a dog
through a mosquito bite! Worm moves to the heart
where they grow and reproduce.
They block the valves that lead to and from the lungs.
Prevention?
Pinworm: Parasite Adult lives in the
large intestine Female migrates to
the anal region to lay her eggs
Prevention?
Phylum: Annelid Live in fresh & salt
water, streams, and soil
Examples: Leech Earthworm
Most common Lubricus terrestris
Characteristics: Approximately 100
segments Outer layer made of
mucus to help the animal glide
Setae- tiny bristles that help in movement
Systems: Closed Circulatory system-
5 pairs of tube hearts
Digestive system- Mouth Pharynx Esophagus Crop Gizzard Intestine Anus
Nervous system- Ganglion Nerve cord
Respiratory system- No organs O2 enters through the
skin & CO2 leaves Reproductive
system- sexual Sperm is exchanged
at the clitellum Clitellum- the band
on the earthworm where the sex cells are located
How do earthworms help the environment?
After organic matter is digested, the earthworm releases waste from their bodies called castings.
Castings contain many nutrients that the plant can use.
Some people even use earthworm castings as garden fertilizer.
Enrich and improve soil for plants, animals & even humans.
Create tunnels in the soil by burrowing, which aerates the soil to allow air, water and nutrients to reach deep within the soil.
Phylum Porifera(Sponges)
Simplest animals of all (some of the oldest too). All are aquatic (freshwater and marine). Only two layers of cells, no tissues or organs! Their skeletons are made of tiny spines called
spicules. Cannot move (grow attached to the bottom). Mostly filter feeders. Uses?
Phylum Cnidaria (aka Coelenterata): Jellyfish and Coral
More advanced than sponges. (for example, they have tissues, but still no organs).
Their body is a hollow cavity with only one opening (for food AND wastes)!
Entirely aquatic (freshwater and marine). All have stinging cells, but not all can harm people. Some are pretty nasty predators. Others filter-feed
on small particles and organisms in the water.
Medusae vs. Polyps
MEDUSAE
Ex. Jellyfish A medusa is free-swimming. Most are solitary. Their opening is on the
bottom of their body.
POLYPS
Ex. Coral Polyps are like an upside
down medusa. Their opening is on the top
of their body. Coral polyps are tiny and live
in huge colonies of thousands.
Corals build their “home” as the colony grows larger and larger.
Jellyfish
Most jellyfish are harmless to people, although not so to small fish and other marine organims.
Roundworms!
One teaspoon of garden soil may contain as many as 10,000 tiny nematodes (roundworms) in it!
Phylum Annelida(Segmented Worms)
Most complex worms of all. Tube-like body divided into segments. Sophisticated digestive system! (mouth, crop and gizzard,
intestine, anus) Many other specialized organs heart, blood vessels, nerve
cords, simple brains) Can move well. Some aquatic (leeches, clam worms), some terrestrial
(earthworms). Some are parasites (leeches), others are very important
decomposers (earthworms). Any other uses for annelids?