This document discusses the organization of tissues and body plans in animals. It explains that animal bodies are composed of specialized tissues which develop from three germ layers - ectoderm, endoderm and mesoderm. Diploblastic animals have only ectoderm and endoderm, while triploblastic animals possess all three layers. The document also outlines the three main types of body cavities in triploblastic animals - a true body cavity called a coelom derived from mesoderm, a pseudocoelom derived from mesoderm and endoderm, and a lack of a body cavity in acoelomates.

1. UNIT 4: BIODIVERSITY OF
ANIMALS:
INVERTEBRATES

2. C. TISSUES
• Animal body plans also vary
according to the organization of the
animal’s tissues:
–Tissues are collections of
specialized cells
• During development, 3 germ layers
develop into tissues & organs of
animal embryo

3. • Ectoderm is the germ layer covering
the embryo’s surface
• Endoderm is the innermost germ layer
and lines the developing digestive
tube, called the archenteron
• Mesoderm: middle layer of some body
plans
GERM LAYERS ARE:

4. • Diploblastic animals have
ectoderm & endoderm
• Triploblastic animals have an
ectoderm, endoderm & intervening
mesoderm layer.

5. D. BODY CAVITIES
• Most triploblastic animals possess a body
cavity
• A true body cavity  coelom & derived from
mesoderm
– Coelomates  animals that possess true coelom
• A pseudocoelom  body cavity derived from
mesoderm & endoderm
– Triploblastic animals that possess pseudocoelom
 pseudocoelomates
• Triploblastic animals  lack body cavity 
acoelomates