Vertebrates all have pronephros during the embryonic stage, but only the embryonic pronephros of fish and amphibians are functional.

The pronephros are located near the front of the body cavity and are composed of many renal tubules.

One end of the renal tubule opens into the body cavity, and the opening expands into a funnel shape. This is the renal orifice, which can directly collect metabolic waste from the body cavity.

Whenever Apple releases a new product, many friends start to suffer from kidney pain.

As the saying goes, "Kidneys are limited, and apples are more expensive. If you are a girl, you can throw away both."

At this time, many people may lament that it would be great if they had two more kidneys, and their girlfriend would no longer have to worry about not having enough money to buy apples.

How terrestrial animals adapt to the environment The terrestrial environment is much more complex than the aquatic environment.

The land climate is relatively dry. To adapt to this, terrestrial animals generally have moisture protection...land animals and mammals.

The most populous animal in the world is not ants. It may be the most populous animal on land, but in this world, krill is the most populous animal in the world. According to statistics from zoologists, there are currently about

There are 1.5 million species.

Mules are rarely capable of reproducing; for example, they are interspecific hybrids born from the cross between a male horse and a female donkey. They are similar in shape to donkeys, so they are commonly known as "donkey mules."

A mule is larger than a donkey and stronger than a horse. Its strength is reflected in its waist.

The pelvis behind it cannot open and close, so it cannot give birth.

The second smallest mammal in the world, native to Ireland, but found in Alaska, Canada and the United States. They are active day and night. Their average weight is 4 grams. They have a high metabolic rate and a large heart. They account for 10% of the body mass.

1.2%.

They usually live alone and live only a year and a half.

The largest animal in history has a huge heart. The aorta of the heart is about 9 inches. Their heartbeats are 8 to 10 times per minute. Therefore, the huge heart of the blue whale helps this huge animal gain strength and ensures that it has enough energy.

Blood circulation keeps the body functioning.