Classes:
mammal: 5
reptile: 3
fish: 3
amphibian : 2
bird: 2
Entropy E(D)=-(5/15*log(5/15)+3/15*log(3/15)+ 3/15*log(3/15)+ 2/15*log(2/15)+ 2/15*log(2/15))=2.23
BODY TEMPERATURE (BT)
warm-blooded: 7	(MMMBMBM) Pm=5/7; Pb=2/7
cold-blooded: 8	(RFARFRFA) Pr=3/8; Pf=3/8; Pa=2/8

Entropy (BT)= - (7/15*(5/7*log(5/7)+2/7*log(2/7) + 8/15(3/8*log(3/8)+3/8*log(3/8)+2/8*log(2/8)))=1.23
SKIN COVER (SC)

hair: 3 (MMM)	Pm=1
scales: 6 (RFRFRF)	Pr=1/2; Pf=1/2; 
none: 2 (AA)	Pa=1
feathers: 2 (BB) Pb=1
fur: 1 (M) Pm=1
quills:1 (M) Pm=1

Entropy (SC)= -(3/15*(1*log 1)+ 6/15*(1/2*log(1/2)+ 1/2*(log(1/2))+ 2/15*(1*log 1)+ 2/15*(1*log 1)+ 1/15*(1*log1)+ 1/15*(1*log1))=0.4

GIVES BIRTH (GB)

yes: 6 (MMMMFM)  Pm=5/6; Pf=1/6;
no: 9 (RFARBRBFA)  Pr=1/3; Pf=2/9; Pa=2/9; Pb=2/9

Entropy(GB)=1.43

AQUATIC(A)
yes: 4 (FMFF) Pf=3/4; Pm=1/4
no: 7  (MRRMBMM) Pm=4/7; Pr=2/7; Pb=1/7
semi: 4 (ARBA) Pa=1/2; Pr=1/4; Pb=1/4

Entropy(A)=1.25

AERIAL(AR)

yes: 2 (MB) Pm=1/2; Pb=1/2
no: 13 (MRFMARMFRBMFA) Pm=4/13; Pr=3/13; Pf=3/13; Pa=2/13; Pb=1/13

Entropy(AR)=2

HAS LEGS(HL)

yes: 10 (MARMBMRBMA) Pm=4/10; Pa=2/10; Pr=2/10; Pb=2/10
no: 5 (RFMFF)  Pr=1/5; Pf=3/5; Pm=1/5

Entropy(HL)=1.72


HIBERNATES (HIB)
yes: 5 (RAMMA) Pm=2/5; Pr=1/5; Pa=2/5
no: 10 (MFMRBMFRBF) Pm=3/10; Pf=3/10; Pr=2/10; Pb=2/10

Entropy(HIB)=1.65

Information Gain:

Body Temperature: E(D)-E(BT)=2.23-1.23=1
Skin cover:  E(D)-E(SC)=2.23-0.4=1.83
Gives Birth: E(D)-E(GB)=2.23-1.43=0.8
Aquatic: E(D)-E(A)=2.23-1.25=0.98
Aerial: E(D)-E(AR)=2.23-2=0.23
HasLegs: E(D)-E(HL)=2.23-1.72=0.51
Hibernates: E(D)-E(HIB)=2.23-1.65=0.58

Split Info:

Body temperature: -(7/15*log(7/15)+8/15*log(8/15))=1
Skin Cover: -(3/15*log(3/15)+6/15*log(6/15)+2/15*log(2/15)+ 2/15*log(2/15)+1/15*log(1/15)+1/15*log(1/15))=2.31
Gives Birth: -(6/15*log(6/15)+9/15*log(9/15))=0.96
Aquatic:
-(4/15*log(4/15)+7/15*log(7/15)+4/15*log(4/15))=1.54
Aerial:
-(2/15*log(2/15)+13/15*log(13/15))=0.574
Has legs:
-(10/15*log(10/15)+5/15*log(5/15))=1.05
Hibernates:
-(5/15*log(5/15)+10/15*log(10/15))=1.05

Gain ratios:
body Temperature (2.23-1.23)/1=1
Skin Cover: (2.23-0.4)/2.31=0.79
Gives Birth: (2.23-1.42)/0.96=0.83
Aquatic: (2.23-1.25)/1.54=0.63
Aerial: (2.23-2)/0.574=0.40
Has legs: (2.23-1.72)/1.05=0.48
Hibernates: (2.23-1.65)/1.05=0.55

So we split on Body temperature