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Transcript
Advanced Biology: Bahe & Deken Basic Ecology Chapter 1 Text Page - 1 - Advanced Biology: Bahe & Deken 1.1 - What is Ecology? Think back to your experiences at Drey Land. Think back especially to your experiences at Bio Drey Land. What do you remember? Do you remember all the work you did? What was the point of all this work? Do you remember the study of Sinking Creek? What was the point of this study? What was the point of the forest study? The point was for you to learn about the interactions between organisms and their environment. Ecology is the study of how living things interact with one another and with their nonliving environment. As we will find this semester, ecology is a critically important field of biology, with implications for all forms of life on Earth. The interactions between living organisms and the nonliving environment are two-way: 1) organisms are affected by their environment, and 2) an organism’s very presence and activities will change the environment. As an example, plants extract carbon dioxide from the air and emit oxygen in the process of making food for themselves (and in turn for organisms that eat them). Remember photosynthesis: 6CO2 + 6H20 C6H12O6 + 6O2 Ecologist study environmental interactions at several different levels (from a very narrow perspective to a very broad perspective). They may study at the organism level, population level, community level, or ecosystem level. At the organism level an ecologist would examine how one kind of organism interacts with the environment. At the population level an ecologist would examine how a group of the same species interacts with the environment. At the community level an ecologist would examine how groups of different species living in the same area Text Page - 2 - interact with the environment. At the ecosystem level an ecologist would examine both the living and nonliving factors in a certain area. The biotic components of an ecosystem include all of the living things making up a community. The abiotic components include all of the nonliving things in that environment. Questions at the organism level might include: How does an organism meet the challenges posed by its environment? How does the physiology of the organism meet these challenges? How does its behavior meet these challenges? Questions at the population level might include: What challenges limit species number in a certain population? How do members of the same species interact with one another? Questions at the community level might include: How do members of different species interact? What are the predator and prey relationships? Do groups of organisms benefit one another? Do they harm one another? Questions at the ecosystem level might include: How are chemicals cycled? How does energy flow in an environment? How do abiotic factors affect biotic factors? And vice versa? Ecologists studying at any of these levels use the scientific process: posing hypotheses and using observations and experiments to test these hypotheses. Ecologist may perform experiments in the controlled environment of a laboratory or in the field. Advanced Biology: Bahe & Deken What is a species? Organisms can be classified into species, or groups of organisms that resemble one another in appearance, behavior, chemistry, and genetic makeup. Some species reproduce asexually. Unicellular organisms, such as bacteria or amoeba, reproduce by dividing into two cells identical to one another as well as to the original parental cell. live on the soil and within the first meter or two. The thin layer from the lower atmosphere to the bottom of the oceans makes up the biosphere. Other than the need for the sun for warmth and for photosynthesis, the biosphere is selfcontained, or closed. Energy can enter the system but matter cannot (except for the occasional meteorite). Most organisms reproduced sexually, producing offspring by combining gametes, sperm and egg, from two separate parents. Each offspring will be a combination of characteristics from each parent and thus different from each parent and from any siblings (except for identical twins). This variation in the offspring increases the likelihood of species survival in the face of environmental change. Organisms that reproduce sexually are classified as members of the same species if, under natural conditions, they can breed with one another and if they can produce live, fertile offspring. 1.2 – The Biosphere – Home of Life “On that small blue-and-white planet below is everything that means anything to you. National boundaries and human artifacts no longer seem real. Only the biosphere, whole and home of life.” Apollo astronaut Rusty Schweickart. The biosphere is the sum of all the ecosystems on Earth. It includes part of the atmosphere called the troposphere, all of the water called the hydrosphere, and all of the soil that contains life called the lithosphere. Organisms live in the lower part of the atmosphere as well as in almost all the bodies of water on earth. Organisms Text Page - 3 - If you look at the stylized depiction of the Earth above you will notice its patchiness. On the global scale you notice the different continents and islands. On the regional scale you would notice the deserts, forests, grasslands, streams, lakes, etc. Even on a local scale you would notice that forests are a mixture of dense trees, small lakes, meandering streams, and open meadows. There is patchiness even on a smaller scale. For example, you would find that each stream has different habitats (specific environments in which organisms live). Each habitat has characteristic abiotic factors that determine what kinds of organisms will inhabit that environment – water depth, temperature, dissolved oxygen, pH, etc. The merging of two ecosystems in a transitional zone is called an ecotone. Ecotones contain a mixture of species from Advanced Biology: Bahe & Deken adjacent ecosystems and often species not found in either of the bordering ecosystems. 1.3 – Major Biomes of the Biosphere A biome is a large geographic terrestrial area with a characteristic climate and specific life forms, especially vegetation that is adapted to the climate. You are undoubtedly familiar with some biomes. The desert biome has very low rainfall and often very warm temperatures. Other examples of biomes are tropical rain forests, grasslands, taigas (TEYE guh), and deciduous forests. Each biome also has a characteristic set of plants and animals. Coniferous trees, pines, cedars, and spruces with moose, wolves, weasels, and black bear residing among the trees dominate the taiga biome. Biomes are not restricted to land, although watery regions are called aquatic life zones instead. The open-ocean, coral reefs, estuaries, and freshwater lakes are aquatic life zones. Text Page - 4 - The distribution of the biomes mainly depends on two climatic characteristics, annual rainfall and temperature variations. The same biome can occur in two different geographic locations (different continents) if the climatic characteristics are very similar. For example, deserts occur in North and South America, in Africa, in Asia, and in Australia. Biomes are characterized by the type of communities that live there not by specific populations. For example, the groups of species living in the Sahara desert in Africa and in the North American deserts are different but each species is adapted similarly to living in such a dry and warm environment. Separated biomes may look alike because of convergence, the evolution of similar traits that evolved independently in similar environments (we will discuss convergence more when we study evolution). Advanced Biology: Bahe & Deken Name: Questions 1. An ecologist monitoring the number of great apes in a wildlife refuge over a five-year period is studying ecology at which level? a. Individual b. Population c. Community d. Ecosystem 2. Which of the following is the most complex? a. community b. individual c. species d. ecosystem e. population 6. Is the following statement correct? Why or why not? A male horse and female donkey produce sterile offspring called a hinny. Because a horse and a donkey can successfully mate they are the same species. 7. What is a habitat? 3. Which of the following is not an abiotic factor that shapes ecosystems? a. soil minerals b. predators c. fire d. rainfall e. storms 4. Which of the following shows how biotic environmental factors can affect an organism? a. Maple trees will not grow in waterlogged soil. b. Some shrubs grow only where forest fires scorch their seeds. c. Trout will not live in shallow, warm water. d. Monarch butterflies live only where there are milkweed plants for food. 5. Biomes depend most on a. the plants and animals that live there. b. continental location. c. annual rainfall and temperature variations. d. solar energy and wind. Text Page - 5 - 8. What kinds of organisms live in an ecotone? Advanced Biology: Bahe & Deken Text Page - 6 - Advanced Biology: Bahe & Deken 1.4 Biodiversity To develop a meaningful understanding of life on Earth, we need to know more about species than their population size, such as the composition of species on Earth. In its simplest meaning biodiversity (or biological diversity) is the variety of life on Earth. Commonly biodiversity describes the number of species among various groups of organisms. It has been estimated that there may be between 5 and 50 million species in all; if so, many species are still to be found and described. Ecologists describe biodiversity on three levels: 1) Species diversity. All the species in a particular area, including singlecelled bacteria and protists as well as the species of the multicellular kingdoms (plants, fungi, and animals). 2) Genetic diversity. The genetic variation within members of a population, both among geographically separate populations and among individuals within single populations. 3) Ecosystem diversity. The different biological communities and their associations with the abiotic environment. Landscape diversity involves a group of interacting ecosystems; for example, there may be plains, mountains, and rivers. Of course, biodiversity is somewhat dependent on landscape diversity. By no means is biodiversity evenly distributed throughout the biosphere. Biodiversity is highest at the tropics, and it declines toward each pole on land, in freshwater, and in the ocean. In aquatic ecosystems a higher Text Page - 7 - degree of biodiversity is found in coral reefs than any other part of the ocean. Some regions of the world are called biodiversity hotspots because they contain an unusually large concentration of different species. These hotspots contain about 44% of all known higher plant species and 35% of all terrestrial vertebrate species but cover less than 1% of the Earth’s land area. The island of Madagascar, the Cape region of South Africa, Indonesia, the coast of California, and the Great Barrier Reef of Australia are all biodiversity hotspots. Currently there are only about 1.75 million species that have been described. As stated above the undescribed species probably number far more than those species that have been described. Amazingly, around 20,000 new species are described each year. Most birds, mammals, and temperate flowers are well known, while in groups such as insects, spiders, mites, nematodes, and fungi, the number of described species is still increasing at the rate of 1-2% per year. A huge number of these species have yet to be discovered, especially in the tropical rain forests. Of these known species, nearly 1,200 species in the United States and 30,000 species worldwide are in danger of extinction. Advanced Biology: Bahe & Deken Name: Questions Determine if the following statements is describing (a) species diversity, (b) genetic diversity, (c) ecosystem diversity, or (d) landscape diversity. Put the most appropriate letter next to each statement. 1. _______ Human hunters in the 1890s reduced the population of northern elephant seals in California to about 20 individuals. Since then, this mammal has become a protected species, and the population has grown back to over 30,000 members. However, in examining 24 genes in a representative sample of seals, researchers found no variation. 2. ________ In the 1830s Charles Darwin observed the Galapagos Islands off the coast of South America. He recorded the islands were home to many unique organisms, most of which were similar to, but different from, the plants and animals of the nearest mainland. 3. ________ North of the Missouri River Missouri is characterized by rolling hills, open, fertile plains, and well-watered prairie land. Southwest of the river the land is rough and hilly with deep, narrow valleys. Southeast of the river the land consists of alluvial plains. Short Answer 4. Describe the uneven distribution of diversity in the biosphere. Text Page - 8 - 5. What is the implication of uneven distribution for conservation biologists?