Jessica Green is co-founder of phylogeny that is building a microbial map of the world.

杰西卡·格林是名为" 系统发育" 组织的联合创始人，该组织正在绘制张微生物世界地图。

Here is a phylogeny of the land plants that are alive today.

这是现存陆地植物的系统发育图。

So, as zoologists using maximum parsimony, we'd choose the phylogeny that shows feathers evolving once.

所以，当动物学家使用最大简约法时，选择羽毛只进的进树。

Phylogenies are complicated because they're tracking many different traits, animals, and time all at once.

建立进树很复杂，因为它同时追踪许不同的特征、动物和时间。

But by making phylogenies and examining DNA, we do know they're the closest non-animal relative we've got.

但是通过系统发育和 DNA 检测，少知道它是最亲近的非动物亲戚了。

Using the maximum likelihood approach, we'd end up with a phylogeny where the sequence of events has the highest probability.

使用最大似然方法，可以得出序列事件在进树有最高的可能性。

There are many organisms out there whose phylogeny is a total mystery to us.

那里有许生物，它的系统发育对来说完全是个谜。

In a phylogeny, individual species or groups of species sit at the tips of the tree.

在进树中，单个物种或组物种群位于树的顶端。

So zoologists will often make several phylogenies using different approaches.

所以，动物学家通常会使用不同的方法来建立进树。

So, let's go to the phylogeny.

因此，接下来让看看进树。

Keeping track of who's related to who can get messy, so we study animal relationships using a diagram called a phylogeny or a phylogenetic tree.

记录谁与谁是有关系的会变得很混乱，因此利用个图示来研究物的关系，那就是系统发生树，或进树。

To actually build our clades, the simplest approach is to go for maximum parsimony, where the phylogeny with the fewest number of gains or losses of a trait wins.

要真正构建的进枝，最简单的方法是使用最大简约法，根据个性状的得或失，用最少的数字，来构建进树。

If we keep getting the same answer, we know our phylogeny is a good guess for how different animals are related to each other.

如果直得到相同的答案，知道这的进树对于不同的动物是如何相互联系的猜测是合理的。

And they can rotate around their nodes, so this phylogeny, this phylogeny, and even this phylogeny are exactly the same.

它还会变换节点，因此，这个进树，和这个进树都是同个进树。

And, in this tree, time moves from the root of the tree to the tips of the branches, meaning that branches towards the bottom of the phylogeny diverged before the branches at the top.

在这棵树上，时间从树根向树枝顶端移动，这意味着系统发育底部的树枝比顶部的树枝先分。

There's no best way to make a phylogeny, and one phylogeny is really just a hypothesis for all the evolutionary relationships between species or clades based on specific traits or groups of traits.

没有最好的方法来建立进树，棵进树也只是个假设而已，根据具体的性状或广泛的性状来对所有种群和进枝之间的进关系做假设。

So using observations and the molecular clock approach, we can decide which traits will help us group animals into clades, or a group with all the descendants of the same common ancestor, and fit those clades together into a phylogeny.

因此，通过观察和分子钟方法，可以决定哪些特征可以帮助归类动物到进枝，或者把所有同共同祖先的后代归为类，这些进枝就这样集合在起形成进树了。