The Largest and Smallest Living Organisms Ever


We live in a world full of contradictions, the strangest among them all may be the vast differences in the sizes of living organisms. Some organisms weigh thousands of kilograms, while others are less than a millimeter in length. Hereunder, we present the largest and smallest organisms we know to be currently living on Earth.


The ostrich is currently the largest known bird on Earth; it weighs about 150 kilograms, and its height can reach up to 180 cm (6 feet). It runs at a speed of 70 kilometers per hour, making it the fastest bird. The ostrich also lives in groups of ten to fifteen and feeds on fruits, seeds, and small insects.

The hummingbird is the smallest bird known to date; its weight does not exceed two grams, and its height is about six centimeters at puberty. This bird lives in Cuba and feeds on small flowers; its female lays eggs in a nest as small as the size of a coin.


The rhinoceros beetle is the largest known living insect; its length exceeds 12.5 cm and its width is 4 cm. These insects live in the Amazon rainforest and have a solid shield that protects them, so they almost have no predators.

As for the smallest insect, it is the fairy wasp, with an average length of less than 1 mm. This insect includes large species, the smallest of which is the female kikiki the length of which is about 0.15 mm. Most fairy wasps live in the state of Hawaii; in the last decade, however, scientists have discovered new species in Costa Rica.


The komodo dragon lizard is the largest known living reptile in our time; it is more than three meters in height and weighs up to 136 kilograms. This lizard inhabits some islands of Indonesia and is characterized by its frightening appearance that resembles the monsters of ancient myths, which is the reason it is called a dragon.

The predator komodo dragon lizard feeds on smaller animals; such as deer, pigs, buffalo. It can also eat carrion and depends on trickery to hunt its prey.

The garagua lizard, which lives on an island in the Caribbean Sea near the coast of the Dominican Republic, is the smallest known living reptile; some scientists consider it one of the smallest creatures, including mammals and birds.

The adult male is about 1.6 cm long and feeds on plants and leaves of small trees; however, these species are endangered due to excessive logging.


The bird-eating spider is the largest known spider on Earth today; the length of its legs exceeds 30 cm and it weighs up to 170 grams. The bird-eating spider lives for a long time; the average age of the male spider ranges between 3-6 years, while the female's lifespan may reach up to 20 years.

This spider feeds on small birds and insects; that is why it is called a bird eater. Despite its scary appearance, it is not poisonous; however, it can be harmful and can cause wounds due to its sharp claws. The smallest known spider is Bato Dejo, which is about 0.37 mm long and lives in Colombia.

The Largest and Smallest Living Organisms

The blue whale is considered the largest known organism now; it is about 30 meters long and may weigh up to 200 tons. The weight of its tongue alone is equivalent to the weight of an elephant. The adult blue whale feeds on nearly 4 tons of krill, shrimp-like arthropods, daily.

The blue whale swims alone or in small groups, at a speed that exceeds 5 miles per hour, but its speed can reach 30 miles per hour. It lives in all oceans except the Arctic. The blue whale also lives for 80 to 90 years, but it can also live up to 110 years.

It is very difficult to identify the smallest organisms ever, as scientists discover new small creatures every day.

Cover image

About Us

SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
Continue reading

Contact Us

P.O. Box 138, Chatby 21526, Alexandria, EGYPT
Tel.: +(203) 4839999
Ext.: 1737–1781

Become a member

© 2023 | Bibliotheca Alexandrina