Diversity in Living Organisms

Foxes, tigers, cheetahs, and dogs mark their territories primarily using urine and scent gland secretions. Urine marking is a common territorial behavior among these carnivores, making option C correct.

Snakes have an extremely well-developed sense of smell using their Jacobson's organ (vomeronasal organ). They flick their tongues to collect scent particles and detect prey, predators, and mates from considerable distances.

Herpetophobia is the specific phobia of reptiles, particularly snakes. The prefix 'herpeto-' comes from Greek herpeton meaning 'creeping thing,' referring to reptiles and amphibians. Ailurophobia is fear of cats, cynophobia is fear of dogs, and ornithophobia is fear of birds.

Chameleons have specialized eyes that can move independently of each other, with one eye looking forward while the other looks backward. This gives them 360-degree vision and helps them spot prey and predators simultaneously.

Owls have specialized neck vertebrae that allow them to rotate their heads up to 270 degrees in either direction. This extreme rotation is necessary because their eyes are fixed in their sockets, so they must turn their entire head to look around. Most birds can rotate only about 180 degrees, and 360 degrees would cause physical damage.

Mammals did indeed diversify after the Cretaceous-Paleogene extinction about 65 million years ago, and early hominids like Orrorin tugenensis (about 6 million years old) show adaptations for bipedalism. Orrorin is considered one of the earliest known hominins that could walk upright.

Early English settlers in Australia during the late 18th century incorrectly called koalas 'koala bears' due to their bear-like appearance. Despite this common misnomer, koalas are marsupials (not bears) and are only distantly related to the bear family.

Some cats can be born without claws due to a congenital condition called onychodystrophy or other genetic abnormalities. While rare, this birth defect does occur naturally. All cats have claws by default, but birth defects exist.

Crocodiles are reptiles and lack sweat glands. They thermoregulate by gaping their mouths to evaporate moisture and release excess body heat. This behavior is commonly seen in crocodilians basking in the sun.

Mammals are characterized by hair/fur, warm-blooded metabolism, and lungs for breathing air. Gills are respiratory structures found in fish and some amphibians, not mammals.

A blue whale's heart is enormous - typically around 600 kg and can reach 900 kg in exceptional cases, making it the largest heart of any animal. The aorta is remarkably wide at about 23 cm in diameter, allowing massive blood flow. Options A and B are incorrect because the tongue weighs ~2,700 kg (not 2.7 kg) and the mouth can hold ~90 metric tons (not kg).

Birds possess air sacs as a unique anatomical feature of their respiratory system. These air sacs allow for unidirectional airflow through the lungs, enabling efficient gas exchange even during both inhalation and exhalation. This adaptation supports the high metabolic demands of flight. Fish use gills, elephants have mammalian lungs, and frogs primarily use cutaneous and buccopharyngeal respiration.

Both humans and giraffes have 7 cervical vertebrae (neck bones), despite the giraffe's extremely long neck. This is a consistent trait across almost all mammals - from mice to giraffes. The difference is in the size of each vertebra, not the number. This is a classic example of evolutionary conservation.

True. Scientific classification of the smallest living organism remains an active area of research. New microscopic organisms continue to be discovered, and definitions of what constitutes 'life' at the smallest scales are debated among scientists. What was once considered the smallest may be superseded by new discoveries.