The sea is full of unusual species and life cycles - from fish to marine mammals to invertebrates such as jellyfish there is a whole range!
Bladder wrack seaweed has a simple life cycle similar to plants on land - male and female seeds are released into the water in summer and when they meet a new plant forms in autumn. The new plants will breed the next summer. Can you think of 3 things that seaweed (underwater plants) do not need that a land plant does?
In more complicated life cycles, like we saw in the frog yesterday, there will be a juvenile or larval stgae in the cycle and the species might look quite different at this point.
Jellyfish have a complex life cycle - you jellyfish larvae develop inside the mother and once they are ready they swim out into the sea and attach to the sea bed - here they are called polypsand look quite different to the adults. As they grow they develop into adult jellyfish.
Can you think of another marine life cycle?