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 The life cycles of marine animals can be as different as the animals themselves 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
5 Bottlenose Dolphins Bottlenose dolphins are one of more than 30 species of dolphin Each of these species has a different life cycle Bottlenose dolphins must survive many dangers in order to complete their life cycle Dolphins are Mammals Dolphins look and swim like fish but they are actually mammals Mammals are warm blooded animals that breathe air and care for their young All female mammals produce milk which they feed to their young Living Together Bottlenose dolphins are social animals that live together in small groups These groups are always changing but are usually made up of between 2 and 15 dolphins By living in groups and helping each other dolphins have a better chance of surviving and completing their life cycles Bottlenose dolphins swim together in groups helping and protecting each other throughout their life cycles Dolphins are Related to Hippos It is believed that dolphins evolved from land animals millions of years ago Today the closest living relatives of dolphins are hippopotamuses
6 6 Size more than 9 feet 3 m long Weight up to 800 pounds 400 kg Color gray on their back fading to almost white on their underside VITAL STATISTICS a sleek streamlined body to glide through the water thick rubbery skin with a layer of blubber under the surface to keep it warm pectoral fins to steer and stop A dolphin’s tail has two flukes By moving its tail up and down it can push itself through the water Female dolphins produce milk to feed their calves Young dolphins suckle on teats on the underside of their mother’s body a dorsal fin to help the dolphin balance as it swims fast through the water What Do Bottlenose Dolphins Look Like Over millions of years bottlenose dolphins have adapted to life in the ocean The shape of their bodies has changed over time to make them great swimmers They can swim at speeds of more than 21 miles 35 km per hour
7 The dolphin’s bottle shaped nose is called a rostrum It can be used to dig in the sand and under rocks to find food Dolphins hear using their lower jaw Dolphins can hear very well and use sound to communicate and hunt for food Dolphins have between 80 and 100 teeth They use their teeth to grab and hold their prey Dolphins cannot chew with their teeth so they swallow their food whole or tear it into smaller pieces Length Comparison Large Brains Dolphins have large brains which allow them to communicate They use clicks whistles grunts and squeaks to call to each other This communication helps dolphins to work together when they hunt in groups Killer whale 29 feet 9 m Bottlenose dolphin 10 feet 3 m Common dolphin 6 5 feet 2 m Spinner dolphin 6 5 feet 2 m Scuba diver 5 6 feet 1 7 m Dolphins have good eyesight and can see in very low light Instead of nostrils dolphins have a blowhole on the top of their head Dolphins breathe through their blowhole when they surface for air Maui’s dolphin 4 feet 1 3 m
