多系群
Multi tool use
恆溫動物一般指鳥類與哺乳類（圖中藍底部分），在此概念下，「恆溫動物」一詞所包含的是一個多系群。
多系群(英语:Polyphyletic group)在生物系統發生學中，是指一個分類群當中的成員，在演化樹上分別位于相隔著其他分支的分支上；也就是說，該分類群並不包含其所有成員的最近共同祖先。一般而言，生物的科學分類會盡量避免使一個正式的分類群成為多系群。
舉例而言，「恆溫動物」（溫血動物）通常指鳥類與哺乳類，但是鳥類與哺乳類的祖先皆為變溫動物（冷血動物），因此哺乳類與鳥類的恆溫性是分別發展出來，也因此「恆溫動物」是一個多系群，且並非一個系統發生學上的分類群。
參見
參考文獻
系统发生学主題
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| 相关领域 |
- 计算系统发生学
- 分子系统发生学
- 支序分類學
- 进化分类学
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| 基本概念 |
Phylogenesis
系統發生樹
- 演化網路
- 長枝吸引效應
演化支 與 Evolutionary grade
Lineage (evolution)
- Ghost population
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| 推理方法 |
- Maximum parsimony
- 最大簡約法
- Probabilistic methods
Distance matrices in phylogeny
- 近鄰結合法
- UPGMA
Least squares inference in phylogeny（見最小平方法）
- Three-taxon analysis
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| 当前的课题 |
- PhyloCode
- DNA条形码
- 分子系统发生学
- Phylogenetic comparative methods
- Phylogenetic niche conservatism
- List of phylogenetics software
- Phylogenomics
- 系統地理學
- DNA phylogeny
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| Group traits |
Primitive (phylogenetics)
- Plesiomorphy
- Symplesiomorphy
- Derived
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| 群組種類 |
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| 名稱 |
- Phylogenetic nomenclature
- Crown group
- 旁系群
- 基群
- Supertree
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 进化生物学的课题列表
 演化生物学
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演化生物学
