Chapter 19: Introduction to Ecology

19-1 Ecology

19-2 Ecology of Organisms

19-1 Ecology

• Interactions BETWEEN species AND non-living components of their environment.

I. Ecology (1866)

(1) Evaluate the following: “Though the field of ecology had not been defined in Charles Darwin’s day, Darwin was in all likelihood, an ecologist.

Critical Thinking

II. Today’s Environment

• SURVIVAL depends on KNOWLEDGE of ENVIRONMENT.

(i.e., Learning HOW to improve our IMPACT on environment is critical to the survival of MANY species).

(A) The Exploding Human Population• MOST significant change is our GROWTH and USAGE of resources.

Ex: In 1930…2 billion people

Ex: In 2004, 74 years later…6.4 billion people

*Projected for 2050, between 7.8 and 12.5 billion people*

NOTE: Ecologists estimate that about 20% of ALL species in the world may disappear by the year 2100. (mostly in the developing countries)

(B) The Sixth Mass Extinction (We are living it)• Paleontologists use FOSSIL evidence to note FIVE major mass extinctions in the history of the earth.

NOTE: Currently species are disappearing FASTER than at any time since the last extinction (i.e., the disappearance of dinosaurs 65 m.y.a.)

(C) The Thinning Ozone Layer (CFCs react and deplete ozone)• ~ 1% of UV radiation passes THROUGH the ozone shield resulting in over 500,000 new cases of MELANOMA a year.

(D) Climatic Changes

• Although CO2 and H2O vapor are TRANSPARTENT to visible light, they intercept much of the reflected HEAT and direct it BACK to Earth.

(1) Greenhouse Effect (i.e., driving force behind GLOBAL WARMING)• Carbon dioxide and water vapor BLOCK the heat reflected by Earth and REDIRECT it back to the surface.

III. Levels of Organization

• Biosphere Ecosystem Community Population Organism

Organisms, Populations, Community

Ecosystems

The Biosphere

(A) The Biosphere

• The broadest, MOST INCLUSIVE level of organization in ECOLOGY.

NOTE: If Earth is an APPLE, the biosphere would only be AS THICK as the apple’s SKIN.

(B) Ecosystem (supported in the biosphere)

• Level that includes ALL of the species (BIOTIC) and the non-living (ABIOTIC) forces found in a habitat (Ex: A pond)

NOTE: The types of biodiversity found in an ecosystem are largely determined by abiotic factors (physical and chemical aspects, temperature, amount of sunlight, pH)

(C) Communities, Populations, and Organisms

• When considering these 3 levels of organization, we only include BIOTIC (or living) components. (i.e., the organisms)

(1) Community (not AS inclusive as an ecosystem, still can be complex)• Interacting SPECIES inhabiting a geographical area at a point in time.

(2) Population (smallest unit CAPABLE of evolution)

• All members of a single SPECIES inhabiting one location at one TIME.

IV. A Key Theme in Ecology (Isolation does NOT exist)

• INTERCONNECTEDNESS. All species interact with biotic and abiotic components of their ecosystem.

(2) The gypsy moth is a destructive insect pest. In a deciduous forest ecosystem, the caterpillars of the gypsy moth negatively affect oak trees by consuming their leaves. The number of caterpillars in the forest fluctuates, and every few years the caterpillar population increases dramatically. What do you suppose would be the effects that a large increase population might have on the other members of this ecosystem? (white-tailed deer, Red oak-yielding acorns, deer mouse, deer tick, Borellia burgdorferi—Lyme disease bacteria, and humans) How might an increase in caterpillars affect the incidence of Lyme disease?

Critical Thinking

(A) Disturbances in Ecosystems• A RISK to interconnectedness is that DISTURBANCES in an ecosystem can spread quickly setting off a series of ECOLOGICAL chain-reactions.

Ex: The EXTINCTION of 60% NATIVE bird species on the Hawaiian islands

(1)Habitat Destruction

(2) Over-Hunting

(3) Introduced Predators and Diseases

V. Ecological Models (can be visual, verbal, or mathematical)• Ex: A graphical model can show HOW sunlight, rainfall, and temperature affect the growth of plants.

(i.e., Models allow ecologists to make PREDICTIONS about how forces may change the ecosystem of an environment)

I. Ecology of Organisms• To understand WHERE a SPECIES lives, WHY it lives there, and HOW it interacts with OTHER species..

19-2 Ecology of Organisms

(1) Habitat (WHERE an organism lives)

• A habitat includes both BIOTIC and ABIOTIC factors.

II. Biotic and Abiotic Factors (TWO classes of environmental forces)• Living and non-Living factors in a habitat.

(1) Biotic Factors (Ex: a pollinator to a flower)• Include all LIVING species that INFLUENCE a community.

(2) Abiotic Factors (Ex: Tropical Rainforest vs. Tundra)• Temperature, humidity, pH, salinity, oxygen concentration, availability of elements (C, N, P), and precipitation.

(A) The Changing Environment• Factors VARY with time, seasons, other conditions (i.e., the environment is dynamic, NOT static)

(3) In the fall, many kinds of songbirds migrate from the United States to Central America or South America. Suggest what some of the benefits for songbirds may be? What could be some consequences for this behavior?

Critical Thinking

(B) Responses to a Changing Environment• Species are adapted to SURVIVE within a SPECIFIC RANGE of environmental factors (temperature, pH, etc…)

NOTE: It is possible to research this RANGE for a species by measuring HOW efficiently it performs at different values (of temp, etc…)

(1) Tolerance Curve• A graph depicting ACTIVITY vs. values (environmental VARIABLE).

(C) Acclimation• ADJUST their tolerance to abiotic factors; however, acclimation is NOT adaptation.

[NOTE: Acclimation occurs within the LIFETIME of an individual, adaptation is a genetic change that reflects changes in the GENE POOL.]

Ex: Erythrocytes (RBC) Synthesis ~ Habitat Altitude

(D) Control of Internal Conditions• Habitats fluctuate in ABIOTIC conditions. (i.e., a species MUST cope with a changing environment)

(1) Conformers• Species whose INTERNAL conditions will fluctuate with the environment (e.g., ectotherms)

(2) Regulators• Species that use NRG to MAINTAIN their homeostasis within a HEALTHY range. (e.g., endotherms)

NOTE: Pacific salmon spend PART of their lives in SALT water and PART in FRESH water. They are CONFORMERS to environmental temperatures BUT are REGULATORS of their internal salt concentration.

(E) Escape from Unsuitable Conditions• Some species can SURVIVE unfavorable conditions by ESCAPING from them temporarily. (e.g., ? behavior in the desert)

(1) Dormancy (stationary)• REDUCED metabolic activity lasting WEEKS or months at a time.

(e.g., hibernation is found among amphibians, reptiles, mammals)

(2) Migration (mobile)• Moving to a MORE favorable habitat for a period of TIME.

(i.e., seasonal MIGRATORY PATTERNS of birds, spending spring & summer in the COOLER climates, then migrating to WARMER climates in the fall)

(F) Resources (result in COMPETITION in a community)• Food, energy, nesting sites, water, and sunlight (all are LIMITED).

III. The Niche (HOW an organism lives; TWO ecological types)• The ROLE or “way of life” for a SPECIES in a community.

(Ex: Included in the niche may be WHERE it lives (its habitat), HOW it obtains nutrition, what TIME of day it is ACTIVE, etc…)

(4) Suggest a rationale behind why the fields of evolutionary biology and ecology are inextricably linked.

Critical Thinking

(1) Fundamental Niche (BROAD set of conditions)

• Range of CONDITIONS a species can (potentially) TOLERATE and RESOURCES it can (potentially) USE.

(i.e., when evading PREDATION and COMPETITION are considered)

(2) Realized Niche (more NARROW set of conditions)• Range of CONDITIONS a species ACTUALLY TOLERATES and the RESOURCES a species ACTUALLY uses.

(A) Niche Differences• A species’ niche can CHANGE during an organism’s LIFETIME.

(Ex: A caterpillar will eat the LEAVES off a plant; after feeding for some time, it will undergo a metamorphosis to become a butterfly, which feeds on NECTAR)

(1) Generalists (a.k.a. opportunists BROAD niche)• CAN tolerate a range of conditions and use a VARIETY of resources. (e.g., Virginia opossum)

(2) Specialists (NARRROW niche)• UNABLE to tolerate a wide range of conditions MUST have SPECIAL resources for survival. (e.g., koala bear)

(5) Ecologists have identified several characteristics that increase the likelihood that a species will become extinct. Specialization is one such characteristic. Suggest why a very specialized species may be more likely to be more vulnerable to extinction.

Critical Thinking

Extra Slides AND Answers for Critical Thinking Questions(1) Darwin collected data about the ranges, habits, and

interrelationships of organisms during his voyage. Furthermore, the central theme of natural selection is the interaction between the organism and the environment.(2) An outbreak of gypsy moth caterpillars would damage the oak trees and probably reduce the amount of acorns they produce. As a result, populations of deer mice and deer could fall, causing a reduction in the population of deer ticks as well. Such an outbreak also would likely reduce the incidence of Lyme Disease.

(3) By migrating south, songbirds escape the extreme cold and food shortages of the winter, but this behavior costs a large amount of energy and risk in flying long distances.

(4) Changing environmental conditions set the stage for adaptation through the evolutionary mechanism of natural selection.

(5) A specialized niche requires a narrow range of environmental conditions and resources. Such a species is vulnerable to environmental fluctuations that shift conditions outside the species’ tolerance range.

Revisiting Interdependence of Organisms

• A set of crucial interactions take place between living organisms and the living and nonliving environment.

Assessing Prior Knowledge

• How might a constantly changing environment affect natural selection?

• The theme of ecology is INTERDEPENDENCE.

• In what ways do humans have a unique impact on the environment over other species?