WEEK 11 Phylogenetics & Speciation

Macroevolution

Big changes in life over a long time that can create new species

Species

A group of living things that can mate and have babies that can also have babies

Speciation

The process where one species splits into two or more new species

Subspecies / Ecotype

A smaller group within a species that looks or lives slightly differently but can still mate with others of the same species

Reproductive Isolation

When two groups can’t make babies together anymore

Morphological Species Concept

Defines a species by how it looks or its body features

Biological Species Concept

Defines a species as a group that can interbreed and produce fertile offspring, but cannot do so with other such groups.

Evolutionary Lineage Concept

A species is a group that shares a common ancestor and keeps changing over time

Ecological Species Concept

Defines a species by how it fits into its environment (its “job” or niche)

General Lineage Concept

A species is a group that keeps moving through time as one connected family line

Prezygotic Isolation

Barriers that stop mating or fertilization from happening (example: different mating calls or mating times)

Postzygotic Isolation

Barriers that happen after fertilization

Allopatry / Allopatric Speciation

New species form when groups are separated by a physical barrier like a mountain or river

Sympatry / Sympatric Speciation

New species form even though they live in the same area

Polyploidy

Having extra sets of chromosomes

Alloploidy

When two different species mix their DNA and make a new species with combined chromosomes

Taxonomy

The science of naming and classifying living things

Systematics

The study of how living things are related through evolution

Cladistics

A way to group organisms based on shared traits from common ancestors

Taxon / Taxa

A group used in classification

Phylogeny / Phylogenetic Tree

A “family tree” that shows how species are related

Anagenesis

When one species slowly changes into another without splitting

Cladogenesis

When one species splits into two or more new ones (branching evolution)

Common Ancestor

An older species that two or more species came from

Outgroup

A species used for comparison that is outside the main group being studied

Node

A point on a phylogenetic tree where one species splits into two

Clade

A group of species that includes one ancestor and all its descendants

Monophyletic Group

Includes one ancestor and all of its descendants

Paraphyletic Group

Includes one ancestor and some but not all of its descendants

Polyphyletic Group

A group made up of species with different ancestors

Homology / Homologous Trait

A feature shared by species because they got it from a common ancestor

Character

A trait or feature used to study relationships like wings or fur

Shared Ancestral Character (Symplesiomorphy)

A trait that came from a distant ancestor and is shared by many groups

Shared Derived Character (Synapomorphy)

A new trait that evolved in a recent ancestor and is shared by its descendants

Ingroup vs. Outgroup

The ingroup is the main set of species being studied while the outgroup is used for comparison

Parsimony

The simplest explanation with the fewest changes is usually the best one