胚胎在形成腸胃道的雛形時, 會出現一個開口, 稱為胚孔.
腔腸動物如扁蟲的胚孔既能進食也能排泄, 同時扮演嘴巴和肛門的角色; 而紐蟲胚胎時期的胚孔會變成嘴巴, 其他如軟體動物, 環節動物與昆蟲等, 也有類似的情況, 牠們被稱為原口類動物(Protostomia); 但如棘皮動物與脊椎動物等, 胚胎時期的胚孔會變成肛門, 之後再長出嘴巴, 被稱為後口類動物(Deuterostomia).
兩類動物在胚胎階段的分裂方式完全不同, 原口類的初期卵裂, 細胞是螺旋狀排列, 而後口類則是輻射排列; 原口類動物在卵裂階段, 細胞的未來走向已然確定(定型), 這種"策略"的好處是可以快速產生後代, 然而, 若在分裂完成前有部分細胞被拿走, 將無法長成完整的個體, 因此幼體死亡率較高; 反之, 後口類動物在卵裂階段的細胞屬未定型, 即使有部分細胞被拿走, 日後仍能長成完整的個體, 相對而言, 幼體死亡率較低.
2011年9月20日
academic writing 08 constructing a research paper II (continued)
Results deal with facts, which are descriptive; Discussions deal with points, which are interpretive. The There are also three moves. In a long article, the Discussion sections run the sequence more than once.
In my field (describing and solving social problems with ecological data), move 2 is as important as move 1 because social research is too complex to finish in a single paper. As empirical research filling the gap between theory and practice, move 3 is also necessary. Followings are some useful opening:
beginning with a discussion of the literature, such as someone (year) recovered .... and found that ....
offering a general conclusion, such as from this data, it is clear that ....
reminding the reader of the original purpose, such as the objective of the survey was to ...
giving a summary, such as this report brings together all known records of ....
referring to theory, mentioning the methodology or study site, and discussing the limitation.
Besides, in Results, statements may be quite specific while in abstract, space restrictions may lead to a high level of generality. Discussion is expected between these two levels. It is common to use there "phrases of generality", for example, on the whole or in the main.
In order to avoid the limitation to become the weaknesses in the research, there are some typical formulations:
(Swales, J. M. and Feak, C. B. 2007, Academic Writing for Graduate Students, University of Michigsn Press, Ann Arbor.)
- points to consolidate the research space (obligatory)
- points to indicate the limitations of your study (optional but common)
- points to recommend a course of action and/or to identify useful areas of further research (optional and only common in some fields)
In my field (describing and solving social problems with ecological data), move 2 is as important as move 1 because social research is too complex to finish in a single paper. As empirical research filling the gap between theory and practice, move 3 is also necessary. Followings are some useful opening:
beginning with a discussion of the literature, such as someone (year) recovered .... and found that ....
offering a general conclusion, such as from this data, it is clear that ....
reminding the reader of the original purpose, such as the objective of the survey was to ...
giving a summary, such as this report brings together all known records of ....
referring to theory, mentioning the methodology or study site, and discussing the limitation.
Besides, in Results, statements may be quite specific while in abstract, space restrictions may lead to a high level of generality. Discussion is expected between these two levels. It is common to use there "phrases of generality", for example, on the whole or in the main.
In order to avoid the limitation to become the weaknesses in the research, there are some typical formulations:
- It should be noted that this study has been primarily concerned with ...
- This study has addressed only the question of ...
- However, the findings do not imply ...
- The results of this study cannot be taken as evidence for ...
(Swales, J. M. and Feak, C. B. 2007, Academic Writing for Graduate Students, University of Michigsn Press, Ann Arbor.)
academic writing 08 constructing a research paper II
Finally, it's that last unit. Since Unit 7 has paid attention to writing results, unit 8 therefore focuses on introduction sections and discussion sections.
One of the important functions of introduction sections is creating a research space. There are three moves to follow: establishing a research territory, establishing a niche, and occupying the niche. The obligatory steps are following:
(There are some more optional steps in each move.)
There are some "skeletal" sentences to give a strong opening:
One of the other important language focuses is the tenses of citation:
In occupying the niche, there are two main variants:
If the author refers to the type of text, such as paper, article, or report, he should use present tense. On the other hand, is the author refers to the type of investigation, such as experiment, study, or survey, he should use past tense.
(Swales, J. M. and Feak, C. B. 2007, Academic Writing for Graduate Students, University of Michigsn Press, Ann Arbor.)
One of the important functions of introduction sections is creating a research space. There are three moves to follow: establishing a research territory, establishing a niche, and occupying the niche. The obligatory steps are following:
- Establishing a research territory by introducing and reviewing items of previous research in the area.
- Establishing a niche by indicating a gap in the previous research, or by extending previous knowledge in some way.
- Occupying the niche by outlining purposes or stating the nature of the present research.
(There are some more optional steps in each move.)
There are some "skeletal" sentences to give a strong opening:
- Recently, there has been growing interest in ...
- The development of ... is a classic problem in ...
- Knowledge of ... has a great importance for ...
- Many researchers have recently turned to ...
- Numbers of recent studies have focused on ...
One of the other important language focuses is the tenses of citation:
- past: researchers' activities in a single reference
- present perfect: an inquiry or a finding
- present: current knowledge
In occupying the niche, there are two main variants:
- purposive: indicating the main purpose(s). For example: The aim of the present paper is to ...
- descriptive: describing the main feature of research. For example: This paper reports on the results obtained ...
If the author refers to the type of text, such as paper, article, or report, he should use present tense. On the other hand, is the author refers to the type of investigation, such as experiment, study, or survey, he should use past tense.
(Swales, J. M. and Feak, C. B. 2007, Academic Writing for Graduate Students, University of Michigsn Press, Ann Arbor.)
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