Call:
lm(formula = heat ~ bodymass + worklev)

Residuals:
    Min      1Q  Median      3Q     Max 
-14.723  -6.720  -1.548   6.435  22.936 

Coefficients:
            Estimate Std. Error t value Pr(>|t|)    
(Intercept)  28.3126    20.0806   1.410    0.173    
bodymass      1.6965     0.3355   5.057 5.24e-05 ***
worklev       3.9395     0.1351  29.153  < 2e-16 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Residual standard error: 10.6 on 21 degrees of freedom
Multiple R-squared: 0.9764,     Adjusted R-squared: 0.9741 
F-statistic: 434.1 on 2 and 21 DF,  p-value: < 2.2e-16 

> anova(model1)
Analysis of Variance Table

Response: heat
          Df Sum Sq Mean Sq F value    Pr(>F)    
bodymass   1   2053    2053  18.279 0.0003363 ***
worklev    1  95478   95478 849.895 < 2.2e-16 ***
Residuals 21   2359     112                      
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 
> drop1(model1)
Single term deletions

Model:
heat ~ bodymass + worklev
         Df Sum of Sq   RSS    AIC
<none>                 2359 116.11
bodymass  1      2873  5232 133.23
worklev   1     95478 97837 203.51
>