Animal Kingdom
Which of the following organisms shows radial symmetry in its adult form?
A
Starfish
B
Earthworm
C
Butterfly
D
Fish
Correct Answer:
A. Starfish
Starfish (Echinodermata) exhibits radial symmetry in adults, while earthworms show bilateral symmetry. Butterflies and fish are bilaterally symmetric.
The absence of which structure distinguishes jawless fish (Agnathans) from jawed fish (Gnathostomes)?
A
Paired fins
B
Vertebral column
C
Swim bladder
D
Gill arches
Correct Answer:
A. Paired fins
Agnathans (lampreys, hagfish) lack paired fins and jaws, while gnathostomes possess these structures along with true jaws derived from gill arches.
Which class of animals shows maximum biological diversity and why?
A
Mammalia - due to complex behavior
B
Insecta - due to adaptability, shorter life cycles, and diverse ecological niches
C
Aves - due to flight adaptations
D
Pisces - due to aquatic diversity
Correct Answer:
B. Insecta - due to adaptability, shorter life cycles, and diverse ecological niches
Insects represent over 80% of described animal species due to their adaptability, rapid reproduction, metamorphosis, and ability to occupy diverse ecological niches.
The development of amnion and allantois in embryos is an adaptation for:
A
Aquatic reproduction
B
Internal fertilization only
C
Terrestrial reproduction independent of water
D
Placental nutrition
Correct Answer:
C. Terrestrial reproduction independent of water
The amnion protects the embryo in fluid, and allantois stores waste products, allowing amniotes to reproduce on land without dependence on water.
Which of the following represents a more recent evolutionary relationship (sister group)?
A
Arthropods and Molluscs
B
Birds and Reptiles
C
Fish and Amphibians
D
Cnidarians and Echinoderms
Correct Answer:
B. Birds and Reptiles
Modern cladistic analysis shows birds are derived from theropod dinosaurs (reptiles), making them sister groups with a more recent common ancestor.
In the phylogenetic tree of animals, which phylum is believed to be ancestral to arthropods?
A
Annelida
B
Mollusca
C
Platyhelminthes
D
Nematoda
Correct Answer:
A. Annelida
Annelids and arthropods share similarities in segmentation and structure, suggesting arthropods evolved from annelid-like ancestors.
A mammal is defined by the presence of:
A
Four-chambered heart and dry skin
B
Mammary glands and hair
C
Warm blood and fur
D
Internal fertilization and placenta
Correct Answer:
B. Mammary glands and hair
Mammals are uniquely characterized by mammary glands for milk production and hair/fur for insulation, not all have placenta (monotremes lack it).
Which of the following statements about sponges (Porifera) is correct?
A
They have true tissues and organs
B
They reproduce only asexually
C
They are predominantly marine organisms
D
They possess a nervous system
Correct Answer:
C. They are predominantly marine organisms
Most sponges are marine organisms. They lack true tissues, organs, and nervous systems but can reproduce both sexually and asexually.
The presence of a single atrium in the heart is characteristic of which class?
A
Amphibia
B
Fish
C
Reptilia
D
Mammalia
Fish possess a two-chambered heart with one atrium and one ventricle, unlike amphibians and reptiles which have three chambers.
Amphibians can respire through their skin because:
A
They have more efficient lungs
B
Their skin is thin, moist, and highly vascularized
C
They lack true lungs
D
They possess gills throughout their life
Correct Answer:
B. Their skin is thin, moist, and highly vascularized
Amphibian skin is thin, moist, and richly supplied with blood vessels, enabling efficient cutaneous respiration.
