Concept 1: Structural and functional adaptations contribute to prokaryotic
success
Prokaryotic populations have diversified through natural selection.
Prokaryotic cells are typically unicellular and smaller than eukaryotic cells (0.5-5
μm).
Prokaryotic cells exhibit various shapes, including rod-shaped, spherical, and spiral.
Cell-Surface Structures
Prokaryotic cells have a cell wall that maintains shape, protects against bursting in
a hypotonic environment, and differs in structure from eukaryotic cell walls.
Prokaryotic cell walls contain peptidoglycan (modified suger polymer), while
eukaryotic cell walls are made of cellulose or chitin.
The Gram stain technique categorizes bacterial species based on cell wall
composition, with Gram-positive bacteria having a thick layer of peptidoglycan so
it will appear dark, and Gram-negative bacteria having less peptidoglycan and an
outer membrane with lipopolysaccharides so it will appear light.
Capsules and slime layers protect prokaryotes from dehydration and shield them
from the host's immune system.
Fimbriae are hairlike appendages that allow prokaryotes to adhere to surfaces or
other individuals.
Motility
Prokaryotes exhibit taxis, a directed movement toward or away from a stimulus.
Chemotaxis is a type of taxis where prokaryotes change their movement pattern in
response to chemicals.
, The most common structure that enables prokaryotes to move is flagella.
Prokaryotic flagella differ from eukaryotic flagella in size, composition, and
mechanism of propulsion.
Bacterial and archaeal flagella are similar in size and rotational mechanism but
composed of different proteins. The flagella of bacteria, archaea, and eukaryotes
arose independently and are analogous structures.
Bacterial flagella originated as simpler structures and evolved through modification
in a stepwise fashion. Only half of the flagellum's protein components are necessary
for its function.
The bacterial flagellum evolved through exaptation, where structures originally
adapted for one function take on new functions through descent with modification.
Internal Organization and DNA
Prokaryotic cells are simpler than eukaryotic cells in terms of internal structure and
DNA arrangement.
Prokaryotic cells lack membrane-enclosed organelles but may have specialized
membranes and protein-based compartments.
Prokaryotic genomes have less DNA and typically consist of one circular
chromosome, while eukaryotes have multiple linear chromosomes.
Prokaryotes lack a nucleus, and their chromosome is located in the nucleoid.
Prokaryotic cells may also have smaller rings of independently replicating DNA
called plasmids.
Prokaryotic ribosomes are smaller and differ in protein and RNA content compared
to eukaryotic ribosomes.
Certain antibiotics can bind to prokaryotic ribosomes and inhibit protein synthesis
without affecting eukaryotic ribosomes.
Reproduction
Prokaryotes reproduce quickly through binary fission, dividing into two, four,
eight, and so on.
Rapid population growth in prokaryotes is due to their small size, binary fission
reproduction, and short generation times.
Concept 2: Rapid reproduction, mutation, and genetic recombination
promote genetic diversity in prokaryotes
Genetic variation is crucial for evolution.
Prokaryotes show diverse adaptations, indicating high genetic diversity.
success
Prokaryotic populations have diversified through natural selection.
Prokaryotic cells are typically unicellular and smaller than eukaryotic cells (0.5-5
μm).
Prokaryotic cells exhibit various shapes, including rod-shaped, spherical, and spiral.
Cell-Surface Structures
Prokaryotic cells have a cell wall that maintains shape, protects against bursting in
a hypotonic environment, and differs in structure from eukaryotic cell walls.
Prokaryotic cell walls contain peptidoglycan (modified suger polymer), while
eukaryotic cell walls are made of cellulose or chitin.
The Gram stain technique categorizes bacterial species based on cell wall
composition, with Gram-positive bacteria having a thick layer of peptidoglycan so
it will appear dark, and Gram-negative bacteria having less peptidoglycan and an
outer membrane with lipopolysaccharides so it will appear light.
Capsules and slime layers protect prokaryotes from dehydration and shield them
from the host's immune system.
Fimbriae are hairlike appendages that allow prokaryotes to adhere to surfaces or
other individuals.
Motility
Prokaryotes exhibit taxis, a directed movement toward or away from a stimulus.
Chemotaxis is a type of taxis where prokaryotes change their movement pattern in
response to chemicals.
, The most common structure that enables prokaryotes to move is flagella.
Prokaryotic flagella differ from eukaryotic flagella in size, composition, and
mechanism of propulsion.
Bacterial and archaeal flagella are similar in size and rotational mechanism but
composed of different proteins. The flagella of bacteria, archaea, and eukaryotes
arose independently and are analogous structures.
Bacterial flagella originated as simpler structures and evolved through modification
in a stepwise fashion. Only half of the flagellum's protein components are necessary
for its function.
The bacterial flagellum evolved through exaptation, where structures originally
adapted for one function take on new functions through descent with modification.
Internal Organization and DNA
Prokaryotic cells are simpler than eukaryotic cells in terms of internal structure and
DNA arrangement.
Prokaryotic cells lack membrane-enclosed organelles but may have specialized
membranes and protein-based compartments.
Prokaryotic genomes have less DNA and typically consist of one circular
chromosome, while eukaryotes have multiple linear chromosomes.
Prokaryotes lack a nucleus, and their chromosome is located in the nucleoid.
Prokaryotic cells may also have smaller rings of independently replicating DNA
called plasmids.
Prokaryotic ribosomes are smaller and differ in protein and RNA content compared
to eukaryotic ribosomes.
Certain antibiotics can bind to prokaryotic ribosomes and inhibit protein synthesis
without affecting eukaryotic ribosomes.
Reproduction
Prokaryotes reproduce quickly through binary fission, dividing into two, four,
eight, and so on.
Rapid population growth in prokaryotes is due to their small size, binary fission
reproduction, and short generation times.
Concept 2: Rapid reproduction, mutation, and genetic recombination
promote genetic diversity in prokaryotes
Genetic variation is crucial for evolution.
Prokaryotes show diverse adaptations, indicating high genetic diversity.
