Unit 8 - AP Biology

Evidence of Evolution

1) The fossil Record

2) Comparative Morphology

3) Biogeography

Fossils

remains or traces of past organisms

fossil record

gives a visual of evolutionary change over time

comparative morphology

analysis of the structures of living and extinct organisms

homology

characteristics in related species that have similarities even if the functions differ

embryonic homology

many species have similar embryonic development

Vestigial Structures

structures that are conserved even though they no longer have a use

• tailbone and appendix in humans

Molecular Homology

many species share similar DNA and amino acid sequences

Homologous Structures

characteristics that are similar in two species because they share a common ancestor

• Ex. arm bones of many species

Convergent Evolution

similar adaptations that have evolved in distantly related organisms due to similar environments

Analogous Structures

structures that are similar but have separate evolutionary origins

• Ex. wings in birds vs bats vs bees

• Each species have wings, but the wings did not originate from a common ancestor

Cellular Examples of Common Ancestry

1) Membrane-bound organelles

2) Linear Chromosomes

3) Introns in genes

Biogeography

the distribution of animals and plants geographically

• Ex. Species on oceanic islands resemble mainland species

• Ex. Species on the same continent are similar and distinct from species on other continents

Populations continue to evolve

• Antibiotic resistance in bacteria

• Insect resistance

• Pathogens cause emerging (new) diseases

Systematics

classifications of organisms and determining their evolutionary relationships

Taxonomy

Naming and classifying species

Phylogenetics

Hypothesis of evolutionary history

Scientists use … to determine evolutionary relationships

• Fossil records

• Dna

• Proteins

• Homologous Structures

Phylogenetic Trees

Diagrams that represent the evolutionary history of a group

Trees vs CladogramsTrees

Trees show time while cladograms dont

Cladograms

Each line represents a lineage. Each branching point is a node.

Cladogram Nodes

Common Ancestors

Root

Common Ancestor

Sister Taxa

Two clades that emerge from the same node

Basal Taxon

A lineage that is evolved from the root and remains unbranched

Synamorphy

Derived character shared by clade members

Derived Characteristics

Similarity inherited from the most recent common ancestor of an entire group

Ancestral Characteristic

similarity that arose prior to common ancestor

Monophyletic Group

includes the most recent common ancestor of the group and all of its descendants (clade)

Paraphyletic Group

includes the most recent common ancestor of the group, but not all its descendants

Polyphyletic Group

does not include the most recent common ancestor of all members of the group

Principles of Parsimony

Use the hypothesis that requires the fewest assumptions (DNA changes)

Species

A group able to interbreed and produce viable, fertile offspring

Speciation

Formation of new species

Allopatric Speciation

Physical barrier divides population or a small population is separated from main population

• Populations are geographically isolated

  • Prevents gene flow

  • Often caused by natural disasters

Sympatric Speciation

• A new species evolves while still inhabiting the same geographic region as the ancestral species

  • Usually due to the exploitation of a new niche

Prezygotic Barriers

Prevent mating or hinder fertilization

Prezygotic Barrier Types

• Habitat isolation

• Temporal isolation

• Behavioral isolation

• Mechanical isolation

• Gametic isolation