Chapter 33: Invertebrates (Part I)
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Basal animals are also known as:
Parazoans. Non-coelomate invertebrates
What are two things that basal animals do not have?
- Do not have tissues and organs
- Do not have a definite symmetry
Phylum Porifera aka...
What is the major group of basal animals (parazoans)?
Phylum Porifera (Sponges)
How many species are in phylum Placozoa?
- Only one
- Trichoplax adhaerens
Trichoplax adhaerens looks like a...
- "hairy pita bread"
- A bilayer of a few thousand cells
How does Trichoplax Adhaerens reproduce?
By dividing into two individuals or by budding off many multicellular individuals.
6 traits of Phylum Porifera:
- 1. Marine AND freshwater
- 2. Size ranges from a few mm to 2 meters in diameter
- 3. Most asymmetrical... a few with radial symmetry
- 4. Larval sponges are free swimming
- 5. Adult sponges remain attached to substrate for the remainder of life
- 6. Sponges defend themselves by producing chemicals that repel predators
Sponges reproduce (sexually/asexually)
Both! Sexually and asexually
What is unique about larval sponges?
They are free swimming
How do sponges defend themselves?
Producing chemicals that repel predators
Phylum porifera (sponges) exist in what type of water environment?
Both marine and freshwater.
What is unique about the cells of a sponge?
- If all the cells are separated, the cell types will seek each other out and reassemble the entire sponge.
- No other animal can do this!
In sponges, there are 8 types of cells with specialized functions (CAPPMOSS)...
- 1. Choanocytes
- 2. Amoebocytes
- 3. Pinacodem
- 4. Porocytes
- 5. Mesohyl
- 6. Osculum
- 7. Spicules
- 8. Spongin
Specialized sponge cell type 1: choanocytes
- collar cells
- water circulation through sponge
- capturing, engulfing, digesting food particles
Specialized sponge cell type 2: Amoebocytes
- Distribute nutrients through sponge
- TOTIPOTENT CELLS
Specialized sponge cell type 3: Pinacoderm
- made of flattened cells
- make up other epithelium
Specialized sponge cell type 4: Porocytes
flattened cells that line the pores of the ostia
Specialized sponge cell type 5: Mesohyl
- Gelatinous, protein-rich matrix
- located between inner and outer cell layers
- NOT THE SAME AS MESODERM!
Specialized sponge cell type 6: Osculum
- Large openings where water exits the sponge
- Osc= mouth
Specialized sponge cell type 7: Spicules
needlelike structures made of calcium carbonate or silica
Specialized sponge cell type 8: Spongin
tough protein fibers that make up the skeleton of some sponges
Differentiate between ostia and oscula:
- Ostia: where water enters the sponge
- Oscula: where water exits the sponge
In sponges, asexual reproduction occurs by...
In sponges, sexual reproduction involves...
fusion of sperm and egg
Sponges are hermaphroditic, meaning...
they have both male and female parts
Parazoan vs Eumetazoa:
- Parazoan: Animals without true tissue
- Eumetazoa: Animals WITH true tissue
True or false: All cnidarians are carnivores...
Most of the 10,000 species of cnidarians are (marine/freshwater) but very few live in (marine/freshwater).
- Most are marine
- Few are freshwater
Are cnidarians diplo or triploblastic? Why?
- They have no mesoderm
Cnidarians have (organs/tissue) but no (organs/tissue).
- They have tissues
- They do not have organs
Which of the following systems does the cnidarian have?
they have a nervous net
(this multiple choice question has been scrambled)
Nematocycts are unique to this phylum.
What are the two body plans of cnidarians?
- Polyp -- typically sessile
- Medusa -- swims freely in water
In both basic body plans of cnidarians, the mouth opens into a _____ and is surrounded by tentacles.
GVC (Gastrovascular cavity)
True or false: The GVC in cnidarians is a stomach.
- Cnidarians do not have ANY organs
They two-layered body wall of cnidarians is made up of: ______ and _____.
epidermis and gastrodermis
What holds the epidermis and gastrodermis together in cnidarians?
An acellular mesoglea-middle glue
The GVC in cnidarians serves as a ______ skeleton.
In cnidarians, polyps will sometimes build an exoskeleton of ____ or _____ _____ for extra support.
chitin or calcium carbonate
True or false: Sea anemones have no skeleton; neither do Medusae.
Medusa forms are (solitary/colonial) while polyps can be (solitary/colonial).
- Medusa -- Solitary
- Polyps -- Colonial
In the life cycle of cnidarians, some have...
- 1. Polyps only
- 2. Medusa only
- 3. Both polyps and medusa (sexes are separate)
- Refers to the life cycle of cnidarians having both polyp and medusa.
- Both sexes are seperate
The life cycle of cnidarians:
In some, but bot all species of cnidarian, the polyp can produce other polyps asexually by...?
- Or breaking off bits that regenerate
What is a major evolutionary innovation of cnidarians?
Why can cnidarians take in larger prey items than a sponge?
- Extracellular digestion of food inside the GVC.
- Once partial digestion occurs in the GVC, other cells take up fppd fragments by phagocytosis.
microscopic stinging capsules
What are some details about nematocysts?
- capsule everts upon proper stimulation
- Releases barbs (some have venom) that immobilize or kill prey
- Only discharged once
Cnidarians are grouped into four (or five) classes:
- 1. Class Anthozoa-flowering animals
- 2. Class Cubozoa-box jellies
- 3. Class Hydrozoa-the hydroids
- 4. Class Scyphozoa-cup animals
- 5. Class Staurozoa-star jellies
Cnidarian class #1: Anthozoa
- "Flowering animals"
- include sea anemones and corals that exist as solitary or colonial polyps
- Form Coral Reefs
Cnidarian class #2: Cubozoa
- Box Jellies
- medusa stage dominant (polyp reduced or unknown)
- poison stronger than cobra venom
- image-forming eyes
Cnidarian class #3: Class Hydrozoa
- The hydroids
- both polyp and medusa stages in life
- only class with freshwater members
- some marine hydroids and medusae are bioluminescent
- Portuguese man-of-war
Cnidarian class #4: Scyphozoa
- Jellyfish or "cup animals"
- medusa more prominent and conspicuous
- propel through ocean by jetting water from GVC
Cnidarian class #5: Staurozoa
- Star Jellies
- Once included in class scyphozoa
- resembles a medusa but is attached to substrate by a stalk like structure
- Planula larva creeps rather than swims or drifts
Phylum Ctenophora aka...
Comb jellies (cteno = comb)
Do ctenophora live in freshwater or ocean water?
In the ocean, never freshwater
4 unique characteristics of Phylum Ctenophora:
- 8 rows of combelike plates of fused cilia along two long retractable tentacles
- colloblasts: cells that release strong adhesive
- largest animal to use cilia for locomotion
- many are bioluminescent
- may be triploblastic and have bilateral symmetry
This is the largest animal to use cilia for locomotion...
Ctenophora (comb jellies)
Bilatarian Acoelomates key feature:
- Bilateral symmetry
- functional specializations: anteriorly located nerve receptors
Phylum Platyhelminthes aka...
- (platy=flat + helminthe= worm)
General traits of phylum platyhelminthes:
- flattened and solid body (aside from incomplete digestive cavity)
- free-living flatworms live in marine, freshwater, and moist terrestrial habitats
- scavengers or carnivores
- move with cilliated epithelial cells and well developed muscles
- parasitic flatworms live inside bodies of other animals; rage from 1 mm to many meters.
Digestion in flatworms:
- incomplete gut that is branched
- functions in both digestion AND distribution of food
Excretion and Osmoregulation in platyhelminthes:
- primary function of excretory system is water balance
- waste diffuses into gut and expelled through the mouth
- flame cells with "flickering" flagella move water and excretory substances
What are flame cells and where are they found?
- cells with "flickering" flagella that move water and excretory substances
- Found in excretory system of platyhelminthes
Nervous system and sensory organs of platyhelminthes:
- anterior cerebral ganglion
- nerve cords and cross connections that have ladder-like appearance
- eye spots distinguish light from dark
- most are hemaphroditic
- cross-fertilization is internal
- can regenerate missing parts
What are the 3 classes of Platyhelminthes?
- 1. class Turbellaria (turbulant air=flame cells)
- 2. Class Trematode: flukes
- 3. Class Cestoda: tapeworms
Platyhelminthe class 1: Turbellaria
- "turbulent air=flame cells"
- free-living flatworms such as Planarians
Platyhelminthe class 2: Trematoda
- life cycle most often involves two or more hosts
- many flukes cause disease in humans (schistomiasis - blood fluke)
Explain the life cycle of Class Trematoda (flukes):
- involves two or more hosts
- intermediate host usually snail
- final host some type of vertebrate
Platyhelminthes class 3: Cestoda
- no digestive cavity -- absorbs nutrients through outer surface from host's intestine
- body portions: scolex, neck, proglottids
Name the body portions of Platyhelminthes class Cestoda:
- Scolex for attachment
- proglottids=repetitive sections that are largely reproductive
Pseudocoelomates have a body cavity that lies between tissues derived from ____ and tissues derived from ____.
Pseudocoelom serves as _____ ______.
Phylum nematoda aka...
General characteristics of Nematoda:
- ecdysozoans that molt cuticles
- 20,000 recognized species
- marine and freshwater form
- many are parasites of animals and plants
- highly abundant in soil (millions)
Explain the nematode structure:
- Bilateral, unsegmented worm
- flexible cuticle is molted as they grow
- oxygen and carbon dioxide exchange occurs through cuticle
- have longitudinal muscles, but NO circular muscles so can lengthen or shorten but can't change diameter.
This type of worm has longitudinal muscles but no circular muscles.
Traits of Nematode reproduction:
- sexual reproduction
- gonochoric (seperate sexes)
- sexual dimorphism
- internal fertilization
- indirect development
Separate sexes (nematodes)
Sexual dimorphism means...?
Male and female look different
Nematode lifestyles include the following...
- parasites of plants or animals
Nematode-caused human disease: Necator
- found in southern states causes anemia
Nematode-caused human disease:Trichinella
- causes trichinosis
- mature worms form high resistant calcified cysts in muscle tissue
- Don't eat raw pork or bear meat
This disease is caused by eating raw or undercooked pork or bear meat.
Nematode-caused human disease: Enterblus vermicularis
- infect 30% of children and 16% of adults in the US.
- Live in human rectum and cause itching
Pinworms are caused by what type of nematode?
Nematode-caused human disease: Ascaris lumbridoides
- Infects 1 in 6 people worldwide
- less common in areas of modern plumbing
- Lives in human intestines
Nematode-caused human disease: Wuchereria Bancrofti
- filarial worms that cause elephantiasismainly seen in tropical areas
- transmitted by an intermediate bloodsucking host such as mosquito
This nematode causes elephantiasis.
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