The tendency for dogs to bark while trailing is determined by a dominant gene, S, whereas silent trailing is due to the recessive gene, s. In addition, erect ears, D, is dominant over drooping ears, d. What combination of offspring would be expected from a cross between two erect-eared barkers who are heterozygous for both genes?

Herbaceous stems are supported by

Which is the best example of a coupled human–natural system?

In many areas of the Rocky Mountains, both squirrel and bird species extract and eat the pine seeds from cones of lodgepole pines. In a few areas, however, birds called red crossbills are the only consumers of the pine seeds. Where this one-on-one relationship occurs, both the birds and the pine trees have changed over generations. The crossbills have developed deeper, shorter, and straighter bills that are more efficient at extracting pine seeds, and the pines have developed larger, thicker scales on the cones that defend the seeds from extraction. This bird–tree interaction appears to be an example of

All organisms in the kingdoms Protista, Plantae, Fungi, and Animalia are:

Pinus banksiana, Pinus strobus, and Pinus radiata are:

If both homologous chromosomes of each pair exist in the same nucleus, that nucleus is

If the F1 plants in the classic monohybrid cross (purple/white flowers) were crossed with each other, what would be the phenotypic ratio of the F2 generation plants?

A population growing without environmental limits would

According to Aristotle, all living things could be divided into two groups: