Levels of Organization in an Organism MCQ - Practice Questions with Answers

The cellular level of organization: 

• The body is made up of loose cells that perform specific functions. 
• Animals called parazoa have cellular organization. 
• It is the most primitive type of organization and is suited for sedentary life-forms, e.g., Sponges.

Tissue level of organization: 

• A group of cells performing a common function is called the tissue. 
• Presence of various such tissues results in tissue level of organization, as seen in coelenterates,ctenophora

Organ level of organization: 

• When a group of tissues that perform related functions combines together, an organ is formed.
•  For example, stomach, heart etc. 
• Animals that have specific organs for specific functions show the organ level of organization.
• It is seen in animals of Phylum Platyhelminthes

Organ system level of organization: 

• Many organs that have related functions form an organ system, such as the digestive system and circulatory system.
• These are seen from Phylum Aschelminthes to Chordates

Digestive System:

• It can be of two types :

1. Incomplete digestive system: The digestive tract open into a single opening that functions as both mouth and anus. Such type of body plan is called ‘blind sac’. Cnidaria and Platyhelminthes show blind sac body plan
2.  Complete digestive system: The digestive tract is provided with two openings as a mouth that performs ingestion and anus that performs egestion. Such type of body plan is called ‘tube-within-tube’. 

  Circulatory System:

1.  Open type circulatory system: Blood does not flow within defined vessels. It fills the cavity and tissues of the body are bathed in blood.Arthropods and Molluscs show open circulation
2.  Closed type circulatory system: Blood flows within defined vessels termed as arteries, capillaries and veins. Each organ is connected to the heart via these vessels.Annelids, Echinoderms and Chordates show close circulation