Invertebrates Practice Questions
20 free Invertebrates practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following invertebrate phyla is characterized by having a body organized around a central gastrovascular cavity with only a single opening that serves as both mouth and anus?
- A Porifera
- B Cnidaria
- C Annelida
- D Arthropoda
Correct answer: Cnidaria
Cnidarians, such as jellyfish and sea anemones, possess a sac-like body plan with a gastrovascular cavity. This central compartment functions in both digestion and nutrient distribution, utilizing a single opening for ingestion and egestion.
The specialized 'collar cells' in sponges that create a water current and trap food particles are known as:
- A Amoebocytes
- B Spicules
- C Choanocytes
- D Cnidocytes
Correct answer: Choanocytes
Choanocytes line the interior canals of sponges and feature a flagellum surrounded by a mesh-like collar. The beating flagella pull water through the sponge, while the collar filters out microscopic food particles like bacteria.
Which of the following is a key distinguishing feature of the phylum Arthropoda?
- A Closed circulatory system
- B Jointed appendages
- C Calcium carbonate endoskeleton
- D Radial symmetry
Correct answer: Jointed appendages
The name Arthropoda literally means 'jointed foot,' referring to the articulated appendages that allow for complex movement. This phylum is also characterized by an exoskeleton made of chitin and segmented bodies.
Flatworms (Platyhelminthes) lack a respiratory system and circulate oxygen primarily through which process?
- A Active transport
- B Simple diffusion
- C A water vascular system
- D Hemolymph pumping
Correct answer: Simple diffusion
Because flatworms are dorsoventrally flattened, all their cells are close enough to the external environment for gas exchange to occur via simple diffusion. This physiological constraint limits their body thickness but eliminates the need for a complex circulatory or respiratory system.
In mollusks, the specialized tissue layer that secretes the shell and covers the visceral mass is called the:
- A Radula
- B Foot
- C Mantle
- D Ctenidium
Correct answer: Mantle
The mantle is a fold of tissue that drapes over the visceral mass and creates the mantle cavity. In many species, it contains glands that produce calcium carbonate to form the protective shell.
Which class of echinoderms is characterized by a globe-shaped body, lacks arms, and moves using long, movable spines?
- A Asteroidea (Sea stars)
- B Holothuroidea (Sea cucumbers)
- C Echinoidea (Sea urchins)
- D Crinoidea (Sea lilies)
Correct answer: Echinoidea (Sea urchins)
Echinoids, which include sea urchins and sand dollars, have a compact body encased in a shell-like test made of fused plates. They utilize both tube feet and their characteristic spines for locomotion and protection.
What is the primary excretory organ found in many annelids, such as earthworms?
- A Flame cells
- B Malpighian tubules
- C Metanephridia
- D Kidneys
Correct answer: Metanephridia
Metanephridia are excretory tubes found in each segment of an annelid that collect fluid from the coelom. They process this fluid to retain useful solutes and expel nitrogenous waste through external pores.
Arachnids, such as spiders and scorpions, are distinguished from insects by having how many pairs of walking legs?
- A Three
- B Four
- C Five
- D Six
Correct answer: Four
Arachnids belong to the subphylum Chelicerata and possess four pairs of walking legs (eight total). In contrast, insects are hexapods, meaning they always possess three pairs of legs.
The 'polyp' and 'medusa' stages are two distinct body forms found in which invertebrate phylum?
- A Porifera
- B Cnidaria
- C Mollusca
- D Echinodermata
Correct answer: Cnidaria
Cnidarians often exhibit dimorphism, alternating between a sessile, cylindrical polyp stage and a motile, umbrella-shaped medusa stage. Some groups, like jellyfish, spend most of their life cycle as medusae, while others, like corals, exist only as polyps.
Which of the following invertebrates is a 'pseudocoelomate'?
- A Earthworm
- B Planarian
- C Roundworm
- D Snail
Correct answer: Roundworm
Nematodes possess a body cavity that is only partially lined with mesoderm, known as a pseudocoelom. This fluid-filled space acts as a hydrostatic skeleton and facilitates the transport of nutrients.
What is the function of the 'green glands' found in some crustaceans like crayfish?
- A Digestion of plant matter
- B Production of pigment for camouflage
- C Excretion and osmoregulation
- D Secretion of silk
Correct answer: Excretion and osmoregulation
Green glands, also known as antennal glands, are the excretory organs of certain crustaceans. They are located near the base of the antennae and help the organism maintain salt balance and eliminate waste.
Which invertebrate group is known for having 'torsion' during larval development, causing the visceral mass to rotate 180 degrees?
- A Bivalvia
- B Cephalopoda
- C Gastropoda
- D Polyplacophora
Correct answer: Gastropoda
Gastropods, such as snails and slugs, undergo torsion during their veliger larval stage. This developmental process results in the anus and mantle cavity being positioned above the head.
Insects that undergo 'complete metamorphosis' pass through which of the following sequences of stages?
- A Egg -> Nymph -> Adult
- B Egg -> Larva -> Pupa -> Adult
- C Egg -> Larva -> Adult
- D Larva -> Nymph -> Pupa -> Adult
Correct answer: Egg -> Larva -> Pupa -> Adult
Complete metamorphosis (holometabolous development) includes a pupal stage where the organism undergoes a total tissue transformation. This is seen in butterflies, beetles, and bees, whereas incomplete metamorphosis lacks the pupal stage.
Which phylum contains organisms that are the only invertebrates to possess a 'notochord' (at least in their larval stage)?
- A Echinodermata
- B Chordata (Invertebrate subphyla)
- C Hemichordata
- D Arthropoda
Correct answer: Chordata (Invertebrate subphyla)
Invertebrate chordates, such as tunicates (sea squirts) and lancelets, belong to the phylum Chordata. They possess the four hallmark chordate features—notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail—even though they lack a bony backbone.
The 'book lungs' used for respiration in many spiders are named so because:
- A They are found in the cephalothorax
- B They resemble the pages of a book
- C They were discovered by a librarian
- D They are used to sense vibrations
Correct answer: They resemble the pages of a book
Book lungs consist of many stacked, thin, leaf-like structures (lamellae) that resemble pages. This arrangement provides a large surface area for gas exchange between the hemolymph and the air.
Which of the following describes the 'water vascular system' of echinoderms?
- A A system for digesting coral
- B Hydraulic canals used for locomotion
- C A circulatory system containing hemoglobin
- D A sensory system for detecting light
Correct answer: Hydraulic canals used for locomotion
The water vascular system is unique to echinoderms and functions in gas exchange, feeding, and locomotion. By manipulating water pressure within this system, the animal can extend or retract its tube feet to move across the seafloor.
A 'clitellum' is a reproductive structure found in which group of invertebrates?
- A Leeches and earthworms
- B Clams and oysters
- C Grasshoppers and crickets
- D Tapeworms and flukes
Correct answer: Leeches and earthworms
The clitellum is a thickened, glandular section of the body wall in certain annelids. It secretes a viscid sac or cocoon in which the eggs are deposited and fertilized during reproduction.
Which type of symmetry is most common among adult mollusks and arthropods?
- A Asymmetry
- B Radial symmetry
- C Bilateral symmetry
- D Spherical symmetry
Correct answer: Bilateral symmetry
Bilateral symmetry allows for cephalization—the concentration of sensory organs at the anterior end. This symmetry is characteristic of the 'Bilateria' clade, which includes mollusks, arthropods, annelids, and chordates.
Malpighian tubules are an adaptation for which of the following functions in terrestrial insects?
- A Silk production
- B Water conservation and excretion
- C Flight muscle attachment
- D Pheromone production and chemical signaling
Correct answer: Water conservation and excretion
Malpighian tubules are efficient at removing nitrogenous wastes from the hemolymph while minimizing water loss. By excreting waste as nearly dry uric acid, insects are able to thrive in arid terrestrial environments.
Which of the following invertebrates belongs to the class Cephalopoda?
- A Scallop
- B Cuttlefish
- C Nudibranch
- D Abalone
Correct answer: Cuttlefish
Cuttlefish are cephalopods, a class of mollusks characterized by bilateral symmetry, a prominent head, and a set of arms or tentacles. They are known for their sophisticated nervous systems and rapid color-changing abilities.