Teaching analysis of biological invaders

1, self-reading accumulation, master the main content of this article;

2. Master the basic instruction sequence and instruction method;

3. Cultivate students' scientific spirit of seeking truth and improve their awareness of environmental protection.

The focus of learning is the order and method of this article.

Learning difficulties explain the expression effect of this method.

Knowledge link

1, topic interpretation

When it comes to invasion, we immediately think of the battle of sword and shadow. As we all know, there is also a "war" in the biological world. You know, this is a war started by human beings without smoke, and we have to be highly vigilant. "Biological invasion" refers to the process that organisms invade into another new environment from the original habitat by natural or artificial means, causing economic losses or ecological disasters to biodiversity, agriculture, forestry, animal husbandry and fishery production and human health in the invaded area.

Step 2 approach the author

Mei Tao, male, contemporary popular science writer. Executive deputy director, researcher and doctor of Hefei Institute of Intelligent Machinery, Chinese Academy of Sciences, doctoral supervisor of China University of Science and Technology, and vice chairman of Youth Federation of China Academy of Sciences. 1962 was born in nancheng county, Jiangxi province. 1982 received a bachelor's degree in precision machinery from Zhejiang university, and 200/kloc-0 received a doctorate in mechanics from China university of science and technology. 1982, engaged in research work in Hefei Institute of Intelligent Machinery, Chinese Academy of Sciences. He used to be a member of the special robot professional group in the field of automation in the national "863" plan and a member of the space robot special group in the field of aerospace in the national "863" plan.

3. Relevant information

Do you know any other "biological invaders"? Have you ever found biological invasion in your life?

① In China, a South American aquatic plant-water hyacinth greatly reduced the water area of Dianchi Lake in Kunming, and the local climate was obviously dry, and 38 species of 68 species of fish in the lake no longer existed.

② In Western Europe, a North American shrimp disease is attacking local shrimps, causing local shrimps to disappear in many rivers.

In the Mediterranean Sea and Adriatic Sea, a Pacific seaweed covers 3000 hectares of the sea floor.

④ From East Africa to the Indo-Pacific region, a A Lang grass from South Asia invaded millions of hectares of tropical forests, seriously affecting the natural regeneration of local trees.

⑤ A pathogenic fungus from Australia, possibly from Papua New Guinea, invaded from 1920, resulting in the destruction of thousands of hectares of forests. This fungus is harmful to three quarters of plants, including tall trees and short shrubs.

In New Zealand, a nocturnal kangaroo from Australia is estimated to eat 265,438+0 tons of local forest every night.

⑦ The palm tree snake from Papua New Guinea made the wild 1 1 species of birds and some lizards and bats extinct in Guam in the Pacific Ocean.

Autonomous learning

1. The incorrect phonetic notation in the following words is ()

A. (Does Lu plunder? Very bright. Swiss surveillance (jiān) strange (ji? ?

C. Habitat (qι) imbalance (H column). Bad luck (mount? ǎ? n)

2. Find the item without typo ()

A. A species must follow the laws of natural selection in a new environment.

B.it may breed indefinitely.

C. There are no natural enemies that can breed brown snakes on the island of Hawaii.

D transnational Pangwu trade also provides convenience for "biological invaders".

3. Point out the explanation methods used in the following sentences.

1) Experts call these "immigrants" who originally lived in a foreign country and moved to a new ecological environment by unnatural means "biological invaders"-they will not only destroy the original ecosystem in a certain area, but also cause incalculable economic losses to human society. ( )

2) In the United States alone, the annual economic losses caused by "biological invaders" are as high as more than 200 billion dollars. ( )

3) Some foreign pets, such as snakes, lizards and bobcats. Often escape from the fence due to the negligence or abandonment of the owner and gather in the mountains to harm one party. ( )

Cooperative investigation

Read the text by yourself and grasp the meaning of the text as a whole.

4. What is a "biological invader"?

5. What else does this article tell us?

6. Discuss and explain the sequence and method of this paper.

7. Discuss what other biological invaders are there in nature?

8. How can we effectively curb biological invasion?

9. Explore the enlightenment of learning this article?

Intensive reading and refining

Read the following paragraphs and complete the following questions.

Some scholars in biology and ecology believe that human beings should not interfere too much in the migration process of biological species, because the imbalance is temporary and a species must follow the law of natural selection in the new environment. Not all "biological invaders" can survive, but the strong can survive. Even the strong in the ecosystem are restricted by various factors in the system and cannot do whatever they want. Therefore, the natural balance will eventually be achieved. However, more scholars are against it. They think that the process of natural adjustment is very long. If "biological invaders" are allowed to develop freely, many native species will be doomed to extinction and the species diversity in nature will be seriously damaged. In addition, the economic losses caused by "biological invaders" to human society are also amazing. In the United States alone, the economic losses caused by "biological invaders" are as high as more than 200 billion US dollars every year. How can people be indifferent to such astronomical figures?

At present, many countries in the world have begun to realize the seriousness of this problem and taken corresponding measures. For example, the US House of Representatives passed a bill in 1996, requiring relevant agencies to strengthen the monitoring of vehicles that may carry alien species. To this end, the US government is planning an inter-departmental monitoring plan.

10. The first paragraph summarizes two views of scholars.

1 1. What are the hazards of invasive organisms?

12. The interpretation method used in the first paragraph is _ _ _ _ _ _ _ _ _ _ _.

13. The sequence explained above is _ _ _ _ _ _ _ _, which summarizes the central meaning of this article.

Subject reading

The mystery of longevity of trees

Bardie Bao

Some ancient trees have lived for thousands of years. Why can they live so long? It turns out that trees have a special ability to delay aging: they can completely update all living cells in batches, and the number of updates (cell division) is infinite; Because of its special structure (convenient for the birth, death and abandonment of cells) and constant thorough renewal, the body of trees can be kept in order, which makes trees not easy to age and may live for thousands of years or thousands of years. Other animals and plants can only update some living cells in their bodies (not completely) or not at all, so their life span is limited by the life span of cells that are not updated in their bodies-they can live for 200 to 300 years at most.

So how can all the living cells in the whole body of trees be completely updated in batches to keep the body orderly?

One layer in the bark stem is cambium. It keeps dividing into two new cells, outward and inward respectively. What grows outward are new phloem cells. Phloem is the inner layer of bark, which consists of living cells and contains sieve tubes for transporting organic nutrients. After a period of time, rotten phloem cells are pushed outward, and dead cells form the outer layer of bark protection tissue. The outermost layer of bark is discarded: it will slowly peel off or rot. Due to the thickening of the trunk, the outer layer of the bark gradually expands and cracks into many vertical and oblique cracks, and the living cells in the trunk exchange gas with the outside world through these cracks (lenticels). All living cells in the trunk form a tubular living cell layer slightly thinner than the trunk. They can only grow near the outer bark. No matter how thick the trunk is, the tubular layer of living cells is not allowed to be too thick; Otherwise, the living cells in the inner layer will not be able to exchange gas with the outside world.

The cambium is inward, and new xylem cells grow, which makes the annual rings increase by one circle every year. After aging, the dead xylem cells become conduits and tracheids that communicate up and down, transport water and inorganic salts, and play a supporting role. In the middle of the trunk (all dead cells can be discarded), trees can live normally even if they are hollowed out and rotted (but enough cambium and xylem must be preserved). There are many such hollow ancient trees. For example, in the Tree House Park in Leightonville, California, there is a famous giant redwood tree, which is over 4000 years old. The hollow tree hole on the trunk has been arranged as a living tree layer, covering an area of about 52.7 square meters.

The existence of many hollow ancient trees shows that the cores of all kinds of trees can be abandoned. Abandoned xylem, if not rotted, is beneficial to trees; If there is too much decay, it will be harmful to trees if it is not removed.

Inside the trunk, from the cambium, inward and outward, coils of cells divide, grow, age, die and discard. From the inside out, it can be divided into three cell layers: birth, death and abandonment (there is no interface between the dead cell layer and the abandoned cell layer). The living cell layer and the dead cell layer have their own functions. Each cell gradually grows, dies and is discarded, and gradually moves away from the cambium. The cambium gradually expands to the periphery-gradually moves to a new position. Because all layers of cells and tissues in the trunk grow so reasonably and are arranged so reasonably, even if the tree lives to 10000 years old, all tissues in the trunk are always regular and orderly, and there are always enough unobstructed ducts.

Roots, like trunks, also have cambium and structures that grow, die and abandon in both directions, as well as sieve tubes and conduits. The cross section of the root also has annual rings, which gradually thicken. Therefore, roots and trunks, like their living cells, can be completely updated from generation to generation in an orderly manner.

It goes without saying that the branches, small stems, small roots and trunk of the stem are all the same structure, so the living cells in these parts can be completely updated continuously; Moreover, new small roots and stems can grow from the old parts. Leaves, flowers, root hairs and other parts are old and dead, while others grow new ones. They are easier to be completely updated than the backbone. In short, living cells in all organs of trees (including roots, stems, leaves, flowers, etc.). ) you can be born in batches in an orderly way, or you can die in batches and be abandoned completely, so the life span of all kinds of trees is particularly long.

14, please summarize the important role of cambium in your own words.

15. Many ancient hollow trees can still grow normally. What is the reason?

16, four sentences in the first natural paragraph of the article. Sentence 1, 2,3 and sentence 4, sentence 1 and sentence 2,3 are first and then.

17, the fourth paragraph is explained by sum.

Ability improvement

23. Sichuan is known as the hometown of dragon phobia.

24, Weifang is known as the hometown of dinosaurs is

25, access to information to understand Darwin's "natural selection" and "survival of the fittest" theory.

Teaching postscript

Reference answer

Lesson 19

1.a (animal husbandry -l? , Francisco-fā n) 2.b (a. Competition; C. suffocation; Pets)

3.( 1) Interpretation (2) Numbers (3) Examples, 4, the first paragraph

5. The paper also talks about the great harm brought by biological invaders, the reasons and ways of increasing biological invasions, the different attitudes of biologists and ecologists towards "biological invaders", and the corresponding measures taken by countries all over the world at present.

6. Explain the order: use the function of logical order: conform to people's cognitive laws, and make the article clear in structure and hierarchy. Explanation: List numbers, examples and metaphors. (Look for examples in the article)

7. There are supplements in the "related materials" before class.

8. Raise awareness of preventing "biological intruders"; Strictly guard against "biological invaders", strengthen the legal supervision of international trade, and effectively protect the natural ecological balance.

9. This is an essay on ecological problems. It explains to us what a biological invader is and the great harm caused by biological invasion, which makes us highly alert to this special ecological phenomenon. We study this text not only to gain some ecological knowledge, but also to improve our awareness of environmental protection and cultivate our sense of responsibility to society.

10, ① Humans should not interfere too much with the migration process of biological species.

② The process of natural adjustment is very long, and the "biological invaders" cannot develop freely.

1 1, which makes native species extinct, destroys species diversity and causes amazing economic losses to mankind.

12, column number, example, classification

13. Biological invasion will lead to the imbalance of nature, the extinction of native species, the serious destruction of species diversity and amazing economic losses in logical order, so many countries have begun to take measures to prevent it.

14. The cambium can continuously divide into two new cells: new phloem cells and new xylem cells, which keep the active cells of the trunk breathing with the outside world, transport nutrients and play a supporting role.

15. There are cambium and xylem in the middle of the trunk.

16, reasons for comparison results

17, example of column number

23.zigong

24. Zhucheng

25, omitted