Why Are There Different Environments?

Understand the relationship between the climate of an area and the biome that it is in. Also, understand why rain falls in certain places and what that has to do with temperature.


Biomes

Here in Northeastern Ohio, we have four seasons: summer in June, July and August, winter in January, February and March. But this isn’t the case all over the world. Some places in the world have a very long winter and a short summer, like in northern Canada. Other places have a very long summer and a short winter, as in Sub-Saharan Africa. Obviously, Canada feels a lot different than Africa. We can see that temperature has a big effect on climate.

How sunlight hits the earth

Take another scenario: even though the temperatures and locations are very similar, Miami and Los Angeles are very different. Miami gets almost 5 feet of rain every year, while Los Angeles only receives slightly more than a foot of rain annually. Cleveland, by comparison, is in between Los Angeles and Miami at about 3 feet of precipitation per year. Los Angeles is in a climate that can be considered a desert but Miami is not. Precipitation (rain, snow, sleet, hail, etc.) also has a big effect on climate.

So what is climate? Climate is the group of conditions of the atmosphere near the earth’s surface at a certain place on Earth. We can say that the climate of East Cleveland is that we have warm, humid summers and cold, snowy winters. Of course, there is a lot more that we could say about the climate of East Cleveland, but that’s enough to start talking about biomes.

Deserts throughout the world

A biome is the combination of a particular climate and the living things on Earth that live in that climate. An easy way to describe a biome is to say what the temperatures, precipitation, plants and animals are in that particular biome. In our biome (temperate deciduous forest), we have a lot of deciduous trees, which are the ones that lose their leaves in fall. We also have plenty of grasses, small mammals, insects and a high population of humans.

Winds on Earth

A biome depends greatly on climate. Certain animals and plants cannot survive in certain climates: just like there can’t be evergreen trees in the desert, palm trees don’t survive well in Antarctica! Likewise, certain animals are adapted to certain biomes, but not other ones. It’s hard to imagine an elephant in a snowy field or a polar bear on a tropical island. Of course, if global warming continues, this type of situation may happen.

Speaking of global warming, it’s important to understand how certain parts of the world get more heat than others. The sun remains about the same distance away from the Earth all year, every year. What causes the change in seasons is the amount of direct sun that a certain area gets. Because the Earth is slightly tilted on its axis, the sunlight that we get in the summer is much more direct than the sunlight that we get in the winter. Summer is like shining a flashlight directly into someone’s eyes, and winter is like shining the flashlight from underneath your chin as if you were telling a scary ghost story. From the diagram, you can see that indirect sunlight gets spread out over the surface of Earth more than direct sunlight.

Precipitation, or when water falls from the atmosphere in any form, is caused by a combination of factors. The sunlight that hits the Earth and the rotation of the Earth both play a role in the winds that control Earth’s climate zones. From the diagram, you can see that winds take moisture away from certain parts of Earth and deliver precipitation to other parts. Depending on the temperature of that air, the precipitation will be rain, snow, or something in between.  And if global warming causes the temperature of the oceans to continue to rise, then more and more water will evaporate, causing more and more precipitation!

Questions
Remember
1. What is climate, in your own words?
2. State the relationship between climate and biomes.
3. List at least five different types of precipitation (you need to come up with one of them on your own).
Put it together
4. Support the following statement with two pieces of evidence (including pictures) from this chapter: “The equator is the hottest place on Earth.” One of your pieces of evidence must have to do with winds.
5. Why are most of the world's deserts around 30°N or 30°S latitude? Use the diagrams and pictures in this chapter to help illustrate your answer, including “How Sunlight Hits Earth” and “Winds on Earth”.
Think about it
6. Draw a diagram showing the Earth's axis and the United States during the four seasons in the northern hemisphere. Include the sun in the middle and show how direct the sunlight is in each season.
Review
7. Name one unsustainable behavior for each of farming, mining and timber.
8. What are the four major biotic roles in an energy pyramid?
9. For each of proteins, carbohydrates and lipids, list what foods they can be found in.
10. Name the four layers of the Earth and describe briefly what is inside each one.
Coniferous Forest

Temperature:

-40°C to 20°C, average summer temperature is 10°C

Precipitation:

300 to 900 millimeters of rain per year

Vegetation:

Coniferous-evergreen trees (trees that produce cones and needles; some needles remain on the trees all year long)

Location:

Canada, Europe, Asia, and the United States

Other:

Coniferous forest regions have cold, long, snowy winters, and warm, humid summers; well-defined seasons, at least four to six frost-free months

Description:

Between the tundra to the north and the deciduous forest to the south lies the large area of coniferous forest. One type of coniferous forest, the northern boreal forest, is found in 50° to 60°N latitudes. Another type, temperate coniferous forests, grows in lower latitudes of North America, Europe, and Asia, in the high elevations of mountains.

Coniferous forests consist mostly of conifers, trees that grow needles instead of leaves, and cones instead of flowers. Conifers tend to be evergreen, that is, they bear needles all year long. These adaptations help conifers survive in areas that are very cold or dry. Some of the more common conifers are spruces, pines, and firs.

Precipitation in coniferous forests varies from 300 to 900 mm annually, with some temperate coniferous forests receiving up to 2,000 mm. The amount of precipitation depends on the forest location. In the northern boreal forests, the winters are long, cold and dry, while the short summers are moderately warm and moist. In the lower latitudes, precipitation is more evenly distributed throughout the year.

Temperate Deciduous Forest

Temperature:

-30°C to 30°C, yearly average is 10°C, hot summers, cold winters

Precipitation:

750 to 1,500 mm of rain per year

Vegetation:

Broadleaf trees (oaks, maples, beeches), shrubs, perennial herbs, and mosses

Location:

Eastern United States, Canada, Europe, China, and Japan

Other:

Temperate deciduous forests are most notable because they go through four seasons. Leaves change color in autumn, fall off in the winter, and grow back in the spring; this adaptation allows plants to survive cold winters.

Example: Staunton, Virginia, United States

Description:

Temperate deciduous forests are located in the mid-latitude areas which means that they are found between the polar regions and the tropics. The deciduous forest regions are exposed to warm and cold air masses, which cause this area to have four seasons. The temperature varies widely from season to season with cold winters and hot, wet summers. The average yearly temperature is about 10°C. The areas in which deciduous forests are located get about 750 to 1,500 mm of precipitation spread fairly evenly throughout the year.

During the fall, trees change color and then lose their leaves. This is in preparation for the winter season. Because it gets so cold, the trees have adapted to the winter by going into a period of dormancy or sleep. They also have thick bark to protect them from the cold weather. Trees flower and grow during the spring and summer growing season.

Many different kinds of trees, shrubs, and herbs grow in deciduous forests. Most of the trees are broadleaf trees such as oak, maple, beech, hickory and chestnut. There are also several different kinds of plants like mountain laurel, azaleas and mosses that live on the shady forest floor where only small amounts of sunlight get through.

Desert


Temperature:

Average of 38°C (day), average of -3.9°C (night)

Precipitation:

About 250 mm of rain per year

Vegetation:

Cacti, small bushes, short grasses

Location:

Between 15° and 35° latitude (North and South of the equator); examples are Mojave, Sonoran, Chihuahua, and Great Basin (North America); Sahara (Africa); Negev (Middle East); and Gobi (Asia)

Other:

Perennials survive for several years by becoming dormant and flourishing when water is available. Annuals are referred to as ephemerals because some can complete an entire life cycle in weeks.

Example: El-Oasr el-Akhdar, Egypt

Description:

Desert biomes are the driest of all the biomes. In fact, the most important characteristic of a desert is that it receives very little rainfall. Most deserts receive less than 300 mm a year compared to rainforests, which receive over 2,000 mm. That means that the desert only gets 10 percent of the rain that a rainforest gets! The temperature in the desert can change drastically from day to night because the air is so dry that heat escapes rapidly at night. The daytime temperature averages 38°C while in some deserts it can get down to -4°C at night. The temperature also varies greatly depending on the location of the desert.

Since desert conditions are so severe, the plants that live there need to have adaptations to compensate for the lack of water. Some plants, such as cacti, store water in their stems and use it very slowly, while others like bushes conserve water by growing few leaves or by having large root systems to gather water or few leaves. Some desert plant species have a short life cycle of a few weeks that lasts only during periods of rain.

Grassland


Temperature:

Dependent on latitude, yearly range can be between -20°C to 30°C

Precipitation:

About 500 to 900 mm of rain per year

Vegetation:

Grasses (prairie clover, salvia, oats, wheat, barley, coneflowers)

Location:

The prairies of the Great Plains of North America, the pampas of South America, the veldt of South Africa, the steppes of Central Eurasia, and surrounding the deserts in Australia

Other:

Found on every continent except Antarctica

Example: Ingeniera White, Argentina

Description:

Grasslands are generally open and continuous, fairly flat areas of grass. They are often located between temperate forests at high latitudes and deserts at subtropical latitudes. Grasses vary in size from 2.1 m (7 ft) tall with roots extending down into the soil 1.8 m (6 ft), to the short grasses growing to a height of only 20 to 25 cm (8 to 10 in) tall. These short grasses can have roots that extend 1 m (about 3 ft) deep.

The height of grass correlates with the amount of rainfall it receives. Grasslands receive about 500 to 900 mm of rain per year compared to deserts, which receive less than 300 mm and tropical forests, which receive more than 2,000 mm. While temperatures are often extreme in some grasslands, the average temperatures are about -20°C to 30°C. Tropical grasslands have dry and wet seasons that remain warm all the time. Temperate grasslands have cold winters and warm summers with some rain.

The grasses die back to their roots annually and the soil and the sod protect the roots and the new buds from the cold of winter or dry conditions. A few trees may be found in this biome along the streams, but not many due to the lack of rainfall.

Oceans



Temperature:

An average of 3.8°C

Precipitation:

An estimated 398,000 cubic kilometers (95,000 cubic miles) of rain falls on the oceans each year.

Vegetation:

Zooplankton, algae

Location:

All over the world

Other:

Life on Earth is thought to have started in the oceans more than 3 billion years ago. Over 70 percent of the Earth’s surface is covered by water. Even though we refer to the Pacific, Atlantic, Indian, Arctic and Southern Oceans, it is really just one huge ocean!

Example: North Atlantic Ocean

Description:

The Pacific Ocean is the largest of the four main oceans. Although its name means peaceful, if can be very rough! It is 64 million square miles.

The Atlantic Ocean is the busiest. Many ships cross the Atlantic, carrying cargo between the Americas, Africa, and Europe. It is 32 million square miles.

The Indian Ocean is located in an area bordered by the continents of Asia, Africa, Antarctica, and Australia. It is 28 million square miles.

The Arctic Ocean is the smallest and coldest. It is 5 million square miles.

The average temperature of all oceans is about 39 degrees F (3.8 degrees C).

The average depth of all oceans is about 2.3 miles.

There are mountains, volcanoes, and deep trenches in the ocean.

Currents flow like rivers, carrying warm water from the tropics, and cold water from the north and south poles.

Tides change twice a day, all over the world, as the oceans rise and fall along the shoreline. Scientists think this is caused by the pull of the sun and moon on our earth.

Coral reefs are vast, rocky areas located in shallow, tropical waters. They are like the tropical rain forest of the ocean! The greatest variety of plant and animal life in the ocean live there. Coral reefs are formed from the bodies of small sea creatures called polyps.

Rainforest


Temperature:

20°C to 25°C, must remain warm and frost-free

Precipitation:

2,000 to 10,000 millimeters of rain per year

Vegetation:

Vines, palm trees, orchids, ferns

Location:

Between the Tropics of Cancer and Capricorn

Other:

There are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equator and temperate rainforests are found farther north near the coast. The majority of common houseplants come from the rainforest.

Example: Campa Pita, Belize

Description:

There are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equator where it is warm. Temperate rainforests are found near the cooler coastal areas further north or south of the equator.

The tropical rainforest is a hot, moist biome where it rains all year long. It is known for its dense canopies of vegetation that form three different layers. The top layer or canopy contains giant trees that grow to heights of 75 m (about 250 ft) or more. This layer of vegetation prevents much of the sunlight from reaching the ground. Thick, woody vines are also found in the canopy. They climb trees in the canopy to reach for sunlight. The middle layer, or understory, is made up of vines, smaller trees, ferns, and palms. A large number of plants from this level are used as common houseplants. Because of the small amount of sunlight and rainfall these plants receive, they adapt easily to home environments. The bottom layer or floor of the rainforest is covered with wet leaves and leaf litter. This material decomposes rapidly in the wet, warm conditions (like a compost pile) sending nutrients back into the soil. Few plants are found on the floor of the forest due to the lack of sunlight. However, the hot, moist atmosphere and all the dead plant material create the perfect conditions in which bacteria and other microorganisms can thrive.

Shrubland


Temperature:

Hot and dry in the summer, cool and moist in the winter

Precipitation:

200 to 1,000 mm of rain per year

Vegetation:

Aromatic herbs (sage, rosemary, thyme, oregano), shrubs, acacia, chamise, grasses

Location:

West coastal regions between 30° and 40° North and South latitude

Other:

Plants have adapted to fire caused by the frequent lightning that occurs in the hot, dry summers.

Example: Middelburg, South Africa

Description:

Shrublands include regions such as chaparral, woodland and savanna. Shrublands are the areas that are located in west coastal regions between 30° and 40° North and South latitude. Some of the places would include southern California, Chile, Mexico, areas surrounding the Mediterranean Sea, and southwest parts of Africa and Australia. These regions are usually found surrounding deserts and grasslands.

Shrublands usually get more rain than deserts and grasslands but less than forested areas. Shrublands typically receive between 200 to 1,000 millimeters of rain a year. This rain is unpredictable, varying from month to month. There is a noticeable dry season and wet season.

The shrublands are made up of shrubs or short trees. Many shrubs thrive on steep, rocky slopes. There is usually not enough rain to support tall trees. Shrublands are usually fairly open so grasses and other short plants grow between the shrubs.

In the areas with little rainfall, plants have adapted to drought-like conditions. Many plants have small, needle-like leaves that help to conserve water. Some have leaves with waxy coatings and leaves that reflect the sunlight. Several plants have developed fire-resistant adaptations to survive the frequent fires that occur during the dry season.

Tundra


Temperature:

-40°C to 18°C

Precipitation:

150 to 250 mm of rain per year

Vegetation:

Almost no trees due to short growing season and permafrost; lichens, mosses, grasses, sedges, shrubs

Location:

Regions south of the ice caps of the Arctic and extending across North America, Europe, and Siberia (high mountain tops)

Other:

Tundra comes from the Finnish word tunturia, meaning “treeless plain”; it is the coldest of the biomes

Example: Yakutsk, Russia

Description:

The tundra is the coldest of the biomes. It also receives low amounts of precipitation, making the tundra similar to a desert. Tundra is found in the regions just below the ice caps of the Arctic, extending across North America, to Europe, and Siberia in Asia. Much of Alaska and about half of Canada are in the tundra biome. Tundra is also found at the tops of very high mountains elsewhere in the world. Temperatures are frequently extremely cold, but can get warm in the summers.

Tundra winters are long, dark, and cold, with mean temperatures below 0°C for six to 10 months of the year. The temperatures are so cold that there is a layer of permanently frozen ground below the surface, called permafrost. This permafrost is a defining characteristic of the tundra biome. In the tundra summers, the top layer of soil thaws only a few inches down, providing a growing surface for the roots of vegetation.

Precipitation in the tundra totals 150 to 250 mm a year, including melted snow. That’s less than most of the world’s greatest deserts! Still, the tundra is usually a wet place because the low temperatures cause evaporation of water to be slow. Much of the arctic has rain and fog in the summers, and water gathers in bogs and ponds.

Vegetation in the tundra has adapted to the cold and the short growing season. Mosses, sedges, and lichens are common, while few trees grow in the tundra. The trees that do manage to grow stay close to the ground so they are insulated by snow during the cold winters.

Biome Display

You will make a free-standing biome display that meets the following characteristics:

  1. Biome Name, in letters at least 1 inch tall.
  2. A written description of the biome summarizing the biotic and abiotic factors.
    1. Can be single or double spaced. Length to be between 1/2 and 1 page.
  3. A chart of the average precipitation for one month, gathered for one year.
  4. A chart of the average temperature for one month, gathered for one year.
  5. A graph plotting temperature and precipitation on the same paper.
  6. Food web, using the common names (not pictures) of the common plants and animals found in the biome and include the following: Animals, green plants, fungus (by name), animals found near or in the ground, bacteria (by name)
  7. Construct a pyramid of energy for the biome using the names of common plants and animals you have researched.
  8. A labeled diagram of a typical soil profile of the biome.
  9. A map of North America with the biome colored or highlighted.
  10. List two organisms in that biome that illustrate mutualism.
  11. List two organisms in the biome that illustrate commensalism.
  12. List two organisms in the biome that illustrate parasitism.
  13. List a common example of interspecific competition.
  14. List National Parks and Monuments found in the biome. Tell the location (state, province, or country if outside Canada or the U.S.)
  15. Identify the main causes of environmental damage.
  16. Identify solutions that are developed or being developed to correct this environmental problem.
  17. Various pictures typical of your biome. May be photocopied and colored, may be originals which come from magazines (your own, not the schools) newspapers, and so forth, May be hand drawn or computer drawn.
Biomes & Climate
  1. Label the continents.
  2. Using the climograph for your biome:
    1. What is the average temperature in January? July?
    2. What is the average precipitation in April? October?
    3. In terms of temperature and precipitation, describe both summers and winters. For example, you could say that summers are very hot and very wet, while winters are frigid and very dry.
  3. In your group, research your assigned biome. You will need to look at all of the biomes in order to determine some of the following information:
    1. A specific place on Earth where this biome can be found
    2. On a scale of 1-4, how hot the biome is
    3. On a scale of 1-4, how greatly the temperature ranges
    4. On a scale of 1-4, how much precipitation the biome gets
    5. On a scale of 1-4, approximate height of vegetation
    6. A summary of this biome in less than 30 words
  4. Present your research from #3. As you present, other students will be filling out a biome strip and will place it in the correct place on the map.

Weekend Climate Tracking
  1. Keep track of the following over the weekend:
    1. Average temperature in the morning and the afternoon each day
    2. High and low temperature for the day
    3. Amount of precipitation each day
  2. Summarize the information in a climograph!
Biome Display for Temperate Deciduous Forest

You will make a free-standing biome display for the temperate deciduous forest that meets the following characteristics:

  1. Choose a place in the world that has the TDF.  Make this location your title.
  2. Make a written description of the location summarizing the biotic and abiotic factors.  Can be single or double spaced. Length to be 2 paragraphs (5 – 7 sentences per paragraph).
  3. A chart of the average precipitation for one month, gathered for one year, and average temperature for one month, gathered for one year.  Also, make a graph plotting temperature and precipitation on the same paper.  You can use http://rssWeather.com/ to help you.
  4. Construct a pyramid of energy for the biome using the names of common plants and animals you have researched.
  5. List two organisms in that biome that illustrate mutualism, two that illustrate commensalism, two that illustrate parasitism and an example of interspecific competition.
  6. Identify the 3 main causes of environmental damage in the location and solutions that are developed or being developed to correct this environmental problem.
  7. A picture typical of your location. May be photocopied and colored, may be originals which come from magazines, newspapers, or the internet.
Exponential Population Growth

From Stevens Institute of Technology

When looking at the growth of a population of any organism, it can seem to go up at a regular rate.  For example, take the approximate population in Cleveland between 1880 and 1930:

1880 	  160,146
1890 	  310,353
1900 	  460,768
1910 	  610,663
1920 	  760,841
1930 	  910,429

1. Every ten years, about how many people did Cleveland add?

2. What would you predict Cleveland’s population to be in 1940?

This type of growth is called linear growth.  Linear growth can result in large populations of organisms, but in a very predictable way.  On the other hand, populations can seem to go up at a regular rate but it may very quickly change.  For example, a viral infection may get worse in your body until it suddenly causes you to feel very sick, and you may pass out.

While a linear function can be used to model population growth that has a constant increase or decrease in the number of people, an exponential function can be used to model population growth that has a constant percentage change in population.  In other words, we use exponential functions to model increasingly increasing populations.

Exponential Function

f(t) = a * ebt

f(t) = population after t years
a = initial value
e = natural log
b = base or growth factor
t = time in years

3. Using the Exponential Function, find the following values for the final population:

a) When the initial population is 100, the growth factor is .02 (equal to 2%), and 5 years pass

b) When the initial population is 10,000, the growth factor is .01 (equal to 1%), and 10 years pass

c) When the initial population is 2, the growth factor is .10 (equal to 10%), and 10 years pass

4. From the U.S. Census Bureau’s Historical National Population Estimates, 1900 to 1999, record the estimated national population in 1999 and the estimated average annual percent change (growth rate given in percent) for that year.  Using the 1999 data, predict the population in:

a) 2000

b) 2010

c) 10,000 A.D. (Yes, the year 10,000!)

5. Compare your results to the estimated values given in the International Database (IDB) Summary Demographic Data for the U.S. as well as the U.S. Population Clock.

a) How close were your results?

b) Why might they be different?

6. From the IDB, find a country other than the United States.  Find its current population and its growth rate, then predict the population in:

a) 2011

b) 2020

c) 10,000

7. From what you’ve learned:

a) Is this exponential model good for predicting population in the short term?

b) In the long term?

c) What about over thousands of years?

Which Biome?

You may think of biomes as a scientific idea, with little connection to you. But how you experience life is connected to the biome in which you live. Are your winters warm or cold? Are your summers so hot that it’s hard to stay outside? What kinds of plants and animals do you find in your environment? All these aspects of your life are related to the biome in which you live. Three numbers help define your biome. The first number indicates where you are in the world, the latitude of where you live. The second is the amount of precipitation. The third is temperature.

Ecologists typically work with temperature and precipitation when they study climate. The graph shows monthly average temperatures over the course of a year for two locations. In Location A, the total precipitation for the year was 273 cm. The total precipitation for the year was 11 cm in Location B.

predatorprey3

Analyze and Conclude

  1. Which variable is plotted on the horizontal axis? Which variable is plotted on the vertical axis?
  2. During which months do both locations have almost the same average temperature? How can you tell?
  3. When are the highest and lowest average temperatures in Location A? In Location B? What are these temperatures?
  4. How would your understanding of the climate be different if the only temperature data you had was a yearly average? Hint: Use the graph to estimate the average yearly temperature. Compare that temperature with the highest and lowest temperatures from Question 3.
  5. Suppose you were going to spend a year in Location A. What type of clothes would you pack and why? Recall that this location gets about 273 cm of precipitation in a year. What form will this precipitation take? Hint: Use this memory device to help: When it’s 0, it’s freezing. When it’s 10, it’s not. When it’s 20, it’s warm. When it’s 30, it’s hot.
  6. In which biome would you expect to find each location? Why?

Build Science Skills

You are going to use the graph grid on the next page to make a climate diagram that shows the monthly averages for both temperature and precipitation. Ask your teacher whether you should (1) collect temperature and precipitation data for your area and record it in the table below or (2) use the data provided for Austin, Texas. Remember to include a title for your diagram. Hint: Use the climate diagrams in your textbook as a model.

After you are done, answer the following questions. What biome do you live in? What does the biome tell you about the plants and animals you share the environment with?

 

Location:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Average Temperature (°C)

Average Precipitation (mm)

 

Location: Austin, Texas

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Average Temperature (°C)

10

13

17

21

24

27

29

29

27

21

15

11

Average Precipitation (mm)

48

51

54

64

128

97

50

59

74

101

68

62

 

The Geography of Malaria

There is an interesting connection between malaria and sickle cell disease. Malaria is an infectious disease. It is caused by a parasite that infects red blood cells. Malaria is transmitted by mosquitoes and can be fatal, especially for children.

Sickle cell disease is a genetic disorder. A person with an allele for the sickle cell trait produces red blood cells that are sickle shaped. These cells cannot deliver as much oxygen to body tissues as normal red blood cells can. A person who is homozygous for sickle cell disease will suffer from damage to different organs and will require ongoing treatment.

People who carry one copy of the allele for sickle cell disease usually do not show signs of sickle cell disease. They are also highly resistant to malaria. The connection between the two diseases became clear when maps showing the distribution of both were put side by side. The dark regions on Map 1 show places where malaria is common. On Map 2, the dark regions show places where many people have the sickle cell allele.

malaria

Analyze and Conclude

  1. According to Map 1, where is malaria common? According to Map 2, where is it common for people to have the sickle cell allele?
  2. What do you observe about areas where malaria is common and areas where the sickle cell allele is found?
  3. In 1805, a Scottish explorer named Mungo Park led an expedition of European geographers in Africa. Forty-five Europeans began the journey. While they were in Africa, most of the Europeans died from malaria. Their native African guides survived. Why do you think the guides survived?
  4. According to Map 2, the sickle cell allele is not common in people native to southern Africa. Form a hypothesis that could explain this fact.

Build Science Skills

The sickle cell allele may have become common in African populations as an adaptation to the malaria parasite. After the mutated sickle cell allele appeared in a population, individuals who carried it were more likely to survive malaria. Therefore, they were more likely to reproduce and pass the allele onto their children.

Draw two Punnett squares. In the first, show a cross between a carrier of the sickle cell allele and a person without the allele. In the second, show a cross between two people who are carriers of the allele. Describe the phenotypes that would likely result from each cross. Use S to represent the sickle cell allele and s to represent the normal allele.