Download prokaryotes

Diversity of livinng
Organisms
Read pages 18-30
Department of biology
Cell Structure is Evidence
for Relatedness
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There are two main types of cells, prokaryotes and
eukaryotes.
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Prokaryotes are bacteria. (Monera)
Prokaryotes are much simpler and usually much
smaller than Eukaryotes.
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Eukaryotes are represented by the remaining four
kingdoms: Animalia, Plantae, Fungi, and Protista.
• Monera (Prokaryota) :
• Prokaryotes are simple cells.
• The DNA is loose in the cytoplasm—there is no separate
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nucleus.
The ribosomes are also in the cytoplasm.
In prokaryotes, transcription (synthesis of RNA) and
translation (synthesis of proteins) occurs simultaneously.
The cell is surrounded by a membrane, but there are no
internal membranes.
Outside the membrane is a cell wall, and sometimes an
outer capsule which can have structures projecting form
it.
Bacteria move using flagella: whip-like hairs similar to
the flagellum of a sperm cell.
http://fig.cox.miami.edu/Faculty/Dana/monera.html
http://community.webshots.com/photo/95521344/95541019zbQjjB
Bacterial Reproduction
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Bacteria reproduce by the
process of binary fission. The
circular chromosome replicates
its DNA. Then, the cell splits
into 2 halves, each containing a
single chromosome
No spindle apparatus (as exists
in eukaryotic mitosis and
meiosis).
Shape: coccus (spheres) and bacillus (rods).
Spirillum (spiral) is less common.
Aggregation of cells: single cells, pairs (diplo), chains
(strepto), clusters (staphylo).
Thus we have types such as diplococcus (pair of
spheres) and streptobacillus (chain of rods).
Exercise one
Eukaryotic cell components
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Cell wall (optional)
Plasma membrane
Cytosol containing organelles:
* Nucleus – DNA in chromosomes
* Other membrane-bound organelles
• Mitochondria
• Chloroplasts (optional)
* Ribosomes
* Membrane system
Flagella (optional)
Eukaryotic vs. prokaryotic cells
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Size
* Prokaryotes ≤ 10 µm
* Eukaryotes ≥ 10 µm
Bacteria & Archea
protists, Fungi, Plants, Animals
Complexity
* Prokaryotes – simple
* Eukaryotes – complex
Location of chromosomes
* Prokaryotes – free in cytosol
* Eukaryotes – within a nucleus
Flagellar mechanisms differ
Figures 7.4, 7.7, 7.8
Bacterium
(prokaryote)
(Actual size relative to
eukaryotes below)
Animal
(eukaryote)
Plant
(eukaryote)
• Protista – single celled with a nucleus
http://www.mcwdn.org/Animals/Paramecium.html
• Euglena sp.
* Members of the Euglenid group of the clade
Euglenozoa
* Characterized by an anterior pocket from which
one or two flagella emerge, and the storage
polysaccharide paramylon
- The eyespot functions as a light shield allowing
only certain light rays to strike the light detector
- The pellicle is constructed of protein bands
beneath the plasma membrane and provides
strength and flexibility
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Nutrition
Euglena are mixotrophic –
Perform photosynthesis in the light
Lose chlorophyll in the dark & absorb organic molecules via the
plasma membrane
Locomotion
Locomotion is either swimming (flagellar motion), gliding, or
euglenoid movement1
Euglena exhibit positive phototaxis – the light detector senses
light, the flagellum propels the Euglena toward it
Osmoregulation
Euglena are hypertonic to their freshwater environment
Water enters by osmosis and needs to be removed
The contractile vacuole fills with water and then fuses with the
gullet to release it
II. Protista
A. General Info
B. Groups
1. Protozoa (“Animal-like”)- heterotrophs
Amoeba use “pseudopodia” to move
Paramecium-uses cilia to move
Undulating membrane in groove
(ciliary)
Food vacuoles
Oral groove on surface
Macronucleus
w/ micronuclei
behind
Cilia
Contractile
vacuoles
Paramecium, a ciliated protozoan
Food
Site of cell “anus”
particles