An ecosystem is best described as
A) a system that is composed of nonliving or inorganic matter.
B) a system composed of living organisms.
C) a group of living organisms and the abiotic spheres with which they interact.
D) all living organisms in the atmosphere, hydrosphere, and lithosphere.
E) a group of living plants and the soil types that is present.
Question 2
What is the difference between density and concentration? Density is the ________ with which something occurs in ________, and ________ is the extent of a feature's spread over space.
A) space, concentration, frequency
B) frequency, space, concentration
C) period, space, time
D) period, concentration, space
E) frequency, time, space
Circulatory System
Female Reproductive System Issues
Blood Flow Through the Cardiorespiratory System
Overview of the nervous system.
The skeletal system.
Human Lungs (Respiratory System)