Classifying living things
Introduced| English | Meaning |
|---|---|
| classify/ˈklæsɪfaɪ/ | To place organisms into groups according to shared features. |
| species/ˈspiːsiːz/ | A group of organisms whose members can usually interbreed to produce fertile offspring. |
| fertile/ˈfɜːtaɪl/ | fertile |
| binomial system/baɪˈnəʊmɪəl ˈsɪstəm/ | The naming system giving every species a genus name and a species name. |
| genus/ˈdʒenəs/ | A taxonomic group containing one or more closely related species. |
| kingdom/ˈkɪŋdəm/ | A broad taxonomic rank below domain and above phylum. |
| dichotomous key/daɪˈkɒtəməs kiː/ | dichotomous key |
Bringing order to millions
- Scientists have named over a million kinds of living thing — and there are millions more.
- To make sense of them, we classify 分类: sort them into groups by shared features.
Classification rank lab
Place examples at the right level in the biological hierarchy.
A species is a group of organisms that can:
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Members of a species breed to give fertile offspring.
Members of the same species breed to produce ______ offspring.
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Fertile offspring can themselves reproduce.
Species 物种 and naming
- A species is a group of organisms that can breed together to make fertile 可育的 offspring.
- Each species has a two-word Latin name (the binomial system 双名法): genus 属 then species, e.g. Homo sapiens.
Living organisms are sorted into five kingdoms 界 by their main features
In the binomial system, the first word of the name is the:
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The binomial is genus then species, e.g. Homo sapiens.
Put these classification groups in order from largest to smallest.
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Kingdom → phylum → class → order → family → genus → species.
The classification hierarchy
- Organisms are sorted into ever-smaller groups: kingdom → phylum → class → order → family → genus → species.
- The more features two organisms share, the more groups they share — and the more closely related they are.
A fungus: the fly agaric, a mushroom
A dichotomous key identifies an organism using:
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Each step offers two choices, narrowing down the organism.
Using a dichotomous key 二歧检索表
- A dichotomous key identifies an organism through a series of paired (either/or) questions.
- Each answer leads to the next question, until the organism is named.
Worked example. The binomial name Panthera leo (lion) shares its genus (Panthera) with Panthera tigris (tiger) — telling you at a glance that lions and tigers are closely related.
You've got it
- a species can breed to make fertile offspring; named by the binomial system (genus + species)
- classification hierarchy: kingdom → phylum → class → order → family → genus → species
- a dichotomous key identifies organisms through paired questions
Write from a binomial name
- An organism is named Panthera leo.
- A key offers two descriptions at each step.
What does the two-word name tell you, and what is the key for?
The first word is the genus and the second is the species.
In Panthera leo, which word is the species?
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The species is the second word.