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1 The Web of Life Chapter 1 The Web of Life CONCEPT 1.1 Events in the natural world are interconnected. CONCEPT 1.2 Ecology is the scientific study of.

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Presentation on theme: "1 The Web of Life Chapter 1 The Web of Life CONCEPT 1.1 Events in the natural world are interconnected. CONCEPT 1.2 Ecology is the scientific study of."— Presentation transcript:

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2 1 The Web of Life

3 Chapter 1 The Web of Life CONCEPT 1.1 Events in the natural world are interconnected. CONCEPT 1.2 Ecology is the scientific study of interactions between organisms and their environment. CONCEPT 1.3 Ecologists evaluate competing hypotheses about natural systems with observations, experiments, and models.

4 Concept 1.1 Events in the natural world are interconnected.

5 Concept 1.1 Connections in Nature Even species that do not interact directly can be connected by shared environmental features. Ecologists ask questions about the natural world in order to understand these connections.

6 Introduction Humans have an enormous impact on the planet. It is important that we try to understand how natural systems work. Ecology is the scientific study of how organisms affect, and are affected by, other organisms and their environment.

7 Deformity and Decline in Amphibian Populations: A Case Study There is a high incidence of deformities in amphibians. Amphibian populations are declining worldwide.

8 Figure 1.2 Amphibians in Decline

9 Deformity and Decline in Amphibian Populations: A Case Study Amphibians are “biological indicators” of environmental problems. o Skin is permeable; pollutant molecules can pass through easily. o Eggs have no protective shell. o They spend part of their life on land and part in water—exposed to pollutants and UV in both environments.

10 Assignment Read material regarding Pacific Tree frogs in chapter 1 Pseudacris regilla

11 Ecology

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13 Concept 1.2 Ecology is “The scientific discipline that is concerned with the relationships between organisms and their past, present and future environments, both living and non-living.” Official ESA Definition* *August 2000 Annual Meeting of the Ecological Society of America

14 Official ESA Definition Understanding these relationships will explain the patterns of distribution and abundance we see in nature.

15 Key words used to define Ecology

16 Overview of Ecology Ecology is not “Environmentalism” Ecology is a Science o “The study of the patterns and processes that determine the distribution and abundance of organisms.” o Based on observations, hypotheses, empirical tests, theory, models and more tests!

17 Environmentalism Philosophical/social movement Based on idea that humans are “stewards” of nature A bit odd since humans are part of nature. We are simply the species that has the most effects on its environments. General public gets this mixed up with Ecology Not all environmentalists are ecologists and not all ecologists are environmentalists.

18 Concept 1.2 What Is Ecology? Ecology is the scientific study of interactions between organisms and their environment. Environmental science incorporates concepts from the natural sciences (including ecology) and the social sciences and focuses on how people affect the environment and how to address environmental problems.

19 Ecologist vs Environmental Scientist Environmental science is to Ecology as Engineering is to Physics.

20 Ecologists vs Naturalists Example: Consider the American Robin, Turdus migratorius Naturalist: Writes about behaviors, songs, giving feelings and impressions Ecologist: Asks, “What causes the robin’s behavior? Seeks to explain the natural history. Environmentalist: Seeks action to preserve the habitat of the robin.

21 Defining Ecology There are many variations on the definition of ecology, all sounding slightly different but kind of the same. If you ask 10 different Ecology professors, you will get 10 slightly different definitions of ecology. This tends to create CONFUSION among undergraduate students.

22 Definition 1 The scientific study of the interactions between organisms and their environments. From Ernst Haeckel (1869)

23 Defining Ecology Ernst Haeckel o The leading German disciple of Charles Darwin o Coined the term “Ecology” in 1869 o Originally used the Greek spelling Oecologie, and defined it as “the science of the relations of living organisms to the external world, their habitat, customs, energies, parasites, etc.”

24 Defining Ecology Haeckel derived the new label from the same root found in the older word “economy” (“Oekonomie”): the Greek oikos, referring originally to the family household and its daily operations and maintenance The reason was that at that time, people thought that national economic affairs could be understood as an extension of the housekeeper’s budget. Haeckel thought that the Earth constituted a single economic unit

25 Haeckel’s original Oikologie Based on Darwin’s Economy of Nature o The investigation of the total relations of the animal both to its inorganic and its organic environment; including, above all, its friendly and inimical relations with those animals and plants with which it comes directly or indirectly into contact. o Ecology is therefore the study of all those complex interrelations referred to by Darwin as the conditions of the struggle for existence.

26 Defining Ecology Plant Ecologists o Henry Chandler Cowles (USA) o Theory of dynamic vegetational succession o 1899 classic paper The ecological relations of the vegetation of the sand dunes of Lake Michigan

27 Defining Ecology Plant Ecologists o Arthur Tansley (UK) o Role of competition o 1904: ecology is defined as “those relations of plants, with their surroundings and with one another, which depend directly upon differences of habitat among plants.”

28 Defining Ecology Plant Ecologists o Frederick Clements (USA) o Concept of “climax” in succession o 1916: Plant Succession: An Analysis of the Develop- ment of Vegetation

29 Defining Ecology Animal Ecologists o Victor Shelford (USA) o Key early studies on succession in the Indiana dunes and on experimental physiological ecology. o Collaborated with F. Clements o Animal Communities in Temperate America as Illustrated in the Chicago Region: A Study in Animal Ecology (1913) o This paper inspired C. Elton's work on food webs.

30 Defining Ecology Animal Ecologists o Charles Elton (UK) - the food web and ecosystem o 1927: Ecology is the science “chiefly concerned with what may be called the sociology and economics of animals, rather than with the structural and other adaptations possessed by them.”

31 Defining Ecology Animal Ecologists o Herbert Andrewartha (Australia) o 1954: The Distribution and Abundance of Animals, with Louis Birch. o 1961: Ecology is “the scientific study of the distribution and abundance of organisms.”

32 Definition 2 (1972) Ecology is the scientific study of the interactions that determine the distribution and abundance of organisms. Charles Krebs. Studies migration and population dynamics in lemmings and other small mammals.

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34 But this leaves out the environment, which is everything outside the organism that influences it.

35 Kinds of explanations Proximal o This kind of explanation gives IMMEDIATE reasons for or understanding of phenomenon o Ecological in scope Ultimate o Explanation lies in the ecological experiences throughout evolutionary history o This kind of explanation is the evolutionary/long- term explanation Ecologists often look for both kinds of explanations

36 Ecology is a Science Tansley: o …ecology must move from the merely descriptive and unsystematic stage to the experimental or systematically planned “scientific analysis.” Clements: o …the bane of ecology is … the widespread feeling that anyone can do ecological work, regardless of preparation…

37 Ecology is a Science Ecology uses the Scientific method o Uses tools such as Observation Experimentation Mathematical modelling

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39 Experimental Design, Statistics, etc. A huge part of ecology is about asking a good question and designing a study with the right kind of observations, experiments and statistics to get a reliable answer. Both pure and applied Ecology use the Scientific method

40 Stats, experimental design, etc. Data interpretation requires the use of statistics o Data sets are often very large and complex. o Statistics allows us to express a mathematically tested level of confidence in the outcome of a study.

41 Concept 1.2 What Is Ecology? Early ecological views: o There is a “balance of nature” in which natural systems are stable and tend to return to an original state after disturbance. o Each species has a distinct role to play in maintaining that balance.

42 Concept 1.2 What Is Ecology? Ecologists now recognize that natural systems do not necessarily return to their original state after a disturbance, and seemingly random perturbations can play an important role. Evidence suggests that different species often respond in different ways to changing conditions.

43 Concept 1.2 What Is Ecology? Scientists now recognize that ecological interactions are more complex than previously thought. One view that has stood the test of time: Events in nature are inter-connected. A change in one part of an ecological system can alter other parts of that system.

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46 Concept 1.1 Connections in Nature Observation of Pacific tree frogs suggested that a parasite can cause deformities. Small glass beads implanted in tadpoles to mimic the effect of cysts of Ribeiroia ondatrae, a trematode flatworm, also produced deformities.

47 Concept 1.1 Connections in Nature Further studies: o Deformities of Pacific tree frogs occurred only in ponds that also had an aquatic snail, Helisoma tenuis, an intermediate host of the parasite. o All frogs with deformed limbs had Ribeiroia cysts.

48 Figure 1.3 The Life Cycle of Ribeiroia

49 Concept 1.1 Connections in Nature Controlled experiment : Experimental groups are compared with a control group that lacks the factor being tested. Tree frog eggs were exposed to Ribeiroia parasites in the lab. Four treatments: 0 (the control group), 16, 32, or 48 Ribeiroia parasites.

50 Figure 1.4 Parasites Can Cause Amphibian Deformities

51 Concept 1.1 Connections in Nature A field experiment: Six ponds, all with Ribeiroia, three with pesticide contamination. Wood frog tadpoles were placed in 6 cages in each pond; 3 had mesh size that allowed parasites to enter.

52 Figure 1.5 Do the Effects of Ribeiroia and Pesticides Interact in Nature?

53 Concept 1.1 Connections in Nature Hypothesis : Pesticides decrease the ability of frogs to resist infection by parasites. In another lab experiment, tadpoles reared in the presence of pesticides had fewer white blood cells (indicating a suppressed immune system) and a higher rate of Ribeiroia cyst formation.

54 Figure 1.6 Pesticides May Weaken Tadpole Immune Systems (Part 1)

55 Figure 1.6 Pesticides May Weaken Tadpole Immune Systems (Part 2)

56 Concept 1.1 Connections in Nature Synthetic pesticide use began in 1930s; use has increased dramatically. Amphibian exposure to pesticides has likely also increased, helping to explain the increase in limb deformities.

57 Concept 1.1 Connections in Nature Fertilizer use may also be a factor. o Fertilizer in runoff to ponds increases algal growth. o Snails that harbor Ribeiroia parasites eat algae. o Greater numbers of snails result in greater numbers of Ribeiroia parasites.

58 Concept 1.1 Connections in Nature When people alter one aspect of the environment, it can cause other changes that we do not intend or anticipate. When we increased use of pesticides and fertilizers, we did not intend to increase deformities in frogs, but we seem to have done just that.


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