Select the one animal that has all of the placental mammal traits listed above.
Red-headed poison frogs have moist, smooth skin. Female red-headed poison frogs lay their eggs on plants. The eggs have no shells and are protected by their father. When the eggs hatch, the father frog carries the tadpoles to water. Sea otters have very thick fur. Their fur helps keep them warm in cold water. Female sea otters give birth to live offspring in the water.
Placental mammals are a group of animals with similar traits. The following traits can be used to identify placental mammals:
They give birth to live offspring.
They have fur or hair. Observe the animals and read the descriptions.
Scientists sort animals with similar traits into groups. This is called classification. Classification helps scientists learn about how animals live.
How do scientists classify animals? First, they make observations about an animal. Scientists observe the animal's traits, including its body parts and behavior. Then, scientists compare the animal's traits to other animals' traits. Scientists classify animals with similar traits into a group.
To decide if an animal is part of a group, look at the traits of the group.
Placental mammals have the following traits:
They give birth to live offspring.
They have fur or hair.
Compare each animal's traits to the group's traits. Select the animal with traits similar to the group's traits.
A red-headed poison frog has the following traits:
It spends part of its life in water and part on land.
It has moist skin.
It makes eggs with no shells.
A red-headed poison frog does not have all of the traits of a placental mammal. A red-headed poison frog is an amphibian.
A sea otter has the following traits:
It gives birth to live offspring.
A sea otter has the traits of a placental mammal. A sea otter is a placental mammal.