Zoology Questions and Answers

Answer: C

The correct match is P-I, Q-III, R-IV, S-I.

• Archaezoa, such as Giardia and Trichomonas, move with flagella (P-I).
• Amoebozoa move by pseudopods (Q-III).
• Ciliophora, such as Paramecium, are defined by their cilia (R-IV).
• Apicomplexa, such as Plasmodium, lack appendages in most stages; motile male gametes have flagella (S-I).

Fimbriae and pili are prokaryotic surface structures for attachment and conjugation, not protozoan motility appendages, so options using II or V are wrong.

Answer: B

Lampreys belong to the class Cephalaspilomorphi (usually spelt Cephalaspidomorphi).

In the traditional classification of jawless fishes (Agnatha), lampreys are placed in Cephalaspidomorphi (also called Petromyzontida or Hyperoartia), together with fossil cephalaspids, because they share a single median nostril and a dorsal nasohypophyseal opening.

Myxini is the class of hagfishes, the other living jawless fishes. Conodonta are extinct eel-like animals known mainly from their tooth-like elements, and Anaspida are extinct armoured jawless fishes.

Answer: B

Book lungs are found in the scorpion.

Book lungs are respiratory organs of arachnids such as scorpions and many spiders: each is a cavity holding thin, leaf-like folds of tissue stacked like the pages of a book, between which air circulates and exchanges gases with haemolymph.

An earthworm breathes through its moist skin, an octopus uses gills in its mantle cavity, and a starfish exchanges gases through dermal branchiae (papulae) and tube feet. None of them has book lungs.

Answer: A

The segmented phylum is Annelida.

Annelids, the segmented worms such as earthworms, leeches and polychaetes, show true metameric segmentation: the body is a series of repeated segments, each with its own coelomic compartment, muscles, nerve ganglia, excretory nephridia and often bristles (chaetae).

Cnidarians (jellyfish, Hydra) are radially symmetric with a simple sac-like body. Echinoderms are pentaradial as adults and unsegmented. Sponges (Porifera) have no true tissues or organs, let alone segments.

Answer: C

The group with a non-arthropod is Group 3: millipedes, horseshoe crabs, sponges, earthworms.

Arthropods have jointed legs, a segmented body and a chitinous exoskeleton. Millipedes (myriapods) and horseshoe crabs (chelicerates) qualify, but sponges belong to the phylum Porifera and earthworms to Annelida. Earthworms are segmented but have no exoskeleton or jointed limbs.

Group 1 holds only arthropods: crustaceans, scorpions and mites (arachnids), and insects. Group 2 also does: trilobites are an extinct class of arthropods, and horseshoe crabs and centipedes are living ones. Group 4 consists of insects.

Answer: D

Binary fission occurs in all of these.

Binary fission is asexual division of one cell into two daughter cells. Amoeba divides by simple (irregular) binary fission, Paramecium by transverse binary fission, and Euglena by longitudinal binary fission.

Since all three organisms reproduce in this way, no single one of them is the complete answer.

Answer: B

The organism is yeast.

Yeasts are unicellular fungi that reproduce asexually either by budding (as in Saccharomyces) or by fission (as in Schizosaccharomyces), and they are conventionally divided into budding yeasts and fission yeasts on this basis.

Bacteria reproduce by binary fission and are classified on shape, staining and biochemistry. Myxomycetes (slime moulds) and actinomycetes reproduce by spores, so budding and fission do not classify them.

Answer: D

The connecting link is Proterospongia.

Proterospongia is a colonial choanoflagellate: a protozoan whose collared flagellate cells are embedded in a jelly, resembling the choanocytes (collar cells) of sponges. It therefore links the Protozoa with the Porifera.

Euglena links animals and plants, Chlamydomonas is a green alga, and Protopterus is the African lungfish, a link between fishes and amphibians.

Answer: B

The basic unit of classification is the species.

A species is a group of similar individuals that can interbreed in nature and produce fertile offspring. It is the lowest of the main taxonomic categories, and the higher ranks (genus, family, order and so on) are built by grouping species.

The genus is a group of related species, so it is a higher category. Genes and cells are units of heredity and structure, not of taxonomy.

Answer: A

Reptiles in fresh water are hyper-osmotic.

Their body fluids are much more concentrated than the dilute fresh water around them. Water therefore tends to enter their bodies by osmosis and salts tend to leak out, so freshwater reptiles must limit water uptake and conserve salts.

Hypo-osmotic describes animals in sea water whose fluids are more dilute than the sea, such as marine bony fishes. Iso-osmotic means equal concentration, and hypotonic is the wrong way round for freshwater animals.