Reproductive strategies in water animals and land animals are quite different. These differences mainly come from where they live and how they grow. Let's break it down into simple parts.
1. Reproductive Methods
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Water Animals:
- Many fish, like cod, use a method called external fertilization. This means females release their eggs into the water, and males swim in to fertilize them. About 90% of fish do this!
- Other species, such as sharks and some frogs, use internal fertilization. This method helps keep the baby fish or frogs safer.
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Land Animals:
- Most land animals use internal fertilization. This helps prevent the eggs from getting too dry. For example, 99% of mammals reproduce this way.
- Some animals, like reptiles, lay eggs on land, allowing them to grow outside the mother's body. On the other hand, viviparous mammals give their babies nutrients while they are still developing inside.
2. Parental Care
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Water Animals:
- Generally, water animals don’t care for their young much after laying their eggs. About 70% of fish do not take care of their eggs after they are released.
- However, some types of fish, like seahorses, show a lot of care. Male seahorses carry their babies in a special pouch until they are ready to be free.
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Land Animals:
- A lot of land mammals—around 80%—spend a great deal of time caring for their young until they can take care of themselves.
- Birds often keep their eggs warm and feed their chicks after they hatch, which helps more of their babies survive.
3. Developmental Processes
- Water Animals:
- In water, eggs and young animals can drift along in the currents. Species like jellyfish can lay up to 100,000 eggs, but very few actually survive.
- Land Animals:
- On land, animals often have fewer eggs, usually between 2 and 12 in many mammals. They spend more energy on each baby, which helps them survive better.
In short, water animals often focus on having a lot of babies, while land animals usually try to make sure a smaller number of babies survive.