Plant Diversity and Morphology Introduction

Introduction to Diversity Studies

• The course PEBO 102 focuses on the study of diversity in plant forms (mosses, ferns, cone-bearing plants, flowering plants, fungi, and algae).
• Diversity in plant life can be understood from various aspects: classification, habitat, habit or life form, size, life cycle, nutrition, and economic importance.

Classification of Living Things

• Taxonomy is the scientific discipline that deals with the classification of living things.
• There are at least 5 million different kinds of organisms in the biosphere, necessitating the classification of living things into groups with similar characteristics.
• Carolus Linnaeus introduced a simpler system of classification in the 18th century, using a binomial system consisting of two words: the generic name and the specific epithet.
• The scientific name of every species is a binomial, with the generic name always preceding the specific epithet.

Major Groups of Living Things

• A classification that depicts genetic relationships is said to be a natural or phylogenetic classification.
• Plants are classified into divisions based on differences in photosynthetic pigments, manner of leaf development, structure of the conducting or vascular tissues, and modes of reproduction.
• The most fundamental distinction in living organisms is that between prokaryotes and eukaryotes.

Prokaryotes

• Prokaryotes do not have true nuclei, lack membrane-bound cellular organelles, and have a single circular molecule of DNA.
• Genetic material is not associated with proteins, and reproduction is predominantly by cell division.
• Prokaryotes are mainly absorptive, photosynthetic, or chemosynthetic, and exhibit solitary unicellular or colonial unicellular organization.
• The cell walls of most prokaryotes contain muramic acid, distinguishing them from other organisms.
• Prokaryotes are recognized as a separate kingdom, the Kingdom Monera, which comprises all bacteria, including cyanobacteria (blue-green algae).

Eukaryotes

• Eukaryotes have a definite nucleus bounded by a double membrane, complex chromosomes, and DNA associated with proteins.
• Eukaryotes possess complex cellular organelles, such as mitochondria, and vacuoles bounded by a single membrane or tonoplast.
• Many eukaryotes exhibit integrated multicellularity and sexual reproduction, which are absent in prokaryotes.
• Plant eukaryotes have protoplasts connected by plasmodesmata, whereas in animals, protoplasts are in more direct contact due to the absence of cell walls.

Unicellular and Multicellular Organisms

• Plants are generally multicellular, photosynthetic organisms found in water and on land.
• However, few plants are single-celled or unicellular.
• The concept of uni- and multicellularity is important in understanding the diversity of plant life.

Introduction to Plant Diversity

• Plant diversity can be understood through various aspects:
  • Classification (Representatives)
  • Habitat
  • Habit or Life form/Morphology
  • Size
  • Life-Cycle or Life-Span
  • Nutrition
  • Economic Importance or Usefulness

Classification of Living Things

• Taxonomy is the scientific discipline that deals with the classification of living things
• There are at least 5 million different kinds of organisms in the biosphere, necessitating classification into groups with similar characteristics
• The practice of referring to organisms by Latin names began in the Middle Ages (between the 5th and 15th centuries)
• Initially, organisms were grouped into genera (singular: genus) and were then identified by descriptive Latin phrase names, known as polynomials

Binomial System of Classification

• The binomial system of classification was introduced by Carolus Linnaeus in the 18th century
• The scientific name of every species consists of two words: the generic name and the specific epithet
• The generic name is always capitalized, and the specific epithet is not
• The specific epithet is descriptive and is usually written in lowercase letters
• The scientific name is always printed in italics or underlined when written or typed

Major Groups of Living Things

• A classification that depicts genetic relationships is said to be a natural or phylogenetic classification
• Plants are classified into divisions based on features such as photosynthetic pigments, leaf development, vascular tissues, and modes of reproduction
• Early taxonomists classified living things as either plant or animal, but this classification was later revised to include fungi and bacteria

Prokaryotes and Eukaryotes

• Prokaryotes do not have true nuclei, lack membrane-bound cellular organelles, and have a single circular molecule of DNA
• Prokaryotes reproduce predominantly by cell division, and their mode of nutrition is mainly by absorption
• Prokaryotes are recognized as a separate kingdom – the Kingdom Monera, which comprises all bacteria, including cyanobacteria
• Eukaryotes have a definite nucleus bounded by a double membrane, complex chromosomes, and complex cellular organelles such as mitochondria
• Eukaryotes also exhibit integrated multicellularity and sexual reproduction, which are absent in prokaryotes

Concept of Uni- and Multicellularity

• Unicellular organisms are single-celled, while multicellular organisms are composed of multiple cells
• Plants are generally multicellular photosynthetic organisms, but few are single-celled or unicellular
• In plant eukaryotes, the protoplasts of contiguous cells are connected by plasmodesmata, allowing for integration and communication between cells