organizm

/orɡanizm/

Cases

SingularPluralWhen to use it
nominativeorganizmthe organismorganizmlethe organismsthe plain dictionary form — the doer of the sentence
genitiveorganizmnithe organism'sorganizmlenithe organisms'the owner — whose it is
accusativeorganizmnithe organism (as the object)organizmlenithe organisms (as the object)a specific, known object — whom or what
dativeorganizmgeto the organismorganizmlegeto the organismsdirection or recipient — to where, to whom
locativeorganizmdeat / in the organismorganizmledeat / in the organismswhere it is; also having — mende bar, "I have it"
ablativeorganizmdenfrom the organismorganizmledenfrom the organismswhere it comes from; also "than" when comparing
When to use each case
nominative
the plain dictionary form — the doer of the sentence
genitive
the owner — whose it is
accusative
a specific, known object — whom or what
dative
direction or recipient — to where, to whom
locative
where it is; also having — mende bar, "I have it"
ablative
where it comes from; also "than" when comparing

The endings are the same ones the pronouns wear — that page explains when each case is used.

With an owner

One ownedSeveral owned
myorganizmimmy organismorganizmlerimmy organisms
yourorganizmingyour organismorganizmleringyour organisms
his / herorganizmihis / her organismorganizmlerihis / her organisms
ourorganizmibizour organismorganizmleribizour organisms
you all'sorganizmigizyou all's organismorganizmlerigizyou all's organisms
theirorganizmleritheir organismorganizmleritheir organisms

The overlap in the last rows is real, not a mistake: organizmleri can mean "his / her organisms", "their organism", or "their organisms" — context decides.