BI111 FINAL EXAM COMPLETE

WLU BI111 FINAL EXAM REVIEW

Systematics

The scientific study of biological diversity and evolutionary relationships among organisms

Phylogenetics

A branch of systematics focused on determining evolutionary relationships based on shared ancestry

Species Misidentification

The mistaken grouping of multiple distinct species under a single name due to similar appearances

Reproductive Isolation

A condition in which different species cannot interbreed successfully, maintaining separate identities

Ecological Differentiation

The use of different habitats or ecological niches by closely related species, contributing to speciation

Morphological Similarity

When distinct species appear nearly identical in adult form, making visual identification unreliable

Importance of Accurate Classification

Correctly identifying species is crucial for understanding disease transmission and ecological roles

Systematics in Disease Control

Identifies disease-carrying species for targeted, effective eradication

Invasive Species

Non-native organisms that spread due to human activity and climate change

Taxonomy

The science of identifying, naming, and classifying organisms based on shared traits

Binomial Nomenclature

Two-part Latin name for species: genus + specific epithet

Genus

A taxonomic group containing species with similar characteristics; the first part of a binomial name

Specific Epithet

The second part of a species' binomial name, identifying the species within a genus

Morphological Species Concept

Defines species based on shared anatomical features

Importance of Scientific Names

Scientific Binomial names prevent confusion by uniquely identifying each species across languages and regions

Common Name Issues

Common names vary by region and language, leading to confusion and misidentification of species

Advantage of Binomial Nomenclature

Provides a universal, standardized name for each species, avoiding confusion caused by local names

Descriptive Binomials

Scientific names that reflect a species' traits, habitat, or honor a notable figure

Formal Naming Process

New species must be described and published in scientific literature and approved by international commissions

Taxonomic Hierarchy

A system that organizes species into nested, increasingly specific categories from domain to subspecies

Taxon (Taxa)

A group of organisms classified together at any level in the taxonomic hierarchy

Traits Shared by Taxa

Lower-level taxa (e.g., genus) share many traits; higher-level taxa (e.g., kingdom) share fewer traits

Systematist

A biologist who studies organism diversity and evolutionary relationships through identification, naming, and classification

Phylogenetic Tree

Diagram showing hypothesized evolutionary relationships among organisms

Phylogeny

Evolutionary history of a species or group of species.

Root (of a Tree) - Phylogeny

The most recent common ancestor of all organisms in the phylogenetic tree

Node - Phylogeny

A branching point on a tree where a common ancestor gives rise to descendant lineages

Clade

A group of organisms that includes a common ancestor and all its descendants

Sister Clades

Two clades that split from the same node; each other's closest relatives

Anagenesis

Gradual transformation of a species over time without increasing biodiversity

Cladogenesis

Splitting of one species into two, increasing biodiversity

Monophyletic Taxon

A group containing a common ancestor and all its descendants—no more, no less

Evolutionary Classification

A system that reflects phylogenetic (evolutionary) relationships

Nested Clades

Smaller clades are contained within larger, older clades in a tree structure

Modern Systematics and Evolution

Modern systematics aims to classify organisms based on shared ancestry and evolutionary branching

Temporal Structure of Trees

Trees show time from root (past) to tips (present); recent events are near the tips

Goal of Modern Systematics

To define taxa as monophyletic groups in evolutionary classifications

Phylogenetic Data Sources

Heritable traits (genetic, anatomical, behavioral) used to infer evolutionary relationships

Morphological Characters

Physical traits used to classify organisms; assumed to reflect genetic differences

Homology

Similarity due to shared ancestry; inherited from a common ancestor

Homologous Characters

Traits in different species derived from the same ancestral feature

Functional Divergence

Homologous traits may change in function or form over time

Convergent Evolution

Independent evolution of similar traits in unrelated species due to similar environments

Homoplasy

Similar traits that evolved independently, not from a common ancestor

Analogous Characters

Homoplastic traits with similar functions in different species

Identifying Homology

Homologous traits have similar anatomy and connections to surrounding structures

Fossil Evidence for Homology

Supports trait inheritance from a common ancestor through evolutionary history

Bird and Bat Wings (Homology)

Wing bones are homologous—same structural elements inherited from a tetrapod ancestor

Bird and Bat Wings (Homoplasy)

Wing surfaces and flight evolved independently; traits are homoplastic

Assessing Homology

Bones in bird and bat wings are homologous; wing surfaces are homoplastic due to different tissues

Embryonic Homology

Homologous traits often arise from the same embryonic tissues and similar developmental paths

Evolutionary Developmental Biology

Reveals shared genetic controls of development across diverse organisms

Developmental Characters

Early life stage features can indicate evolutionary relationships

Limits of Morphology

Morphological similarity doesn't always reflect genetic or behavioral differences

Behavioral Characters

Useful for distinguishing species that are morphologically similar

Molecular Characters

DNA or RNA sequence changes used to determine evolutionary relationships

PCR (Polymerase Chain Reaction)

Technique that amplifies DNA for sequencing, even from preserved or ancient samples

Genome Sequencing

Enables large-scale comparisons of genetic data across species

Molecular Data Advantage

Provides abundant characters; each nucleotide or amino acid is a data point

Distant Comparisons

Conserved genes allow comparisons between distantly related species

Close Comparisons

Detects subtle genetic differences in closely related species

Molecular Data Limitation

Few character states per position make homology harder to confirm

Homology in Molecular Data

Requires statistical tools since molecular traits lack developmental or fossil context

Molecular Phylogenetics

Uses sequence data to resolve relationships organismal traits can't

Traditional Systematics

Classifies organisms by both branching patterns and degree of phenotypic divergence

Anagenesis vs. Cladogenesis

Anagenesis is gradual change; cladogenesis is lineage splitting into new species

Paraphyletic Group

A group that includes a common ancestor and some, but not all, of its descendants. Different to poly (ancestor not included).

Example of Paraphyly: Reptilia

Reptilia excludes birds, even though birds share a common ancestor with crocodilians

Justification for Traditional Reptilia

Grouped by morphology (e.g. scaly skin), despite not forming a true clade

Traditional Classification Limitation

May not accurately reflect evolutionary history or true relationships

Cladistics

Classifies organisms strictly by evolutionary branching, not by morphological divergence

Character State

A version of a trait—either ancestral or derived

Ancestral Character State

Trait present in a common ancestor; shared with outgroup

Derived Character State

Trait that evolved in the ingroup; not present in the outgroup

Apomorphy

A derived character state

Synapomorphy

A derived trait shared by two or more species; indicates a clade

Identifying Derived Traits

Fossil record or outgroup comparison reveals which traits are derived

Outgroup Comparison

Compares ingroup to a related species outside it to identify ancestral traits

Ingroup

The group of organisms being studied in a phylogenetic analysis

Cladogram Construction

Based on grouping species by shared derived traits (synapomorphies) only

Limits of Ancestral Traits

Ancestral traits are not useful for defining a clade

Example of Mammal Clade

Defined by synapomorphies like hair and mammary glands, not by shared ancestral traits

Cladistic Tree Structure

Shows hypothesized branching sequences; every branch represents a monophyletic group

Synapomorphies in Trees

Derived traits that define clades; often listed on branches of phylogenetic trees

Molecular Synapomorphies

Shared molecular traits used to group species in cladistic analysis

Cladistic Classification

Reflects branching patterns only; each group is defined by shared derived traits

Tetrapod Clade (Cladistic View)

Divided into Amphibia (no amnion) and Amniota (with amnion), following strict branching logic

PhyloCode

A proposed naming system that replaces Linnaean ranks with clade-based names

Evaluating Phylogenetic Trees

Researchers use software to compare many possible trees and identify the best hypothesis

Tree Complexity

Larger datasets create many tree possibilities; analysis requires computational tools

False Indicators of Relatedness

Traits from convergent evolution (not synapomorphies) can mislead phylogenetic analyses

Reversals in Traits

Derived traits can be lost or reverted, complicating phylogenetic interpretation

Principle of Parsimony

The simplest explanation with the fewest evolutionary changes is preferred

Use of Parsimony in Trees

Selects the tree with the fewest total evolutionary steps as the best hypothesis

Challenge with Molecular Data

Only four DNA bases, so identical changes may occur independently at the same site

Fast-Evolving DNA Regions

Noncoding and third codon positions mutate more rapidly and accumulate neutral changes

Transition vs. Transversion

Transitions (purine↔purine or pyrimidine↔pyrimidine) are more common than transversions

Statistical Models

Account for variation in mutation rates across DNA regions and over time

Maximum Likelihood Method

Picks the tree most likely to produce the observed molecular data under a given model

Genetic Distance Method

Builds trees by comparing the proportion of base differences between species