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Bio 3 Study Guide Ch 15
1. The oldest prokaryote fossils date back to 3.5 billion years ago (photosynthetic anaerobes). It is
hypothesized that more simple/non-photosynthetic prokaryotes evolved prior to this time – with
estimates dating back to 3.9 billion years ago. Photosynthetic anaerobes released oxygen into the
atmosphere; first it saturated the oceans and then it was added to the atmosphere. Oxygen
accumulated in the atmosphere by 2.4 bya. This caused many anaerobes to die because oxygen was
toxic to them, but a variety of metabolic modes evolved in the prokaryotic survivors. For example many
evolved a mechanism to deal with oxygen and evolved into aerobes that undergo cellular respiration.
Other anaerobes had niches where the conditions were anaerobic and survived. Unicellular eukaryotic
fossils date back to 2.1 bya. They evolved from a prokaryotic community, a host cell anaerobe
containing even smaller prokaryotes. Multicellular eukaryotes evolved at least 1.2 billion years ago.
2. Autotrophs or producers – make their own food using carbon dioxide as their carbon source
3. Heterotrophs or consumers – require food (organic molecules they eat are their carbon source)
a. By ingestion: take in food into their bodies; it will be digested by enzymes, nutrients released
b. By absorption: secrete digestive enzymes outside the body, then absorbing the nutrients into the
body
4. Know these terms for modes of nutrition:
a. Phototrophs – obtain energy from sunlight
b. Chemotrophs –obtain energy from the breakdown of chemicals (organic/inorganic compounds)
c. Autotrophs – obtain C from CO2 (to produce their own food/glucose): producers
d. Heterotrophs – obtain C from organic molecules (i.e. glucose) (consume food): consumers
e. Mixotrophs –can switch between being autotrophs and heterotrophs & their energy source
5. Classifying a species’ mode of nutrition:
a. Photoautrophs: energy from sunlight & C from CO2 to make food
i. Some prokaryotes: cyanobacteria
ii. All plants & algae (protists)
b. Chemoautotrophs: energy from inorganic compounds & C from CO2 to make food
i. Some prokaryotes
c. Photoheterotrophs: energy from sunlight & C from organic molecules
i. Some prokaryotes: photosynthetic purple & green sulfur bacteria
d. Chemoheterotrophs: energy & C from organic compounds
i. Some prokaryotes & protists
ii. All fungi & all animals
6. Know the general characteristics of prokaryotes:
a. Most are heterotrophs, some are autotrophs
b. Lack a nucleus and other membrane bound organelles
c. Have a cell wall (peptidoglycan in bacteria) outside of the plasma membrane
d. About half of the species are mobile; many are propelled with one or more flagella (long whiplike filaments); flagella rotate and push bacteria along like a propeller.
e. General shapes: spherical (cocci), rod (bacilli) and spiral or curved (vibrios- like a comma;
spirilla – helical, short and rigid; spirochete – helical, long and flexible)
f. Unicellular, but some species exist as a group of two or more in clusters (staphylo-) or in
chains (strepto-); some grow branching chains (actinomycetes) and some species exhibit a
simple division of labor among specialized cell types of cells (cyanobacteria)
g. Some can attach to surfaces in a highly organized colony, called a biofilm, which consists of one
or more prokaryote species and may include protist or fungi (dental plaque)
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h. Gram-negative bacteria have an outer membrane outside the cell wall (source of endotoxin)
i. Some bacteria have a capsule: a slime layer usually of polysaccharides that prevents the cell
from drying out, helps trap other cells & it helps it evade being destroyed by phagocytosis (by
immune cells); found most commonly outside the outer membrane of Gram-negative bacteria.
j. Some have hollow hair-like pili to help adhere to another cell (sex pilus is for reproduction
called conjugation- lateral gene transfer)
k. Some survive very harsh conditions by forming specialized cells called endospores (in rods, like
the anaerobe Clostridium tetani and C. botulinum); thick-coated, protective cells that are formed
inside the bacteria when the prokaryote is exposed to adverse conditions, and that are maintained
once the bacteria die. They lay dormant until conditions are good at which point they absorb
water and resume growth. They ensure survival!
l. Reproduction: asexual binary fission and lateral gene transfer (conjugation)
m. They have diverse habitats yet are specialists (moderate conditions to extreme conditions, but
within each within a narrow range of conditions)
n. They are decomposers (fungi too) – they break down organic wastes and dead organisms via
secretion of digestive enzymes, and in the process return elements to the environment in
inorganic forms that can be used by other organisms (important for recycling of elements like
carbon and nitrogen)
o. Know some characteristics specific to archaea and specialist.
7.
Gram staining procedure: There is a stain that is crystal violet. It stains the thick peptidoglycan cell
wall of Gram-positive bacteria violet. However, it cannot stain the cell wall of bacteria that have an
outer membrane outside the cell wall. These bacteria are called Gram-negative bacteria
a. Gram + : Clostridium (a rod, forms spores; obligate anaerobes)
b. Gram - : Escherichia coli ( a rod, facultative anaerobe)
8. Prokaryote metabolic modes;
a. Obligate aerobes – require oxygen for growth/survival (cellular respiration)
i. Die without oxygen
ii. Bacillus, a Gram + rod (some species of this genus are facultative anaerobes)
b. Obligate anaerobes – grow/survive without oxygen (fermentation/anaerobic respiration)
i. Oxygen is deadly to most
ii. Clostridium, a gram-positive rod, that forms endospores
c. Facultative anaerobes - anaerobes, but if oxygen is present they can switch to aerobic
respiration
i. Oxygen is not deadly
ii. Escherichia coli, a Gram - rod
9. Define symbiosis. Symbiosis is a close interactive association between 2 or more organisms/species.
Mutually beneficial means that the two organisms both benefit from the relationship.
10. Describe the mutually beneficial symbiotic relationship (mutualism) between ruminant herbivores and
prokaryotic microflora. Prokaryotes live in the digestive tracts of organisms that depend heavily on
cellulose (ruminants such as cows) for nutrition. The problem is that ruminants can’t break down the
cellulose. The prokaryotes (i.e. archaea) aid the ruminant in the digestion of cellulose and in return they
get a stable environment with a regular food supply (partially digested grass).
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11. Pathogens and our health: We are healthy most of the time due to our immune system keeping the
growth of pathogenic (disease causing) bacteria and other bacteria populations in check. When our
immune systems are weak, our defense is weakened and growth of these bacteria increases. We then
become ill.
12. Some bacteria are infectious, entering the body through the mouth, nose or a wound/scrape in the skin.
Bacteria are pathogenic when they cause disease due to some molecules they possess (virulence
factors). These virulence factors allow them to colonize a site within the host, evade and inhibit the host
immune system, and obtain nutrition from the host. Ways they do this is through:
a. Toxic chemicals (toxins): this is the way most bacteria cause illness
i. Exotoxins: proteins secreted by bacteria
1. Clostridium tetani - releases tetanus neurotoxin
2. Clostridium botulinum – releases botulinum toxin
3. Lyme bacteria – release neurotoxin that causes Lyme disease
ii. Endotoxins: a lipid component (LPS) of the outer membrane of Gram-negative bacteria
that is released when the cell dies or is digested by a defense cell.
1. Causes fever, aches & sometimes a dangerous drop in blood pressure.
2. Examples: E. coli and Salmonella
b. Bacterial enzymes that digest host antibodies that are secreted in response to the infection.
c. Bacterial enzymes that destroy tissue.
d. The capsule (a slime layer of mostly carbohydrate found outside the outer membrane of Gram
negative bacteria): it helps the bacteria evade being destroyed by phagocytosis
13. Kingdom Protista is a very large & diverse collection of organisms. Some have characteristics that are
plant-like, animal-like (protozoans) & fungi-like. Protist classification is a work in progress. One
current hypothesis of protist phylogeny proposes 5 monophyletic supergroups (we will not discuss). It is
now clear that there are multiple clades of protists with some lineages that are more closely related to
plants, fungi or animals than they are to other protists.
a. Protist Supergroup Archaeplastids: 2 separate lineages gave rise to red algae and green algae.
i. Closest living protist relatives of plants are green algae: charophytes
b. Protist Supergroup Unikonta: 2 separate lineages gave rise to fungi and animals
i. Closest living protist relatives of animals: choanofalgellates (resemble sponge collar
cells)
ii. Closest living protist relatives of fungi: nucleariids (algae & bacteria feeding amoebas)
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14. General facts about protists:
a. Most are single-celled, some are colonial, and some are multicellular
b. Most are aquatic (oceans, lakes, ponds) & few are terrestrial (damp soil or leaf-litter)
c. Reproduction: sexual and asexual (binary fission, conjugation, and other forms)
d. Some are mobile (pseudopodia, flagella, or cilia)
i. Pseudopodia- Amoeba & Forams
1. Pseudopods are temporary extensions of the cell membrane; as the membrane
is contracted forward the cytoplasm of the cell flows forward in the direction of
the extended cell membrane. They are used to move and to eat through
phagocytosis.
ii. Cilia- Paramecium and Didinium, Stentor, Vorticella
1. Cilia are short hair like extensions from the plasma membrane; they beat in
rhythmic waves for swimming or they create currents to sweep food into the
mouth.
iii. Flagella – Euglena, Trypanasoma, Dinoflagellates, and green algae (Chlamydomonas &
Volvox)
1. Flagella are long appendages, whip-like extension from the plasma
membrane; they rotate and pull the organism along in the direction of the
flagellum.
e. Some are autotrophs (photoautotrophs), but most are heterotrophs (chemoheterotrophs)
i. Autotrophs – algae (single-celled, colonial, and multicellular)
ii. Heterotrophs – consumers
1. Protozoans (animal-like): live primarily by ingesting bacteria or other protists;
some are parasitic (get nutrients from a living host, which is harmed).
2. Slime molds – amoeboid type cells that use pseudopods to take in nutrients from
their environment and are fungus-like in appearance and life-style.
f. Mixotrophs (switch between photosynthesis and heterotrophy)- Euglena
g. Some protists exist in mutually beneficial symbiotic relationships as endosymbionts:
i. Unicellular algae live inside bodies of reef-building corals forming coral reefs.
ii. A protist symbiont (Trichonympha) lives in the gut of termites and digests cellulose.
15. Amoeba (heterotrophic protozoan with pseudopods): lack most eukaryotic organelles; most species
move and feed with pseudopodia (temporary extensions of the plasma membrane); most are free-living
predators and some parasitic species (i.e. amoebic dysentery); freshwater, salt water and soil.
16. Forams or Foraminiferans (heterotrophic protozoan with a shell and thin pseudopods): amoeboid
body with thread-like pseudopods that extend through a calcium carbonate shell; freshwater and salt
water.
17. Ciliates (heterotrophic protozoan with cilia): cilia on surface is used for movement & to sweep food
into its mouth; some have cilia in arranged in bundles along the length of the cell allowing them to crawl
over a surface (Euplotes); accomplished predators; most are free-living & aquatic; heterotrophs and
mixotrophs.
a. Paramecium – cilia uniformly distributed in rows all over its body (eats bacteria)
b. Didinum – cilia in two rows (eats Paramecium!)
18. Flagellates that are heterotrophic protozoans: have a flagella; most are free-living, but some are
parasitic.
a. Parasitic Giardia: reproduces within vertebrate intestines and causes severe diarrhea in humans
b. Parasitic Trichomonas: a sexually transmitted parasite: know about T. vaginalis
c. Parasitic Trypanasoma brucei: infects mammalian blood and causes sleeping sickness; has two
hosts: transmitted to mammalian host through the bite of an infected Tsetse fly (insect vector).
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19. Apicomplexans (heterotrophic protozoans with an apex): all are parasitic; named for structure at
their tip (apex) that is specialized for penetrating host cells/tissues
a. Plasmodium: malaria parasite: it is transmitted through the bite of an infected Anapholes
mosquito; it eventually the enters red blood cells of the human host, where it multiplies and
ruptures the cell (see picture of its apex).
20. Slime molds (heterotrophic): have the appearance of fungi, but are more closely related to amoebas
a. Move & eat with pseudopodia through soil and rotting logs in its feeding stage; eat bacteria and
fungi by phagocytosis; decompose decaying material.
b. Plasmodial slime mold – a usually colorful and large amoeboid mass of cytoplasm with many
nuclei in its feeding stage; it has many extensions; but stops eating and growing when food and
water are scarce; it then differentiates into a reproductive structure that produces spores; when
conditions are favorable spores release cells with haploid nuclei & the cells fuse to form a zygote
and the life cycle continues.
c. Cellular slime mold (Dictyostelium) – solitary amoeboid cells that move and feed; when food is
scarce they aggregate to form a slug-like colony; it soon extends a stalk and develops into a
multicellular asexual reproductive structure with spores.
21. Euglena (mixotroph): non-parasitic flagellate (2 flagella, but only one is visible) & mixotroph
(photosynthetic and heterotrophic): It has a red eyespot (a plate of red pigment/light filter) that shields a
light-sensitive region (or receptor) that lies near the base of the flagellum. The red eyespot filters
certain wavelengths of light to the light receptor, allowing euglena to move towards light for
photosynthesis. If light is low, then it switches to heterotrophy (phagocytosis)
22. What are algae? Photosynthetic protists with chloroplast; support food chains in freshwater and marine
ecosystem
a. Unicellular: diatoms, dinoflagellates, and single-celled green algae (Chlamydomonas)
b. Colonial: colonial green algae (Volvox)
c. Filamentous: filamentous green algae (Spirogyra)
d. Multicellular – called seaweeds (green, red and brown)
23. What are seaweeds? Multicellular algae that are differentiated by the pigments that they possess.
24. What is phytoplankton? The communities of mostly microscopic organisms that float or swim weakly
in aquatic environments. Many unicellular algae are components of phytoplankton
a. Important photosynthetic members: protists including diatoms & dinoflagellates and
cyanobacteria are important members of aquatic food webs.
25. Diatoms (photosynthetic, unicellular algae): have silica shells that fit together like a lid & bottom of a
shoebox/petri-dish; have a golden yellow color due to chlorophyll and accessory pigments; store food
reserve as oil which helps keep buoyant; in marine/freshwater/ moist soil surfaces; may form chains or
colonies.
26. Dinoflagellates (50% are autotrophic, unicellular algae): most are marine; many swim with 2 flagella
(one wraps around body); covered by a theca or sheath that can be smooth or decorated (cellulose cell
walls resembling an armor plate); many are bioluminescent; 60 of 2,000 species are able to produce
toxins and are the cause of red tides.
27. What is a red tide? When conditions are favorable, a population explosion of dinoflagellates (or
bloom) may occur which can be detrimental due to the toxin contamination of fish and shellfish; it also
posses a threat to humans and animals that consume these fish and shellfish.
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28. Green algae – most are photosynthetic and are freshwater dwellers; (most closely related to plants:
green chloroplast and cell walls of cellulose/pectin)
a. Some species are unicellular and flagellated – Chlamydomonas (2 flagella; freshwater)
b. Some species are colonial and flagellated – Volvox colony is a hollow sphere with numerous
flagellated cells and daughter colonies inside. (see worksheet 2)
c. Some species are filamentous (multicellular) – Spriogyra form long chains of cells joined end
to end; move with currents in the water; spiral chloroplasts
d. Some species are large multicellular marine seaweeds – Ulva/sea lettuce.
29. Brown algae (all are multicellular algae) their color is brown to olive brown due to photosynthetic
pigments being a mixture of brown, yellow plus green chlorophyll; most are marine cool waters (near
shore to off shore); kelps are the largest seaweeds and grow as marine forests in relatively deep water
beyond the intertidal zone
30. Red algae –most are multicellular seaweeds; accessory pigment masks chlorophyll; abundant in warm
coastal waters of the tropics; encrusted red species are common reefs.