Animals 4th Grade

Vertebrates& Invertebrates

ReproductionandNutrition

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How do vertebrates reproduce

Vertebrates reproduce sexually: they have separate female and male sexes. Fertilisation may take place inside or outside the female body.

Internal Fertilisation

External Fertilisation

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External fertilisation

Always takes place in water In Oviparous anaimals, like frogs, the female lays the eggs in water. The eggs do not have a hard shell. The male releases his sperm directly onto the eggs. The eggs hatch outside. The eggs float in the water until they hatch.

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Internal fertilisation

May take place on land or in water.

• In viviparous animals, the male releases sperm inside the female body. The young develop inside the female. The baby is born alive.

• In oviparous animals like birds, the male releases the sperm inside the female body. The egg has a hard shell. The female lays the fertilised egg outside the body.

• In ovoviviparous animals, like some snakes, the male releases the sperm inside the female body. The eggs hatch inside the female body and are born alive.

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Do all vertebrates eat the same food?

Most reptiles and amphibians are carnivores. Mammals, birds and fish can be herbivores, carnivores or omnivores.

Carnivores

Omnivores

Herbivores

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Carnivores

Carnivores hunt for food. They have long sharp teeth and claws on their feet. Tigers, wolves and polar bears are carnivores.

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Omnivores

Omnivores, like bears, eat both meat and plants. They have sharp front teeth, and flat teeth at the back.

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Herbivores

Many Hervibores, like giraffes, have wide, flat teeth to help them chew grass and plants. Some hervibores, like sheep and cows, are ruminants. This means they chew grass to break it down, and then swallow it again. The grass returns to the digestive system where the process is completed.

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How do vertebrates breathe?

Animals need to take in oxygen and expel carbon dioxide to stay alive. This exchange of gases is called respiration.

Fish and other aquatic animals

Mammals, birds and reptiles

Amphibians

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Mammals, birds and reptiles

Take oxygen form the air. Air passes into the lungs. Waste carbon dioxide leaves the body through the lungs.

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Fish and other aquatic animals.

Take oxygen from water. The water enters the body through the mouth and leaves again through the gills. Waste carbon dioxide leaves the body through the gills.

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Amphibians

When they are young, amphibians are aquatic animals. They take in the oxygen they need from the water through the gills. During metamorphosis, their gills close and they develop lungs. Adult amphibians also breathe through their skin.

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