Chapter 33: Pt 1. An Introduction To Invertebrates Flashcards
Invertebrates are animals that lack a back bone. They account for ___% of known animal species.
95%
_________ are basal animals that lack true tissues.
Sponges
Define sessile
Fixed in one place, immobile.
Sponges have organized cells supported by a skeleton made of 3 different things. What are they?
- Spongin fibers
- Calcareous spicules
- Silica spicules
Or sometimes, no skeletal structure at all.
How do sponges eat?
They are suspension/filter feeders.
- choanocytes create a current that draws water in through the sponge’s pores into the spongocoal and out of the osculum
- food particles from the water get trapped in the mucus that coats the projections
- food is transferred to amoebocytes
How do sponges break down the food particles?
Phagocytosis
In some reef systems, sponges are __________ feeders - taking in enough biomass to double every 2-3 days.
voracious
organisms who devour great quantities of food
Sponges have a chamber called an _______, which consists of many spongocoel and choanocytes.
atrium
What is the mesophyl?
The center layer of a sponge, between the outer and inner layer of cells.
Both the outer and inner layer of a sponge’s wall have contact with water. What does this mean?
Gas exchange and waste removal can occur by diffusion across the cell membranes of both the inner and outer wall.
What are amoebocytes?
Cells that move through the mesophyl. They take up absorbed food and carry nutrients to other cells.
Sponges have three body types. What are they and what are their differences?
- Asconoid
- smallest, simplest body design.
- looks kind of like a tear drop.
- Syconoid
- middle sized, somewhat complex design.
- looks like the tear drop, but has flagellated canals along the sides.
- Leuconoid
- largest, most complex design.
- looks like a typical sponge with many oscula.
How do sponges contribute to the antibiotics we have today?
There are many bacteria that live within the sponges that help with antibiotics.
Sponges are refuges
What does this mean?
They provide habitats for a wide variety of animals
What phylum do sponges belong to?
Phylum Porifera
Define eumetazoa
Clade of the animal kingdom that includes all multicellular animals except sponges
What is gastrovascular cavity?
Cavity in the body that digests food and transports nutrients throughout the body
- only has one opening, mouth and anus are the same
What are cnidarians?
A phylum of animals belonging to the clade eumetazoa
- jellyfish, anemonies etc.
What are characteristics of cnidarians?
- Two body types
> sessile polyps
> motile medusas - Simple diploblastic, radial body plans
- Central digestive compartment (gastrovascular cavity)
- Mouth and anus are same opening
What is the body plan of a cnidarian?
Sad with a central digestive compartment (gastrovascular cavity)
What is a polyp?
A sessile cnidarian that adheres to substrates.
- they extend their tentacles to catch prey
E.g., sea anemone and hydras
What is a medusa?
A motile cnidarian that swims freely.
- their tentacles face downward for locomotion
E.g., jellyfish
What are the 3 layers of a cnidarian’s wall?
Epidermis
Mesoglea (gel-like)
Gastrodermis
What is a unique trait to cnidarian tentacles?
They are composed of cnidocytes
- cnidocytes are cells that consist of specialized organelles called nematocysts that eject a stinging thread to catch prey
True or false:
Cnidarians have no brain
True
Electrical synapses dominate in Cnidarians with nerve nets. What does this mean?
If you touch the tentacle of a cnidarian, the entire cnidarian will retract because it cannot exactly sense where it is being touched.
- echinoderms do the same, have radial nerves in each arm.
(Humans do not do this; if you touch someone’s hand they will retract their hand only, not all of their limbs.)
What are characteristics of sponges?
- No true tissues or organs
- No symmetry
- No nerves, muscles, mouth or digestive system
- Sessile
- Reproduce sexually and asexually
- Filter feeders
What are the 4 classes of Phylum Cnidaria?
Hydrozoa
Scyphozoa
Cubozoa
Anthozoa
What are the characteristics of Class Hydrozoa?
- Has polyp and medusa stages
- Marine (a few freshwater)
E.g., Portuguese man-of-wars, freshwater hydras, Obelia
What are the characteristics of Class Scyphozoa?
- Live as medusas (polyp stage is absent)
- Marine
- up to 2m in diameter
E.g., true jellyfish
What are the characteristics of Class Cubuzoa?
- Live as box-shaped medusa
- Marine
- complex eyes, potent venom
E.g., box jellies, sea wasps
What are the characteristics of Class Anthozoa?
- Live in polyp stage, medusa stage absent.
- Marine
- mostly sessile, many colonial
- secrete hard exoskeleton
What are bilaterians?
A phylum of animals belonging to the clade eumetazoa with bilateral symmetry
What are the phylums of the clade Bilateria?
Lophotrochozoa
Ecdysozoa
Deuterostomia
What are the 4 phylums of lophotrochozoans?
- Phylum Platyhelminthes
- Phylum Rotifera
- Phylum Mollusca
- Phylum Annelida
What are the characteristics of the phylum platyhelminthes? What are the classes?
- Triploblasts
- Bilaterial symmetry
- Dorso-ventrally flattened
- Gastrovascular cavity
- No blood vessels or structures for gas exchange
- flat bodies = large surface area for gas exchange
Classes:
- Turbellaria - flatworms
- Cestoda - tapeworms
- Trematoda - flukes
Describe the body of a turbellaria (flat worm).
- Two eyespots
- Two ventral nerve cords (lined along its stomach)
- Ganglia (where the nerve cords meet at the head)
- Gastrovascular cavity (food enters through the mouth and pharynx)
- needs water/damp environment
Explain the life cycle of a parasitic trematode, Schistoma (bilaterians in the phylum platyhelminthes).
- Male and female flukes (trematodes) reproduce sexually in a human host.
- Human excretes feces and the fertilized eggs within the feces develop into larvae (with water contact) and infect snails as their new host.
- Flukes reproduce asexually in the snail and the larvae swim freely in the water.
- The larvae penetrate the skin of the humans working in the ponds and infect them again.
What are monogeans?
Parasites of the phylum platyhelminthes that infect fish
- life cycle is the same as a trematode, except we injest infected fish instead.
What are the characteristics of tapeworms (phylum platyhelminthes, class cestoda)?
- lack a digestive system
- absorb nutrients from host’s intestine
- sexually reproduce and humans excrete the fertilized eggs
- mostly infect vertebrates
Describe the body of a tapeworm (phylum platyhelminthes, class cestoda).
- has a head (scolex) with suckers and hooks
- body segments (proglottids) contain eggs that break off as they ripen with eggs
- lack gastrovascular cavity
- hermaphrodites (but still cross mate)
What prevents tapeworms from being digestive while they live in the intestine?
They have a protective mucus layer
