- What is the primary characteristic of the class Hydrozoa?
- A) They have a complex nervous system.
- B) They can exist in both polyp and medusa forms.
- C) They lack stinging cells.
- D) They are all freshwater species.
Answer: B) They can exist in both polyp and medusa forms.
- Which of the following is a common example of a Hydrozoan?
- A) Jellyfish
- B) Sea anemone
- C) Portuguese man o’ war
- D) Coral
Answer: C) Portuguese man o’ war
- What type of reproduction is commonly observed in Hydrozoa?
- A) Budding
- B) Binary fission
- C) Fragmentation
- D) Sexual reproduction only
Answer: A) Budding
- Which structure in Hydrozoa is responsible for capturing prey?
- A) Gastrovascular cavity
- B) Tentacles
- C) Medusa
- D) Foot
Answer: B) Tentacles
- What is the primary mode of locomotion for Hydrozoans in the medusa stage?
- A) Walking
- B) Jet propulsion
- C) Pulsating contractions
- D) Crawling
Answer: C) Pulsating contractions
- Which of the following is a key feature of the Hydrozoan life cycle?
- A) Alternation of generations
- B) Asexual reproduction only
- C) Direct development
- D) Metamorphosis
Answer: A) Alternation of generations
- What type of symmetry is exhibited by Hydrozoans?
- A) Bilateral symmetry
- B) Asymmetry
- C) Radial symmetry
- D) Pentaradial symmetry
Answer: C) Radial symmetry
- In Hydrozoans, what is the name of the structure that aids in buoyancy?
- A) Bell
- B) Foot
- C) Mesoglea
- D) Polyp
Answer: C) Mesoglea
- Which Hydrozoan is known for forming large colonies?
- A) Hydra
- B) Obelia
- C) Aurelia
- D) Chironex
Answer: B) Obelia
- What is the function of the gastrovascular cavity in Hydrozoans?
- A) Locomotion
- B) Digestion and circulation
- C) Reproduction
- D) Sensory perception
Answer: B) Digestion and circulation
- Which Hydrozoan is known for its ability to reproduce both sexually and asexually?
- A) Hydra
- B) Sea wasp
- C) Moon jelly
- D) Box jellyfish
Answer: A) Hydra
- What is the typical habitat of most Hydrozoans?
- A) Terrestrial
- B) Freshwater and marine
- C) Arctic
- D) Desert
Answer: B) Freshwater and marine
- Which structure is responsible for the movement of water in Hydrozoans?
- A) Cilia
- B) Flagella
- C) Siphon
- D) Tentacles
Answer: A) Cilia
- What type of feeding strategy do Hydrozoans primarily use?
- A) Filter feeding
- B) Predatory feeding
- C) Herbivorous feeding
- D) Parasitic feeding
Answer: B) Predatory feeding
- In the Hydrozoan life cycle, which stage typically produces gametes?
- A) Polyp stage
- B) Medusa stage
- C) Planula stage
- D) Larval stage
Answer: B) Medusa stage
- Which of the following Hydrozoans is often used in scientific research for its regenerative abilities?
- A) Physalia
- B) Hydra
- C) Aurelia
- D) Cassiopeia
Answer: B) Hydra
- What are the specialized cells that contain nematocysts in Hydrozoans called?
- A) Muscle cells
- B) Epithelial cells
- C) Cnidocytes
- D) Neurons
Answer: C) Cnidocytes
- Which environmental factor can significantly affect the distribution of Hydrozoans?
- A) Temperature
- B) pH levels
- C) Salinity
- D) All of the above
Answer: D) All of the above
- What is the primary function of the bell-shaped structure in medusa forms of Hydrozoans?
- A) Feeding
- B) Defense
- C) Propulsion
- D) Attachment
Answer: C) Propulsion
- In Hydrozoa, the term “polyp” refers to which form?
- A) Free-swimming stage
- B) Sessile, cylindrical stage
- C) Larval stage
- D) Sexual reproductive stage
Answer: B) Sessile, cylindrical stage
- Which type of Hydrozoan is known for its strong sting and is considered dangerous to humans?
- A) Hydra
- B) Physalia
- C) Obelia
- D) Gonionemus
Answer: B) Physalia
- What is the role of the mesoglea in Hydrozoans?
- A) Support and buoyancy
- B) Digestion
- C) Sensation
- D) Circulation
Answer: A) Support and buoyancy
- How do Hydrozoans typically respond to environmental stimuli?
- A) With complex behaviors
- B) Through simple reflex actions
- C) They do not respond
- D) By changing color
Answer: B) Through simple reflex actions
- Which Hydrozoan is often referred to as a “jellyfish” despite being a Hydrozoan?
- A) Aurelia
- B) Chironex
- C) Velella
- D) Physalia
Answer: D) Physalia
- What type of ecological role do Hydrozoans primarily fulfill?
- A) Primary producers
- B) Herbivores
- C) Predators
- D) Decomposers
Answer: C) Predators
- Which of the following is a feature of the Hydrozoan’s nervous system?
- A) Centralized brain
- B) Nerve net
- C) Complex ganglia
- D) Absence of nerve cells
Answer: B) Nerve net
- What adaptation allows Hydrozoans to capture small prey effectively?
- A) Fast swimming
- B) Stinging cells
- C) Strong jaws
- D) Camouflage
Answer: B) Stinging cells
- In Hydrozoans, what is a planula?
- A) A reproductive cell
- B) The larval stage
- C) A feeding stage
- D) The adult stage
Answer: B) The larval stage
- Which Hydrozoan is often associated with the term “by-the-wind sailor”?
- A) Physalia
- B) Velella
- C) Aurelia
- D) Gonionemus
Answer: B) Velella
- What environmental condition can lead to a bloom of Hydrozoans?
- A) Pollution
- B) Increased nutrients
- C) Climate change
- D) All of the above
Answer: D) All of the above