生物讨论专区

Jec

这是楼上的答案。

Have fun!

生物难题

哇！连马marking scheme都有，这样方便多了。那里弄来的？谢啦。

生物难题

这题不会做，有谁可以解答？是stpm2001来的。

Which of the following are involved in the production of root pressure?

I   Water and ion flow into the endodermis.
II  The movement of water molecules through the mass flow mechanism and transpirational pull.
III Ions are actively transferred through the cell membrane of the root into the cytoplasm.
IV  Ions in the cytoplasm are transferred freely into the stele through plasmodesmata.
       
A  II and III       
B  II and IV
C  I, II and III
D  I, III and IV

wooly

请问一下是不是所有的bacteria都有plasmid?

Jec

原帖由 wooly 于 17-10-2007 08:49 PM 发表
请问一下是不是所有的bacteria都有plasmid?

I think it's most likely.

根据MSN Encarta的解释：＂Plasmids are present in almost all bacteria and may also be found in some yeasts and other fungi, protozoa, and even some plants and animals. They are separate from chromosomes, the primary structures that contain DNA in cells. Plasmids are important tools used in genetic engineering—the deliberate manipulation of an organism’s genetic material—and they are also key to scientists’ understanding of how bacteria cause human disease.＂

另外，根据Wikipedia的解释：＂A plasmid is a DNA molecule separate from the chromosomal DNA and capable of autonomous replication. In many cases, It is typically circular and double-stranded. It usually occurs in bacteria, and is sometimes found in eukaryotic organisms (e.g., the 2-micrometre-ring in Saccharomyces cerevisiae).＂

这样看来，plasmid（也称细菌质粒）是独立于细菌染色体的自主复制的环状双链DNA分子。质粒是染色体外能够进行自主复制的遗传单位，包括真核生物的细胞器和细菌细胞中染色体以外的脱氧核糖核酸(DNA)分子。

现在习惯上用来专指细菌、酵母菌和放线菌等生物中染色体以外的DNA分子。在基因工程中质粒常被用做基因的载体。许多细菌除了染色体外，还有大量很小的环状DNA分子，这就是质粒(plasmid)。

[ 本帖最后由 Jec 于 27-11-2007 08:37 PM 编辑 ]

Jec

我把今年的试卷１post上来，请大家热烈讨论。
Lower 6同学，欢迎参考和当作revision。
（时间真是残酷，２００７年的考试转眼已变成过去式啰！）

Jec

没有人呼应?假期时书本都给抛掉了？

angelit

果然是用心良苦。。。
帮你顶一下

Jec

哈哈哈哈，谢啦。。。 你不妨试试做。不要只是精神支持。

原帖由 angelit 于 13-12-2007 05:31 PM 发表
果然是用心良苦。。。
帮你顶一下

markovnikoff

Q & A

How does the theory of Evolution proposed by Darwin differ from that proposed by Lamarck ?                                                                        (3m)



Answers :

Darwin’s Theory
Evolution occurs by natural selection, due to change in environment, acting on variation of characteristic which can be inherited.
The most advantageous phenotype in term of adaptation to environment will be able to survive to maturity and reproduce and to pass its genes to next generation as well.
In modern genetics, Darwin’s Theory means that the phenotype is controlled by genotype.



Lamarck’s Theory
Evolution occurs by inheritance of acquired characteristics which are developed as a result of specific need felt by the organisms due to change in environment.
Organisms will modify their body part so as to accommodate the need of environment which changes constantly.
Organ or body part which are always utilized will keep on develop while those rarely used will degenerate slowly.
Lamarck’s theory means that the genotype is determined by the phenotype.

vinclam

看了几题。。但是不懂对不对啦。。
但是。。在看多几题。。发觉是 U6 的课程，还没有学到，所以没有心情再看下去了。。哈哈。。

想问一下。。那些 cyles cyles de... 需要记起来的吗？因为那些。。好像很难记哦。。

[ 本帖最后由 vinclam 于 7-1-2008 01:36 AM 编辑 ]

angelit

原帖由 vinclam 于 7-1-2008 01:34 AM 发表
看了几题。。但是不懂对不对啦。。
但是。。在看多几题。。发觉是 U6 的课程，还没有学到，所以没有心情再看下去了。。哈哈。。

想问一下。。那些 cyles cyles de... 需要记起来的吗？因为那些。。好像很难记哦。 ...

那些东西一定要记起来，因为还蛮重要的。 比方说，calvin cycle, kreb's cycle 都很重要的。photosynthesis 的 cycle 在哪里会产生 ADP, NADPH, 之类的问题。
cycle 的问题，个人觉得老师超爱，因为我学校在一年半的时间内，已经出了几次。所以你说，需要记吗？


老实说，要是不难的话，考试到不会出啦。
还有一样要提醒你的，考试出的题目通常都会问到很仔细的。你看2006年的考卷就知道了。

所以要表记就看你自己咯。

angelit

你有答案吗？很想检查一下。

vinclam

哦。。谢谢您

我想在请教一下，你们是如何找到植物的科学名称的?
尤其是当你们在做那个植物的 PROJECT 时..

angelit

这个问题基本上我们是向上一年的学长拿的，而有一部分是上网找的。网上有很多啊！之前有一些都是在网上找到的。

不过要提醒你，植物的标本一定用足够的时间来做（如果使用压的方法），因为压不够的话，植物会很容易发霉。 但是如果使用烘干的方法的话，我就不知道要用几久的时间了。

这些都是个人的意见，希望能够帮到你啦。

kentawan

原帖由 angelit 于 8-1-2008 11:34 PM 发表



那些东西一定要记起来，因为还蛮重要的。 比方说，calvin cycle, kreb's cycle 都很重要的。photosynthesis 的 cycle 在哪里会产生 ADP, NADPH, 之类的问题。
cycle 的问题，个人觉得老师超爱，因为我学校在 ...

Cycle 的东西常常练习之后要忘掉都难。。。
我甚至在发梦时都梦到。。。

vinclam

urm.. 请问。。
如果生物只单单读课本能应付考试吗？
需不需要解释得非常清楚？

kentawan

原帖由 vinclam 于 12-1-2008 02:23 PM 发表
urm.. 请问。。
如果生物只单单读课本能应付考试吗？
需不需要解释得非常清楚？

要记得point就可以了。。。

还有要顾时间。。。

morphv02c01

原帖由 Jec 于 8-10-2007 05:56 PM 发表
Essay那一部分，只须找一下参考书，不会难倒大家的。所以我不post上来咯。Essay的答案很长，若有人volunteer做做看，当然最好啦！

Ok...让我分享一下我的题目库。

The diagram shows the process of filtratio ...

(i) Ultrafiltration process that occurs only allows molecules with a RMM lower than 76,000   
     to pass through the filtration membrane. Protein molecules are too large.
    (filtration membrane also consists of podocytes to enhance the filtering process)

(ii) During the selective reabsorbtion at the proximal convoluted tubule, useful substance like glucose are reabsorb back by means of active process. A person with a normal blood sugar level will have a reasonable amount of glucose that present during the selective reabsorbtion process. Therefore glucose are not normally present in urine.

(iii) ADH is responsible for maintaining the amount of water that is reabsorb back at the distal tubule at kidney. After exercise the athlete must have lost alot of water, causing the intercelluar fluid to become more hypertonic, thus stimulating the pituitary gland to secrete more ADH to absorb back more water and thus producing concentrated urine.

ps: long time didnt study, just simply try, i suppose the ans has many mistakes..

恩儿

其实我想问一下。biology里头的polar and non-polar究竟是指什么意识？我查了字典，问了老师，也不懂