Biology Monerans and Protists Overview

Monerans

• Unicellular organisms
• Contain 70S ribosomes
• Naked DNA, not enclosed by a nuclear membrane
• Lack organelles such as mitochondria, lysosomes, plastids, Golgi bodies, endoplasmic reticulum, centrosome
• Reproduce asexually through binary fission or budding
• Rigid cell wall composed of peptidoglycan
• Flagellum used for locomotion
• Exhibit various modes of nutrition: autotrophic, parasitic, heterotrophic, saprophytic
• Examples: Archaea and Bacteria

Protists

• Simple eukaryotic organisms that are not plants, animals, or fungi
• Mostly unicellular, but can form colonies
• Typically found in water, damp environments, or as parasites
• Eukaryotic, meaning they have a membrane-enclosed nucleus
• Mostly aquatic, found in soil or moist areas
• Most species are unicellular, but some are multicellular like kelp, which can grow over 100 feet tall
• Cells have a nucleus and membrane-bound organelles
• Can be autotrophic or heterotrophic
• Exhibit symbiosis, such as the relationship between kelp and sea otters
• Can be parasitic, like Trypanosoma, which causes sleeping sickness in humans
• Locomotion can be achieved through cilia, flagella, or pseudopodia
• Reproduce asexually, sexual reproduction is rare and occurs under stress
• Examples: algae, amoebas, euglena, plasmodium, slime molds

Sub-groups of Protista

• Chrysophytes:
  • Include golden algae (desmids) and diatoms
  • Found in marine and freshwater habitats
  • Often heterotrophic, depending on other organisms for food
  • Have muscle cells that contract and relax body parts
  • Reproduction is typically sexual, but asexual reproduction occurs in lower forms
  • Zygote develops into a multicellular embryo
  • Require oxygen for aerobic respiration

Coelom

• A fluid-filled body cavity present between the alimentary canal and the body wall
• Derived from the mesoderm during embryonic development
• Lined by mesodermal epithelium cells
• Provides space for organs
• Functions as a shock absorber, providing flexibility to organs and cushioning internal organs
• Coelomic fluid acts as a hydrostatic skeleton, aiding in locomotion of soft-bodied animals and providing body shape
• Coelomocyte cells support the immune system by initiating humoral immune response and phagocytosis
• Transports gases, nutrients and waste products
• Enables the development and function of organs, such as the heart and uterus

Types of Coelom

• Acoelomate:
  • Lack a coelom
  • Blastocoel is completely occupied by mesoderm
  • Examples: Porifera, Coelenterata, Platyhelminthes
• Pseudocoelomate:
  • Lack a true coelom
  • Blastocoel is partly filled by mesodermal cells
  • Body cavity is lined by mesoderm only towards the body wall, not towards the gut
  • Examples: Aschelminthes
• Eucoelomate:
  • Possess a true coelom
  • Coelom is lined by mesoderm on both sides, towards the body wall and towards the gut
  • Blastocoel is completely replaced by a true coelom
  • Body organs are suspended in the coelom by mesenteries
  • Examples: Annelida to Chordata

Formation of Coelom

• Schizocoelom:
  • Found in protostomes
  • Coelom originates from splitting of the mesoderm
  • One part attaches to ectoderm, the other surrounds endoderm
  • Space between them develops into the coelom
  • Blastopore forms the mouth
  • Examples: Annelida, Arthropoda, Mollusca
  • In Arthropoda and Mollusca, the coelom is filled with blood and known as Haemocoel
• Enterocoelom:
  • Found in deuterostomes
  • Coelom forms from the fusion of internal outgrowths of the archenteron
  • These outgrowths pinch off and fuse to form a coelom lined by mesoderm
  • Examples: Echinodermata, Chordata

Taxonomic Hierarchy

• A system for classifying and arranging organisms into successive levels
• Hierarchy progresses from kingdom to species in decreasing order or vice versa
• Kingdom is the highest rank followed by division, class, order, family, genus, and species
• Each organism has a unique scientific name using binomial nomenclature

Binomial Nomenclature

• A standardized system for naming organisms
• Each scientific name has two parts: generic name and specific epithet
• Rules of binomial nomenclature:
  • Scientific names are typically in Latin
  • Written in italics
  • Genus name is capitalized, species name is lowercase
  • Handwritten names are underlined
• Importance:
  • Provides a unique name for each organism, ensuring global recognition and consistency
  • Avoids confusion arising from common names that can vary geographically
  • Helps understand relationships between species through their scientific names
• Drawbacks:
  • The law of priority states that if multiple names exist, the earliest name used takes precedence
  • Synonyms can arise when different names describe the same species.