Coral Reefs
Geography: Cambridge International GCSE (2027 Exams), topic 2.5.1
Coral Reefs
Corals are small animals that live in the sea. They require certain conditions for growth.
Description
- Corals are small animals called polyps.
- Their body is sack-like and they have tentacles to sting predators around a mouth (entrance) to the sack.
- They use calcium carbonate (limestone) to make an outer shell (exoskeleton) to protect themselves.
- They use their tentacles to feed - normally at night time
- Algae live inside the polyps and provide it with oxygen.
- The algae are coloured. Polyps are generally transparent (see-through).
Conditions needed for growth 1
- Clear water that allows sunlight through.
- When boats churne water and lift sediment, they can really hinder coral growth.
- Coral does not like particles, sediments or pollutants in the sea water because these block out sunlight.
- This is bad for growth.
- Warm water temperatures of 20-32oC. Corals can survive at colder temperatures than this, but will not grow either quickly or well.
Conditions needed for growth 2
- Sunlight.
- Coral have a symbiotic (mutually dependent) relationship with algae.
- Algae provide coral with oxygen.
- Algae need sunshine, so coral are only found where there is sunlight.
- Corals grow best in brightly lit (sunlight) water about 5 to 10 metres deep.
- They can also grow in depths of 90 metres.
- Saltwater.
- Coral does not grow near river mouths.
- It needs salty conditions to thrive.
Test yourself on Coral Reefs
What conditions are needed for coral growth?