Dead or weakened pathogens used to stimulate the production of antibodies.

What is the purpose of a flower's petals

An oak tree gets nourishment from the Sun and produces acorns. Squirrels eat the acorns. What has happened to the matter consumed by the squirrel?

In tropical climates, where strong insolation makes temperatures high, all that is needed for intense daily convectional storms is: in

20,000 years ago, two populations of the black-tailed rats became separated from each other by the formation of a large canyon, thus preventing their interbreeding. The condition described is A) mass extinction. B) selective breeding.

How does density of ocean water affect how heat is distributed in the ocean?

Your alien friend from planet Xenon is visiting and wants to learn how to breed pea plants. You show your friend a recent batch of pea plants with purple flowers that you grew by crossing plants that had purple flowers with plants that had white

The green stem ant has three (autosome) chromosomes. During meiosis, chromosome 1 and 3 separate normally, but chromosome 2 homologs do not separate during meiosis I. Meiosis II happens normally. What will the resulting cells of meiosis look like?

A population is growing at a rate of 2,4,8, 16, 32. Which type of growth does this describe?

Which epithelial tissue type is most often found lining large ducts, such as those of the salivary glands or pancreas?

Evolution led to certain fishes, such as lung fishes to adapt to terrestrial mode of life. These fishes were the ancestors of modern amphibians. Which evolutionary mechanism is represented by this example?