An entry level position at a zoo requires a bachelor's degree in one of the following animal science, zoology, conservation biology, wildlife management, animal behaviour which takes 3-4 years of university to complete. If your looking into caring for marine animals you will need a bachelor's degree in animal science, biology, marine biology, zoology, pyschology, plus have strong swimming skills and a SCUBA certification, which is 3-4 years of university.
Chance of advancement is possible but rather limited. Being a zookeeper is not a glamorous, or even a high paying job. Zookeepers with limited education and experience start at minimum wage. A median salary for zookeeper is about $14 per hour or $28,00 a year. The top zookeepers can make more than $40,000 with benefits. You should have a love of animals.