In the classroom students learn about inherited traits. In the field, students examine the traits of juniper trees and play a game to model how the environment can act on traits and affect how trees appear. Students also examine kit fox traits and play a game to discover what happens when a trait provides an advantage for survival.
Essential Question: How do traits affect the survival of plants and animals? Utah Science with Engineering Education Standards: Strand 3.2: Effects of Traits on Survival Organisms (plants and animals, including humans) have unique and diverse life cycles, but they all follow a pattern of birth, growth, reproduction, and death. Different organisms vary in how they look and function because they have different inherited traits. An organism’s traits are inherited from its parents and can be influenced by the environment. Variations in traits between individuals in a population may provide advantages in surviving and reproducing in particular environments. When the environment changes, some organisms have traits that allow them to survive, some move to new locations, and some do not survive. Humans can design solutions to reduce the impact of environmental changes on organisms.
Standard 3.2.3 Construct an explanation that the environment can affect the traits of an organism. Standard 3.2.4 Construct an explanation showing how variations in traits and behaviors can affect the ability of an individual to survive and reproduce.
Background
Traits are characteristics inherited from parents. The traits passed down can be influenced by the environment. Some traits are more common in a population than others. Each individual has many traits in common with others of the same species. Different organisms vary in how they appear and function because they also have different inherited traits. An individual’s overall combination of traits makes them unique. For example, every individual human has their own unique set of traits. Variations between individuals in a population may provide advantages for surviving and reproducing in particular environments. For example, juniper trees have different capacities for producing a waxy outer coating on their needles and berries. Some individuals produce a heavy waxy coating and others a thin coating. In a drought or if the climate becomes more dry, plants with thicker wax coverings dry more slowly than those with thinner coatings, making them more likely to survive to set a crop of seeds. These traits are passed onto succeeding generations because those with the best protection against drying will survive and reproduce. In reality, plants possess a whole range of traits that work together. The population, not the individual, adapts. When the environment changes, some organisms have traits that allow them to survive, some move to new locations, and some do not survive. The Utah juniper (Juniperus osteosperma), along with the pinyon pine, forms the most prevalent plant community of the Colorado Plateau—the pinyon-juniper woodland—between 4,500 and 7,000 feet above sea level. Junipers can be identified by their bark, leaves, and fruit. Their bark is gray or light brown and often hangs in loose, fibrous strips. Leaves are dark green, flat and scaly and do not drop in the fall. Their fruit is technically a tiny pinecone. This pea-sized light blue berry contains one or two seeds and is covered with a drought-resistant waxy coating. Junipers can withstand drought conditions that often kill other plants and trees. Their hidden secret is a massive underground root system, which accounts for two-thirds of a tree’s total mass. A juniper’s taproot can penetrate 40 feet straight down in search of water. It also sends out lateral roots, which may reach 100 feet or more from the tree. The roots are especially hardy. Even when knocked over by wind, junipers often continue to grow. Junipers can self-prune some branches to conserve water and ensure the survival of the tree. Junipers grow very slowly, usually only about 0.05 inches in diameter per year. A juniper standing only five feet tall may be 50 years old. Under severe conditions, Utah juniper trees persist in stunted forms. A 6-inch tree with a 24-inch taproot may also be over 50 years old. Junipers typically live from 350 to 700 years. No two junipers ever seem to look alike. Some are bushy, some have multiple trunks, and many have poorly formed crowns that are a mixture of live and dead branches. After they reach 30 years old, Utah junipers produce abundant seeds most years. Because seeds contain dormant embryos and impermeable seed coats, they need a period of “after-ripening” and usually germinate the second season following maturity. The seeds are long-lived. In one study, 17% of Utah juniper seeds germinated after 45 years. In general, around 8 to 49% of seeds germinate. Kit Foxes (Vulpes macrotis) are the smallest canid in North America. They are buff-colored with large, bushy, black-tipped tails roughly one third of their total length. Typical kit foxes weigh 4 or 5 pounds and stand about a foot tall at the shoulder. They have large ears, big eyes, furry feet, and a very narrow pointy muzzle. Kit foxes dig multiple dens and are the only canines to use dens year-round. They use their claws to dig dens in the sandy areas of grasslands and desert scrub. They are nocturnal. Retreating to the relative coolness and humidity underground during the day helps them to survive in hot, arid environments. Kit foxes prey mainly on kangaroo rats and rabbits; however, they also eat reptiles, ground-nesting birds, insects, and very little plant material. They use their keen senses of smell and hearing to find occupied burrows, which they dig into to catch mice or ground squirrels. They chase down rabbits and pounce on grasshoppers. Kit Foxes can survive long periods without water, gaining what they need from the blood and moisture in their prey.
