Phylogenetic Trees

Organizing Nature

Clarification

7.2 7.3 Analyze and make

sense of phylogenetic trees E.g. determine

relationships, common ancestry, which traits in each species, which tree fits data

Create phylogenetic trees based on data

Sort the Animals Into GroupsMake as many groups as you choose

Groups are entirely up to you – there’s no right or wrong answer

Be ready to share your groups and reasons for making them

Original Taxonomy – Before Evolution

Group organisms by similar physical characteristics

The Problem Nature is sneaky Sometimes things look really similar But a closer look reveals major differences

Phylogenetic Trees Organize species by evolutionary

relationships Like a family tree

Make groups based on evolutionary origins, not just appearance

How Do We Make Trees?

Finding Common Traits

Comparing DNA/Proteins

Either way – the more traits and genes analyzed, the more accurate the tree becomes.

More simple More accurate

Tree BasicsY-

axis

= t

ime (

roughly

wit

h n

o e

xact

sc

ale

)

Common ancestor of everyone

(Microevolution of that population)

Separation + Divergence

Common ancestor of species 1 and 2

Common ancestor of species 3and 4

Species 1

Species 4

Species 3

Species 2

Notice Species 2 and 3 are NOT closely related. Being

next to each other doesn’t matter

Common ancestor of everyone

Common ancestor of species 1 and 2

Common ancestor of species 3 and 4

Species 1

Species 4

Species 3

Species 2

We could draw this tree like this and it’s the same

Common ancestor of everyone

Common ancestor of species 1 and 2

Common ancestor of species 3 and 4

Species 2

Species 3

Species 4

Species 1

Or Even

Common ancestor of everyone

Common ancestor of species 3 and 4

Common ancestor of species 1 and 2

Species 4

Species 2

Species 1

Species 3

Notes** Tree can go

horizontal as well – same basic idea

Shape of branches may differ (tree vs. cladogram)

Trees often do not show every single descendant – because then they get crazy!!!

PracticeWhat species is most closely related to the Corsac fox?A. Kit fox B. Red foxC. Rupelle’s fox D. B and C equally

Which species is most distantly related to the Bat-eared fox?A. Raccoon Dog B. Fennec foxC. Short-eared Dog D. Artic fox

Trees can also show when traits evolved

Common ancestor of everyone

-Trait A originates

-Trait B originates

Should be found in all 4 species

Should be found in species 3 and 4 only

Species 1

Species 4

Species 3

Species 2

-Trait C originatesShould be found in species 4 only

ExampleWhich species should have vascular tissue and seeds but no flowers?

Which species is most closely related to the pine tree?

Draw another way this tree could look

Photosynthetic Ancestor

Vascular Tissue

Moss

Seeds

Ferns

Flowers

Pine Tree Rose Bush

Pine Trees

Rose Bush

Goal of Modern Phylogeny

Group organisms who are closely related

I.e. are on the same branch

Animals (Kingdom)

Deuterostomes (Superphylum)

Chordata (Phylum)

Vertebrates (Subphylum)

Tetrapods (Superclass)

Mammals (Class)

Marsupials (subclass)

Reptiles

Why Should Birds Be Considered Reptiles?

Rapid Review

Trees show common ancestry

Based on similarities in DNA and anatomy

More recent common ancestor = closer relative

Make groups based on shared common ancestry

7.2.II Reproductive Barriers

Pre-Zygotic

No successful union of sperm and egg

Post-Zygotic

Zygote forms, but the resulting offspring is not fertile and viable

Reproductive Barrier Vine

Short, to-the-point, memorable video Don’t have to use Vine app Maximum of 20 seconds Prepare a 1-2 minute presentation

Explain Vine and how reproductive barrier evolved DUE next class period