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Biodiversity 2: Domains
Transcript of Biodiversity 2: Domains
This presentation reflects a very brief explanation of some of the relationships among living organisms.
The "branches of the tree" only represent general (though generally accurate, phylogenetically) relationships, not time or abundance or anything else.
Focus on the "Big Picture" questions (the "hows"), instead of the nitty-gritty details (the "whats") A Major dividing line of cellular life. Prokaryotes: "Before the center"
No nucleus or membrane-bound organelles
2 of the 3 major domains of life, 1 of the classic 5 kingdoms. Eukaryotes: "True center"
Have a nucleus & membrane-bound organelles
1 of the 3 major domains of life, 4 of the classic 5 kingdoms Bacteria live EVERYWHERE!
Bacteria are the foundation of all ecosystems on the planet.
They tolerate vast ranges of environmental conditions.
Prokaryotes have a wide diversity of nutritional modes The 3 Domains diverged very soon after life's last universal common ancestor Not sure what it looked like, but we can make some inferences:
DNA as genetic information General Characteristics:
prokaryotic, unicellular, various nutritional modes
cell walls made of peptidoglycan Anatomy of a bacterium Bacterial Genetics Bacteria can be distinguished by the shape of their cells, and the colonies they form. The bacterial cell wall is made of peptidoglycan.
There are two major ways the cell wall can be arranged. gram staining: a way to determine the type of cell wall Some bacteria have a capsule outside their cell wall gram positive cocci (purple) & gram negative bacilli (pink) This can make them more pathogenic (why?) The bacterial cell membrane is the major organelle used for bacterial metabolism.
Bacteria have evolved all major forms of metabolism Flagellum enable bacteria to move Pilli help bacteria adhere The bacterial flagellum evolved independently of eukaryotic flagella The bacterial chromosome is a single circular piece of DNA
Bacteria also have small extrachromosomal DNA segments called plasmids Binary fission: Bacterial reproduction.
The cell copies the chromosome and splits in half.
This is asexual, and can happen very fast.
1 bacterium can reproduce every 20 minutes Ribosomes make proteins.
Bacterial ribosomes are smaller than eukaryotic ribosomes.
This makes them a good target for antibiotics (why?) Horizonal transfer: exchange of genetic information between bacterial cells
increases and spreads genetic diversity.
examples of "recombination" of DNA from 2 sources Transformation: bacteria take in plasmids from the environment Conjugation: bacteria exchange DNA through a direct connection Transduction: bacteria acquire new DNA from a phage (bacterial virus) Bacterial Evolution Happens Very Fast (why?) spirochete (spiral) bacillus (rod-shaped) coccus (sphere-shaped) E.coli transformed with green flourescent protein Griffith's transformation experiment Data from the long term evolution experiment by Richard Lenski's lab, showing the evolution of E. coli's growth rate over 20,000 generations (~20 years) Bacterial Ecology: Some Useful Examples Bacteria as Pathogens:
a very small number of bacterial species can cause disease (a) Borellia burgdorferi, a spirochete that causes lyme disease, endemic to Long Island.
(b) The Deer Tick, the organism that spreads lyme disease.
(c) The characeristic "Bull's Eye" rash that is an early sign of the disease. (a) (b) (c) Bacterial infections can be treated with antibiotics... Cyanobacteria: the original photosynthetic organisms Deinococcus radiodurans:
can tolerate massive amounts of radiation. Lives in nuclear power plant containment chambers. Vibrio fischeri:
lives in marine organisms, providing bioluminescence Alexander Flemming-
discovered the antibiotic penicillin, accidentally in 1928 (Nobel prize in f1945) The Pennicillium mold produces penicillin (why?) General Characteristics:
prokaryotic, unicellular, various nutritional modes
live in extreme environments ("extremophiles") Why? A Domain of weirdos Discovered in the 1970's
Thought to be bacteria until the 1990's
Have enough unique properties/combinations of the other 2 domains to qualify as their own domain Yellowstone's hot springs (a), Acidic mining runoff (b), and your water heater (c) are examples of the extreme environments where archea live. (a) (c) (b) Sulfolobus, an acidothermophillic bacterium Methanogenic archea are able to convert complex hydrocarbons into methane. A Classic Bacterial Cell Colorized EMG of Bacteria (orange) on the head of a pin (purple) Fungi Plants Protists More on us later... How can we think about organizing the diversity of life?
What are the major features of organisms that we use to classify them at the domain level? Determine if a particular organism is eukaryotic or prokaryotic.
Identify the common structures of a prokaryotic cell and explain how each contributes to the overall functioning of the organism
Compare the major modes of prokaryotic genetic recombination.
Compare the biology and ecology of bacteria and archea. Chlamydomonas: a Protist Mammalian cells Blue: Bacteria
Red: Eukarya Bacteria play very important roles in helping plants absorb soil nutrients every day, half of the bacteria in the ocean are killed by phages Life has diverged into 3 domains