5.7 Key deer: Evolution and species survival
Essential question: How does geological change influence biological evolution?
Students will gain an understanding of the theory of biological evolution and creation of species.
- Key deer handout
- U.S. map, large enough to display for students (If you have access to a computer with internet access and a projector, a Google map would be ideal.)
- Blank paper
- Colored pencils/markers
Time required for lesson
Approximately one class period (50-55 minutes)
(Note: The following background information also appears on the student handouts.)
The Key deer is a small, endangered deer native to the Florida Keys. Scientists believe that the Key deer (Odocoileus virginianus clavium) is a subspecies of the white-tailed deer (Odocoileus virginianus). According to the most commonly held theory, white-tailed deer migrated from the mainland to the Florida Keys during the most recent ice age, which peaked twenty thousand years ago. Because the seawater was locked up in glaciers, the sea level was lower and the Florida Keys were not a series of islands as they are today, but a continuous ridge of land.
As the glaciers receded ten thousand years ago, the water levels rose and the white-tailed deer were isolated on the islands we now call the Florida Keys. Scientists believe this isolation led to the Key deer’s distinctive small size: Through evolution, large mammal species isolated on islands typically become smaller over time, probably as an adaptation to the limited resources available. Thus, adult male Key deer weigh half as much as typical white-tailed deer and stand about 30 inches tall at the shoulder.
Over recent decades, the Key deer’s native habitat has been changing quickly with the rapid growth of human populations in the islands. The deer have struggled to adapt to these changes and, as a result, have become endangered. Some of the factors threatening Key deer populations include:
- Road kills: Increased traffic and the creation of more paved roads have led to an increase in Key deer killed by motor vehicles. In addition, illegal roadside feeding of Key deer by humans has led to more road deaths by encouraging the deer to approach roadways.
- Dogs: Free-roaming packs of dogs prey on fawns and chase adult deer to roadways where they’re killed by cars.
- Mosquito ditches: The Florida Keys are crisscrossed by narrow canals called mosquito ditches. The ditches are dug to provide a habitat for a species of African fish used to control the mosquito population. Unfortunately, the ditches can also trap Key deer. Although the deer can swim, they sometimes drown in the ditches when they fall in and can’t escape.
- Habitat loss and fragmentation: As more development comes to the Keys, the deer’s natural habitat is diminished. Additionally, development leads to the elimination of natural corridors that allow the deer to roam freely. As the deer become concentrated in fragmented parcels of habitat, they become more susceptible to disease.
See sources below.
- Anticipatory set: Ask the questions, “Why do animal species change over time?” and “How can animals adapt to environmental and geological changes?” Have students brainstorm possible answers. Discuss variations in species that result in adaption to changing environments. (Remember: biological evolution may result from variations which are caused by mutations or changes in the genetic make-up of a species. Adaptations are the usefulness of these genetic changes to the animal’s survival and the subsequent inheritance of these genes by offspring.)
- On a U.S. map, show students the location of the Florida Keys. Introduce the endangered species of deer known as the Key Deer (scientific name: Odocoileus virginianus clavium) that inhabits the Florida Keys. Read the background information to students, or have students read the information from their handouts.
- Discuss how geological changes influence evolutionary changes in animals.
- Have students complete the Key deer handout. Activities:
- Students consider what scientists, environmentalists, zoologists, and politicians can do to help ensure the survival of the Key deer species.
- Students suggest how the Key deer might evolve to adapt to the current challenges presented by their changing habitat.
- Extra credit: Students conduct research and construct a terrestrial food web for the Key deer’s habitat.
- Write the following four categories of professions on the board: Biological scientists; conservation scientists and foresters; elected officials and legislators; and environment, conservation, and wildlife advocates. Have students share their answers regarding how members of each profession might support the survival of the Key deer. Write their answers on the board. (See career information below.)
- Follow-up: Have students design a “Save the Key Deer” flier for the Key Deer Refuge in Florida. The fliers should include facts about how feeding the deer threatens their survival. Display the students’ fliers around the classroom.
Have students research and create evolutionary trees for the Key deer and other subspecies of animals in North America.
Career information comes from the Bureau of Labor Statistics’ Occupational Outlook Handbook.
- Biological scientists
- Biological scientists study living organisms and their relationship to the environment. They perform research to gain a better understanding of fundamental life processes or apply that understanding to developing new products or processes. Most specialize in one area of biology, such as zoology (the study of animals) or microbiology (the study of microscopic organisms).
- Conservation scientists and foresters
- Conservation scientists and foresters manage the use and development of forest and range lands and help to protect them. Some advise landowners on the use and management of their land. Conservation scientists and foresters often specialize in one area, such as wildlife management, soil conservation, urban forestry, pest management, native species, or forest economics.
- Elected officials and legislators
- Chief executives, general and operations managers, and legislators establish government policy and develop laws, rules, and regulations. They are elected or appointed officials who either preside over units of government or make laws. Chief executives include governors, lieutenant governors, mayors, and city managers. General and operations managers include district managers and revenue directors. Legislators include State senators and representatives, county commissioners, and city council members.
- Environment, conservation, and wildlife advocates
- Environment, conservation, and wildlife organizations promote the preservation and protection of the environment and wildlife. They address issues such as clean air and water; conserving and developing natural resources, including land, plant, water, and energy resources; and protecting and preserving wildlife and endangered species.
Supplementary information and sources
- Roger Di Silvestro, “What’s Killing the Key Deer?” National Wildlife, 35 (2), 1997.
- U.S. Fish and Wildlife Service National Key Deer Refuge website
- Florida Fish and Wildlife Conservation Commission, “Key Deer”
Optional resources for more information on the topics covered in this lesson
- USDA Living Science Careers
- The USDA describes careers in the living sciences, including information on hiring agencies, degree and practical experiences required, and classes to take in high school. Careers relevant to this lesson include conservation biologist, wildlife biologist, and forester.
- Ecology as a Career
- The Ecological Society of America tells students what ecologists do, what kinds of jobs there are, what kind of background students need, and the current job outlook.
- Evolution: Students
- The Evolution project features online lessons, videos, and a library of multimedia resources to help students understand evolution.
- Florida Key Deer
- This Florida website gives facts and information about the Key deer, including their habitat and how they have evolved and adapted to it.
North Carolina curriculum alignment
- Goal 5: The learner will conduct investigations and utilize appropriate technologies and information systems to build an understanding of evidence of evolution in organisms and landforms.
- Objective 5.02: Correlate evolutionary theories and processes:
- Objective 5.02: Correlate evolutionary theories and processes:
- North Carolina Essential Standards
- Science (2010)
- 8.L.3 Understand how organisms interact with and respond to the biotic and abiotic components of their environment. 8.L.3.1 Explain how factors such as food, water, shelter and space affect populations in an ecosystem. 8.L.3.2 Summarize the relationships among...
- 8.L.4 Understand the evolution of organisms and landforms based on evidence, theories and processes that impact the Earth over time. 8.L.4.1 Summarize the use of evidence drawn from geology, fossils, and comparative anatomy to form the basis for biological...
- Science (2010)