4 Life Cycles of Marine Animals Scientists believe that all life on Earth began in the ocean hundreds of millions of years ago Today thousands of different animal species live in and around the ocean No one knows exactly how many different species of marine animals there are hundreds of new species are discovered every year Although they share the same saltwater habitat all marine animals grow and change differently over time Each species has its own unique life cycle Life Cycles All living things have a life cycle An animal’s life cycle begins when it is born and is completed when it has young of its own During their life cycles different species grow and change in different ways Everything an animal does throughout its life cycle happens so that it can survive long enough to reproduce Without this circle of life all living things would become extinct The life cycles of marine animals can be as different as the animals themselves
5 Whales Once Walked On Land Millions of years ago whales were land animals Over millions of years their legs evolved into fins and they moved into the water The bones inside a whale’s fin still look like the hand of a land animal Humpback Whales Humpback whales are a large species of whale They have a unique life cycle that can take them halfway around the world Always on the move humpback whales must overcome many challenges to complete their life cycle Whales Are Mammals Whales are mammals All mammals are warm-blooded breathe air and feed milk to their young Living Together Humpback whales often travel together Mothers will always stay close to their young called calves and adults will sometimes hunt together By hunting together and protecting their calves humpback whales have a better chance of completing their life cycles Female humpback whales protect their young giving them a better chance to survive and complete their life cycle
6 6 Size grows to more than 52 5 feet 16 m long Weight up to 38 6 tons 35,000 kg Color usually gray with white patches under the head and fins VITAL STATISTICS a thick layer of blubber to stay warm even in very cold water teats that produce milk for feeding their calves hidden by a flap of skin under the female’s body very large pectoral fins to steer through the water and communicate with other whales a strong tail with two flukes for pushing itself through the water a streamlined shape for gliding through the water What Do Humpback Whales Look Like Humpback whales are one of the largest animals in the world Even though they are large their bodies are shaped so they can swim easily through the water good eyesight both under and above the surface of the water two blowholes for breathing through when the whale surfaces for air
7 Length Comparison Blue whale 108 feet 33 m Sperm whale 59 feet 18 m Humpback whale 39 feet 16 m Minke whale 33 feet 10 m A Huge Heart A humpback whale’s heart weighs as much as three adult people stretchable skin for opening its mouth very wide to swallow large prey baleen instead of teeth to strain the water out of its mouth and leave the food behind a huge tongue to push water out of its mouth Scuba diver 5 6 feet 1 7 m Narwhal 16 feet 5 m 9 8-foot 3-m tusk
