Below are lists of related words that have been put into a code. Each “real” letter has been replaced by a “code” one, and the replacements remain the same throughout each list. Each list has its own code. Provide the decoded answers plus their relationship.

-1.
XMFQKERP
HETBEPG
LMMYQ WZAVY
QEOPT WROX
CEBG-QTQX
OMWRD CMMX
QELPQ YJMZK
DRLCK MBP
KZOGQT KOMK
YBED YMDL
YKMMP VRLQMD

-2.
KEJC
IOQXJKPOW
VWCQXLE
CLLXVL
QPEOSI
XZEXVL
JKWED
QDJOV
KVJS
LFF
WMQXLE

-3. (Serpents)
ZPJJTMBTSR
YPS
AORTLOFRTM
LSHTM UPZZSAOF
SFSZPFRS
DSMHTM AFSCT
COFD ZPYMS
MSHHVTM
JEHBPF
USUYS
GOJTM

-4. (About teeth)
CFDDFGS
TZDVH
FGJFEZH
ZRWHLFAW
LHVJWE
WGVTWD
JVGFGW
JDWVGFGS
HZZA
AVHAVH
JVRFAI

-5.
FPR IOZZJRI
RQQPRVZ
WI TIRRSR
UOGQ FHF
JHEUN DORIIR
FPR DRGQHOG
EPVGZRJJ
DYOMYG OAN
EVFLYWVG
FLY-TVER
FPR XYURI

2. Things with shells


crab
pistachio
lobster
beetle
shrimp
turtle
acorn
snail
clam
egg
oyster

5. Batman Baddies

The Riddler
Egghead
Mr Freeze
King Tut
Lucky Pierre
The Penguin
Chandell
Poison Ivy
Catwoman
Two-Face
The Joker

Sondi and Jema, well done!

1. Words/phrases containing birds

dovetail
jaywalk
goose bumps
early bird
hawk-eyed
Robin Hood
Eagle Scout
night owl
turkey trot
swan song
stool pigeon

Excellent solve, Jema!

I've added the two missing categories.

4. good hint
filling
molar
incisor
overbite
braces
enamel
canine
cleaning
root
tartar
cavity

3.
Copperhead
Boa
Sidewinder
Water Moccasin
Anaconda
Garter Snake
King Cobra
Rattler
Python
Mamba
Viper

Well done, guys!