● Why is an appropriate outgroup choice important?: outgroup sequences should be somehow related to the ingroup. Then it will be clear, where to place it. Otherwise, if we take something very-very distant, we would not know where to place it.

● What is an ultrametric tree?: it is a shape of phylogenetic trees. The distance from the root to each leaf is exactly the same.

● How do we put real times on a phylogeny?: The ultrametric trees show us only the relative time. But we can get the age of some fossils and place them on the phylogenetic tree. We can use this point as a reference for the other ages. More fossils placed on the tree → more accuracy

● What input data can be used to build phylogenies?: The molecular data (aligned sequenses) can be used to build phylogenetic trees. But also the morphological traits, that can be encoded in strings. For example the type of eyebrobs, the shape of skull bones etc.

● What can we do with phylogenies?: we can identify the new unknown DNA sequences with them. We can take the reference phylogenetic tree, and try to find the best insertion place with different algorithms. For example we can see a new covid variant, and figure out, from which old covid variant is this one derived.

● How many unrooted binary trees exist for n taxa?: The amount is exponential.