kingdom protista - mr. volkmann's virtual classroom
Post on 03-Feb-2022
3 Views
Preview:
TRANSCRIPT
Kingdom Protista
• simplest eukaryotes but an incredibly diverse group
• defined by exclusion :
- not bacteria (they are prokaryotic)
- not plants or animals (they develop embryos)
- not fungi (they develop from spores)
• they represent an important step in early evolution, evolving from prokaryotes and eventually giving rise to the entire line of eukaryotes
[The common point for all eukaryotic branches]
• the first protists probably evolved between 1.5 and 1.7 billion years ago, 2.3 billion years after the origin of life, from simple communities of prokaryotic cells
• most unicellular
• some colonial
• some simple multicellular (protoctista)
[anybody know any multicellular protists?]
• some are autotrophic photosynthesizers (algae), rest eat bacterial or other protistan cells, or small suspended or dissolved organic particles
• thrive in aquatic habitats
• movement provided by one or more flagella and/or cilia
• nuclei contain multiple DNA strands
• can reproduce mitotically, some can do meiosis
• cellular respiration is primarily aerobic, some are strict or facultative anaerobes
• nearly every animal, plant, and fungus – perhaps every species – has protist associate
• no one knows how many species of protists there really are; thousands have been described
• distinguishing species of free-living protists often requires
time-consuming genetic and ultra-structural studies and funding is limited because they are of no direct economic importance
• remarkable variation in cell organization, patterns of cell division, and life cycle
• far more diverse in life style and nutrition than are animals, fungi, or plants, they are far less diverse metabolically than the bacteria
• suggested that the major protist phyla are so distinct as to
deserve kingdom status
top related