Biosystematics2-支序系统学的原理和方法.ppt

Similar structures evolving in separate lineages as adaptations to the same environmental pressures Convergent structures did not evolve from a common ancestor Comparison Between Homology and Analogy 4. 类群趋势(group trend): 生物在不同的类群往往表现出一定的演化趋势，比如昆虫和蜉蝣身体往往呈现出由大到小、翅由多到少、结构由分离到愈合的演化极向。 6. 生物地理学上分布递进标准：生物的扩散往往是由近到远，因此离大陆较远的岛屿上的生物所具有的特征一般要比离大陆近的生物具有的特征来得晚。 Reading phylogenetic trees A phylogeny, or evolutionary tree, represents the evolutionary relationships among a set of organisms or groups of organisms, that are believed to have a common ancestor. （2）不同表示树图 For any speciation event on a phylogeny, the choice of which lineage goes to the right and which one goes to the left is arbitrary. These three phylogenies are therefore equivalent. Trees can be represented by a shorthand notation that uses nested parentheses. Each internal node is represented by a pair of parentheses that enclose all descendants of that node. clades A clade（支系） is a group of organisms that are all descendent from a common ancestor; thus a clade includes an ancestor and all its descendents You can think of a clade as a branch on the tree of life. Some examples of clades and non-clades in a phylogenetic tree are shown here clade A clade is made up of an ancestral species and its descendents. . Monophyletic group (单系群）Includes common ancestor and all descendents. Also called a clade. Paraphyletic group（并系群）: Includes common ancestor but not all descendents Polyphyletic group(多系群)： Includes descendents but missing common ancestor Monophyletic group Includes common ancestor and all descendents 名词解释： Taxon、Character、Homology、Homoplasy、Reversal、Convergence、Symplesiomorphy、Synapomorphy、 Autapomorphy、Outgroup、sister group、node、Monophyletic group、Paraphyletic group、Polyphyletic group 问答： 最大简约法则 根据性状推测物种之间的关系 Paraphyletic Class Reptilia 错误的分类：并系的爬行纲 人类的归属？ 课后习题 对于系统发育关系树图的理解练习题 X Y 长颈鹿 河马 海豹 最大简约性法则（maximal parsimony) 奥卡姆剃刀原理 (Ockhams Razor): “如无必要，勿增实体” （Entities sho