Animal Development

Question 1

Fertilisation in Sea Urchins

Answer 1

• Sperm makes contact with egg
• Mitotic division begins
• Triggers embryonic development:
- acrosomal reaction stimulated by sperm contact with jelly
- hydrolytic enzymes from acrosome digest jelly
- Sperm causes increase in Ca2+ ions, stimulate action.
polymerisation to form acrosomal process
- Acrosomal process sticks to vitelline envelope via binding proteins A. in egg membrane
- Sperm acrosomal process fuses with egg membrane