1
How Cold Has It Been?
STEM
How Cold Has It Been? Ecosystems and Climate UnitArctic Plant Adaptations
OVERVIEW
Plants of the arctic region have developed unique strategies to survive in the harsh arctic environment. Many of the plants are small, growing close to the ground and very close together to avoid the wind and conserve heat. Some possess a light, fuzzy covering to insulate the buds so they can grow. Many are dark colors of blue and purple to absorb the heat from the sunlight even during the winter months. Because of the cold and short growing seasons, arctic plants grow very slowly. Some grow for ten years before they produce any buds for reproduction. These two activities are designed to highlight some of the adaptations that plants in the arctic have acquired over time in order to survive their extreme climate. The first activity, Willows in the (Arctic) Wind is suitable for grades K-8, the second activity, Macro Ecosystems is suitable for grades 6-8.
BACKGROUND
Tundra plants are often dwarf relatives of similar plants from milder climates. Short plants can better avoid drying and abrasive winds and stay warmer in the near ground microclimate. Their small flowers save energy. Many tundra plants also wear adaptive coats – furry and waxy coatings on their leaves and stems. Fine hair or fuzz slows the wind, thus reducing drying and
preserving heat. Dense hairs around the flowers of the woolly lousewort also act like the glass of a greenhouse – trapping solar energy. This surrounds the flowers with relatively warm air, sometimes 34ºF (18ºC) warmer than the environment. This is important because cell division, necessary for seeds to form, cannot occur at cold temperatures. The waxy coating of many plants also reduces water loss and evaporative cooling by the wind. Many tundra plants retain, rather than shed, their dead leaves each year. The dead leaves insulate fragile new buds from the wind and cold. Grass tussocks provide a good example of this. Many of the tundra’s summer flowers are purple or blue because these colors absorb more heat than do white or light yellow. Indeed, the percentage of dark-colored flowers is greater in the tundra than in
warmer environments Many tundra plants, such as the tundra grass, are able to photosynthesize at temperatures of 25°F (–4°C) because they produce antifreeze that
keeps their cell fluids liquid even at this low temperature. Plants need antifreeze not only to prevent freezing, but also so that they can make enough food to survive. Because the process of photosynthesis requires water, many plants cannot function if the temperature is less than 32°F (0°C), the freezing point of water. But air temperatures in tundra environments frequently drop below freezing in spring, fall, and even summer.
Many tundra producers beat the short growing season with long life cycles. As with an iceberg, there is more to tundra plants than what you see on the surface. Aerial parts are reduced in favor of root mass in the protective soil. This is also an adaptation used by many desert plants. Tundra plants tend to form clumps or cushions, which create milder microclimates (as much as 20 degrees warmer) to insulate growing tissues and preserve moisture. Keeping their dead leaves is such an adaptation. Arctic tundra plants can grow at lower temperatures than can similar plants in milder environments. The energy and minerals stored in their large roots allow the plants to start to grow instantly in the spring – even under the snow. Tundra plants further make up for the short growing season by adopting long life cycles to accomplish reproduction. Many tundra plants grow for 10 years or more before saving enough energy to form flower buds. Even then a plant might form flower buds one year, bloom the next, and make seed a year later. The fragile flower buds develop underground or encased by dead leaves so they are well insulated. When spring comes, the tundra can literally burst into bloom because the flower buds were formed in previous years. Many plants reproduce by rootstocks or runners instead of, or in addition to, seeds. The tiny plants that sprout from rootstocks are identical to their parent plant. The parent plant nourishes the clone plants until the clones have many leaves of their own. Some plants, such as the alpine poa, produce seeds that germinate and begin to develop while still attached to the parent. This is an advantage, because when the young plants drop from the parent, they already have tiny leaves and can begin photosynthesis immediately. Alpine tundra plants can photosynthesize under widely fluctuating temperatures, in brilliant light, and in short periods of daylight. Arctic tundra plants can photosynthesize at low temperatures, at low light intensities, and for long periods of daylight. Most tundra plants are several years or decades old. The age of some woody tundra plants has been estimated at 200 to 300 years, based on counts of their annual rings.
TUNDRA ADAPTATIONS
Activity: Willows in the (Arctic) Wind
Tundra willow trees grow to only about 6” tall and hug the ground to escape the fierce Arctic winds, which would topple taller trees. In the winter, snow blankets these little trees and protects them from sharp tundra ice crystals.
Procedure
Create models to demonstrate the effect of wind on trees of different sizes.
Twist two pipe cleaners together to create a tree trunk, leaving about 1" loose at one end to represent the roots. Have them attach and shape pipe-cleaner branches that extend in several directions. Then ask students to shape another pair of pipe cleaners into a tiny, short tree with long, low limbs and roots. "Plant" both trees in a mound of clay "soil" and press firmly onto a tabletop. Position a fan to blow on the trees. How do the two trees respond? What happens when tall trees are exposed to strong, sustained wind?
Experiment with both low and high wind and different materials
Extension - Try this:
Collect a variety of plants or parts of plants that include, needles, broad leaves, narrow leaves, lichen, moss, succulent, etc and place them in the freezer. Check them over time to see how they react. If microscopes are available look at the samples before and after freezing.
Biological Succession in a MicroecosystemHeating Degree Days
The following formula is used to calculate the number of degree days that accumulate during a time period.
Degree days = (number of days) (65ºF - average temperature)
When the degree day formula results in a positive value, the number of degree days are referred to as heating degree days because the average outside temperature was below 65º and a heating system may be used to keep a building comfortably warm
Average Temperatures
The following data can be used to calculate the average temperature.
Data Table #1: Sample January Temperature DataDate / Low Temperature / High Temperature
2nd / 17º / 35º
3rd / 14º / 36º
4th / 12º / 16º
5th / 11º / 15º
6th / 11º / 22º
7th / 12º / 23º
8th / -2º / 12º
Question 1: What was the average temperature on January 8th?
Question 2: What was the average temperature for the week?
Introduction:
In any biological community, certain species of living things are more numerous than others. Usually a community contains one dominant organism. However, some communities are able to have two dominant species, such as the oak-hickory forest.
Some communities do not remain stable because slight modifications of physical and biological factors alter the habitat. When the habitat changes, the dominant organism(s) can be replaced or reduced in number. When a new species replaces a species as the dominant organism, succession has occurred.
Succession in some communities is scarcely visible because of the length of time it takes for noticeable changes to occur. However, in cultures containing protists and microinvertebrates, it is possible to observe succession. Also, the factors causing the succession can be determined.
In this investigation, you are to set up six culture dishes containing various protozoans. You are able to place these dishes in areas of specific temperature and light conditions. Over a period of time, you are to determine the order of the stages of succession in the dishes. You are to describe succession as it occurred in each dish.
Purposes:
To observe the order of stages of succession in cultures containing bacteria, protists, and microinvertebrates.
To determine the factors causing succession.
To learn population sampling techniques.
To observe food chains in a microecosystem.
Your team (of four) should have the following:
Medium size culture dishes - 6Boiled pond or spring water
Droppers - 6
Cooked wheat grain
Stereomicroscope
Microscope (compound light)
Glass Slides
Cover slips
Graph paper / Paramecium culture
Mixed rotifer culture
Blepharisma culture
Eudorina culture
Peranema culture
Euglena culture
Amoeba culture
Procedure:
Half fill each of six culture dishes with boiled pond or spring water. Label the dishes A through F. With a dropper , add ten drops of each culture to each of the six dishes. Stir each culture prior to transferring it to one of the six culture dishes.
Mark the fluid levels of each culture dish with tape. To dishes A, B, and C add three grains of cooked wheat. Do not add any grains to dishes D, E, or F. Place the culture dishes in the proper environment see table 1. Add boiled pond or spring water to each dish as needed to keep the fluid level constant.
Add food (wheat grains) to the appropriate culture dishes (A,B, and C) on days 7, 14, 21, 35, and 42. Sample the cultures prior to adding the food.
On the appropriate sampling day, stir the material in the culture dish to be sampled and obtain a sample with a dropper. Prepare a wet mount. Observe the slide with the low power objective lens of your microscope. Count the number of each species assigned to you by your instructor. Each member of the group will be responsible for counting a different group of organisms.
To obtain an average number of organisms, do the following. Count the number of each species in each of five fields of view ( count in each of the four corners of the cover slip and one view in the center of the cover slip), add the total number, and divide by five. Record the numbers of each species for which you are responsible on the data table for your group.
Each group should turn in a completed data table on each sampling day to the instructor. Tallies of class averages will be compiled by the instructor for use in preparing a final lab report. Remember: you must sample all six dishes on each sampling day. Bacteria will appear in the culture dishes and may reach uncountable numbers. We will note only if the numbers appear to be low, medium, high, or very high.
Some generalizations you should try to make include:
In which culture dish did the greatest changes in numbers take place? Why?
Which organisms appeared to rise and decline the most? The least?
Which environmental factors were necessary for the survival of most organisms? What is the ideal temperature for survival with or without food?
Do photosynthesizers survive without food? If so, why?
Who is eating whom? Construct a food chain or web illustrating this.
Assuming that no new organisms were added each week when food was added,
account for the presence of more organisms in the culture dishes.
Did "new" types of organisms appear in later examinations of the cultures? If so, from where did these organisms come? From where did the bacteria come?
What causes successional changes to occur in a community?
Which physical and biological factors could have caused the succession in the culture dishes?
Why did we use a sampling technique to determine the population numbers of the various species?
Calculate the number of heating degree days.
Use the degree day formula to answer the next two questions.
Question 3: How many heating degree days accumulated on January 8th?
Question 4: How many heating degree days accumulated during the week?
A STEM ED Program at the University of Massachusetts, funded by the National Science Foundation and supported by the
Climate System Research Center in conjunction with the International Polar Year
Heating SeasonsTable 1
During the summer, very few days have an average temperature below 65º in most locations in the United States. Even so, heating seasons begin on July 1st of one year and ends on June 30th of the next calendar year so that a continuous sequence of cold weather months can be analyzed. .
Heating Degree Days Accumulate
Many newspapers publish heating degree day data that includes the number of heating degree days that accumulate in a day, a month, and a heating season. They often use a table similar to Data Table #2 shown below.
Data Table #2: Sample Heating Degree Day Data1CultureYesterday / Dish/Food / Environmental11
ASo far this month / 3 grains / Unlighted refrigerator (remove bulb)121
BSo far this heating season (since July 1st) / 3 grains / Lighted shelf in classroom ( 18-27 0C)605
CSo far in an average season (a 30 year average) / 3 grains / Lighted incubator (28-32 0C)561
D / none / Unlighted refrigerator
E / none / Lighted shelf in classroom
F / none / Lighted incubator
(Macro) Analyzing a Heating SeasonEcosystems and Climate
Climate, which is average weather conditions over a period of time, is the primary environmental influence on ecosystems. Plants, animals, insects and microbes are adapted to small changes in climate. However, climatic conditions vary widely over the earth. Organisms adapted to your state might not do well in a desert or tropical climate. Even extremes in your climate can result in destruction of some members of the ecosystem.
The two most important climatic factors for ecosystems are sunlight and water.
Sunlight is necessary for plants to grow, and to provide energy to warm the earth's atmosphere. Light intensity controls plant growth. Light duration affects plant flowering and animal/insect habits.
All living organisms require some amount of water. Organisms in dry ecosystems are adapted to the conditions by storing water for use over long periods or becoming less active. At the other maximum, some plants and animals only survive by being submersed in water.
The present heating season (so far) can be compared with a normal heating season using a ratio. The ratio can then be converted into a percentage formula. The symbol “HDD” will be used for heating degree days.There are three activities within this lab. Each one is designed to illustrate a different climate affect on plants.
Activity 1Sample Percentage Calculation
Materials Needed: Potting soil, three large styrofoam cups or small clay pots, three small tomato plants, florescent light or sunlight if available.
Using the potting soil, plant the three tomato plants in containers. If using styrofoam cups, poke small holes in the bottom for water drainage.
Number each plant 1 through 3. Allow each plant to have the following amounts of light per day:
- Number 1- no light
- Number 2- 6 hours
- Number 3- continuous light
Record the growth of each plant for 10 days. Give each plant equal amounts of water regularly, keeping the soil moist but not saturated.
This activity should show differences in plant growth with differences in light.
_ x _ = ___ HDD so far this heating season_____
100 HDD so far in an average heating season
x % = ___HDD so far this heating season ___ x 100
HDD so far in an average season
Heating degree data from Data Table #2 can be entered into the formula.
x % = ____605 HDD so far this heating season____ x 100
561 HDD so far in an average season
x% = 1.078 x 100 = 107.8%
The heating season represented in Data Table #2 is 7.8% colder than an average heating season.
After 10 days you should be able to answer the following questions:
1. Which tomato plant grew the most?
2. Which plant grew the least?
3. How does sunlight affect plant growth?
4. Are there ways that a location on earth would receive less sunlight
5. How would less sunlight affect an ecosystem?
Analyze the Present Heating Season
Data Table #3: Heating Degree Day DataYesterday (January 31, 2008)
So far this January
So far in the present heating season (since July 1st)
So far in an average season (a 30 year average)
Question 5: How does the present heating season (From July 1st, 2007 to January 31st, 2008) compare with a normal heating season?
How Far Are We Through the Heating Season?Activity 2
Materials Needed: Potting soil, two large styrofoam cups or clay pots, Kentucky Bluegrass seed.
Place potting soil in the cups or pots. If using styrofoam cups, poke small holes in the bottom for drainage.
Plant the bluegrass seed, and allow it to grow until it is three inches tall. While it is growing to this height, keep the soil moist, but not saturated. After the grass is three inches, try this experiment with Sample 1, do not water it. With Sample 2, water it enough to keep the grass growing vigorously. Complete this routine until Sample 1 is almost completely brown. Begin watering Sample 1 at this point until it is growing vigorously again.
A 30 year average of heating degree days accumulated during an entire heating season is indicated in the following table.