connecting link and missing link between two organism ?

1. Virus

Connecting link Between living and non-living

Non-living Characters  Living Characters
  •  These can be crystallized like inorganic and organic compound.
  •  Cell organelles remain absent.
  • Lack of growth and metabolism
  •  Undergo mutation
  •  Reproduction in the living cell.
  • Shows recombination and heritability.

 

2. Euglena

Connecting link Between plants and animals

 Animal Characters  Plant Characters
  •  The body is covered by the pellicle. cell wall absent.
  • Reproduction is like animals.
  • Having chlorophyll and chloroplast.
  • Nutrition is holotypic or autotrophic.
  • Synthesize their food through photosynthesis.

 

3. Peripatus

peripatus

Connecting link Between Annelida and Arthropods

Annelidan Characters  Arthropods Characters
  •  The presence of thick cuticle.
  • Body is pseudo segmented and worm-like.
  • The excretory organ is nephridia.
  •  Presence of antennae
  • Respiratory organ is trachea

4. Neopilina

Connecting link Between Annelida and Mollusca

 Annelidan Characters Molluscan Characters
  •  The presence of trochophore larva.
  • Presence of 5-6 pairs of ctenidia, 6 pairs of nephridia, 8 pairs of retracer muscles and two pairs of auricles
  • Presence of shell and mantle.
  • The presence of a flat muscular foot as found in Chiton.

 

5. Balanoglossus

Connecting link Between Non-Chordate and Chordate

 Chordate Characters  Non-chordate Characters
  • Presence of a dorsal hollow nerve cord
  • Notochord is present.
  • Presence of pharyngeal gills slits (Pharyngotremy)
  •  Body vermiform
  • Burrowing habit.
  • Dorsal position of the heart.
  • The nervous system is poorly developed and form epidermal nerve plexus.

6. Proterospongia

Connecting link Between Protozoa and Porifera

 Protozoan Characters Sponge Characters
  •  It is a colonial protozoan
  •  Its cells are similar to choanocytes or collar cells of sponges

 

7. Prototherians(Egg-laying mammals)

 Connecting link Between Reptiles and Mammals

Reptilian Characters  Mammalian Characters
  •  Presence of cloaca.
  • They lay eggs which are reptilian in structure and development.
  • Embryonic development is similar to reptiles.
  • Presence of hairs.
  • They produce milk and nourish their children.
  • They have mammary glands.
  • Presence of diaphragm.

 

8. Lung fish (Group-Dipnoi)

Connecting link Between Fish and Amphibian

Fish Characters  Amphibian Characters
  •  The presence of paired fins.
  • Gills are present.
  • The presence of lateral line sense organ.
  • Ear represented by internal ear only.
  •  The presence of internal nostrils of chonae.
  • Presence of lungs i.e., modified air bladders.
  • Heart with imperfectly divided auricle.

 

9. Archaeopteryx

Missing link Between Reptiles and Birds

Archaeopteryx (also called lizard-bird). The fossils of Archaeopteryx litho-graphica were discovered in 1861 A.D. by Andreas Wagner from the Upper Jurassic limestone rocks (about 180 million years old) of Solenhofen in Bavaria, Germany.It is a missing link between reptiles and birds. It was about the size of a crow and had both reptilian and avian characters.

The extinct connecting link is known as the Missing link.Its fossil was discovered by Wagner from limestone rocks of Jurassic Period on Germany.The characters below show that the birds have evolved from the reptilian ancestors. Huxley called the birds as glorified reptiles.

Avian Characters  Reptiles Characters
  •  The presence of feathers on the body.
  • Rounded cranium with the intimate fusion of bones.
  • Forelimbs modified into wings and have only three fingers.
  • Presence of 4-toes in each foot and adapted for perching as in the birds.
  • Presence of furcula or wishbone.
  • Presence of teeth in beak.
  • Each finger ending into a claw.
  • A long tail with free caudal vertebrae.