What normally serves as the pacemaker of the entire heart?

Below, the levels of organization in a multicellular organism are shown from least to most complex. Which level of organization can be described as several different types of tissues working together to perform a common task?

Horestails feel gritty because their stems contain

The ___ is the main organ of the circulatory system.

Which of the following evidence supports that the "RNA World" hypothesis is valid? A. Creation of suitable environments for long-term study of single-celled organisms B.

How is bacteria similar to birds?

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?