Corn plants from a test plot are measured, and the distribution of heights at 10-cm intervals is recorded in the following table:  
 Height (cm)      Plants (no.)       
100                    20       
110                    60       
120                    90       
130                   130       
140                   180      
 150                   120       
160                    70        
170                   50        
180                   40 
Calculate 
(a) the mean height, 
(b) the variance, 
(c) the standard deviation, and 
(d) the standard error of the mean. 
Plot a rough graph of plant height against frequency. Do the values represent a normal distribution? Based on your calculations, how would you assess the variation within this population?

Erma and Harvey were a compatible barnyard pair, but a curious sight. Harvey's tail was only 6 cm long, while Erma's was 30 cm. Their F₁ piglet offspring all grew tails that were 18 cm. When inbred, an F₂ generation resulted in many piglets (Erma and Harvey's grandpigs), whose tails ranged in 4-cm intervals from 6 to 30 cm (6, 10, 14, 18, 22, 26, and 30). Most had 18-cm tails, while 1/64 had 6-cm tails and 1/64 had 30-cm tails. If one of the 18-cm-tail F₁ pigs is mated with one of the 6-cm-tail F₂ pigs, what phenotypic ratio will be predicted if many offspring resulted? Diagram the cross.

Erma and Harvey were a compatible barnyard pair, but a curious sight. Harvey's tail was only 6 cm long, while Erma's was 30 cm. Their F₁ piglet offspring all grew tails that were 18 cm. When inbred, an F₂ generation resulted in many piglets (Erma and Harvey's grandpigs), whose tails ranged in 4-cm intervals from 6 to 30 cm (6, 10, 14, 18, 22, 26, and 30). Most had 18-cm tails, while 1/64 had 6-cm tails and 1/64 had 30-cm tails. Explain how these tail lengths were inherited by describing the mode of inheritance, indicating how many gene pairs were at work, and designating the genotypes of Harvey, Erma, and their 18-cm-tail offspring.

In the following table, average differences of height, weight, and fingerprint ridge count between monozygotic twins (reared together and apart), dizygotic twins, and nontwin siblings are compared:   Trait            MZ Reared    MZ        DZ Reared   Sibs Reared                     Together      Reared     Together       Together                                          Apart                                              _Height (cm)      1.7              1.8             4.4                4.5 Weight (kg)      1.9               4.5            4.5                4.7 Ridge count     0.7               0.6            2.4                 2.7 Based on the data in this table, which of these quantitative traits has the highest heritability values?

What kind of heritability estimates (broad sense or narrow sense) are obtained from human twin studies?

The following variances were calculated for two traits in a herd of hogs.

  Trait             Vₚ           VG        VA  _
Back fat        30.6        12.2       8.44
Body length  52.4        26.4     11.70

Calculate broad-sense (H²) and narrow-sense (h²) heritabilities for each trait in this herd.

The following variances were calculated for two traits in a herd of hogs.

  Trait             Vₚ           VG        VA  _
Back fat        30.6        12.2       8.44
Body length  52.4        26.4     11.70

Which of the two traits will respond best to selection by a breeder? Why?

The mean and variance of plant height of two highly inbred strains (P₁ and P₂) and their progeny (F₁ and F₂) are shown here.

   Strain     Mean (cm)     Variance  _
     P₁           34.2                 4.2
     P₂           55.3                 3.8
     F₁           44.2                 5.6
     F₂           46.3               10.3

Calculate the broad-sense heritability (H²) of plant height in this species.