Lecture 6 Flashcards
What is the defining characteristic of Phylum Porifera?
Porifera are “pore-bearing” animals, organized around a system of water canals and chambers
What is the likely ancestral group of sponges?
Phylum Choanoflagellata, single celled eukaryotes similar to sponge choanocytes
What is the ecological importance of sponges?
They serve as microbial symbionts, create habitats for other organisms, and act as filter feeders in aquatic ecosystems
What is the skeletal structure of sponges made from?
Spicules, which provide internal support and protection
Name the five specialized sponge cell types and their functions
- Pinacocytes: thin, contractile epithelial cells covering the exterior
- Porocytes – Tubular cells creating ostia (pores) for water intake.
3.Archaeocytes/Amoebocytes – Totipotent cells involved in digestion, reproduction, and spicule secretion.
- Choanocytes – Flagellated cells that generate water currents and filter food.
- Mesohyl – Gelatinous connective matrix where sponge cells are embedded.
How do sponges feed?
They are filter feeders using choanocytes to trap food particles and archaeocytes to digest them
What are the three types of sponge canal systems?
1) Asconoid – Simplest, water flows through spongocoel and exits via a single osculum.
2) Syconoid – Choanocytes line folded radial canals, increasing surface area for filtration.
3) Leuconoid – Most complex, with choanocyte-lined flagellated chambers and multiple oscula.
What type of reproduction do sponges use?
Both asexual (budding and gemmules) nand sexual reproduction (monoecious, releasing sperm into water)
What is a gemmule?
An overwintering capsule filled with totipotent archaeocytes, used for asexual reproduction
What is the function of parenchymula larvae
They are free-swimming, flagellated sponge larvae that settle and develop into adults
What is the function of spicules in sponges?
Spicules provide structural support and deter predators
How do sponges generate water flow for filter feeding?
Choanocytes use their flagella to create internal water currents, drawing water through ostia and expelling it through the osculum
What is the difference between ostia and osculum?
Ostia are small pores where water enters, while osculum is the large opening where water exits
What are sponges considered protoplasmic organisms?
They lack true tissues and organs, relying instead on specialized cells loosely arranged in a mesohyl matrix
What type of symmetry do sponges have
Most are asymmetrical, though some exhibit radial symmetry
How does a sponge’s body structure influence its size and efficiency?
More complex canal systems (leuconoid) allow for larger body size and more efficient water filtration
What role do archaeocytes play in sponge digestion?
They digest food particles captured by choanocytes and transport nutrients throughout the sponge
What is the main function of pinacocytes?
They form the sponge’s outer layer and contract to slightly alter body shape
How do sponges contribute to aquatic ecosystems?
They filter large volumes of water, remove bacteria and organic debris, and provide habitats for other marine line
What is the evolutionary significance of multicellularity in sponges?
It allows for cell specialization, division of labor, and increased body size, leading to more efficient nutrient absorption and survival
How do sponges regenerate lost body parts?
Totipotent archaeocytes can differentiate into any cell type, enabling regeneration and asexual reproduction
What do sponges lack a nervous system?
Their simple body plan relies on passive water flow rather than active movement or coordinated responses
What are two body forms in Cnidaria?
- Polyp (sessile, asexual)
- Medusa (motile, sexual)
What type of symmetry do Cnidarians have?
Radial symmetry
What are the two tissue layers in Cnidarians?
- Epidermis (outer)
- Gastrodermis (inner)
What is the function of cnidocytes?
They contain nematocysts, which are stinging organelles use for prey capture and defense
How do Cnidarians move?
Medusae use jet propulsion; some polyps can glide, somersault, or “walk”
What is the function of mesoglea?
It is a gelatinous extracellular matrix that provides support and buoyancy
What is the feeding strategy of Cnidarians?
They are carnivorous, using tentacles with cnidocytes to capture prey
What is the alternation of generations in Cnidarians?
Asexual polyp stage and sexual medusa stage
What are planula larvae?
The free swimming larval stage of Cnidarians that develops into polyps
What is strobilation?
The process in Scyphozoa where a polyp forms strobila, which bud into young medusae (ephyrae)
Which class of Cnidaria lacks a medusa stage?
Class Anthozoa (sea anemones & corals)
What mutualistic relationship do corals have?
Corals have zooxanthellae algae, which provide energy via photosynthesis
Why are coral reefs important?
They support 25% of marine life and have high biodiversity
What causes coral bleaching?
Loss of zooxanthellae due to rising sea temperatures and stress
What is the dominant life stage of Scyphozoa?
Medusa Aurelia (true jellyfish)
What do corals secrete?
Secretes calcium carbonate skeletons
What are some general characteristics of Phylum Cnidaria?
- Radial
- Diploblastic
- Gastrovascular cavity (incomplete gut)
- Nerve net (primitive nervous system, no brain)
- Cnidocytes
- Two body forms
What is a polyp?
Cnidarian body form
1. Cylindrical, sessile form
2. Asexual reproduction (budding)
3. Tentacles & mouth at the oral end
What is a medusa?
Other Cnidarian body form
1. Free swimming, bell shaped
2. Dioecious (separate sexes)
3. Reproduces sexually
What is included in a cnidarian nervous/muscular system?
- Nerve net (simplest form of nervous system)
- Epitheliomuscular cells (help with movement)
- Mesoglea (gelatinous matrix between epidermis & gastrodermis)
What is the function of the gastrovascular cavity?
Allows extracellular & intracellular digestion
What type of symmetry do Platyhelminthes have?
Bilateral symmetry
What are the three tissue layers in Platyhelminthes?
- Endoderm
- Mesoderm
- Ectoderm
What is an acoelomate?
An animal with no body cavity; solid tissue (parenchyma) fills space between organs
What are the three classes of Platyhelminthes?
- Turbellaria: free living flatworms (Planarians)
- Trematoda: parasitic flukes
- Cestoda: parasitic tapeworms
How do Planarians (Turbellaria) move?
Use cilia and muscular undulations
What is the function of flame cells?
Osmoregulation (removal of excess water and waste) via nephridiophores
What is unique about Planarian regeneration?
They have totipotent neoblasts that allow them to regenerate lost body parts
How do Trematodes (flukes) attach to their hosts?
Using an oral sucker
What is the life cycle of a Trematode?
- Egg (in host’s feces)
- Miracidium (ciliated larva)
- Sporocyst → Redia (larvae in snail host)
- Cercaria (free-swimming larva)
- Metacercaria (encysted larva in fish or plants)
- Adult fluke (in definitive vertebrate host)
What disease is caused by Schistosome flukes?
Schistosomiasis
What is the function of a tapeworm’s scolex?
Attachment to the host’s intestine using hooks and suckers
What are proglottids in tapeworms?
Reproductive segments that contain eggs and break off in feces
How do tapeworms absorb nutrients?
Through their tegument (body structure), since they lack a digestive system
What are the two hosts in the tapeworm life cycle?
Intermediate host (e.g., cattle, fish) and definitive host (e.g., humans, dogs)
What is the best way to avoid tapeworm infections?
Cook meat thoroughly and practice good hygiene?
List general characteristics of Phylum Platyhelminthes
- Bilateral symmetry
- Triploblastic
- Acoelomate: solid tissue (parenchyma)
- Protosomes: develop mouth first
- Cephalization: sensory structures concentrated at the head
What’s the ecological importance of Phylum Platyhelminthes?
- Free living (mostly marine, some freshwater)
- Parasitic species: impact humans and animals
- Used in reseearch
List some characteristics of Class Turbellaria
- Free living
- Simple nervous system
- Reproduce sexually or asexually
- Incomplete gut
- Pharynx extends to capture food
- No respiratory system
List characteristics for Class Trematoda
- Parasitic (often require 2 hosts)
- Digenetic life cycle: larval stages in intermediate host, adult in definitive host
List characteristics of Class Cestoda
- Parasitic in vertebrate intestines
- Reproduction: monoecious
What is the tapeworm life cycle?
- Eggs released in feces
- Larvae eaten by intermediate host (e.g., cattle, fish)
- Encyst in muscle (Metacestode stage)
- Definitive host ingests raw/undercooked meat
- Adult tapeworm develops in intestines
Which phylum has the greatest number of described species?
Mollusca
A(n) __ circulatory system require more energy to operate, but can deliver oxygen more quickly than a(n) __ circulatory system
Closed; open
Unlike the flagellated spe3rm cells of many animals, the sperm of this phylum must crawl their way to an ovum for successfrul fertilization
Nematoda
Which of the following is NOT true about nematodes?
Roughly 99% are parasitic
Which class of Platyhelminthes includes schistosome flukes?
Trematoda
Which class of Platyhelminthes does not include parasitic forms?
Turbellaria
The __ class of Cnidaria include the true jellyfish, in which the __ stage is dominant
Scyphozoa, medusa
Gemmules are __ that are produced by __
Overwintering capsules, Porifera
In the phylum Cnidaria, the polyp stage is generally ___ and ___
Asexual, sessile
The collar cells (choanocytes) of sponges (Porifera) are very similar in appearance to this closest-living relative of Kingdom Animalia
Choanoflagellates
The heavily branched canal systems of Leuconoid sponges with many well distributed flagellated chambers
Leuconoiod sponges have the most complex and efficient water flow system, allowing for larger body sizes and enhanced filter feeding
Which of the following is true with respect to reproduction in Poriferans
Poriferans are both sexually (monoecious) and asexual (budding and gemmules)
Which feeatures of Cnidarian biology are currently being challenged by climate change
Coral bleaching due to rising ocean temperatures and disruption of symbiotic relationship to red algae
Which feature is synapomorphy of the Hydrozoa
Presence of velum in medusa stage
Flame cells help an organism
Remove waste and excess water through osmoregulation in flatworms
The ___ host is one in which a parasite has not yet reached maturity and asexually reproduces
Intermediate
Both the septa of a sea anemone and highly branched gut of some flatworms
Increase surface area for digestion and nutrient absorption
The blood fluke infects humans as __ larvae,m while the liver fluke infects humans as a ___ larvae encysted in fish flesh
Cercariae, Metaceraria
This nematode genus includes the giant intestinal roundworm of humans
Ascaris
Most nematode species are parasitic (true or false)
False –> large number are free living
Which of the following is true regarding the coelom in mollusks?
Mollusks have a true coelom (eucolomate), but it is reduced to a small cavity around the heart and gonads
All of the following area adaptations for predation in Cephalopods except:
Things that help to catch prey:
Arms (tentacles, suction cups)
Jaws and radula
Octopus inject neurotoxins to immobilize prey
Very fast swimmers
Which of the following is not generally associated with parasitic lifestyle?
Turbellaria?
Which phylum does not include species that parasitize humans?
Porifera
Cephalopod mating involves __ as males transfer their sphermatophore using a specialized arm called a
Internal fertilization; hectocotylus
What are key adaptations for nematoda?
Hydrostatic skeleton
Ecdysis (molting) to grow
High reproductive rates
Which of the three classes of Platyhelminthes have no gut, rather than incomplete?
Tapeworms
What are some ecological importance of cnidarians?
Coral reefs, jewelry, pharmaceuticals, edible
Which class of Cnidaria exhibit alternate generations?
Hydrozoa
Out of the three classes of Platyhelminthes, which one is the only one that has cilia?
Turbellaria
