Chapter 22.2 – Unicellular Organisms
Unicellular Organisms
We are multicellular organismsHowever, many living things are composed
of just one cellThese unicellular organisms are also known
as micro-organisms or microbesThey must also carry out life’s functionsA single cell is responsible for feeding,
digesting, excreting, and reproducing
The Importance of Micro-Organisms
Many micro-organisms cause disease but most are harmless
Dairy products such as buttermilk, cottage cheese, and yogurt are produced by the action of micro-organisms
Bacteria
Bacteria are among the most primitive and also the most plentiful organisms on Earth
Some can make their own foodOthers are parasites
Parasites can live only by invading the body of an animal or a plant
Others can live with little or no oxygen
Bacteria
Bacteria are prokaryotic cellsThey have no nucleus, no mitochondria,
and no ribosomes
BacteriaPili – hair-like structures to help bacterium attach or for movement
Flagellum – whip-like tail for movement
Capsule – Sticky coating of infective bacteria, difficult to destroy
Cell Wall – rigid support
Cell Membrane
Chromosomes – not contained in a nucleus
Protists
Protists are found in water everywhereThey are neither plants or animalsProtists are eukaryotic cellsThey have a nucleus and contain
mitochondria, ribosomes, and lysosomes
Plantlike Protists
Plantlike protists are not true plants but they do contain chlorophyll and produce their own food by photosynthesis
We are going to look at 2 types of plantlike protists:1. Diatoms2. Euglena
Plantlike Protists
DiatomsDiatoms are found in both fresh and salt
waterThey contain chlorophyll and can make their
own foodThey are encased in two thin shells which
are joined togetherEach diatom has a unique shape
Plantlike Protists
EuglenaEuglena are similar to both plant and animal
cells If there is a lot of sunlight the euglena acts
like a plant and makes it’s own food If there is not a lot of sunlight then the
euglena acts like an animal and it will feed on smaller cells
Plantlike Protists
Chloroplasts
Flagellum
Golgi Apparatus
Mitochondria
Contractile Vacuole – expels excess water
Pellicle – flexible cell covering
Animal-like Protists
Animal –like protists cannot make their own food
They must feed on things that are living or were once alive
They have all the organelles of an animal cell
Animal-like Protists
AmoebaeThe amoeba is a blob-like organism that
changes shape as it moves It moves by stretching out a branch of
cytoplasm called a pseudopod (false foot)The pseudopod anchors to an object, and
the rest of the amoeba is dragged toward it
Animal-like Protists
Animal-like Protists
ParameciumThe paramecium uses cilia to help it moveThe cilia beat in unison to create water
currents that move the parameciumCilia around it’s oral groove create a current
that draws food into the groove
Animal-like Protists
Fungi
Some fungi are multicellular and some are unicellular
Bread mold and mushrooms are well known fungi
Harmful fungi include those that cause ringworm and athlete’s foot
Fungi
Yeast is one of the few unicellular fungiYeast relies on other organisms as their
source of energy