2 - Macrotaxonomy: The tree of life - looking at the patterns

Tree of Life

Foundational concept in evolutionary biology, symbolizing the interconnectedness and shared ancestry of all living organisms.

Tree of Life

It serves as a metaphor and conceptual model to explore the evolution of life and describe the relationships between organisms, both living and extinct

Divergent Evolution

A group splits into new species over time, becoming increasingly dissimilar

Convergent Evolution

occurs when unrelated species evolve similar characteristics or adaptations because they occupy similar ecological niches or face similar environmental challenges

Homologous traits

arise through divergent evolution, where a common ancestral trait evolves differently in descendant lineages, often leading to new functions

Analogous characteristics

have developed independently in different species to perform similar functions, despite not sharing a common evolutionary origin

Cladogram

a tree structure that represents the (evolutionary) relationships within a group of organisms.

hypothesis
dendrogram

Cladogram emphasizes that the diagram represents a ________ about the actual evolutionary history of a group, lengths: arbitrary. "_________"

clade

a group of organisms that includes an ancestor and all of its descendants. It consists of a single common ancestor and all its offspring

Descendants
Ancestor

shared history of B and C

clade

determine whether a clade or not

clade

determine whether a clade or not

not a clade

determine whether a clade or not

not a clade

determine whether a clade or not

Phylogenetic pitchforks

depict historical moments when a gene pool was irrevocably split in two

lack of knowledge

Reading trees: Phylogenetic pitchforks

instances where single common ancestor would have several descendants (happens when lack of plannage)

Rapid

Reading trees: Phylogenetic pitchforks

-fast process of evolution (lack of knowledge, undocumented = pitchfork)
-cichlids fishes

evolution

-is not progressive
- doesn’t NOT ALWAYS CREATE “better traits”
-dependent on the selection of environmental pressures

ladder

reading trees, not ________

phylogenetic classification

using trees for classification example

Important Assumptions in Trees

• Change in characteristics occurs in lineages over time

• There is a bifurcating, or branching, pattern of lineage-splitting

• Any group of organisms is related by descent from a common ancestor

Change in characteristics occurs in lineages over time

Important Assumptions in Trees

There is a bifurcating, or branching, pattern of lineage-splitting

Important Assumptions in Trees

Any group of organisms is related by descent from a common ancestor

Important Assumptions in Trees

Monophyletic clades

complete sub-trees

Monophyletic clades

• Contains all descendants of a common ancestor

• Recognized through synapomorphies

• Synapomorphies are homologous traits that are present in two or more taxa (groups of organisms) but not in their common ancestor's closest relatives

synapomorphies

Monophyletic clades are recognized through _________

Synapomorphies

are homologous traits that are present in two or more taxa (groups of organisms) but not in their common ancestor's closest relatives

Paraphyletic clades

Pruned branches

paraphyletic group

contains a common ancestor and some, but not all, of its descendants

shared ancestral character state

a trait that evolved in a common ancestor and is shared by multiple descendants, but not unique to a specific group

Paraphyletic clade

type of clade

Polyphyletic group

collection of organisms that are grouped together based on shared characteristics, but these characteristics are not inherited from a common ancestor

Similarities in polyphyletic groups arise through _____________, , where organisms adapt to similar environments or lifestyles independently

Parsimony principle

tells us to choose the simplest scientific explanation that fits the evidence. In terms of tree building, the best hypothesis is the one that requires the fewest evolutionary changes

Homologous characters

Since a phylogenetic tree is a hypothesis about evolutionary relationships, we want to use characters that are reliable indicators of common ancestry to build that tree

Homologous characters

what trait is the red labeled

Analogies
Homologies

forelimbs evolved into wings are what trait?
How about four limbs evolved only?

using trees

to make predictions about fossils

fossils
poorly- studied
evolution
diversity

Using trees (importance):
- to make predictions about ______
- to make predictions about ____________ species: A new drug
- to learn about order of ______
- to learn about the evolution of _______: The beetles' diet