Chapter 25 and Chapter 26

Chapter 25 - Taxonomy and Systematics

Key Terms and Concepts

• Taxonomy: Science of describing, naming, and classifying living and extinct organisms and viruses.

• Systematics: Study of biological diversity and the evolutionary relationships among organisms, both extinct and modern.

Taxonomic Hierarchy

• Involves a hierarchical system with successive levels.

• Each group at any level is called a taxon (plural: taxa).

• Highest level is Domain, which includes:

  • Bacteria

  • Archaea

  • Eukarya

Historical Classification

• Originally four kingdoms: Protista, Fungi, Plantae, and Animalia.

• Taxonomists now categorize most eukaryotes into seven supergroups that each contain distinctive protist groups.

Features of Domains of Life

Characteristics Comparison

Taxonomic Levels

• Supergroup: Found between Domain and Kingdom.

• Taxonomic hierarchy:

  • Domain

  • Supergroup

  • Kingdom

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species

Classification Example: Gray Wolf (Canis lupus)

Taxonomic Breakdown

• Domain: Eukarya

• Supergroup: Opisthokonta

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Carnivora

• Family: Canidae

• Genus: Canis

• Species: lupus

Changing Nature of Taxonomy

• Taxonomy evolves with new research and data.

• Biologists compare morphological features and DNA samples to determine species relationships.

  • E.g., giraffes previously considered one species; DNA studies suggest four.

Binomial Nomenclature

• Each species has a genus and species name.

  • Genus name is capitalized, species epithet is not.

  • Both names are italicized, regulated by international rules.

Phylogenetic Trees

• Diagrams that show evolutionary relationships.

• Anagenesis: Evolution of a single species into a different species.

• Cladogenesis: Divergence of a species into two or more.

Types of Taxonomic Grouping

• Monophyletic Group: Includes an ancestral species and all its descendants.

• Paraphyletic Group: Contains a common ancestor and some but not all descendants.

• Polyphyletic Group: Consists of members from several evolutionary lines without the most recent common ancestor.

Homology and Morphological Analysis

• Homology: Similarities due to common ancestry (e.g., limb structures).

• Morphological studies often consider traits over generations to identify relationships.

Molecular Systematics

• Analyses molecular data to identify genetic homologies.

• Used for proposing phylogenetic trees based on DNA and protein sequences.

Principle of Parsimony

• The simplest hypothesis is preferred for evolutionary relationships.

• For example, if two species share a rare feature, it is assumed to arise once in a common ancestor, not independently.

Chapter 26 - History of Life on Earth and Human Evolution

Origin of Life

• Life emerged 3.5 to 4.0 billion years ago.

• Early fossils resemble modern cyanobacteria.

Fossil Record

• Fossils are preserved remains, often found in sedimentary rocks.

• Various factors affect fossilization, including anatomy, size, number, and environment.

Radiometric Dating

• Used to date fossils through unstable isotopes.

• Half-life: Time for half the quantity of a radioisotope to decay.

• Carbon-14 is useful for dating recent fossils (less than 50,000 years).

Environmental Changes and Mass Extinctions

• Major changes include temperature shifts, atmospheric composition, and geological events.

• Five significant mass extinctions occurred during various geological periods, influenced by environmental factors.

Evolution of Cells

• Prokaryotic cells originated in the Archean Eon.

• Eukaryotic cells emerged later due to a symbiotic relationship between ancient prokaryotes.

Multicellularity

• First multicellular organisms appeared around 1.5 billion years ago.

• Early animals were invertebrates, with bilateral symmetry facilitating movement.

Evolution of Primates

• Primates evolved from small arboreal mammals about 85 million years ago.

• They exhibit several defining traits, including binocular vision and grasping hands.

Hominins and Human Evolution

• Hominins diverged from apes approximately 7 million years ago.

• Significant species in human evolution include Australopithecus, Homo habilis, and Homo erectus.

• Homo sapiens evolved in Africa around 300,000 years ago and are characterized by cultural evolution.