What holds the base pairs of DNA together? A. Covalent bonding B. Double helix C. Ionic bonding D. Hydrogen bonding

What type of tissue makes up the outer covering and lines organs of animals?

The human body needs energy in order to carry out life processes such as breathing. Where does the body get this energy? A. from eating food B. from sleeping C. from learning about new things D. from lying in the sun

Which of the following is a risk of being underweight? A. Starting to develop arthritis B. Increased possibility of stroke C. Poorly functioning immune system D. Becoming more susceptible to heart disease

All living organisms can be categorized by their response to atmospheric oxygen as obligate aerobes, facultative aerobes, obligate anaerobes, and/or facultative anaerobes. What do the terms facultative and obligate mean in this context?

Is there oxygen on Mars?

Which of the following do fish NOT use to breathe? A. air bladder B. pharyngeal slits C. pores on their back D. olfactory bulbs

Imagine a protein that has been engineered to contain a nuclear localization signal, a nuclear export signal, a C-terminal peroxisomal targeting sequence, and a canonical endoplasmic reticulum (ER) signal sequence.

Which organelle receives protein from endoplasmic reticulum and sorts and packages it for delivery outside cell?

Eukaryotic cells have many different specialized structures that are involved in making, organizing, and delivering a protein molecule. Describe the four organelles that are involved and the sequence of events of this process.

What do scientists call an orderly pattern of change over time? A. homeostasis B. ecological succession C. food web D. an ecosystem