Find some biology competition papers.

Second, multiple judgments (2 points for each small question, the answer is completely correct to score, *** 60 points)

1. Which of the following statements is true about the conformation of DNA molecules?

A. the secondary structure of A.DNA (double helix) mainly has a, b, d, e, z and other conformations.

Type B is right-handed spiral, and the others are left-handed spiral. Type C is the most common and stable in living cells.

D there may be types a, b and z in cells, and some of them will be deformed under certain physiological conditions.

The transcription activity of E is different in different conformations, and the transcription activity of type A is the highest.

Analysis: C conformation is not important; The conformation of A, B, D and E forms is right-handed helix, and Z forms is left-handed helix. Type B is the most common in living cells. Relative humidity, salt concentration in solution, ion type and organic solvent can all cause changes in DNA conformation, and type B activity is the highest.

So choose AD.

2. Please choose the method of observing chromatin:

A. Electron microscope B. Phase contrast microscope C. General optical microscope

Gimsa banding with hematoxylin-eosin staining

Analysis: both electron microscope and ordinary optical microscope can observe cytoplasm at sufficient magnification; Phase contrast microscope is generally used to observe the unstained samples of living cells and the dynamics of organelles; Hematoxylin-eosin staining stained the nucleus to make the cytoplasm easy to observe; Giemsa banding is used to observe chromosome banding.

So choose ACD.

3. Which of the following substances is involved in the translation of mRNA into protein?

A. mRNA B. DNA C. Ribosome D. Multiple amino acids E. Multiple enzymes

Analysis: This is a translation process, which requires mRNA as a template, ribosomes as a place, various amino acids as raw materials, and of course, enzymes as a catalyst.

So choose ACDE

4. In the process of DNA denaturation, which of the following phenomena will occur?

A. phospholipid bond breakage B. hydrogen bond breakage between double helix C. viscosity reduction

D. increase of settling speed e. increase of ultraviolet absorption.

Analysis: the breaking of phospholipid bond is the degradation of nucleic acid; The essence of DNA denaturation is that the hydrogen bond in the double helix region of nucleic acid breaks and becomes two single strands. After denaturation, the ultraviolet absorption luminosity increases, the viscosity decreases, the buoyancy density increases and the sedimentation rate increases.

So choose BCDE

5. Prokaryotic cells and eukaryotic cells have the same characteristics:

A. both of them contain circular DNA. Both contain linear DNA.

C. The basic unit of chromosome is nucleosome D, both of which contain ribosomes as protein synthesis machines.

Analysis: the DNA in the nuclear region or plasmid of prokaryotic cells is circular DNA, while the circular DNA in eukaryotic cells is located in mitochondria or chloroplasts, and only eukaryotic cells contain linear DNA. There are no chromosomes in prokaryotic cells, and only one organelle in prokaryotic cells is ribosome.

So choose AD.

6. The nucleotides that make up DNA consist of three parts. Which of the following descriptions is correct?

A. the same base B. the same phosphate group C. the same deoxyribose D. the above three substances are different.

Analysis: The nucleotides that make up DNA are deoxynucleotides, which are divided into three parts: deoxyribose, phosphate group and N-containing bases, among which four N-containing bases are A, T, C and G, and different bases make up different nucleotides.

So choose BC

7. Active transmembrane transport of energy consumed by cells includes:

A. simple diffusion B. proton pump C. coordinated transport D. facilitated diffusion E. sodium and potassium pump

Analysis: Simple diffusion and facilitated diffusion both diffuse from high concentration to low concentration, which belong to passive transportation without energy consumption.

Select BCE

8. The following statement about cloned sheep is correct:

A. cloned sheep are produced through asexual reproduction.

B. Dolly, a cloned sheep, uses maternal mammary epithelial cells.

C. Three sheep were used in the production of Dolly the cloned sheep.

D. Implanting 16 cell "embryo" into surrogate ewe, and cloning Dolly.

Analysis: Dolly was cloned with 8- 16 cells implanted in surrogate ewe.

So choose ABC

9. The virus is characterized by:

A. The morphological characteristics of the virus can be observed through an optical microscope.

B. the virus can't produce ATP and can't carry out various life processes independently.

C. virus particles contain DNA and RNA.

D. the virus can pass through the bacterial filter e. No cell structure.

Analysis: viruses are smaller than bacteria and can pass through bacterial filters. Viruses need an electron microscope to be seen. A virus contains only one kind of nucleic acid, DNA or RNA. Without cell structure, viruses cannot metabolize independently.

So choose BDE.

10. Generally, leguminous plants are divided into three subfamilies, and any subfamily has the following characteristics:

A. butterfly corolla B. diploid stamens C. pods D. most of them are compound leaves

Analysis: Leguminosae is divided into three subfamilies: one is Mimosa subfamily, which has many stamens and petals arranged in tweezers; Second, iris subfamily: butterfly-shaped corolla, two stamens, slightly symmetrically separated on both sides of the flower; Third, Magnoliaceae: the flower height is symmetrical on both sides. AB is a characteristic of the butterfly family.

So choose CD.

1 1. The following are several treatments for wheat sowing. Which treatments can make the plants blossom and bear fruit normally after sowing?

A. Sow before winter B. Sow in spring

C, low-temperature treatment (0-5 DEG C) is carried out after the seeds germinate, and then the seeds are sown in spring.

D, sowing in spring after low temperature (0-5 DEG C) treatment.

Analysis: After sowing, it needs low temperature induction to make the plants blossom and bear fruit normally, which is called vernalization, and it is the shoot tip growth point that receives low temperature treatment.

So choose AC.

12. Generally speaking, there are many differences between the primary structures of roots and stems. Which of the following differences is correct?

A. the arrangement of vascular bundles is different. The development of phloem is different

C. xylem develops in different ways. Is the endodermis obvious?

Analysis: the vascular bundles of roots are staggered, and the vascular bundles of stems have a bundle structure composed of xylem and phloem. The development pattern of phloem of roots and stems is exogenous; The xylem of the root is outside, and the xylem of the stem is inside; The endodermis of roots is obvious, but the endodermis of stems is not obvious.

So choose ACD.

13. The reproduction modes in the life history of Plasmodium vivax are:

A. binary division B. spore reproduction C. sexual reproduction D. fission reproduction

Analysis: Plasmodium belongs to sporozoite, which can reproduce asexually in human body, and can have sex gametes and asexual spores in Anopheles. Secondary division is common in flagellates and ciliates.

So choose BCD.

14. Which two animals are responsible for kala-azar and sleeping sickness?

A. Schistosoma japonicum B. Trichophyton C. Leishmania D. Trypanosoma

Analysis: Kala-azar, also known as visceral leishmaniasis, is caused by Leishmania and spread by sandflies. Symptoms: irregular fever, splenomegaly, emaciation and anemia; Sleeping sickness is caused by trypanosoma, and it will starve to death without considering tea and rice; Schistosomiasis is caused by snails.

So choose CD.

15. Which of the following combinations is correct?

A. Crocodiles have alveoli, double occipital condyles and closed temporal fossa. Birds have a occipital condyle, attachment joints and double temporal fossa.

C. axial bones-sternum, clavicle and scapula D. human combined temporal fossa, colon and bilateral occipital condyles.

Analysis: Crocodiles have fluted teeth, single occipital condyle and double temporal fossa; Birds are single occipital condyle, accessory joint and double temporal fossa; Axial bones include skull, spine, sternum and clavicle; The scapula belongs to the appendage bone; In humans, the temporal fossa, colon and occipital condyle are combined.

So choose BD.

16. Which of the following combinations is an early bird?

A. crane-albatross B. red-crowned crane-domestic chicken C. eagle-woodpecker D. swan goose-peacock

Analysis: Early adult birds mean that chickens don't need to be fed after hatching, and complete birds mean that chickens need to be fed after hatching. Hemiptera chickens, albatrosses, eagles, woodpeckers, etc. are late-maturing birds, generally raptors; The chicks of Crane Order (Red-crowned Crane), Chicken Order (Domestic Chicken, Peacock) and Goose Order (Hongyan) are all precocious birds. Premature birds are generally gentle terrestrial and migratory birds.

So choose BD.

17. The secretion of salivary gland is controlled by which of the following nerves?

A. seventh cranial nerve b sympathetic nerve c seventh cranial nerve

D. hypoglossal nerve e. trigeminal nerve

Analysis: The seventh cranial nerve is a mixed nerve, and visceral motor fibers are connected with submandibular gland and sublingual gland. Sympathetic nerve promotes the secretion of viscous saliva, and the mixed nerve of glossopharyngeal nerve of the seventh cranial nerve is connected with parotid gland. The hypoglossal nerve dominates the movement of the tongue muscle, which has nothing to do with saliva secretion, and the trigeminal nerve does not distribute salivary glands.

So choose ABC

1 8. Some people define that animal play is a behavior that has no adaptive significance. For this definition, do you think the following statement is correct:

The definition of A doesn't hold water, because in the process of natural selection, those behaviors that have no adaptive meaning will be eliminated.

B. Actually, playing is adaptive. C. animal play is not a behavior.

D. none of the above is true

Analysis: Animal play is an animal behavior, and all animal behaviors are an adaptation to the environment.

So choose AB

19. The following statements about the relationship between hormones and behavior are correct:

A. A hormone can only affect one behavior. B. the process of hormone-initiated behavior is independent of the nervous system.

C. hormone levels are sometimes affected by behavior. D. the regulatory effect of hormones on behavior is related to genetic factors.

Analysis: The process of hormone starting behavior usually needs the coordination of nervous system. A hormone can affect many behaviors. Prolactin can not only promote lactation, but also participate in stress response, which in turn affects hormone secretion. Hormone regulation of behavior is often related to genetic factors.

So choose CD.

20. Human beings have a rare disease caused by autosomal dominant pathogenic genes, which is found in an island population.

The incidence rate is very high. Human geneticists may be involved in discussing the reasons for the high incidence of this congenital disease.

Which of the following factors:

A. The mutation rate of this gene is very high. B. there may have been events on this island that led to human disasters.

C. the few immigrants who first developed the island D. the genes are not affected by natural selection.

Analysis: Because it is rare, the mutation rate of this gene is very low, and some events that lead to human disasters may make people with this gene live, which is caused by natural selection; In other words, if the gene frequency among the immigrants who first developed the island is high, this result may also occur, which is the so-called founder effect.

2 1. If the cytoplasm of animal cells contains high levels of reverse transcriptase, it may lead to:

A.mRNA was transferred back to DNA sequence B. These transferred DNA will be different from the DNA sequence of the genome.

These transferred DNA may be integrated into the genome through homologous recombination process and cause mutation.

D. the transcription level of genomic DNA has been improved.

Analysis: the process of reverse transcription catalyzed by reverse transcriptase, in which mRNA is reverse transcribed into DNA sequence. Because there may be errors in this process, there may be differences between the transferred DNA and the genomic DNA. Both of them have double-stranded DNA, which can be homologous recombination, but the transcription level will be reduced.

So choose ABC

22. Darwin's theory of evolution with natural selection as the core dealt a fatal blow to creationism, making evolution become

Get rid of the shackles of theology. Darwin's theory of evolution is related to which of the following influences:

A. Malthus's population theory B. Ryle's geological evolution principle

C. Mendel's genetic principle D. Fossils of animals and plants observed in global travel

Analysis: Mendel's law of heredity reveals the basic law of heredity, which has nothing to do with the evolutionary thought here.

So I chose ABD.

23. Polymerase chain reaction (PCR) is widely used in forensic medicine, mainly because this technology:

A. high sensitivity. B.less target DNA is needed.

C. short reaction time D. no need to synthesize primers with specific sequences.

Analysis: Polymerase chain reaction (PCR) needs a short DNA as a primer.

So choose ABC

24. Among the following options, bioaccumulation can occur in the food chain of the ecosystem:

A. heavy metals B. heat C. carbohydrates D. chlorinated hydrocarbon pesticides

Analysis: Bioenrichment means that the concentration of some substances in organisms increases with the increase of trophic level, and heavy metals and some pesticides are not easy to degrade and lose, so they are easy to be enriched.

So choose AD.

25. In the process of ecosystem development, its structural and functional characteristics will change obviously, including:

A. developing ecosystem, P/R (total production/total respiration) >1; In the mature and stable period, P/R

B during the development of the ecosystem from infancy to maturity, the mineral nutrition cycle tends to be more closed from relatively open.

C. During the development of the ecosystem from infancy to maturity, the diversity of organic matter gradually increased, and the products discharged into the environment during the community metabolism increased.

The entropy value of the development system is obviously higher than that of the mature period.

Analysis: When P/R

So choose BCD.

26. From the analysis of nutritional structure, the basic biological components of the ecosystem are:

A. producers and consumers decomposers of abiotic environment

Analysis: Abiotic environment, producers and decomposers are all indispensable components of ecosystem, but abiotic environment is neither a nutritional structure nor a biological component.

So choose BD.

27. The formation of a plant community can start from bare land or another existing community. However, in the process of forming any community, there are at least several stages.

A. Propagation of propagules B. Above-ground canopy of plants

C. The underground parts of plants are intertwined.

E. competition among plants

Analysis: The succession of the community begins with the settlement of the living things, and the living things must arrive at the settlement first, which requires the reproduction of the propagules. After propagator propagation and plant settlement, there must be competition between plants to realize community succession. .

So choose Ed.

28. The following description of the characteristics of the ecosystem food web is correct:

A. The links in the food chain are infinite. There is more than a predatory relationship between creatures on the food web.

C. An organism may belong to different trophic levels. D. The more complex the food web, the more stable the ecosystem.

Analysis: Because the fixed energy of producers is limited, the links in the food chain are also limited, generally not exceeding 5 trophic levels; The creatures on the food web may be in a competitive relationship.

The reference answer is that CD should be BCD.

29. Which of the following characteristics belongs to seed plants?

A. the sporophyte is parasitic on the gametophyte. The gametophyte is parasitic on the sporophyte.

C. developed sporophytes

Analysis: The vegetative body of seed plants is diploid, called sporophyte, while the haploid produced by reproductive organs is called gametophyte. The gametophyte of seed plants is parasitic on the sporophyte, and the sporophyte is developed and the gametophyte is degraded.

So choose BC

30. Among the following structures of cucurbitaceae plants, those that contribute to spore transmission are:

A. tooth B. elastic wire C. cap D. endless belt

Analysis: Pumpkin has no elastic structure. After the spores mature, the bottle cap falls off by itself, and the ring belt is located between the bottle cap and the kettle. The teeth on the inner side of the girdle can do dry-wet telescopic movement to eject spores from the capsule, which involves the girdle.

The reference answer is that ABD should be AD.