Upload
antonia-andrews
View
216
Download
0
Embed Size (px)
Citation preview
Protist Kingdom - Ch. 15 p. 311-316
• Droplets of pond water are filled with Protists!
• Protists are the first eukaryotes to evolve from prokaryote (bacteria) ancestors. They are much more complex than prokaryotes.
• Protists are the ancestors to all other eukaryotes – plants, fungi, and animals.
• The fossil record indicates that eukaryotes evolved from prokaryotes (bacteria) more than 1.7 billion years ago.
• How did eukaryotic cells evolve, and
how did their membrane-enclosed organelles evolve?
• A widely accepted theory is that eukaryotic cells evolved through a combination of two processes:
#1: All organelles (except mitochondria and chloroplasts) evolved from inward folds of the plasma membrane of a prokaryotic cell.
# 2: Endosymbiosis • The Endosymbiosis Theory was largely developed by Lynn Margulis of the University of Massachusetts:
“Chloroplasts and mitochondria evolved from small prokaryotes that established residence within other, larger host prokaryotes.”
• Ex : mitochondria ancestors may have been aerobic bacteria that were able to use oxygen to release large amounts of energy from organic molecules by cellular respiration.
• The host cell may have injested these for food; if they remained alive, they continued to perform respiration within the cell.
• Ex: Similarly, chloroplasts may have come to live inside a larger host cell.
• Because almost all eukaryotes have mitochondria but only some have chloroplasts, it is likely that mitochondria evolved first.
• Endosymbiosis eventually became mutually beneficial. How? ____________________
The Diversity of Protists
- Vary in structure and function more than any other group or organism.
• Most are unicellular, but some are colonial or multicellular.
• Each cell must carry out all the basic functions of an entire organism.
• Four major categories of protists: (are grouped more by their lifestyle than by their evolutionary relationships)
• 1. Protozoans
• 2. Slime molds
• 3. Unicellular Algae
• 4. Seaweeds
1. Protozoans• Ingest food and thrive in all types of aquatic
environments, including wet soil and the watery environment inside animals.
• Include:
• 1) Flagellates: move by means of one or more flagella. Most free-living, but some are parasitic: cause diarrhea (infected drinking water) or sleeping sickness from the tsetse fly.
• 2) Amoebas: move by means of pseudopodia
• 3) Forams: move with pseudopodia; flexible
• 4) Apicomplexans: are all parasitic and are named for an apparatus at their apex which is specialized for penetrating host cells. Plasmodium -malaria.
• 5) Ciliates: use cilia to move and feed.
Amoeba
Forams
ApicomplexanCiliate: Paramecium Flagellates