Leading Question: Rare Breeds: What makes them unique?
The fourth grade unit uses rare breeds and their uniqueness to explore several core concepts integral to the national science standards, with a special focus on the core concept of adaptation. Through slideshows, classroom research, field research, and accompanying activities, students delve into the subject of adaptation using rare breeds as a window for understanding.
Students use background material to gain a true appreciation of these animals, while simultaneously learning core science concepts. In this unit, students plan and carry out a field research project. If a field trip is not possible, on-line research is an alternative, or follow-up activity.
The leading question for this unit is simple. What makes rare breeds unique? Just looking at rare breed farm animals one can see that they look different from common breeds such as the black and white spotted Holstein cow and typical white Leghorn chicken. They have unique physical traits, such as multi-colored feathers, long hair, long horns or small stature.
But it takes deeper study to gain insight into these unique traits as specific adaptations. Adaptation is a challenging concept because it is abstract. The accessibility of rare breeds takes the mystery out of otherwise intimidating and sometimes confusing topic*. Rare breeds provide a wonderful opportunity for students to experience, research and understand adaptation first hand, while also learning about genetic diversity, human selection, traits that are inherited versus environmentally shaped, habitats, and structure and function in living systems.
Through exposure to multiple breeds and their unique traits, students learn to recognize diversity within a species. They learn more about particular species, as well as the animal kingdom, the environment, and human cultures. In closing, students consider the influence of humans on the development and continuation of rare breeds.
* Concerning heredity, younger middle-school students tend to focus on observable traits, "Understanding adaptation can be particularly troublesome at this level. Many students think adaptation means that individuals change in major ways in response to environmental changes (that is, if the environment changes, individual organisms deliberately adapt"). (Source: National Science Education Standards)
• Structure and Function in Living Systems
• Diversity and Adaptations of organisms
What is an adaptation: behavior, body structure. Specific animal adaptations
• Genetic diversity and human selection
• Form and Function
• Describe observed events.
• Develop questions on scientific topics
• Collect data for investigations.
• Compare observations of individual and group results.
Domestic species – such as chickens, cows, and horses – are not endangered and will probably never become extinct. Breeds within each of these species, however, may become rare and even extinct. This is due to changes in agriculture, which can be compared to a loss of habitat for wild animal species. Rare breeds help keep small farms viable. Small farms can use rare breeds for sustainable practices. Small farms play important roles in maintaining open space, clean water, and fresh air. The loss of farms that support rare breeds represents both an environmental and cultural loss.
Genetic Diversity and human selection: (from the General Introduction) There are a limited number of farm animal species (10-15) but within each species is a wide array of breeds with unique characteristics. Domestic species are divided into breeds, which are distinct and consistent groups of animals. Breeds are genetic units that have been shaped by environmental adaptation and by selection for the jobs people needed them to perform. Rare breeds are often uniquely adapted to specific environments, and may have useful characteristics not found in other breeds. Having a variety of breeds in each domestic species strengthens the overall health of the species. When we consider the animals' ability to adapt to the elements, disease and infestation, heavy weather or temperature extremes, human habits and land pressure issues, we begin to get an idea of the wealth of genetic diversity that exists in our rare breed animals.
A number of the domestic species, including cattle, goats, horses, pigs, sheep, and poultry were historically distributed over a large geographical area. Adaptation to different environments and human selection for different uses created many breeds within these species. (Some domesticated species, such as reindeer, were not widely distributed and did not become extensively differentiated into breeds. )
While domestication of animals took several thousand years, and distinct types have existed for many centuries, the development of breeds within each species has occurred primarily over the past two hundred years.
Over the course of development, breeds were generally isolated one from another, and they became genetically consistent. As a result, members of each breed are also consistent in appearance and behavior. When two members of a breed are bred together they reproduce this distinguishing type or breed. In other words, breeds "breed true. " The distinctiveness and predictability of breeds make them significant genetic resources within each farm animal species. This is the most important reason for conservation of rare breeds. Heritage breeds represent a tremendous genetic resource for the future.
Some groups of animals that are organized and promoted as breeds, however, are not really breeds in a genetic sense. Horse breeds that are defined simply by a certain color, for example, are not true genetic breeds. They are not consistent in appearance and behavior and cannot produce consistent offspring when bred together.
Adaptations of mammals and poultry are detectable by species when we look at such structures as: hooves, hair, feathers, beaks, etc
Adaptations by breed are evident when we research the origin of specific breeds. Then we see how they have adapted to specific climates. Cattle breeds, for example, serve as an excellent example of these adaptations. The long-haired highland cattle come from the high, wet, cold hills of Scotland. The thin-coated Florida Cracker lives in the hot, humid subtropical southern U. S.
In sheep, we see the adaptation of keeping the coat or shedding it. Hair sheep are so called because they shed their protective covering. Wool sheep are adapted to cold climates and need to be shorn to be rid of thick wool coats.
Adaptations that suit human needs can be seen in domestic livestock. The animal breeds that served desired purposes tended to be the ones humans nurtured along. One example of this is the Runner Duck. It is thought that these ducks had to walk to and from the rice paddies each day to stay with their human caretakers. The ducks with longer legs and the ability to keep up best with the humans tended to survive and reproduce. Long legs is an adaptation in this breed that is based on human selection.
Adaptation reflecting human selection – the Milking Devon is another example of non-evolutionary adjustment to the environmental and human-induced stressors of small farms and a limited food supply. Humans needed a multi-purpose animal who could pull a plow, give milk and be used for meat, while also being hardy and low-maintenance. These factors combined caused the small, useful Milking Devon to become the breed of choice selected over others.
Other types of adaptations include: Adaptation as a behavior – flighty and "leapy" versus lethargic sheep Adaptation as a characteristic – big ears for better hearing Adaptation as a process – Genetic change in the herd or flock over time
For a more in-depth look at examples and a complete description of adaptation, take a few minutes in advance of teaching this unit to view the slideshow. Adaptation2006.ppt
Sheep and goats, both wild and domestic, have horns. Cattle and other bovines, such as water buffalo, also have horns. Deer, elk, antelope, and other similar animals have antlers. Antlers are shed each year and horns are not shed. Horns and antlers are an adaptation.
Horns are hollow so they are not as heavy as they look. Both male and female animals can have horns, depending upon the breed and the species. Horns are always growing, and, in fact, there are annual rings in some species that represent the animal's age. The condition of an animal's horns can be a good indicator of its health and metabolism.
Animals use horns in many ways. These include:
• protection from predators (a defense strategy) • back scratching • bending and breaking trees in order to eat the leaves at the top • making holes in fences and opening up other spaces • butting other animals to determine social order and in play. Horns are designed to receive as well as give blows, so they protect the skull. This is the reason that horned and hornless animals are not generally kept together. • for display and prowess • regulation of head temperature by releasing excess heat when necessary
People have used horns to make buttons, cups, dippers, combs, handles, musical instruments, and many other useful and decorative items. Today, plastic is used for most of these.
"Polled" means naturally having no horns. Humans have selected some breeds of domestic animals to be polled. Animals of other breeds are routinely "de-horned" (or "de-budded," because "buds" of horns are removed). This is done in order to keep animals more closely together and to protect people and other animals from being injured or equipment from being damaged by horns.
People began to use animal fibers thousands of years ago, at first collecting fibers that had been shed by wild sheep. After sheep were domesticated, people selected for animals that bore more fiber and did not shed as readily so that the maximum amount of fiber could be harvested at one time. This was often done by plucking (or "rooing") sheep at shedding time. Today, only the most primitive breeds of sheep still shed their fleeces, and all other wool breeds must be sheared. (Some breeds of sheep do not have wool, but instead have hair, which is shed. These are called "hair sheep. ")
Historically, wool has been used for clothing, blankets, rugs, saddle and furniture stuffing, furniture coverings, insulation, wall hangings, and other decorations. Wool contains fat, called lanolin, which itself has a variety of uses. Wool varies in length, crimp (or curl), texture, diameter of individual fibers, amount of lanolin, and color. Over centuries, human breeders have cultivated this diversity through selection of many different breeds to meet a variety of practical needs and aesthetic goals.
Today, wool is used primarily for garments, carpets, blankets, and other textiles. There are new uses as well. For example, wool is being made into pads, mats, brooms, and mitts to be used in cleaning up oil spills. It can absorb ten to thirty times its weight in oil. The fact that wool is reusable and biodegradable may give it a significant cost advantage over the single-use synthetic materials now used. This practice has been used in Europe since the early 1990s and has been introduced to the U. S. It seems safe to say that wool has found another important role.
Natural fibers in addition to sheep's wool include cashmere and mohair from goats; angora from rabbits; silk from silkworms; camel's hair; wool from alpacas; and cotton, hemp, and linen from plants. Natural fibers continue to have aesthetic and practical qualities that are valuable and unique, even in these days when many things are made of synthetics.