3 Chapter 2: Ecological Concepts Use with fishing skills FLY TYING and READING THE WATER. New Ideas · Competition · Picturing Ecosystems o Handout or Overhead: Three Ways of Looking at an Ecosystem, p. 7 Activities Activity #1: Stream Sense, p. 9 Activity #2: Connect the Critters, p. 11 o Handout: Connect the Critters, p. 13 Introduction A basic understanding of ecology will make conservation education much more interesting and productive. Scientific research, especially in biology, always begins with careful observation and the question, “why?” Activity #1, Stream Sense (p. 9), is designed to cultivate close observation and analogy-drawing skills. It hones the senses that are at the root of biological investigation. Ecological concepts are best taught the same way. Teaching Tips Use students’ own observations and insights to fuel discovery and discussion. This section includes a few important definitions, but once students understand them, it is intuitive and fun. Some Definitions Ecology is the study of organisms (living things) and their environments. It is concerned with ecosystems, populations of interacting organisms and their habitats. The population is the basic functional unit of an ecosystem, a group of organisms of the same species living together in a specific area. Habitat means “home.” It is the physical space in which an organism lives, both its non-living and living elements. For example, a rainbow trout might live in a particular stretch of a freestone stream. Its habitat includes the water, the rocks, and the fallen tree that creates the eddy from which it feeds. It might share the habitat with other organisms, like weeds or diving beetles. Competition Ecological niche includes habitat, but is a more complete description of an organism’s lifestyle. Niche is made up of habitat, food, climate, and behavioral factors, like what time of day something feeds or when its mating season is. Many species can share the same habitat, but in a given habitat, each species has a unique niche. When different organisms’ niches overlap, e.g. when rainbow trout are introduced into golden trout habitat, they compete for resources. Sometimes animals compete by physically 4 fighting. Other times, one species is just better at exploiting the resource than the other, so that the weaker species cannot reproduce as much. Two species with partially overlapping niches can live in the same habitat, even if they eat the same things. Two species whose niches completely overlap cannot coexist; one will always be driven to extinction. Brown and rainbow trout often coexist in a single stream habitat, but they behave differently. Compared to rainbow trout, browns tend to choose lies (sites from which to feed) that are closer to the bottom of the stream, and in slower-flowing water. (In addition to being a good example of partial niche overlap, this is part of the reason that brown trout are more difficult to catch than rainbows are.) In contrast, golden trout are in big trouble, because rainbow trout have been introduced to their habitat in the Little Kern River drainage. Because of geological barriers, golden trout evolved without competition from other trout species. Now competition (plus hybridization) with introduced rainbow trout is such a problem that the Little Kern golden trout is endangered. Rainbow trout are very closely related to golden trout, and their niches overlap completely. The two species cannot coexist forever. The preceding examples were all types of interspecific competition, competition between different species. Organisms also experience intraspecific competition, competition with members of their own species. There is intraspecific competition for food, like farm animals shoving to get to a trough, but the phenomenon is often most apparent when animals are mating. Every male trout wants to mate as many times as possible, but there is only about 1 female per male, so males often have physical confrontations to determine who will get to mate with a female who has prepared a redd (nest). (See Ch. 5, Trout Behavior and Biology.) Picturing Ecosystems Use the handout Three Ways of Describing an Ecosystem (p. 7) to illustrate the terms in this section. Competition is one important type of interaction. Another very important one is consumption, or feeding. We often describe organisms as producers and consumers, or as predators and prey. A producer is an organism that creates its own food (chemical energy) from the sun (light energy). Plants, like algae and green plants, are producers. Primary consumers get energy by eating producers. A predator is a secondary consumer, one that eats other consumers. We use the idea of a food chain to describe the way these relationships fit together. For example, algae (the producer) grows turns sunlight into carbohydrate, which is eaten by a caddis larva (the primary consumer). The caddis is eaten by a damselfly (the secondary consumer), which is in turn eaten by a minnow, which is finally eaten by a trout (the top, or climax, consumer). Organisms are linked together by food chains, and these chains get woven into food webs. Even though there are a few cases in which one organism can only eat a single species, those restricted interactions get drawn into more complicated relationships. That’s not as boring as it sounds. For example, sea urchins can only eat one kind of brown kelp, but they get eaten by both sea otters and sea turtles, which both eat all sorts of different things. Students can play Activity #2, Connect the Critters (11), to see how convoluted things can get. Another way of picturing the interactions between organisms is with an energy pyramid. It is obvious that when one organism eats another, there’s a transfer of matter, 5 but the real story, a hidden story, is that there is a transfer of energy every time an organism eats. This transfer is less than 100% efficient; not all the food energy a moth ingests gets passed on to the frog that eventually eats it. Growing, finding food, escaping from predators, and keeping warm (for warm-blooded animals) all take energy that is “burned off,” i.e. that does not get passed on. A rule of thumb people sometimes use is that just 10% of the energy at one level of an energy pyramid gets passed on to the next level. That’s why there are millions of plants, thousands of mice, and just a few pumas. The amount of energy available to a top consumer is much smaller than all the light energy available to green plants. Extensions and Resources These are surface treatments of very complex topics. Resources abound for teaching ecology, especially as it applies to the environment. · The Private Eye is a program that uses jeweler’s loupes as a tool to develop close observation and analogizing skills. It is very interdisciplinary and applies them to science, art, and writing. · Flying Turtle is a very kid-friendly ecology website, but the writing is very lively, and the drawings are clever enough to keep teens and adults interested. The home page is http://www.ftexploring.com/index.html An in-depth discussion of energy and ecosystems begins at http://www.ftexploring.com/photosyn/photosynth.html. Discussion Questions · Do you think it is important to preserve threatened and endangered species? Why? What is the value of biodiversity? · What is a keystone predator? Why might removing a top predator like trout from an ecosystem be more damaging than removing a species of primary consumer? 6 7 Three Ways of Describing an Ecosystem Producer (green algae) Primary consumer (caddis larva) Secondary consumer (dragonfly) Predator (chub minnow) Top predator (trout) Food Chain Energy Pyramid Food Web Trout, caddis larva, mayflies, and dragonfly by Andy Cooper Caddis adult, chubb minnow, and damselfly by Bob White, Essential Fly Fishing by Tom Meade, http://www.tutv.org89 Activity #1: Stream Sense Introduction This field trip activity helps students discover how their senses provide them with details about stream ecosystems. By making careful observations, students experience how their other senses (besides sight) provide them with additional information about the environment. Safety rules MUST be followed when students explore a stream. Time: 1hr. on-stream, plus discussion Ages: all ages Materials · Pencil and stiff-backed notepad or journal for each student · Optional materials: o Camera o Tape recorder o Binoculars o Magnifying lenses o Sample foods (edible plants and seeds) that could be found near a stream o Spray bottle Prep Work: Instructor should visit field trip site prior to activity. (See Stream Walk Safety Rules below.) Stream Walk Safety Rules Teacher Responsibilities 1. Visit the stream first to determine if it is safe for students to visit. Check stream depth, velocity, and temperature. Also look for walking conditions, potentially dangerous wildlife, poisonous plants, etc. 2. Bring along a first-aid kit. 3. Define stream walk boundaries; make sure students understand that staying within the boundaries protects wildlife and students. 4. Locate a place where students can wash hands after the visit. Rules for Students 1. Students should stay with their assigned buddies. 2. Students should wear old athletic shoes or boots because they will likely get wet and muddy. 3. Students should not enter the stream without supervision. 4. Students should not touch wildlife or taste anything (plants or water) unless permitted by teacher. 10 Procedure 1. Tell students they will be visiting a stream and will be recording how they use their senses to observe the stream. Discuss the Stream Walk Safety Rules. 2. Ask students to record their observations. Students should write things down or draw things as they perceive them. 3. Throughout the trip, remind students about using multiple senses. Ask students to find a quiet spot near the stream and have them sit very still to look, smell, listen, and feel. Older students may want to sit for 15 minutes or more, while for younger children, 2 or 3 minutes is probably enough. Students may want to take photographs or tape record sounds in addition to writing and drawing. 4. Other sensory activities that students could do at the stream include the following: · Have them block one or more of their senses (e.g., close their eyes, cover their ears, plug their noses). How does this affect their other senses? Did students hear better when they could not see? · Have students guide a blindfolded partner to his or her quiet site. Have the blindfolded partner recall sounds, smells, and feelings he or she experienced along the way. · Supply students with ways to improve the ability of their senses (e.g., use binoculars, spray water on their noses [moisture traps scent particles], cup their hands behind their ears). Discussion Questions to ask during or after the stream visit. Sight: What plants and animals do they see? Does the appearance of the stream vary with location? Is the stream fast or slow moving? How can they determine its speed? Sound: What sounds does the stream make? Can they hear animals? What does the wind sound like? Smell: How do smells near the stream compare to those on a road or in a home? Does the water smell the same as tap water? Touch: What does the stream water feel like? How does soil near the stream feel compared to soil in the woods or schoolyard? Are the rocks in the stream smooth or rough? Extensions This activity might be used as an introduction to a stream or watershed that students would later work with in greater depth. Later visits might involve Activity #8, Stream Safari (p. 35) and Activity #9, Water Quality Bioassessment (p. 39) or using the Water Quality Conditions, Land Use Conditions, and Physical Conditions worksheets (pp. 87-92) to investigate the water quality. Adapted from Project WET Curriculum & Activity Guide, “Stream Sense,” pp. 191-3 11 Activity #2: Connect the Critters Introduction This is a fun, quick activity for younger kids. It will also provide insights for later discussions of ideas like biomagnification. Time: approx. 30 min. Ages: up to 6th grade Materials · A copy of the Connect the Critters handout (p. 13) per student · Crayons, markers, or colored pencils Prep Work: gather materials Procedure 1. Ask for student input; as a class, point out each producer. Have students circle each producer with a green crayon. 2. As a class, find the primary consumers. Circle them with another color. Do the same for secondary and tertiary predators. 3. Now have students draw arrows pointing from “eat-en” to “eat-er,” i.e. from plant to herbivore, or consumer to predator. 4. When students are finished, examine drawings as a class. Ask students to think about the assignment as you work through the discussion questions. Discussion · Were any animals circled with more than one color? Discuss the terms herbivore (plant-eater), carnivore (meat-eater), and omnivore (plant and meat-eater). · Is the flow of energy in an ecosystem at all similar to the flow of water in the water cycle? How is it different? · What happens when one organism is removed? How many of the arrows would disappear? How many animals fed on it? · What would happen if a poison was introduced to the web at the level of the producers or some of the primary consumers? Introduce the idea of biomagnification. 12 13 Connect the Critters Andy Cooper:Mayfly, dragonfly, brown trout, caddis Bob White (http://www.tutv.org/general/general_html/trout_food.html): caddisfly, grasshopper, chubb minnow Mouse from http://mammary.nih.gov/services/news.html Draw arrows showing the flow of food, or energy, in this riparian/aquatic community. How many links can you draw? What happens if you remove one member of the ecosystem? How many other organisms lose part of their food supply? Is this ecosystem representative of a real one?14