2( 1) at the cellular level (also at the personal level, because E.coli is a unicellular organism); (2) Group level; (3) Community level.
1.2 1.B。
Self-test: 1×2, ×3, √.
Multiple choice questions/kloc-0 1.c.2.d.3.b Conjunction
Draw a concept map. Three question marks stand for: no, yes, yes.
2. 1 1( 1)? √; (2)×? . 3.B .
2.2 1( 1)√; (2)√2 . a . 3 . b .
2.3 1( 1)√; (2)√? ; (3)√? . 2.C .
2.4 1( 1)√; (2)√2 . c . 3 . c . 4 . c . 5 . c。
2.5 1.C
Self-check: true or false1√. 2× .3, ×. 4。 √。 5,×。 6,×。
Multiple choice questions 1. A 2.B. 3.D. 4.A。
2. Draw concept maps and transfer knowledge
Free water, bound water, free water.
3. 1. 1
3.2 1, figure 1. Note that the word "endoplasmic reticulum" should be Gorky and Gorky should be "endoplasmic reticulum". Note that the position of chromatin is wrong. The centriole in the centrosome should include the following indicator lines. 2. Note that the word nucleolus should be chloroplast, chloroplast should be mitochondria, and ribosome should be central organ.
2.C .
3.3 1( 1)√; (2)×2 . c . 3 . c。
Self-test determines the problem 1. ×. 2 ,×. Select more than one C.
Two interrelated problems, knowledge transfer.
Hint: About the role of lysosomes. After cell death, lysosomal membrane ruptures, various hydrolytic enzymes decompose, and substances such as cells and protein are released, so cooked meat of livestock and poultry is more tender. This process will take some time.
Three skills
In the application of dark vision, there are two methods: one is to open the mirror to reduce the amount of light; Second, choose a small aperture to reduce the amount of light entering.
4. 1 1。 √。 2。 √。 3,×。
4.2 1 hint: the cell membrane is too thin to be seen under the optical microscope. /kloc-in the 0/9th century, whether there is an electron microscope or not, scholars have to start with the physiological function of cell membrane.
2。 Lipids and protein.
It is suggested that the two structural models are considered that the main substances are lipids and membrane proteins, which is their similarity. The differences are as follows: (1) The pseudo-fluid mosaic model of protein distribution in the membrane is uneven, some cross the lipid bilayer, some are partially or completely embedded in the lipid bilayer, and some are embedded inside and outside the lipid bilayer surface; The three-layer structure model holds that protein is evenly distributed on both sides of lipid bilayer. (2) The fluid mosaic model emphasizes that the constituent molecules of the membrane are moving; However, the three-layer structure model thinks that biofilm is static structure.
4d。
4.3 1.D. 2.A
Self-test answers and tips
Concept test
True or false 1. ×。 2,×。 3,×。 4,×。 5,×。
Multiple choice questions1.d.2.c.
Draw a concept map
first part
1 Basic Problems of Pasteur />5. 1(E): About fermentation and living cells, but not the whole cell, some substances in fermented cells are working.
Justus von Liebig: Fermentation is caused by some substances in cells, but these substances can only play a role after yeast cells die and rupture.
Buchner: Some substances in yeast cells can continue to promote the fragmentation of yeast cells, while in living yeast cells.
Sumner: The enzyme is protein.
It is pointed out that when there are thousands of chemical reactions in cells, these chemical reactions need high efficiency, and the catalytic efficiency is much higher than that of inorganic catalysts. (2) Chemical reactions in cells need to be carried out under mild conditions such as room temperature, normal pressure and moderate acidity. Inorganic catalysts often need assistance to have high catalytic efficiency under harsh conditions such as high temperature, high pressure, acid and alkali.
3.D
The second part of the exercise1.b.2.b.
Tip: This model represents some enzymes, B represents reaction substrate, and C and D represent reaction products. The significance of this model is that the specific catalytic reaction between enzyme and substrate B produces products C and D. The combination of these models reveals the specificity of enzyme.
Unfold goods
Point 1( 1): With the increase of reaction substrate concentration, the reaction speed is accelerated. Point B: The reaction rate is the highest at this time. Point C: With the increase of the concentration of longer reaction substrate, the reaction rate remains at a relatively stable level.
(2) If the temperature at point A is 10℃, the curve amplitude will increase less. The intermediate curve shows the change of catalytic rate at the optimal temperature with the substrate concentration diagram. When the temperature is higher or lower than the optimal temperature, the reaction speed will slow down.
(3) The graph shows the concentration of the reaction substrate, and point B is large enough to increase the reaction rate. The amount of enzyme is limited, and when a small amount of enzyme is used, the reaction will be accelerated (not shown).
5.2 1.B。
5.3 1 . c . 2b
Tip: Aerobic respiration is the same as anaerobic respiration in the first stage: no oxygen is needed; Irrelevant mitochondria think that the structure of early earth and prokaryotic cells can be inferred. In the history of biological evolution, anaerobic respiration and aerobic respiration first occurred after anaerobic respiration evolved into aerobic respiration. Then there are eukaryotic cells, such as eukaryotic cells, which are the earliest prokaryotic cells in the evolution of prokaryotic cells.
4。 I can't. Because green plants can also form ATP in the process of photosynthesis. .
5.4 Section1(1) ×; (2)√2. b .(3) The conclusion is that chloroplasts mainly absorb red light and blue light and release oxygen.
The second part of the exercise1(1) √; . (2) × 2.b.3.d.4.c.5.d.6.b. Light source of photosynthesis 7
The reaction stage is light, and the energy source of the dark reaction stage is ATP. sky
8。 If the supply of carbon dioxide is suddenly interrupted, the substance accumulated in the first chloroplast is a 5-carbon compound.
Self-test answers and tips
Concept test
True or false 1. √。 2,×。 3,√。
Multiple choice questions1.d.2.d.
Draw concept map
6. 1. 1.c . 2 . a . 3 . d . 4。 Chinese, English, 5.B.
6.2 1。 When the number increases, the number of chromosomes increases and the stability is poor. 2.C。
6.3 1( 1)×; (2)√; (3)×2 . c .
6.4 1( 1)√; (2)√。 .
The characteristics of cancer: cell proliferation is out of control and can proliferate indefinitely; The cell morphology changed significantly; Easy to disperse and transfer in the body.
Self-test answers and tips
Concept test
True or false 1. ×。 2。 √。
Multiple choice questions/kloc-0 1.c.2.d.3.a.4.a.5.c.6.a
Second, the application of skills: (1)2 to 21.3; (2)2 1.340.6。
2 Cell cycle: 19.3 hours; Duration:. 17.3 hours; Mitosis: 2 hours.
Third, expand thinking.
It is suggested to carry out embryonic cell culture and somatic cell nuclear transfer experiments in mice and adult mammals.
The experimental design and results are expected, which proves that in the highly differentiated animal cells, totipotency is more limited, but it is still totipotency nucleus.
Step 1: isolate an eight-cell mouse embryonic cell, culture it to blastocyst stage, transplant it into the uterus of surrogate mother, and finally develop into a mouse;
Step 2: blastocyst cells were isolated and transplanted into the uterus of surrogate mothers, and the results could not develop into mice;
The third step: the nucleus of the separated blastocyst can be transplanted into oocytes to develop into mice;
Step 4: Isolate small intestinal epithelial cells of mice and transplant them into enucleated oocytes to develop into mice.
Mandatory chapter 2
/& gt； 4. 1 1.TGCCTAGAA & ltbr； UGCCUAGAA3; 3; Cysteine, leucine and glutamic acid. 2.C。
1 the swelling problem suggests that you can change the codon, and then look up the codon table to see which amino acids in the corresponding codon acid have changed. This example describes a simple password, and its change is partly the result of changing the basis to prevent genetic information.
2 Tip: Because several codons can encode the same amino acid, some nucleotide sequences do not encode amino acids, such as termination codes, so the amino acid sequence determined only by the written amino acid sequence is not determined by the written amino acid sequence. The transmission of genetic information was lost in this process.
4.2(5) Skills training
1 It is suggested that the need of wing development is catalyzed by enzyme, which is influenced by enzyme activity under the guidance of gene synthesis, temperature, pH and other conditions.
2。 Genes control biological characteristics and are also influenced by the environment.
(6) Exercise1.a.2 (1) ×; (2)×; (3)√。
Unfold goods
1。 Red-eye normal gene is necessary, but not enough to form red-eye condition. The red-eye gene is normal, and other genes are also involved in the formation of normal red-eye and red-eye fly; If the red-eye gene is abnormal, even if all other genes participate in the normal red-eye formation, red-eye can not form a fruit fly.
The fourth chapter self-test answers and tips
A concept, detection padding
DNA double strand 1 CGT
2 GCA
Gene GCA
The cash generating unit of the problem tRNA
Amino acid alanine (codon GCA)
1kloc-0/.d.2.d.3.a.4.c The answer to the knowledge map (1) has broken the hydrogen bond; Helicase; Energy. (2)acu GAA； Transcription. (3) Complementary base pairing of 2 and (4).
Draw concept map
Second, knowledge transfer.
The combination of ribosome, tRNA and mRNA synthetic protein is essential. By forming antibiotics, it interferes with the combination of ribosome, tRNA and mRNA of bacteria or prevents and interferes with the synthesis of bacterial protein, thus inhibiting the growth of bacteria. Therefore, antibiotics can be used to treat diseases and infections caused by bacteria. .
3. Skill application
1 Tip: You can access the codon table and write down the basic code of each amino acid.
2. This method can only infer the possible nucleotide sequence and make sure that the nucleotide sequence can be omitted. This method is simple, rapid and does not need experiments.
3。 Sequencing must not replace gene sequencing. This is probably because only a few possible nucleotide sequences have been obtained and the nucleotide sequence cannot be determined.
4. Thinking expansion
1 C chapter
5. 1 1( 1)√; . (2)×; (3)×2 . c . 3 . b . 4 . a
Extended radiotherapy or chemotherapy is to copy DNA molecules and produce mutant genes through a certain amount of radiation or chemical interference between tumor cells and cancer cells, thus inhibiting their ability to differentiate or kill cancer cells. Radiotherapy or chemotherapy, radiotherapy agent, has two effects on cancer cells, and also has effects on normal cells. Therefore, the patient is very weak after receiving radiotherapy or chemotherapy.
2。 Sickle cell anemia patients get malaria, which shows that sickle cell mutation has strong resistance to local people in order to survive in the risk area of malaria infection. Although this mutant homozygote has a survival disadvantage, there are also hybrids who favor the locals for survival.
5.2 1( 1)×; . (2)×2 . b。
3。 infilling
Color dye gamete in somatic cells
Color dyes in human cells
Gamete dyeing with color dyes, isomerism and equal group number
It is dozens of times that of animals.
Pea14,721diploid
Common wheat 422 163
The number of hexaploid triticale is 562884, and the title of octoploid is very small.
1。 Strong local mitosis and colchicine treatment of watermelon seedlings with bud tips are beneficial to inhibit the formation of spindle mitosis in cells, thus forming tetraploid watermelon plants.
2。 Hybrid triploid plants can be obtained. The method of polyploidy is to germinate seeds or seedlings with colchicine.
3。 Triploid plants usually cannot form meiotic germ cells, so they cannot form seeds. But there are no seeds at all. The reason during meiosis is that it can form a normal egg.
4。 There are other alternatives. Method one, asexual reproduction. Triploid watermelon plants will get a large number of tissue culture test-tube seedlings and then transplant them. The second method is to treat the pink of diploid pistils with growth hormone or growth hormone analogues to promote the development of ovaries into fruitless seeds. In this process, bagging should be done well to prevent pollination. .
5.3 1( 1)×; (2)×; (3)×。
2。 The list summarizes the types and examples of genetic diseases.
Definition of human genetic diseases
Instance type
Dominant genetic diseases caused by single-gene pathogenic genes refer to polydactyly and other recessive genetic diseases. The recessive genetic disease gene leads to albinism, phenylketonuria and so on.
Polygenic genetic diseases consist of more than two pairs of genetic diseases, such as essential hypertension.
2 1 genetic disease alleles caused by chromosomal abnormalities in trisomy, such as extended questions.
Tip: This woman does not necessarily carry the albino gene; Her unborn child may have albinism.
The fact that the elder brother of an albino woman is his younger brother is called genotype AA, from which the genotype AA of her parents can be inferred. There are two possible genotypes in women: AA and AA. The probability of AA is 1/3, and the probability of AA is 2/3. The probability that a woman carries an albino gene is 2/3. According to the husband's suitcase albino gene, there are three possibilities for his offspring to carry albino gene and suffer from albinism: (1) The husband does not contain albino gene; (2) contains husband albino gene; (3) The husband is an albino. Genetic counseling requires the woman's husband to judge whether he is albino or has a family history, and provide genetic counseling.
Answers and skills of chapter self-test
1, 1。 ×。 2。 √。 3,×。 4,×。 5,×。 6。 √。
B. know the answer to a female role; It contains two х chromosomes. 2.4; 2。
Draw concept map
4. Thinking expansion
1。 Enzyme or enzyme ① ⑤. ② enzyme ③.
Note: From this example, we can see that albinism is a genetic disease that causes some defects in these genes, and may be an important enzyme involved in metabolic pathway. Genes can be obtained through the biosynthesis of reference substances of enzymes in vivo to control biostatistics. Chapter vi
6. 1(D) Problems based on practice 1.B. 2.B. 3 gene mutation; X ray; Ultraviolet rays; Laser.
Suggest an extended question: it may be a cross breeding method. Refer to Illustration 6 of the textbook for the genetic map. 1 draw. Its advantage is strong reproduction, which can achieve the purpose of super-strong characteristics and bad characteristics of varieties. Disadvantages are long breeding cycle and complicated technology.
Chapter VI Self-test Answers and Tips
Concept test
Connect 1-b, 2-c, 3-e, 4-d, floor 5, 6- answer BR/> true or false 1. ×。 2。 √。 3,√。 4。 √ Chapter VII
7.1.1.B. There are many genetic variations in the process of bacterial reproduction, and the resistance changes strongly:
According to Darwin's theory of natural selection, it can be explained as follows. When antibiotics are not used, the variation of drug resistance is not strong, and individuals struggling for survival are not dominant; After using antibiotics, a large number of weak individuals die, and individuals with strong drug resistance have the opportunity to produce more offspring. After a period of time, the bactericidal effect of antibiotics will decrease. This explanation fails to go deep into the gene level and does not explain the mutation in evolution.
1 implies an extended problem: the natural extinction rate of species may be slow, but human activities have greatly accelerated the extinction rate of species. Now why many endangered species are on the verge of extinction is mainly caused by human factors. Therefore, under normal circumstances, the protection of endangered species is to make up for their own fault nature, and can not be said to interfere with the normal nature of natural selection. Of course, because of this maladjustment, or because of natural disasters, the ability of remote pure creatures, if a species is threatened.
It is pointed out that the artificial environment and the natural environment cannot be completely isolated, and there can be no existence without nature. Therefore, it is impossible for human evolution to completely get rid of nature. However, after all, human beings have been camping outside. In the era of "dancing with wolves", with the improvement of industry, agriculture and medical level, people's living conditions and health level have been continuously improved, the infant mortality rate has been significantly reduced and the average life expectancy has been significantly prolonged. In essence, people's factors are increasing, and choices are made in society.
The purpose of these two questions is to activate thinking, and the answer is that there is no need to unify the reasons for support or opposition, as long as the students make a reasonable statement.
7.2 Fourth, answers and tips
(1) discussion
Tip: Students can imagine the following ideas: under the control of traits, individuals who make greater contributions to survival and reproduction may have more genes.
(2) Thinking and discussion 1
1。 (1) Gametes account for 60% and 40% of gametes.
(2) Genotype frequency of offspring: AA accounts for 36%; AA accounts for 48%; AA 16%。
(3) Gene frequency of offspring population: one gene accounts for 60%; 40%。
(4)
The genotype frequencies of parents were AA (30%), AA (60%) and AA (10%) respectively.
Gamete ratio A (30%), A (30%) (30%)-( 10%)
The AA genotype of the offspring is (36%) AA (48%) AA (16%).
Offspring gene frequency A (60%), (40%)
The combination of gene frequency and subgroup in the same generation.
2。 The nature of the population, it can not set the condition of 5 at the same time. For example, the color of wings is more consistent with the environment, and there is less chance of becoming a predator.
3。 Gene mutation leads to the change of gene frequency of the new population produced by this gene. The frequency of A2 gene increases or decreases, depending on whether the mutant microorganism is beneficial or harmful.
explore
1。 The light that affects the individual birth rate is light, because many people may not have carnivores that have been preying before mating and spawning.
2。 It's phenotypic. For example, carnivores see the body color of birch instead of controlling the body color genes.
(4) data analysis
1。 Because there are not enough individuals in these two groups, the gene frequency may be different.
2。 It's different. Because of random mutation.
3。 Different islands have different topography and vegetation conditions, so they will have different effects in the environment, leading to changes in human gene frequency in different directions.
4。 Not because of gene exchange between individuals.
(5) Problems
Moss usually grows next to the first row of bare rock plants. The appearance of lichen promotes the decomposition of rock and soil formation and creates the growth conditions of bryophytes.
(6) Skills training
1 Suppose A: Red-brown fish and goldfish originated from the same gray fish. Suppose B: Lake I was originally a reddish-brown fish, and Lake II was originally a goldfish. During the flood, the fish in the lake mixed together twice.
2。 Suppose a does not consider the role of isolation in speciation or the role of flood.
3。 This evidence supports B.
4。 Can't produce, if red, brown and gold fish and fish can't cross, or cross the hypothesis of offspring, this shows that they are not a species.
(7) Thinking and discussion II
1。 Anaerobic organisms The earliest single-celled organisms lived in the ocean.
There are more than two cells around CAMBRIAN creatures, and they live in the ocean.
3。 The first creatures to go ashore are plants and animals, or when they go ashore, they will be hungry.
4。 Whether on land or in barren land, living in the sea.
Dinosaurs died out in the late Mesozoic. The impact of biodiversity on species extinction is complex. The extinction of dinosaurs is good for mammals.
(8) Practice the basic questions in the first part.
2.C. 3。 C of 1 C
4。 Mutation and gene recombination lead to the evolution of raw materials. If there is no mutation, it is impossible to produce new alleles and gene recombination is meaningless, so it is impossible to produce biological gene mutation and development.
1 topic extension hint: If you choose breeding and cross breeding.
Tip: If other conditions are suitable for the climate and this population has certain reproductive capacity, then the individual population will increase rapidly. Otherwise, it may still be endangered or even extinct. .
(9) Practice
The basic problem of 1( 1) √ Part II; (2)√; (3)√。
2。 This population lives in the northern part of the Variation Canyon. Because of the randomness of gene mutation, the same mutation will not appear in the south of the canyon. Because the two groups are separated by a river, there is no chance to cooperate with each other, that is, there is no exchange of genes, so the two groups are obviously differentiated and may evolve into two species.
Hint extension problem: The offspring of the male tiger and the female lion gave birth to a hybrid-liger, and the hybrid offspring of the lion and the female tiger was born in liger. No tiger mated with the lion tigon, giving birth to evidence to raise offspring.
Let people have more ornamental value to the hybrid offspring of tiger and lion, and students can express their opinions freely.
Supplementary information: 198 1 year, the world's first tiger lion was born in France and died in 200 1 year. On August 22nd, 2002, China was born in Nanjing Hongshan Zoo. Only seven days later, he was the first tiger, lion and beast. On September 2, 2002, three tigers and lions were born in Fuzhou National Forest Park Zoo, and only one survived. On March 27th, 2003, I was born in Changsha, Hunan, the window of Hu Shi's beast in Hunan. Domestic and imported examples of breeding liger for tourists to watch. In the practice of anticlimactic, some experts think that this is of little value in scientific research, but it has certain value in enterprises. Some experts believe that most people should protect wild rare animals and let them reproduce naturally, rather than artificially changing their natural reproductive system.
(10) The topic of the third part is to practice the basics.
1( 1)√; . (2)×; (3)×2 . c。
3。 Sexual reproduction makes recombination possible, improves the diversity of biological variation, and speeds up biological evolution obviously.
1 Prompt to expand the problem: If so, it is difficult to explain complex biological phenomena with a unified theory. As the viewpoint of evolutionary biology, one of the basic ideas will be difficult to establish, and biology can't be studied now, forming such a scientific framework, lacking the basic ideas and methods to guide and learn biological command. .
Hint: it refers to the relationship between ecology and biological evolution environment, and refers to the historical evolution of biosphere; If we look at the historical drama performance of various biological evolution, the stage of this historical drama at that time was the complex relationship between biology and environment. It shows that variety is influenced by the evolution of stage background, and the stage background should be coordinated with the content.
Self-examination answers and tips Chapter VII
First, the concept of judgment test
1。 ×。 2,×。 3,×。 4。 √ multiple choice questions1.a.2.c.
2. Draw concept maps and transfer knowledge
1。 These two groups belong to the same species, and there will be no reproductive isolation.
2. Please refer to 1 for the explanation of bacterial resistance.
Third, the application skills
It is suggested that the intermediate color may be closer to the color of the environment, so people have no chance to find prey that is easier to survive and reproduce, and the corresponding genotype frequency is higher. After long-term natural selection, multiple individual intermediate colors are produced.
4. Thinking expansion
1。 Inevitable. The emergence of new species has opened up the position of survival and development in some new living environments, and it is not necessarily more adaptable than the original species. For example, after marine life landed, the formation of many new species opened up new living space, but it cannot be said that the algae of these new species are more adaptable.
2。 Compared with wild species of the same or similar species, domestic animals tend to change according to their own needs, while humans, cross breeding and other related measures. .
Hint: If Darwin accepts Mendel's theory, he can get rid of genetic reasons and make a more scientific explanation.
1. 1 Three Basic Problems of Coercion 1. C2B.3.B4. The capillary wall cells in the direct living environment are plasma and tissue fluid, and the capillary wall cells and lymphatic tissue fluid in the direct living environment. Dilation problem (1) alveolar wall, capillary wall. (2) Digestion of food and absorption of nutrients. (3) Renal tubular reabsorption. (4) on the skin. .
1.2 basic questions1d.2c.3d.
Self-test:1(1) ×; (2)√; (3)×; (4)√。 .2( 1)D； (2)D； (3)D。
2. 1 basic questions 1.B. 2, brain, cerebellum and brain stem. Expand the question 1. B, C, D and E 。
The secretion of antidiuretic hormone stimulates the osmotic reabsorption of water by the collection tube.
Drink water, urine volume decreases, how much increases.
The increase of lack of juiciness increased and decreased during this period. BR/>； 2.2 1.CD 2
2.3 1( 1)×; . (2)√。
2.4 1( 1)×; (2)√; (3)×2d。
Self-examination: 1 Fill in the blanks (1) Reduce skeletal muscle contraction. Skin capillaries contract. Hypothalamus, adrenal gland, pancreas, thyroid gland, etc. (2) brain stem. (3) foreign bodies. (4) allergic people; Allergens and dust. 2 choose (1) c (2) d.
3. Draw a concept map (1). Neurons of BCD efferent neurons; é effect [knowledge transfer] 1. D 2。 D
3. 1 Basic problem: More sunlight can be evenly received in the factory, and plants and plants can be prevented from bending towards light.
3.2 Basic question 1 .c.2.b. Extended question1Note: Due to gravity, the lower part of high concentration auxin. The stem of a plant can promote the growth of auxin, make the lower part grow rapidly and bend the stem upward. The concentration of auxin in plant roots is the same, but it will inhibit growth, so the lower roots grow slower than the upper ones, and then the roots that bend downward grow out. If it grows on the space station, the plants will not do this, but grow horizontally.
3.3 1.d, because it is a synthetic substance and a plant growth regulator. 2.b is more accurate. This is fundamentally too absolute genetic control. Regulating plant life activities is a very complicated process, and environmental changes will also affect gene expression. Hormone regulation is just a regulation method.
Self-taught:1.d.2. B, C, d.3.d [knowledge transfer] B, because plasma cells are developed from cells such as ovarian wall and placental cells, and the number of somatic cells is the same as that of chromosomes.
4. 1 1。 About 386. The effective density of earthworm can be investigated by marked recapture method, which can be used to investigate the density of rats. 3.B。
4.2 1 hint: under the conditions of sufficient food, vast climate and favorable conditions, if there are no natural enemies, the population may show a "J" type growth. For example, Australian entomologists have studied the thrips population in orchards for more than 14 years, and found that the rapid growth of the population showed a seasonal "J" growth in better years. In limited circumstances, if the initial population density is low, the population may appear quickly. With the increase of population density, intraspecific competition will intensify, so the population will stop growing to a certain extent, which is "S" growth. Such as scenedesmus, green algae and other lower plants, such as population growth, often grow in an "S" shape.
2 Tip: (1) This year's level, the vertical axis is population. Draw a chart according to the table. (2) Adequate food, no natural enemies, climate, etc. (3) A large number of food factories eat it, resulting in food shortage; Natural disasters.
4.3 1.B. 2 hint: when the obstacle is removed, the following situations may occur: as a predator population, there is a population B, and population B decreases the population, while population A increases. . . .