Which one among the following is known as 'Living fossil'?
AShark
BClownfish
CLimulus
DOctopus
Answer:
C. Limulus
Read Explanation:
Phylum Arthrodpoda:
- This is the largest phylum of Animal kingdom which includes insects.
- Over two-thirds of all named species on earth are arthropods
- They have organ-system level of organisation.
- They are bilaterally symmetrical, triploblastic, segmented and coelomate animals.
- The body of arthropods is covered by chitinous exoskeleton.
- The body consists of head, thorax and abdomen.
- They have jointed appendages (arthros-joint, poda-appendages).
- Respiratory organs are gills, book gills, book lungs or tracheal system. (Insects)
- Circulatory system is of open type.
- Sensory organs like antennae, eyes (compound and simple), statocysts or balance organs are present.
- Excretion takes place through malpighian tubules. They are mostly dioecious.
- Fertilisation is usually internal. They are mostly oviparous. Development may be direct or indirect.
Examples:
- Economically important insects – Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect)
- Vectors – Anopheles, Culex and Aedes (Mosquitoes)
- Gregarious pest – Locusta (Locust)
- Living fossil – Limulus (King crab).