1. The Origin of Animal Diversity
Invertebrates

2. Key features of animals
Animals are multicellular, heterotrophic & eukaryotic
Most use ingestion as their mode of nutrition
The store carbohydrates as glycogen
Lack cells walls and have muscle and nervous tissue

3. Reproduction is usually sexual with flagellated sperm and a larger, non moving egg
A developing zygote goes through a series of divisions called cleavage passing through a blastula stage and then a phase called gastrulation

4. Many have a larval phase as part of their lifecycle
METAMORPHOSIS transforms larva into adults

5. Protostomes & Deuterostomes
Shows the origins of phyla & where evolutionary lines diverged
TWO main branches of Kingdom Animalia:
- Protostomes
- Deuterostomes (ex. Chordata- humans)
Deutero = second; Stome = mouth

6. Example: arthropods & molluscs First embryonic cavity: mouth
protostomes
deuterostomes
Example: arthropods & molluscs
First embryonic cavity: mouth
Type of cleavage: spiral
Example: echinoderms & chordates
First embryonic cavity: anus (opening for mouth forms later)
Type of cleavage: radial

7. Cleavage Patterns Radial = Deuterostomes Spiral = Protostomes
Cleavage: Mitotic divisions without cell growth between divisions (occurs as zygote begins development)

8. Coelomate Another term for “coelem” is body cavity
This cavity if completely lined with a tissue called endoderm/mesoderm
This body design allows for more complexity & the formation of internal organs
Examples: earthworms (annelids)

9. Pseudocoelomate The body cavity is partially lined with mesoderm
“Pseudo” means false
Example. roundworms

10. Acoelomate Have no body cavity
Spaces inside their body are filled by body tissues and fluid
Example. flatworms

11. Specialization of internal organs
Complete mesoderm allows for the formation of complex organs (ex. Digestive tract), blood vessels & other complicated organ systems

12. Gastrulation
Follows blastula stage (formation of hollow ball, germ layers begin to form)
Layers of embryonic tissue form  will develop into adult body parts
The resulting stage is called the gastrula
Gastrula: ectoderm, mesoderm & endoderm are formed

13. Gastrulation
During gastrulation, the embryo folds inwards, expands & fills the blastocoel producing embryonic layers of tissue