BIOL 108 Origin of Life, Prokaryotes, Protists

Prokaryotes

Single-celled organisms

Cyanobacteria

Oceanic photosynthetic prokaryotes

Cell Wall

Maintains cell shape, protects the cell, and prevents it from bursting in a hypotonic environment (lower solute concentrations than cell contents)

Peptidoglycan

A network of sugar polymers cross-linked by polypeptides

Gram Stain

Can be used to classify bacteria by cell wall composition

Gram-Positive Bacteria

Have simpler walls with a large amount of external-facing peptidoglycan

Gram-Negative Bacteria

Have less peptidoglycan and an outer lipopolysaccharide membrane

Capsule

A sticky polysaccharide or protein layer that adheres cells to each other and to surfaces

Biofilms

Communities of cells in a slimy extracellular matrix (ex: dental plque)

Fimbriae

Hair-like appendages that help cells adhere to a substrate or other individuals in a colony

Pili (Sex Pilli)

Longer than fimbriae and allow prokaryotes to exchange DNA

Endospores

Small, rounded, resting cells that form inside some prokaryotes when conditions become unfavourable

Taxis

The ability to move toward or away from a stimulus (ex: positive phototaxis is movement towards light)

Plasmids

Small rings of DNA containing a few "extra" genes.

3 Factors Contributing to Genetic Diversity

1-Rapid Reproduction

2-Mutation

3-Genetic Recombination

Genetic Recombination

Combining DNA from two sources, contributes to prokaryote diversity

Horizontal Gene Transfer

When the movement of genes is among individuals from different species

3cWays That Prokaryotic DNA From Different Individuals Can Be Combined

1-Transformation

2-Transduction

3-Conjugation

Transformation

Involves uptake and incorporation of foreign DNA from the surrounding environment

Transduction

The transfer of a portion of DNA between bacteria by bacteriophages (viruses that infect bacteria)

Conjugation

The process where genetic material is transferred between prokaryotic cells through direct contact

Phototrophs

Obtain energy from light

Chemotrophs

Obtain energy from chemicals

Autotrophs

Use simple inorganic molecules (ex: CO2) as carbon sources to produce complex organic compounds

Heterotrophs

Require organic substrates to obtain carbon for growth and development

Obligate Aerobes

Require O2 for cellular respiration

Obligate Anaerobes

Poisoned by O2 and use fermentation or anaerobic respiration

Facultative Anaerobes

Can survive with or without O2

Nitrogen Fixation

The process in which some bacteria and methanogens (Archaea) convert atmospheric nitrogen (N2) to ammonia (NH3)

Domain Bacteria

"true" bacteria (Eubacteria)

Domain Archaea

"ancient/original" bacteria

Bacteria

Include the vast majority of prokaryotic species

Proteobacteria

A large and metabolically diverse group of gram-negative bacteria

Chlamydias

Parasites that live within animal cells

Archaea

Share traits with both bacteria and eukaryotes

Extremophiles

Living in extreme environments characterized by low pH, high salt, or high temperatures

Methanogens

Live in anoxic (low O2) habitats

Extreme Halophiles

Live in highly saline environments

Extreme Thermophiles

Thrive in very hot environments

Decomposers

Break down dead organisms and waste products

Symbiosis

An ecological relationship in which two species live in close contact

Mutualism

Both symbiotic organisms benefit

Commensalism

One organism benefits while neither harming nor helping others in any significant way

Parasitism

An organism harms but does not kill its host

Pathogens

Parasites that cause disease

Bioremediation

The use of organisms to remove pollutants from environment

Cytoskeleton

Internal network of proteins

Phagocytosis

Engulfing particles

Dynamic Membranes

Membranes that facilitate movement and feeding

Meiosis

Creates unique gametes (chromosome recombination, independent assortment of alleles)

Fertilization

Fuses gametes at random, creating unique combinations of alleles

Endosymbiont Theory

States that mitochondria and plastids were formerly small prokaryotes living within larger host cells

Plastids

Chloroplasts and related organelles

Endosymbiosis

A relationship between 2 species in which one organism lives in the cell or cells of another organism

Alpha-Proteobacteria

Uses oxygen and organic matter to generate energy

Serial Endosymbiosis

Hypothesizes that mitochondria evolved before plastids through through a sequence of primary endosymbiotic events

Primary Endosymbiosis

Prokaryotes are taken up as endosymbionts by prokaryotic or eukaryotic cells

Secondary Endosymbiosis

Eukaryotic cells are are taken up as endosymbionts by other eukaryotic cells

Evidence for Endosymbiosis

1-The organelle's inner membranes are homologous to plasma membranes of prokaryotes

2-Mitochondria and chloroplasts have their own small, circular DNA (prokaryote circular genome), which they replicate, transcribe, and translate independently of nuclear DNA

3-Division is similar in these organelles and prokaryotes (binary fission)

4-The organelle ribosomes (sites of protein synthesis) are more similar to prokaryotic than eukaryotic ribosomes

5-The organelles resemble prokaryotes in size and structure

The 3 Domains

1-Bacteria

2-Archaea

3-Eukarya

Protist

The informal name of a taxonomically diverse group of mostly unicellular eukaryotes

Mixotrophs

Combine photoautotrophic (photosynthesis) and chemoheterotrophic nutrition

Excavata

Include unicellular protists with modified mitochondria and protists with unique flagella

SAR

Protists that are grouped by DNA similarities. They may have originated by secondary endosymbiosis, and they dominate eukaryotic diversity in the oceans

Archaeplastida

Includes red algae and green algae, and they are the closest relatives to land plants

Unikonta

Include protists that are closely related to fungi and animals

Diplomonads and Parabasilads

Lack plastids, have modified mitochondria, and most live in anaerobic environments (derive energy anaerobically)

Euglenozoans

Includes predatory heterotrophs, photoautotrophs, and parasites

Kinetoplastids

Have a single mitochondrion with an organized mass of DNA

Kinetoplast

An organized mass of DNA