Name: ___________________________________________________
Background Information
Every species has an optimal environment in which it performs particularly well. All species have a range of tolerance , or limits to the abiotic conditions they can tolerate, such as extremes of temperature, humidity, salinity, and pH. As conditions move further away from the ideal, individuals may be able to survive, and perhaps even grow, but not reproduce. As conditions continue to move away from the ideal, individuals can only survive. If conditions move beyond the range of tolerance, individuals will die. Because the combination of abiotic conditions in a particular environment fundamentally determines whether a species can persist there, the suite of ideal conditions is termed the fundamental niche of the species.
Although the fundamental niche establishes the abiotic limits on a species’ persistence, there are often biotic factors that further limit the physical locations where it can live. Common biotic limitations include the presence of competitors, predators, and diseases. For example, even if abiotic conditions are favorable for a plant species in a particular location, other plant species may be better competitors for water and soil nutrients. Those competitors might prevent the species from growing in that environment. Similarly, even if a small rodent can tolerate the temperature and humidity of a tropical forest, if a deadly disease is present, the disease might kill much of the rodent population and effectively prevent the species from persisting in the forest. Thus, although the match between a species’ traits and the range of possible abiotic conditions defines the species’ fundamental niche, the addition of biotic factors more narrowly defines the parts of the fundamental niche that a species actually uses. The range of abiotic and biotic conditions under which a species actually lives is called its realized niche . Once we understand what contributes to the realized niche of a species, we have a better understanding of the species’ distribution , or the areas of the world in which the species lives.
When we examine the realized niches of species in nature, we see that some species can live under a very wide range of abiotic or biotic conditions, whereas others can live only under a very narrow range of conditions. For example, some insects, such as the meadow spittlebug (a) Philaenus spumarius , feed on a wide variety of plant species. Because they can live in a variety of habitats or feed on a variety of species, organisms such as the meadow spittlebug are considered niche generalists . However, other insects, such as the skeletonizing leaf beetle (b)
Trirhabda virgata , feed on only a single species or genus of plant. Because organisms such as the skeletonizing leaf beetle are specialized to live in a specific habitat or feed on a small group of species, they are called niche specialists . Niche specialists can persist quite well when environmental conditions

remain relatively constant, but they are vulnerable to extinction if conditions change because the loss of a favored habitat or food source leaves them with few alternatives for survival. In contrast, niche generalists should fare better under changing conditions because they have a number of alternative habitats and food sources available.
In this lab you will design and run an experiment to answer the question: How does salinity affect germination in various plant species?
Why salinity? Irrigation is necessary for growing crops especially in areas that are arid or semiarid. As a result large salt buildup is an existing or potential problem in almost all of the
42 million acres of irrigated farmland in the Untied States. Excessive salinity is presently costing the U.S. billions of dollars in lost food crops. This is becoming a huge problem in our own Central Valley, running from Bakersfield, CA to Fresno, CA. Read the article below for further information. http://www.aquafornia.com/index.php/2009/10/19/salinity-in-the-central-valley-a-critical-problem/
As a group you will need to determine the parameters of your experiment. You will have access to the following materials:
-
Seeds
- 4 species: o Crimson Giant Radish o o o
Raphanus sativus
Sunflower
Peas
Helianthus annuus
Pisum sativum
Pinto Beans vulgaris
Distilled water
Salinity solutions
Phaseolus
o
Paper towels
Pipets
1%, 1.5%, 2%, 2.5%, 3%,
3.5%, and 4%
Plastic baggies
Light source
Meter stick
Magnifying glass
Your experiment must include the following:
Testable hypothesis or hypotheses
(you may have more than one)
Control
Data
-
-
Constants
Variables (independent and dependent)
You will be given time each day to collect data and monitor and adjust germination set up
You will be expected to create a formal lab report detailing your experiment and results.