Podcast
Questions and Answers
Which of the following characteristics is NOT a defining feature of cnidarians?
Which of the following characteristics is NOT a defining feature of cnidarians?
- Gastrovascular cavity
- Presence of cnidocytes
- Triploblastic embryonic development (correct)
- Radial symmetry
How does the nerve net in cnidarians function differently from a centralized nervous system?
How does the nerve net in cnidarians function differently from a centralized nervous system?
- It enables the organism to perform complex learned behaviors.
- It allows for faster and more complex decision-making processes.
- It coordinates responses to stimuli throughout the body without a central control point. (correct)
- It provides a direct pathway for sensory information to the brain.
A marine biologist discovers a new species that is small, free-swimming, and has a cube-shaped bell. Which class does this species likely belong to?
A marine biologist discovers a new species that is small, free-swimming, and has a cube-shaped bell. Which class does this species likely belong to?
- Scyphozoa
- Anthozoa
- Cubozoa (correct)
- Hydrozoa
In a coral reef ecosystem, what is the primary role of cnidarians in maintaining biodiversity?
In a coral reef ecosystem, what is the primary role of cnidarians in maintaining biodiversity?
Which of the following is a primary function of the mesoglea in cnidarians?
Which of the following is a primary function of the mesoglea in cnidarians?
A scientist is studying a cnidarian species that alternates between a mobile, bell-shaped form and a sessile, cylindrical form throughout its life cycle. Which class does this cnidarian most likely belong to?
A scientist is studying a cnidarian species that alternates between a mobile, bell-shaped form and a sessile, cylindrical form throughout its life cycle. Which class does this cnidarian most likely belong to?
If a mutation occurred in a cnidarian that disabled its cnidocytes, what immediate impact would this have on its survival?
If a mutation occurred in a cnidarian that disabled its cnidocytes, what immediate impact would this have on its survival?
What is the evolutionary advantage of cnidarians having both sexual and asexual reproductive strategies?
What is the evolutionary advantage of cnidarians having both sexual and asexual reproductive strategies?
Flashcards
Phylum Cnidaria
Phylum Cnidaria
A group of marine animals including jellyfish, corals, and anemones.
Radial symmetry
Radial symmetry
Body plan where body parts are arranged around a central axis.
Cnidocytes
Cnidocytes
Specialized cells in cnidarians that contain stinging organelles called nematocysts.
Medusa form
Medusa form
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Gastrovascular cavity
Gastrovascular cavity
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Nerve net
Nerve net
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Asexual reproduction
Asexual reproduction
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Symbiotic relationship with zooxanthellae
Symbiotic relationship with zooxanthellae
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Study Notes
Cnidaria Phylum Overview
- Cnidarians are a phylum of animals including jellyfish, corals, sea anemones, and hydras.
- They exhibit radial symmetry and are diploblastic, possessing an epidermis (outer layer), gastrodermis (inner layer), and mesoglea (substance between layers).
- Cnidocytes, specialized cells, contain nematocysts, stinging organelles, used for defense and capturing prey.
Body Structure
- Polyp form: Sessile, cylindrical with a mouth surrounded by tentacles (e.g., sea anemones, corals).
- Medusa form: Free-swimming, bell-shaped (e.g., jellyfish).
Digestive System
- Possess a gastrovascular cavity, a single opening acting as both a mouth and anus.
- Employ extracellular digestion, breaking down food in the cavity before absorption.
Nervous System
- Have a nerve net, a network of neurons coordinating responses to stimuli.
- Lack a central brain but exhibit coordinated movements, particularly in medusa forms.
Reproduction
- Reproduce both sexually and asexually.
- Asexual reproduction in the polyp stage occurs through budding.
- Sexual reproduction involves release of eggs and sperm; external fertilization is common; many are hermaphroditic (having both sexes).
Ecological Roles
- Play key roles in marine ecosystems, acting as predators and prey.
- Corals form coral reefs, habitats for diverse marine life.
Cnidarian Types
- Class Hydrozoa: Includes hydra, Portuguese man-of-war, and freshwater species; exhibit both polyp and medusa stages.
- Class Scyphozoa: True jellyfish, predominantly medusa-shaped; free-swimming, often large.
- Class Anthozoa: Sea anemones, corals, sea fans; only polyp form; often sessile.
- Class Cubozoa: Box jellyfish; cube-shaped bell; highly venomous; complex eyes.
Symbiotic Relationships
- Many cnidarians have mutualistic relationships with zooxanthellae (algae).
- Zooxanthellae perform photosynthesis, providing nutrients; cnidarians provide protection and sunlight.
Defensive and Offensive Strategies
- Cnidocytes (stinging cells) containing nematocysts are the primary offensive adaptation.
- Nematocysts inject toxins into prey or predators.
- Some species paralyze prey for capture or use stingers for defense against predators.
Economic and Medical Importance
- Corals are crucial for marine biodiversity and tourism due to coral reefs.
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Description
Explore the Cnidaria phylum, including jellyfish and corals. Learn about their radial symmetry, diploblastic structure, and specialized cnidocytes with nematocysts. Discover the polyp and medusa forms, gastrovascular cavity, nerve net, and diverse reproductive strategies of cnidarians.
