Classification Biodiversity and Conservation#

Domains#

Bacteria和Archaea之间有些相似的地方：

• 没有细胞核
• 有circular DNA和plasmid（大多数）
• 没有membrane-bounmd organelles
• 70S ribosomes
• binary fission
• 通常是unicellular
• 有细胞壁

但也有些区别：

• Bacteria

  • peptidoglycan cell wall
  • no histones but histone-like proteins

• Archaea

  • histone

  • 不同的membrane lipid

  • ribosome更像是真核细胞中的

  • 有些是extremophiles [extrem-o-phile s] 极端生物

    live in extreme environments, such as hot spring, around deep volcanic vents in the ocean

Protoctist#

如果说archaea是介于bacteria和eukaryote之间，那么protoctist就介于动物和植物之间：

• Algae - an example of plant-like cell

  • have cellulose cell wall, vacuole and chloroplast 植物细胞的特征
  • multicellular 不同于单细胞的细菌
  • autotrophic 自给的
  • motile 可以移动

• Protozoa - an example of animal-like cell

  • no cell wall, no chloroplast, and no vacuole
  • unicellular
  • heterotrophic
  • motile

Fungi#

• chitin cell wall

• no cilia, no chlorophyll, and no photosynthesis

• heterotrophic

• reproduce by spores

• can be unicellular, or multicellular and made of thread-like hyphae

  all the hyphae that grow from a single spore, form the mycelium

Large fungi such as mushrooms produce “fruiting bodies” to release spores

Virus#

Features:

• 0.02~0.3 微米
• acellular
• contain DNA or RNA (the nucleic acid can be single-stranded or double-stranded)
• capsid made of capsomeres

They are all parasites, they cannot reproduce on their own without host cells, and only reproduce by infecting living host cells and using biochemical machinery of host cells.

Species richness#

The more species there are, and the more evenly the number of organisms among the different species is distributed, the greater the species diversity. 一个生态系统内，物种数量越多，分布数量越平均，物种多样性越高。

计算物种多样性的方法：

• random sampling using quadrates to avoid bias
• systematic smapling using transects
• mark-release-recapture method for mobile animals

不同的情况下，有不同的方法。

Species Diversity - Simpson’s index of diversity#

to calculate the biodiversity/species diversity of an area

• (n) is the total number of organisms of a particular species

• (N) is the total number of organisms of all species

The range of index (D) is from 0 to 1; the higher the index, the higher the biodiversity/species diversity.

例：计算Shore A的biodiversity

1. 根据表格，计算出Shore A的总个体数
2. 计算每一个物种的$\frac{n}{N}$
3. 在每个物种$\frac{n}{N}$的基础上平方，得$(\frac{n}{N})^2$
4. 将每个物种的$(\frac{n}{N})^2$相加，得$\sum \left(\frac{n}{N}\right)^2$
5. 计算最终的biodiversity $D$：$1 - \sum \left(\frac{n}{N}\right)^2$

For shore A, Simpson’s index of diversity $D = 1 - 0.201 = 0.799$

Correlation#

Statistical tests to determine if there is a correlation between 2 variables (2 species/a species and an abiotic factor)

• Correlation is different from causation (cause-and-effect relationship).

• A correlation coefficient相关系数 ranges from -1 to 1.

  • 0 means no correlation; -1 means the strongest negative correlation; 1 means the strongest positive correlation.

  

• Null hypothesis: there is no correlation between the two variables.

The formula for calculating Pearson’s linear correlation coefficient is:

The formula for calculating Spearman’s rank correlation coefficient is:

Difference in mean - t-test#

使用条件：

• the underlying population follows normal distribution
• data are continuous and quantitative

Hypothesis:

• $H_0$: $\mu_{x} - \mu_y = 0$
• $H_1$: $\mu_{x} - \mu_y \ne 0 \mid \mu_{x} - \mu_y \lt 0 \mid \mu_{x} - \mu_y \gt 0$

Formula:

其中：

• $\bar{X}$ and $\bar{Y}$: 对应数据的平均数

• $\mu_X - \mu_Y$: 来源于上面的null hypothesis $H_0$

• $n_X$ and $n_y$: 对应数据的样本数

• $s_x^2$ and $s_y^2$: 对应数据的方差Variance

  $s_x^2$的计算方式：

  $$S_{XX} = \sum x^2 - \frac{1}{n}(\sum x)^2$$

  $\sum x^2$ 指样本的 Variance.

  $$s_x^2 = \frac{1}{n-1} S_{XX}$$

最后将算出的东西套进$T$的公式里即可算出test-statistic

把test-statistic拿去查表（查得critical value）

degree of freedom $v = (n_1 - 1) + (n_2 - 1) = n_1 + n_2 - 2$

• if test-statistic > critical value: reject $H_0$

Preconditions of carrying out the statistical tests#

• $\chi^2$ test - quantitative, nominal/categoric data 名义/分类数据
• Pearson’s linear correlation
  • continuous, quantitative data
  • data are normally distributed
  • scatter graph shows there is a linear correlation/relationship
• Spearman’s rank correlation
  • not continuous quantitative data
  • data may not show a normal distribution
  • scatter graph shows there is a relationship
• $t$-test
  • continuous, quantitative data
  • data are normally distributed\
  • standard deviations of the two sets of data are very similar

Role of IUCN and CITES in conservation#

International Union for Conservation of Nature (IUCN) 世界自然保护联盟

• Assess the conservation status of animal and plant species around the world.
• IUCN Red List of Threatened Species

Convention 公约 on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

• A global agreement that has been signed by over 150 countries to control the trade of endangered species and their associated products.

CITES Appendices I, II and III (to categorize endangered and vulnerable species)

NOTE

9700/41/M/J/14 With reference to any named species of plant or animal, explain why this species is considered to be endangered and outline the reasons that have caused it to become endangered. [8]

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Mark Scheme:

• fall in numbers ;
• danger of becoming extinct ;
• ref. (IUCN/International Union for Conservation of Nature)/red list ;

one mark for idea, additional mark if qualified with point specific to named example.

e.g.

Idea	注
habitat destruction	栖息地破坏（如砍伐、填埋、开发，导致物种失去生存空间）
climate change	气候变化（温升、极端天气、海平面上升，影响物种繁殖与分布）
increase in disease	疾病增加（环境压力或病原体扩散，导致种群死亡率上升）
increase in predators / grazers	捕食者/食草动物增加（天敌或竞争性食草者数量上升，威胁目标物种）
decrease in food	食物减少（资源匮乏，导致营养不足、繁殖率下降）
named pollutant and habitat affected	特定污染物及其影响生境（如农药污染水体、重金属毒害土壤，直接损害物种健康）
hunting / killing / poaching / removal (plant)	猎杀/偷猎/盗采（植物）（人为非法捕杀动物或采挖植物，直接减少个体数量）
increased competition	竞争加剧（外来种或同域物种争夺资源，挤压本土物种生存空间）
lack of human education	缺乏公众教育（当地居民不了解保护意义，继续破坏或消费濒危物种）
disturbance to breeding sites	繁殖地干扰（人为活动如旅游、施工、噪音，破坏交配、筑巢或育幼场所）

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Exemplar answer:

Red Panda is an endangered species because it is in danger of becoming extinct. It falls in numbers. It is in the IUCN red list of threatened species. The reasons are as follows:

1. Climate change, e.g. global warming and rise in temperature
2. Hunting by humans for sport or food or trade in animal parts
3. Degradation and loss of habitats due to deforestation, pollution, etc.
4. Increased competition for resources, such as food and water, between species and between individuals of the same species
5. Introduction of invasive alien species