My mother once told me such a riddle: "Zhuge Liang in Nanyang, sit tight." Arrange the eight diagrams and catch the flying generals. "This myth tells us that spiders only eat living things, but don't they eat dead things? This aroused my interest and I did the experiment.

I caught a little spider from the corner and put it in a box (with holes around it and glass on it for easy observation). Before the spider could weave a web, I picked up a dead bug and a dead fly and put them in front of the spider. The spider ignored them, then hit the box with her hand, and the spider crawled in other directions.

In order to find out whether spiders eat dead flies completely, the next day, I came to the box to observe and saw that dead insects and dead flies were still in their original places, but there was a net in the corner of the box, and the spider was lying quietly on the net. At this time, I thought: Is it because there is no net that the dead flies and insects didn't eat it yesterday? So I picked up the dead fly and gently put it on the net, but the spider still didn't move. Then, I gently touched the edge of the net with my pen. Gee, the spider seems to have a reaction and started to climb in a trembling direction. I took the pen back and the net stopped shaking. The signal was interrupted and stopped. Soon, the spider climbed to the center of the web again. I touched the dead fly's body on the net with the pen tip again, and the net began to vibrate, and spiders began to crawl here. I took back the nib again and the spider stopped. Like last time, after a while, the spider climbed to the center of the web again. Oh! I finally understand that spiders feel by the vibration of their webs and prey by weaving them. So, I recorded the experimental results.

In order to prove that spiders feel through the vibration of their webs, I did another experiment. Put the pen tip on the dead fly on the net and vibrate for a long time. The vibration of the web is getting bigger and bigger, and the spider seems to feel stronger and stronger. Spiders will come in a hurry. When a spider meets a fly, I will take back the pen tip, only to see that the spider's tail will soon spit out sticky silk to tie the fly, and then look at the spider's back, as if sucking the fly. Soon, there was a complete empty shell left on the Internet. This experiment proves that spiders eat moving insects.

Our secret group went to the library and bookstore to consult a lot of books about spiders. Among them, General Zoology wrote that spiders are carnivores, and their food is mostly insects or other arthropods. But your mouth has no upper jaw, so you don't swallow solid food directly, but suck it slowly. When insects and other animals come into contact with the net, they will struggle desperately on the net to make the net silk vibrate, so that spiders will find it soon. Spiders will crawl along the longitudinal silk to their prey, wrap the prey with spider silk and fix it on the net. First, the venom secreted by the poisonous gland in the claw limb is injected into the captured prey to kill it, then the digestive enzyme secreted by the midgut is injected into the captured tissue torn by the claw limb, which is quickly decomposed into juice, inhaled into the digestive tract, and finally eaten the remaining body shell. These fully prove that flying insects make the spider's web vibrate, and the web vibration will make it feel, and the spider will catch its prey if it feels. So it is confirmed that spiders only eat live animals, not dead insects.

With the improvement of people's living standards, people's demand for flowers is increasing. The flowers are colorful and fragrant, but they all have the defect of short flowering period. Many reagents, such as aspirin, are used to prolong the fresh-keeping period of flowers. We tried to extend the flowering period of plants with rare earths.

Rare earth is a rare element. Agricultural rare earths are mainly compounds of lanthanum and cerium. It can promote the growth of plants to a certain extent. In order to know whether it affects the flowering period and the size of flowers, we did the following experiments.

I. Experimental materials

Nongle powder (a rare earth fertilizer), calendula, beaker.

2. Experimental process and records: Nongle was prepared into five solutions with different concentrations, inserted into calendula, and a control group was established. The list is as follows: the flower diameter is 3-4 cm.

Nongle solution

Situation record

contrast

50 mg/100 ml

1 Flowers bloom and fall in a few weeks.

Thank you in six days.

100 mg/100 ml

The flowers just opened and died two weeks later, and the flowers were in full bloom.

Slightly larger than the control group.

Thank you in six days.

150mg/100ml

Flowers are in full bloom, wither more than 1 week, and the leaf color is good.

Six days after flowering, the leaves on the branches are worse than before.

200mg/100ml

Flowers are in full bloom, wither more than 1 week, and the leaf color is good.

Six days after flowering, the leaves on the branches are worse than before.

300 mg/100 ml

Flowers are in full bloom, wither more than 1 week, and the leaf color is good.

Six days after flowering, the leaves on the branches are worse than before.

Three. Analysis and discussion

From the above experimental records, it can be considered that rare earth can prolong the opening time of flowers to a certain extent. From 50mg/ 100ml rare earth solution to 3 oomg/ 100 ml rare earth solution, the flowering period can be prolonged and the diameter of the flower is slightly increased. The application of rare earth to marigold can generally prolong the flowering period by 2-4 days. We think this is related to the fact that rare earth can promote plant life activities, promote chlorophyll formation and increase organic matter synthesis (the leaves of plants containing rare earth solution are darker in color). Rare earth can promote the absorption of organic nutrients by plant reproductive organs. We also found that the higher the concentration of rare earth (below 300 mg/l00 ml), the longer the flowering time of the extended flower. As for how high the concentration will be, it needs further study in the future.

Rare earth is a compound containing trace elements, which can promote plant growth to a certain extent. Two students, Zhang and Wu, used agricultural rare earth-Nongle as an experiment to prolong the flowering period of flowers, which is of great practical value. Judging from the article, these two students have really done a lot of work and achieved gratifying results, which is commendable.

Of course, like most students who have independently conducted scientific experiments for the first time, they are not mature enough in experimental methods and report expression. But it doesn't matter. In the future, they will do better by carrying out more such activities and reading more extracurricular books. Compared with many of their peers, they are already one step ahead.

First of all, judging from the contents of the report, the author only conducted experiments on the flowering period of marigold, so the title of the report seems to be changed to "the influence of rare earths on the flowering period of marigold". You know, plant is a concept with great extension, and it can't be used indiscriminately in scientific research reports. If rare earth has an effect on one plant, it is unacceptable to assume that it has the same effect on all plants. This is the so-called generalization, which often leads to a big mistake.

Secondly, the concentration of extremely dilute solution should be expressed in ppm (one millionth), such as "50m g/ 100ml" in this paper can be expressed as 500ppm.

Third, the number of experiments with marigold should be clearly recorded in the report (at least 10 marigold, repeated many times).

Fourth, there are early flowering period, full flowering period and withering period, and the specific dates should be recorded clearly and completely. Note that the data in the experimental record must be clear, such as "6 days" and "23 hours", and there should be no vague data such as "over 1 week" and "over 10 days". Otherwise, what is the basis of "the thicker the rare earth, the longer the flowering period"?