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Rick Relyea · Robert Ricklefs

The Economy of Nature
7th edition

Lecture PowerPoint
Chapter 1

Introduction: Ecology,
Evolution, and the
Scientific Method
© 2014 by W. H. Freeman and Company

What is ecology?
Ecology is the scientific study of the abundance and
distribution of organisms in relation to other organisms
and environmental conditions.

Chapter 1 concepts

1
2

Ecological systems exist in a hierarchical
organization.
Ecological systems are governed by physical
and biological principles.

3

Different organisms play diverse roles in
ecological systems.

4

Scientists use several approaches to studying
ecology.

5

Humans influence ecological systems.

Ecological systems are governed by physical and biological principles. 4 Scientists use several approaches to studying ecology.Chapter 1 concepts 1 2 Ecological systems exist in a hierarchical organization. 3 Different organisms play diverse roles in ecological systems. . 5 Humans influence ecological systems.

1 Ecological systems Biological entities that have their own internal processes and interact with their external surroundings Ecosystem Community Population Individual Biosphere .

.1 Individuals Individual: the most fundamental unit of ecology. there are many definitions of species. and produce waste. Individuals acquire nutrients and energy. This definition is not universal. Species: individuals that are capable of interbreeding or share genetic similarity.

or genetics. gender. forest edges) or political (e. . Density is the number of individuals per unit area..g.1 Populations Population: individuals of the same species living in a particular area.. Abundance is the total number of individuals.g. state lines). Composition is the makeup in terms of age. Boundaries can be natural (e.

Boundaries are not always rigid.1 Communities Community: Populations of species living together in a particular area. and may cover small or large areas. . such as predation and competition. Includes many types of interactions.

Boundaries are often not distinct. such as carbon. Research is focused on movement of energy and matter between physical and biological components. hydrogen. . oxygen. and phosphorus. nitrogen.1 Ecosystems Ecosystem: communities of lorganisms interacting with their nonliving physical and chemical environments. This includes the “flow” of material from “pools” of elements.

Distant ecosystems are linked together by exchanges of wind and water and by the movement of organisms.1 The biosphere Biosphere: all ecosystems on Earth. .

or characteristics of an individual’s morphology. density.1 Studying ecology at different levels Individual approach: Understands how adaptations. Population approach: Examines variation in the number. physiology. Community approach: Understands the diversity and interactions of organisms living together in the same place. and behavior enable it to survive in an environment. Ecosystem approach: Describes the storage and transfer of energy and matter. . and composition of individuals over time and space.

.Chapter 1 concepts 1 2 Ecological systems exist in a hierarchical organization. 3 Different organisms play diverse roles in ecological systems. Ecological systems are governed by physical and biological principles. 4 Scientists use several approaches to studying ecology. 5 Humans influence ecological systems.

A dynamic steady state occurs when gains and losses are in balance. first law of thermodynamics). Gains Losses . but can change form (i.e. law of conservation of matter..2 Governing principles of ecology Matter and energy cannot be created or destroyed. Ecological systems gain and lose matter and energy.

behavior.g. determines an organism’s phenotype. Evolution: a change in the genetic composition of a population over time. . morphology).2 Evolution Phenotype: an attribute of an organism (e.. Genotype: the set of genes an organism carries.

Individuals vary in their traits.2 Evolution Natural selection: A change in the frequency of genes in a population through differential survival and reproduction of individuals that possess certain phenotypes. Three requirements 1. and that phenotype will come to dominate. Variation in traits causes some individuals to experience higher fitness (survival and reproduction). Individuals with better fitness will pass more copies of their genes to the next generation. 3. 2. Traits are heritable. .

subsequent generations of caterpillars will have more and more individuals better matched to twig color. If color is heritable.2 Evolution Natural selection: Example Caterpillars with body color that better matches the twig are less likely to be eaten. .

Ecological systems are governed by physical and biological principles. 3 Different organisms play diverse roles in ecological systems.Chapter 1 concepts 1 2 Ecological systems exist in a hierarchical organization. . 5 Humans influence ecological systems. 4 Scientists use several approaches to studying ecology.

Cyanobacteria can photosynthesize.3 Evolutionary patterns First organisms were prokaryotes. sources of energy that most other organisms cannot. such as N2 and H2S gas. . or single-celled bacteria and archaea without distinct Prokaryotes can utilize organelles.

3 Evolutionary patterns At some point. one bacterium engulfed another bacterium. The engulfed bacterium became a mitochondria. Mitochondria evolved into photosynthetic chloroplasts. allowing . and this ancestor gave rise to all eukaryotes. or organisms with distinct cell organelles. These organisms increased the abundance of oxygen in the atmosphere.

some algae.g.. Some protists can grow very large and look like large plants (e.3 Evolutionary patterns Protists are eukaryotes that include protozoa. kelp). . and slime molds.

Some have evolved alternative ways of obtaining nutrients. such as the carnivorous Venus flytrap and the parasitic dodder.3 Evolutionary patterns Plants convert CO2 and water into organic molecules. . Many have roots to extract water from soil or air.

. They secrete acids. Many are decomposers and many are plant mutualists.3 Evolutionary patterns Most fungi have hyphae that extract nutrients from dead or living tissues. and enzymes digest food externally.

They rely on the consumption of other organisms for resources.3 Evolutionary patterns Animals play a wide range of roles in ecological systems. .

Detritivores break down dead organic .3 Categorizing species based on energy source Producers—or autotrophs— convert chemical energy into resources. Mixotrophs can switch between being producers and consumers. Scavengers consume dead animals. Consumers—or heterotrophs— obtain their energy from other organisms.

Competition: when two organisms that depend on the same resource have a negative effect on each other. Parasitism: when one organisms lives in or on Herbivory: when one organism consumes producers. another organism.3 Types of species interactions Predation: when an organism kills and consumes an individual. Commensalism: when two species live in close association and one receives a benefit. Mutualism: when two species benefit from each other. whereas the other is .

3 Habitats and niches Habitat: the place. forests. or physical setting. where an organism lives. Stream Rain forest Tropical grassland . marine. coastal. grasslands. such as dominant plant type. Distinguished by physical features. deserts. Habitat types overlap and absolute distinctions rarely exist. Examples: Freshwater. streams.

No two species have the same niche because each has unique phenotypes that determine the conditions it can tolerate.3 Habitats and niches Niche: the range of abiotic and biotic conditions an organism can tolerate. Example: Different insects prefer to feed on different .

4 Scientists use several approaches to studying ecology. . Ecological systems are governed by physical and biological principles. 3 Different organisms play diverse roles in ecological systems. 5 Humans influence ecological systems.Chapter 1 concepts 1 2 Ecological systems exist in a hierarchical organization.

4 The scientific method .

A particular hypothesis can rarely be confirmed beyond a doubt. Predictions: statements that arise logically from hypotheses.4 The scientific method Hypotheses: ideas that potentially explain a repeated observation. .

4 Manipulative experiments Manipulative experiments: where a hypothesis is tested by altering a factor hypothesized to be the cause of a phenomenon. Treatment: the factor that we want to manipulate in a study. They manipulate the presence of birds by placing cages around oak trees. Control: a treatment that includes all aspects of an Example: Researchers want to test experiment except the factor ofifinterest. Some trees were left uncaged as . birds are an important factor in determining the number of insects on oak trees.

every experimental unit must have an Experimental may equal chance units of being assigned to a particular be natural (e. or artificial (e.e.. Replication: being able to produce a similar outcome multiple times (i.4 Manipulative experiments Experimental unit: the object to which we apply a manipulation.. and may vary in size by several orders of magnitude. microcosms). Randomization: a requirement for manipulation experiments. the number of experimental units per treatment). . lakes) treatment..g.g.

. Mathematical models: representations of a system with a set of equations that correspond to hypothesized relationships among the system’s components.4 Alternative types of experiments Natural experiments: an approach to hypothesis testing that relies on natural variation in the environment to test a hypothesis.

Chapter 1 concepts 1 2 Ecological systems exist in a hierarchical organization. 3 Different organisms play diverse roles in ecological systems. . 5 Humans influence ecological systems. 4 Scientists use several approaches to studying ecology. Ecological systems are governed by physical and biological principles.

5 Human influence on ecological systems .

humans depend on the proper functioning of these systems.5 Human influence on ecological systems Environments dominated by humans (e. farms) are also ecological systems. High amounts of these gases can increase average Earth temperatures. there are many success stories of ecosystem improvement and conservation . Thanks to ecological studies.. and produce large amounts of waste. cities. Humans consume massive amounts of energy and resources. Greenhouse gases: compounds in the atmosphere that absorb infrared heat energy emitted by Earth and then emit some of the energy back toward Earth.g.