Biology: Plant Characteristics and Evolution

Popular Floras and Methods of Classification

• Popular floras (books to identify plants of a certain area) group plants using characteristics like flower color or growth form (trees, shrubs, herbs, etc.).
• There are two main methods of classification: phylogenetic (phyletic) classification and rank classification.

Phylogenetic Classification

• Phylogenetic classification tries to identify the evolutionary history of natural groups.
• To establish phylogenies, decisions must be made concerning which characteristics are “primitive” and which are “advanced”—that is, which taxon is the ancestor of the others.
• Apomorphies (derived features) are used to group taxa that underwent the same evolutionary history.

Rank Classification

• Rank classification is hierarchical, with each higher rank being inclusive of lower ranks.
• The ranks, from highest to lowest, are:
  • Phylum (Example: Magnoliophyta)
  • Class (Example: Liliopsida)
  • Order (Example: Liliales)
  • Family (Example: Liliaceae)
  • Genus (Example: Lilium)
  • Species (Example: Lilium parryi)

Phylogenetic Tree or Cladogram

• A cladogram or phylogenetic tree shows the evolutionary relationships between taxa.
• Taxa are grouped by their shared apomorphies.

Characteristics of Plants

• Plants are:
  • Multicellular
  • Autotrophic (photosynthetic)
  • Have chlorophylls a and b in thylakoid membranes
  • Surrounded by cell walls containing cellulose (polysaccharide)
  • Contain seeds or spores
  • Store reserve food as amylose (starch)
  • Sedentary

Evolution of Plants

• Photosynthesis evolved multiple times.
• Endosymbiosis theory explains the origin of chloroplasts in plant cells.
• Plants evolved from non-photosynthetic organisms with cell walls and spores.

Systematics

• Plant systematics is the study of the relationships (evolutionary history) among plants through time using all types of evidence (morphological, molecular, etc.).

Taxonomy

• Taxonomy is the study of classification of organisms according to their group (taxon/taxa).
• It involves description, identification, nomenclature, and classification.

Kingdom Concept

• The kingdom concept has evolved over time, with different scientists proposing different classifications.
• The five-kingdom classification (Monera, Protista, Fungi, Plantae, Animalia) is widely accepted.
• The six-kingdom classification (Archea, Bacteria, Protista, Fungi, Plantae, Animalia) is also used.

Classification of Organisms

• Domain Archea: includes prokaryotic, extremophilic, and mutualistic bacteria.
• Domain Bacteria: includes true bacteria with peptidoglycan cell walls.
• Domain Eukarya: includes protists, fungi, plants, and animals, all with eukaryotic cells.

Kingdoms

• Kingdom Protista: includes algae, slime molds, and protozoa.
• Kingdom Fungi: includes chitin-containing, heterotrophic organisms that decompose organic matter.
• Kingdom Plantae: includes photosynthetic eukaryotes with cell walls containing cellulose.
• Kingdom Animalia: includes multicellular, eukaryotic, heterotrophic organisms without cell walls.

This quiz covers the characteristics of plants, including their multicellular and autotrophic nature, and their phylogenetic relationships. It also explores the evolution of plants through endosymbiosis theory.