Biology homework in the first year of junior high school, biology homework in the seventh grade

Wash your hands frequently and pay attention to hygiene.

He said everything I had to say, and I didn't say anything.

One is a category that sells substances for inanimate sail rentals: note that coral reefs are made up of polyp excrement.

The others are a class of organisms, which are made up of cells.

2. Viruses, cells.

3. Growth, reproduction, development.

2) With the exception of viruses, living organisms are made up of cells. Lu Xiang.

3) The morphological structure, living habits, and living environment of organisms are very different, but they have the common characteristics of hail, that is, they have metabolism and life activities such as (growth), (development) and (reproduction) that only organisms have on this basis.

-1) Empty over.

After the entrance examination, I don't remember it very clearly. Hope it helps. Look at the textbook, there should be textbooks for the last two topics.

1. The first category: snow, water, wind, coral reefs.

Category 2: Peach Tree Boy Mushroom Puppy Classification Rent Burning By: Whether it has a life of birth and tolerance (raw hole type bright things and non-living things).

Answer; The result observed by Xiao Ming should be that water is flowing out of the pulmonary artery. The reasons are:

Blood circulation in the heart starts in the right heart, and venous blood with little oxygen enters the right atrium, enters the right ventricle, and enters the pulmonary artery, where carbon dioxide is expelled and oxygen is absorbed. Oxygen-rich arterial blood enters the heart again, but this time into the left atrium, into the left ventricle, and through the action of a pump, the arterial blood enters the aorta and finally reaches the entire body.

The heart valve is located between the heart chambers, the tricuspid valve between the right atrium and the right ventricle, the mitral valve between the left atrium and the left ventricle, the pulmonary valve between the right ventricle and the pulmonary artery, and the aortic valve between the left ventricle and the aorta. Heart valves are like a one-way open door, allowing blood to flow in one direction and not regurgitation, that is, from the atria to the ventricles, from the ventricles to the arteries, but not backwards. Therefore, the water that Xiao Ming infuses from the pulmonary artery will also flow out of the pulmonary artery.

It's like if you pour water into a cup and the water overflows when it's full. Because of the heart valves, it only allows blood to flow from the heart to the pulmonary arteries, not from the pulmonary arteries to the heart. That's why the water will flow out, and the reason why it can't continue to flow is because it can't stay, and there is no way, understand?

So you don't understand why.

Because there is an avalve, which allows blood to flow only in one direction, water flows in from the pulmonary arteries, is blocked by the valve, and flows out of the pulmonary arteries.

It's water coming in from the pulmonary arteries, and blood is flowing from the heart into the pulmonary arteries, so the valve blocks the water from flowing back.

Blood flows from the heart into the pulmonary arteries.