生物讨论专区

muse

1.Which event occurs during epigeal germination of a seed planted in the soil?
A.The epicotyl elongates but the cotyledon remains underground
B.The hypocotyl elongates but the cotyledon remians underground
C.The hypocotyl elongates and pushes the cotyledon above the soil surface
D.The plumule elongates and pushes the cotyledon above the soil surface

Answer: C

muse

1.Which of the following descriptions regarding diapause is most accurate?

Dispause occurs
A.only in larval stage
B.when there is sufficient food supply
C.when the  light period exceeds a critical level
D.when there is an inadequancy of hormones which is controlled by external stimuli

Answer: D

muse

1.A tree with the genotype Aa self -crossed .What is the expected genotypic ratio of the endosperm tissue in the seeds produced?
A. 1/2 AAA:1/2 aaa
B  1/4 AAA:1/4 AAa:1/4Aaa:1/4aaa
C  1/4 AAA:1/2 Aaa:1/4aaa
D  1/4 AAA:1/2 AAa:1/4aaa

Answer: B

muse

1.Which is likely to have a harmful effect on an organism?
A. A base-pair substitution
B. A deletion of three bases near the middle of the gene
C. A single base deletion near the middle of the intron
D. A single base insertion near the beginning of a gene

Answer: B

muse

1.The function of the promoter in the lac operon is to
A. code for the regulator gene
B. code for the repressor gene
C. bind to repressor
D. bind with the RNA polymerase

Answer: D

muse

1.The process of putting in recombinant DNA molecules into bacterial hosts when the phage lambda is used a vector is called
A.transformation
B.transition
C.translation
D.restriction

Answer: A

muse

1.Which of the following statements is not true about taxon in taxonomy?
A.Division is not equivalent to phylum
B.Organisms of the same family belong to the same order
C.Organisms of the same genus are species that are closely related in terms of evolution
D.Species that interbreed closely related in  evolutionary  terms to the organisms of the same genus

Answer: A

muse

1.Natural selection that acts to remove one group of extreme phenotype in a population is known as
A.directional selection
B.stabilising selection
C.disruptive selection
D.sexual selection

Answer: A

muse

1.The ecological niche is defined as
A.the habitat in which an organism finds its food supply
B.the habitat in which an organism finds the suitable climate
C.the relationship between an organism and other species
D.the way in which an environment is exploited by an organism

Answer: D

muse

1.Carrying capacity is
A. the minimum population size that can be supported by its environment under certain condition
B. the maximum population size that can be supported by its environment under certains conditions
C.the individual birth rate in a population
D.the individual death rate in a population

Answer: B

muse

1.A woman with normal colour vision,whose father was red-green colour blind, married a red-green colour blind man.The probability that a girl born to this couple will be red-green colour blind is
A. 1.0
B. 0.125
C. 0.0625
D. 0.25

Answer: D

-by muse-

2.A cross of bean variety produce 9744 individuals with dominant tall genotype (T) compared with 256 individuals with recessive short genotype (t).
(a)By assuming that the crossing in the bean population above takes place in equilibrium , calculate the genotype frequency in the crossing .

Individuals with dominant tall genotype (TT or Tt) : 9744
Individuals with recessive short genotype (tt):256
Total:10000

According to Hardy-Wernberg equation ,
p²+2pq+q² =1
and

p+q=1

where,
p²=frequency of genotype of homozygous dominant tall (TT)
2pq=frequency of genotype of heterozygous (Tt)
q²=frequency of genotype of homozygous recessive short (tt)
p=frequency of dominant allele (T)
q=frequency of recessive allele (t)



frequency of genotype of homozygous recessive short (q²)
256/10000=0.03

Frequency of recessive allele (q)
Square root of q² =0.17

Frequency of dominant allele (p)
p+q = 1
p = 0.83

frequency of genotype of homozygous dominant tall (p²)
(0.83)²=0.69

Frequency of genotype of heterozygous (2pq)
2(0.83)(0.17)=0.28

(b) State the necessary assumptions in the above crossing .
-population size is large enough .
-no mutation
-no immigration or emigration occurred. That’s mean no gene flow in and out from the population.
-no natural selection .
-mating is random .

(c) Give the meaning of alleles frequency in a population .
-allele frequency is the ratio of the sum of a particular allele to the sum of the all of the allele in a population .

-chng-

[ 本帖最后由 muse 于 21-9-2007 08:40 PM 编辑 ]

muse

这里都没有bio生吗？
怎么帖子一直沉。。

Jec

原帖由 庄Ch'ng 于 10-9-2007 10:54 PM 发表
(a)State the external factors which influence the germination of seed .   [3]

-temperature
-water
-oxygen


(b)The germination of dormant seeds involves the metabolisation of food reserve ...

好呵。。。再接再厉！

Jec

[size=67%]•The cell walls of most fungi are composed of what material?
A.Cellulose.
B.Keratin.
C.Chitin.
D.Peptidoglycan.




Answer: C




[ 本帖最后由 Jec 于 15-9-2007 01:06 PM 编辑 ]

夕熹

因为他们都贴在STPM生物专区了

Jec

这里有一道问题给大家动动脑筋。

muse

我试试看，如果有错请改正。。
a)acetyl CoA
b)Pyruvate + CoA + NAD+ ---->acetyl CoA + Co2 + NADH + H+
c)matrix of mitocondrion
d)FAD + NAD
e)不会，不明白问题
f)D--->succinate
g)4C

Jec

答案是:
(a) Acetyl CoA
(b) Coenzyme A + oxidised NAD + pyruvate ---> Acetylcoenzyme A + reduced NAD + CO2
(c) Matrix of mitochondrion
(d) NAD & FAD
(e) 18 NAD & 4 FAD
(f) Between the C-D and D-succinate
(g) 4 carbon atoms

Jec

我又有另一道题目啦！

请试试看.

Jec

没有人回答吗？算了。自己提供， 请参考吧。若有错出，盼明察。
(a) 答案是:
A: mitochondrion
B: Synaptic vesicles
C: presynaptic membrane
D: postsynaptic membrane
E: synaptic cleft


(b)答案是:
- When an action potential reaches the synapse, calcium channels open up, causing Ca2+ ions to flow into the cells (synaptic knob).

- Ca2+ ions cause the synaptic vesicles to fuse with the presynaptic membrane, thus releasing their contents (neurotransmitter chemicals) by exocytosis.

- The neurotransmitter diffuses across the synaptic celft. It binds to the neuroreceptors in the postsynaptic membrane, causing the sodium channels to open, so Na+ ions flow in.

- A depolarisation takes place in the postsynaptic membrane, which initiate the action potential.

The neurotransmitter is broken down by a specific enzyme (acetylcholinesterase) in the synaptic cleft.

- It breaks down the neurotransmitter acetylcholine. The products are absorbed by the presynaptic neuron by endocytosis and used to resynthesise more neurotransmitter. Energy is acquired from the mitochondria for this process.