Page 1 - 2.Lesson Notes-Animalia 2

SAI International School
Subject- Biology, Class-IX
Chapter- Diversity in living organisms
Sub Topic- Animalia: Annelida, Arthropoda, Mollusca,
Echinodermata, Protochordata
Module-28

Lesson Notes

Annelida

• These organisms have bilateral symmetry and triploblastic.
• They are mostly aquatic, few are terrestrial.

• These are the first organism to have a true coelom.
• Coelom is compartmentalized by intersegmental septa.
• Body long and metamerically segmented (segmentation from outside and
inside of the body).
• Examples: leech, earthworm etc.
• Locomotory appendages like setae are present.

Arthropoda

• This is the largest phylum with 80% of all known living animals.

• Animals with jointed appendages (in Greek Arthron: jointed, poda: legs).
• The body has three segments/regions as head, thorax and abdomen.
• Body is covered by an exoskeleton made of chitin.
• They are bilaterally symmetrical and have an open circulatory system.
• Compound eyes are present

• most successful group of animals.