Lab 7: Ecology of Organisms

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Introduc on

Organisms have adapted and evolved anatomical, physiological, and behavioral characteris cs that compensate for varia on within the environment. Organisms have the ability to compensate for mini mal temporal and spa al varia on within their environment by regula ng their body temperature or controlling the rate at which water is transpired however, there are limits to an organism’s ability to compensate for environmental factors. No single species can tolerate all of earth’s environments. The geographic distribu on of a species is thus limited by the physical environment. Species distribu on is said to be limited by abio c factors or the non living components of our environment.

All species have a de ned habitat tolerance which is the range of condi ons in which a species can live. For example, some plant species can tolerate a broad range of soil varia on while others are con ned to a single soil type. If a species has a narrow habitat tolerance because of one or more abio c factors then they are limited in their distribu on range. Organisms with a broad range of tolerance are usually distributed widely whereas those with a narrow range have a

Figure 2 Dandelion (Taraxicum o cionale) species like the dande lion are very common and show no aspects of rarity making them

very common handling a broad range of tolerances .

Figure 1 Mountain Gorilla (Gorilla gorilla beringei) mountain gorillas have a restricted geographic range, a narrow habitat tolerance, and a small local popula on classifying them in the “rarest” category, this

species is one of many that is highly vulnerable to ex nc on.

Concepts to explore:

Ecology of organisms Range of tolerance

Concepts to explore:

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more restricted distribu on. Habitat tolerance along with a species geographic range (limited vs. wide spread) and the species local popula on size (large vs. small) determine a species commonness or rari ty. Understanding a species range of tolerance helps to determine whether a species is common or rare which can be a huge determinate in areas such as agricultural produc on and wildlife manage ment.

Experiment 1: E ects of pH on radish seed germina on

Natural soil pH depends on the parent rock material from which it was formed and processes like cli mate. Soil pH is a measure of the acidity or alkalinity of the soil. Acidic soils are considered to have a 5.0 or lower pH value whereas 10.0 or above is considered a strong basic or alkaline soil. The pH of soil a ects the solubility of nutrients in soil water and thus it a ects the amount of nutrients available for plant uptake. Di erent nutrients are available under di ering pH condi ons.

In this lab we will look at the e ect of pH on the germina on and growth rate of radish seeds in order to determine the range of pH tolerance for the seed. Acidic or basic water will be used in order to s mulate acidity or alkalinity in soil.

Procedure

1. Obtain your petri dishes and label them, one for each solu on

2. Cut out the paper towel to t inside the petri dish. Wet each individual towel with its determined solu on.

Materials

50% Vinegar solu on Radish seeds Saturated baking soda solu on Paper towel sheets (cut to t into petri dish)* pH paper

Water* 3 Petri dishes Ruler

* You must provide

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3. Test pH of three solu ons and the paper towels containing the solu on, record your values.

4. Arrange 10 radish seeds on each paper towel in each petri dish. Make sure the seeds have space and are not touching.

5. Place the petri dishes in a sunny or well lit warm place. You must be sure to keep the paper towels moist for the length of the lab with the appropriate solu on and make sure that the solu ons re main at the same rela ve pH.

6. Observe seeds daily for 7 days and record the number of seeds that germinate (note when the seed cracks and roots or shoots emerge from the seed).

Note: During this observa on period, take pictures to document the radish seed growth. This can be done in a number of ways (example, mobile phone, camera, webcam, etc.). Images can then be scanned , uploaded via USB/cable connec on, etc. onto a computer and be integrated into your nal document.

7. On the 7th day record the lengths of radish seed sprouts. Compare and graph sprout lengths below. Don’t forget to tle your graph and label the axes.

Table 1: Radish Seed Observa on and Germina on

*You will need to expand on the table below to record your observa ons and results for all 7 days.

Solu on pH

Days 1 2 Day 3 Day 4

Observa on Seeds

Germinated % Observa on

Seeds

Germinated % Observa on

Seeds

Germinated %

Water

Vinegar

Baking soda

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Ques ons

1. Was there any no ceable e ect on the germina on rate of the radish seeds as a result of the pH? Compare and contrast the growth rate for the control with the alkaline and acidic solu ons.

2. According to your results would you say that the radish has a broad pH tolerance? Why or why not? Use your data to support your answer.

3. Knowing that acid rain has a pH of 2 3 would you conclude that crop species with a narrow soil pH range are in trouble? Is acid rain a problem for plant species and crops?

Figure 3: Sample set up for sprout lengths graph.

Se ed

Le ng th

(m m )

Seed Length vs. Environment Category