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Question: What organelle does a bacteria lack that differs from a eukaryote?
BACTERIA
Prokaryote — unicellular organisms that lack a nucleus; typically range in size from 1 to
5 micrometers.
Prokaryotes are identified by characteristics such as shape, the chemical nature of their
cell walls, the way they move and the way they obtain energy.
SHAPES
Bacilli
rod-shaped
prokaryotes
Cocci
spherical
prokaryotes
Spirilla
spiral and corkscrew
shaped prokaryotes
CELL WALLS — Gram staining is a testing method used to determine if the bacteria’s cell
wall is composed mostly of peptidoglycan or not.
MOVEMENT — some bacteria are propelled by flagella, or whip-like structures, while
others glide on slime they secrete or may be carried by air, water, or
other methods.
FOOD & ENERGY — some bacteria can make own food either using sun or chemicals,
while others need to take in food by consuming other organisms or
food organisms make. Like many other organisms, most bacteria use
respiration to break down food for energy.
REPRODUCTION
Binary fission — reproductive process that involves only one parent (asexual
reproduction) in which one cell divides to form two identical cells
Conjugation — hollow bridge is formed between two bacterial cells and genes move
from one cell to another
Endospore — a spore that is formed when a bacterium produces a thick internal wall
that encloses its DNA and will remain dormant until more favorable
growth conditions.
Question: Why are viruses not considered a living organism?
VIRUSES
Viruses — particles of nucleic acid, protein and in some cases lipids; can reproduce only
by infecting living cells
Viruses come in a wide variety of sizes and shapes. A typical virus is composed of a core
of either DNA or RNA, which is surrounded by a protein coat, or capsid.
Bacteriophages — viruses that infect bacteria
VIRAL INFECTION
Lytic Infection
Virus enters cell, makes copies of itself and
causes cell to burst (cell is lysed)releasing
hundreds of viruses
Lysogenic Infection
Virus integrates DNA into DNA of host
cell, and the viral genetic information
replicates along with hosts DNA
Prophage — viral DNA that is embedded in the hosts DNA during lysogenic infection.
Retrovirus — viruses containing RNA which produce DNA copy of their RNA upon
infecting a cell.
DIFFERENCES BETWEEN VIRUS AND A CELL
CHARACTERISTICS
VIRUS
Structure
DNA or RNA
core, capsid
Reproduction
Only within a host cell
CELL
Cell membrane, cytoplasm;
eukaryotes contain
nucleus/organelles
Independent cell division
Genetic Code
Growth & Development
DNA or RNA
No
DNA
Yes, in multicellular organisms
Obtain & Use Energy
No
Yes
Response to Environment
No
Yes
Change over Time
Yes
Yes
Question: What is one way to classify protists?
PROTISTS
Protist — eukaryotes that cannot be classified as animals, plants or fungi
PROTOZOANS
ALGAE
(animal – like protists)
(plant – like protists)
— Heterotrophs who lack a cell wall and
inhabit most aquatic environments
— Can be classified by how they move:
— Contain chloroplasts and can make their
own food
— many algae are unicellular, some live in
colonies and others are multicellular
 Zooflagellates — protozoans that move
by means of one or more flagella
 Amoebas are a group of protozoans that
move and feed by forming pseudopods,
or temporary bulges of the cell
 Ciliates are named for their use of hairlike projections called to move and feed
 Protozoans called apicomplexans are
parasites that feed on the cells and body
fluids of their hosts
— classified by cell wall, photosynthetic
pigments, structure
 Euglenoids — single-celled protists that
possess one or two flagella and lack cell
walls
 Dinoflagellates — unicellular,
photosynthetic with a cell wall made of
cellulose and 2 flagella
 Diatom — unicellular, glass- like cell wall
containing silica
 Seaweeds — largemulticellular marine
algae (brown, red, green)
SLIME MOLDS, WATER MOLDS & DOWNY MILDEW
(fungus — like protists)
— Heterotrophs with a cell wall and use spores to reproduce
Spores — tiny cell able to grow into new organism
Question: How do fungi obtain energy?
FUNGI
Fungi — most fungi are eukaryotes that have cell walls; are heterotrophs that feed by
absorbing their food; and use spores to reproduce.
Most fungi (except for simplest such as yeast) have cells arranged in structures called
hyphae.
Hyphae — (singular hypha) are tiny threads
cap
of cytoplasm surrounded by a plasma
membrane and covered by a cell wall
usually made of chitin.
gills
spores
Stalk(stipe)
The hyphae of a fungus typically branch as they
grow forming a mat called a mycelium.
Hyphae
mycelium
Fungi absorb food through hyphae that grow into food source.
Fungi usually reproduce by making spores. The lightweight spores are surrounded by a
protective covering and can easily be carried through air or water to new sites. Spores
in reproductive structures are called fruiting bodies which fungus can make asexually
or sexually.
THREE MAJOR GROUPS OF FUNGI
Club Fungi
Sac Fungi
Zygote Fungi
Produce spores in clublike structures
Produce spores in sac - like
structures
Produce very resistant spores
Ex. Mushrooms & puffs
Ex. yeasts & truffles
Ex. fruit & bread mold