@Yoong Liat,
It looks good to me. There are several areas where you might want to rewrite it to remove the use of the passive voice to make it more interesting.
Passive Voice
For a livelier and more persuasive sentence, consider rewriting your sentence using an active verb (the subject performs the action, as in "The ball hit Catherine") rather than a passive verb (the subject receives the action, as in "Catherine was hit by the ball"). If you rewrite with an active verb, consider what the appropriate subject is - "they," "we," or a more specific noun or pronoun.
Instead of: Juanita was delighted by Michelle.
Consider: Michelle delighted Juanita.
Instead of: Eric was given more work.
Consider: The boss gave Eric more work.
Instead of: The garbage needs to be taken out.
Consider: You need to take the garbage out.
I've changed the color of the text in the areas that are in the passive voice:
I was still lazing in my bed on a sunny Saturday morning when I heard my sister screaming with excitement. My father had offered to take us to visit the zoo. Immediately, I jumped out of bed and started getting ready for my trip. We drove in my father’s car. My father had already purchased the tickets online.
The first zoo creature I met turned out to be a rhinoceros. It stared at me warily and I grinned back with a goofy smile. I turned and found myself face to face with a tame hippopotamus. Unlike the rhinoceros, it was more concerned with basking in the morning sun than looking at me. I heard a noise and to my amusement there was a troop of chimpanzees fighting over a cap. The cap looked familiar, that is when I realized it was my mother’s cap.
Then there was a herd of Arabian oryx. The Zoo’s Curator explained to us the efforts initiated by the late President of the U.A.E to breed the Arabian oryx in captivity to prevent them from becoming extinct. The dolphins were my favourite animal. They amused the spectators with their tricks.
They were named Jim, Tim, Kim and Sim. In a huge cage we saw a ferocious lioness licking her cubs.
She growled and let out a roar when she was offered a chunk of meat. This sound made the giraffe scared.
I entered the main building, where the primates and reptiles are housed, and found a king cobra slithering in its enclosure. Also there was a separate section for the birds called the aviary.
Admission to this was closed since the place was under repairs. An environment protection officer briefed us on the efforts of the U.A.E government to preserve endangered species.
All the excitement of the day made me tired and hungry. I slept during our drive back home. I dreamt of hawks and eagles laughing at my jokes, zebras and ostriches running across the open plains, and a tiger pouncing on me. I woke up with a jerk, only to find that it was my sister who pounced on me.