Chapter 2

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