遗传 进化与生态学 1 - The Diversity of Life

新坑来啦！遗传、进化与生态学 Genetics, Evolution, and Ecology. 这一部分的内容是传统大学的第二门生物课，即 General Biology 2。这门课理论上建议在阅读完文集的第一部分的内容之后再开始学习，但基础不足的朋友也可以尝试阅读喔~

这一部分的主要内容均来自 Prof. Angela J. Roles 的课程，因此本文集的这一部分均不会标记为原创。但由于文本来源不清晰，UP主还是一个字一个字码出来的文章，本文禁止非授权的转载，谢谢！

Lesson 1: The Diversity of Life & Classification

[1] Biodiversity Hierarchy

Genetic diversity: molecular, organismal, and population;

Species diversity: populations and communities;

Ecosystem diversity: communities, landscapes, and biomes.

Understanding the diversity and unity of life:

“Nothing in biology makes sense except in the light of evolution.”

- Theodosius Dobzhansky, 1964

    What do we mean by diversity? Why is there diversity?

“The diversity is intelligible as the outcome of adaptation of life to different environments, or, [...] to different ecological niches.”

    What do we mean by unity? Why is there unity?

“The unity is understandable as a consequence of common descent and of universal necessities imposed by common materials.”

    Together, evolution, ecology, and genetics address these questions.

[2] Classification

- Pre-historic cave paintings

Humans have recognized & valued diversity for millennia.

Early human depictions of animals (30,000 years ago)

- Aristotle’s scala naturae (~330 BCE)

Scala naturae translates as ‘ladder of nature’, aka the ‘great chain of being’.

The scala naturae classifies all beings from inanimate (non-living, lacking a soul) to animate (living, possessing a soul). Hierarchical, moving from “less perfect” to “more perfect”.

- Linnaean classification (1700s)

▸In the Systema Naturae (1758), Carolus Linnaeus (aka Carl von Linn´e) described a three kingdom system: Animals, Vegetables, and Minerals.

- Nested hierarchical system: each Kingdom contains Classes which contain Orders which contain Genera (the plural of Genus) which contain Species which contain Varieties;

- Organisms are grouped by similarity in appearance (morphology).

- Binomial nomenclature

▸Linnaeus also systematized the binomial nomenclature we use today;

▸A taxon’s scientific name is simply the genus (capitalized and italicized) followed by the species epithet (italicized but not capitalized);

▸When referring to a particular species, you must always give both genus and species names. But you can refer only to a genus, or to any rank above genus (e.g., kingdom).

- Modern classification

▸The current system of classification we use is modified from the Linnaean system and aims to reflect common ancestry. We retain the use of binomial nomenclature;

▸The current system adds the ranks of domain, phylum, and family.

What does hierarchy signify, in the modern system?

    All organisms in the same group share a common ancestor.

    Example: gorillas and humans are both in the Order Primates.

     Considering species the lowest rank, higher ranks include more different species and generally are older in terms of evolutionary age.

Thinking Question

We’ve just considered how the way people have chosen to describe diversity in the natural world has changed across time:

▸Pre-historic cave paintings (30,000 years ago)

▸Aristotle’s scala naturae (330 BCE)

▸Linnaean 2-kingdom, hierarchical classification (1700s)

▸Modern 3-domain, hierarchical classification system (since the 1990s)

Questions to think about:

▸For each era/method, how are groups defined? Why? What are the implications of belonging to one group versus another?

▸What is similar/different among these systems?

▸What may have changed over time in the implied values of each system?