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THE NATURE OF ECOLOGY

• Ecology is a study of connections in nature. – How organisms

interact with one another and with their nonliving environment.

Figure 3-2

What do you mean by environment?

The environment is made up of two factors:

Biotic factors- all living organisms inhabiting the Earth

Abiotic factors- nonliving parts of the environment (i.e. temperature, soil, light, moisture, air currents)

Autotrophs = Producers = Self feeders

How Ecosystems Use Sunlight As Their Source of Energy

Producers: Basic Source of All Food

• Most producers capture sunlight to produce carbohydrates by photosynthesis:

Producers: Basic Source of All Food

• Chemosynthesis: – Some organisms such as deep ocean bacteria

draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H2S) gas .

Consumers: Eating and Recycling to Survive

• Consumers (heterotrophs) get their food by eating or breaking down all or parts of other organisms or their remains. – Herbivores

• Primary consumers that eat producers – Carnivores

• Secondary consumers eat primary consumers • Third and higher level consumers: carnivores that eat carnivores.

– Omnivores • Feed on both plant and animals.

– Scavengers • Feed on dead leftovers, lazy hunters.

Consumers = Heterotrophs

• Primary consumers = herbivores = rabbit: eat plant material

• Secondary consumers = carnivores = predators = coyotes: prey are herbivores and other animals.

Decomposers and Detrivores

– Detrivores: Insects or other scavengers that feed on organic matter (wastes or dead bodies), breaking it down.

– Decomposers: Recycle nutrients in ecosystems. (Intake organic matter and convert to inorganic substances.

• Bacteria and fungi

Figure 3-13

ENERGY FLOW IN ECOSYSTEMS

• Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem.

Figure 3-17

Food Webs • Trophic levels are

interconnected within a more complicated food web.

Figure 3-18

Biomass Pyramid • Biomass – amount of living matter

Bioaccumulation

• Occurs in one trophic level. • Toxins build up in the tissues of an affected

organism • Persistence – ability of a substance to remain

in an organism • Ex) DDT and Mercury

Biomagnification

• Occurs across multiple trophic levels • Each trophic level accumulates more toxins

than the lower level. • Higher level consumers have higher

concentrations of toxins

Productivity of Producers: The Rate Is Crucial

• Gross primary production (GPP) – Rate at which an

ecosystem’s producers convert solar energy into chemical energy as biomass.

Figure 3-20

Some Terms and Definitions

• Ecosystems: A grouping of plants, animals, and microbes occupying an explicit unit of space and interacting with each other and their environment. – Biotic with abiotic (living with non-living)

• Ecotone: Transitional region between different ecosystems.

Ecotones

• Shares many of the species and characteristics of both ecosystems

• Borders may be: – sharp or “fuzzy” – Narrow or wide – Small or large

• May also include unique conditions that support distinctive plant and animal species

• Shares many of the species and characteristics of both ecosystems

Riparian Zone

• Ecotone between land and a river/stream.

• Important in soil conservation and habitat biodiversity

Biosphere • Atmosphere

– Membrane of air around the planet.

• Stratosphere – Lower portion contains ozone to

filter out most of the sun’s harmful UV radiation.

• Hydrosphere – All the earth’s water: liquid, ice,

water vapor • Lithosphere

– The earth’s crust and upper mantle.

Organism

Population

Community

Biosphere

Ecosystem

Biosphere- life supporting portions of Earth composed of air, land, fresh water, and salt water.

•The highest level of organization

Ecosystem- populations in a community and the abiotic factors with which they interact (ex. marine, terrestrial)

Community- several interacting populations that inhabit a common environment and are interdependent.

Population-a group of organisms of one species living in the same place at the same time that interbreed and compete with each other for resources (ex. food, mates, shelter)

Organism- any unicellular or multicellular form exhibiting all of the characteristics of life, an individual.

•The lowest level of organization

ECOLOGICAL STABILITY

• Living systems maintain some degree of stability through constant change in response to environmental conditions through: – Inertia (persistence): the ability of a living system

to resist being disturbed or altered. – Constancy: the ability of a living system to keep its

numbers within the limits imposed by available resources.

– Resilience: the ability of a living system to bounce back and repair damage after (a not too drastic) disturbance.

Carrying Capacity- the maximum population size that can be supported by the available resources

There can only be as many organisms as the environmental resources can support

Factors that affect population growth

Many organisms

present

Few organisms present

Few organisms present

None None

Limiting Factor- Zone of Tolerance

Factors that affect population growth

Limiting factor- any biotic or abiotic factor that restricts the existence of organisms in a specific environment. – EX.- Amount of water

Amount of food Temperature pH Salinity

Carrying Capacity

Carrying Capacity (k)

Time

J-shaped curve (exponential growth)

S-shaped curve (logistic growth)

Nu

m

b

e

r Minimum

• Niche – The role a species plays

in a community – Determined by limiting

factors

• Habitat – The place where an

organism/population lives out its life

ECOLOGICAL NICHES AND ADAPTATION

• Each species in an ecosystem has a specific role or way of life. – Fundamental niche: the full potential range of

physical, chemical, and biological conditions and resources a species could theoretically use.

– Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.

Generalist and Specialist Species: Broad and Narrow Niches

• Generalist species tolerate a wide range of conditions.

• Specialist species can only tolerate a narrow range of conditions.

Figure 4-7

Reproductive Patterns: Opportunists and Competitors

• Large number of smaller offspring with little parental care (r-selected species).

• Fewer, larger offspring with higher invested parental care (K-selected species).

Figure 8-9

Cockroaches: Nature’s Ultimate Survivors

• 350 million years old • 3,500 different species • Ultimate generalist

– Can eat almost anything. – Can live and breed almost

anywhere. – Can withstand massive

radiation.

Figure 4-A

Two Reproductive Strategies • R Strategists Short life span Small body size Reproduce quickly Have many young Little parental care Early reproductive

age Generalists

Ex: cockroaches, weeds, bacteria

Two Reproductive Strategies • K Strategists long life span large body size reproduce slowly have few young provides parental care Late reproductive age Specialists Ex: elephants, bears

Survivorship Curves: Short to Long Lives

• The way to represent the age structure of a

population is with a survivorship curve. – Late loss population live to an old age. – Constant loss population die at all ages. – Most members of early loss population, die at

young ages.

Biodiversity Hotspots • a region with a significant reservoir

of biodiversity that is under threat from humans.

• it must contain at least 1,500 species of endemic vascular plants, and it has to have lost at least 70% of its primary vegetation.

• Globally, 25 areas qualify under this definition, with nine others possible candidates.

• These sites support nearly 60% of the world's plant, bird, mammal, reptile, and amphibian species.

Species Diversity

• Biological communities differ in the types and numbers of species they contain and the ecological roles those species play. – Species diversity: the number of different species it

contains (species richness) combined with the abundance of individuals within each of those species (species evenness).

Species Diversity and Niche Structure

• Niche structure: how many potential ecological niches occur, how they resemble or differ, and how the species occupying different niches interact.

• Geographic location: species diversity is highest in the tropics and declines as we move from the equator toward the poles.

Genetic Diversity • Individuals of the same species vary slightly in

their genetic makeup and morphology. • The greater the amount of diversity, the more

“fit” a species is to survive.

Natural Selection • “Survival of the fittest” • Those best suited to the environment survive

and reproduce passing their genes to subsequent generations

• Can lead to speciation

Evolution • change in the

inherited characteristics of biological populations over successive generations

• Speciation is the evolutionary process by which new biological species arise

Resource Partitioning • Competition over

resources drives species into different patterns of resource use

• Leads to niche specialization

Piping plover feeds on insects and tiny crustaceans on sandy beaches

(Birds not drawn to scale)

Black skimmer seizes small fish at water surface

Flamingo feeds on minute organisms in mud

Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation

Brown pelican dives for fish, which it locates from the air

Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds

Louisiana heron wades into water to seize small fish

Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak

Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans

Knot (a sandpiper) picks up worms and small crustaceans left by receding tide

Herring gull is a tireless scavenger

Ruddy turnstone searches

under shells and pebbles

for small invertebrates

Specialized Feeding Niches

Niche Specialization • Over time, species

who compete over a shared resource tend to evolve in ways that reduce competition leading to a divergence of the two species.

Evolutionary Divergence • All of the finches in

the diagram are descended from a common ancestor

• Each species has evolved a beak specialized to take advantage of certain types of food.

Figure 4-9

Island Biogeography

• MacArthur and Wilson proposed the species equilibrium model or theory of island biogeography in the 1960’s.

• Model projects that at some point the rates of immigration and extinction should reach an equilibrium based on: – Island size – Distance to nearest mainland (degree of isolation) – Length (time) of isolation

Insular Dwarfism • mainland forms of mammals sometimes

evolve into far smaller forms on resource-constrained islands. (e.g., pygmy elephants, or pygmy humans)

Indicator Species: “Canary in a Coal Mine”

• Species that serve as early warnings of damage to a community or an ecosystem. – Frogs (and other amphibians) are good indicators since they

live in both land and water and are sensitive to changes in the environment

– Presence or absence of trout species because they are sensitive to temperature and oxygen levels.

Keystone Species: Major Players

• a species that has a disproportionately large effect on its environment relative to its abundance and play a critical role in maintaining the structure of a community, affecting many other organisms and helping to determine the types and numbers of various other species in the community.

Keystone Species

• Species that play roles affecting many other organisms in an ecosystem.

• Examples: – Bees/butterflies (pollination) – Top predators like wolf, lion, alligator (population

control) – Dung beetles (waste management, soil aeration)

American Alligators

• Build nesting mounds. – provide nesting and feeding sites for birds. – Keeps areas of open water free of vegetation.

• Dig deep depressions (gator holes). – Hold water during dry

spells, serve as refuges for aquatic life.

Keystone Species Keeps prey away from

open areas near stream banks. Vegetation reestablishes. Species diversity expands.

Reintroducing Wolves to

Yellowstone

Between 1850-1900 two million wolves were destroyed.

Foundation Species • Can create and enhance habitats that can

benefit other species in a community. • Examples:

– Elephants (uproot trees creating forest openings for grasslands)

– Beavers (dams create wetlands or redirect/pool water)

SPECIES EXTINCTION

Species can become extinct: Locally: A species is no longer found in an area it

once inhabited but is still found elsewhere in the world. (Extirpated) Ecologically: Occurs when so few members of a

species are left they no longer play its ecological role. Globally (biologically): Species is no longer found

on the earth.

Global Extinction

Some animals have become prematurely extinct because of human activities.

Endangered and Threatened Species

Endangered species: so few individual survivors that it could soon become extinct. Threatened species: still abundant in its natural

range but is likely to become endangered in the near future.

• Convention on International Trade in Endangered Species of Wild Fauna and Flora

• Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten the survival of the species in the wild, and it accords varying degrees of protection to more than 33,000 species of animals and plants.

The U.S. Endangered Species Act (ESA)

Passed in 1973 ESA forbids federal agencies (besides defense

department) to carry out / fund projects that would jeopardize an endangered species. ESA makes it illegal for Americans to engage in

commerce associated with hunting / killing / collecting endangered or threatened species.

Because of scarcity of inspectors, probably no more than 1/10th of the illegal wildlife trade in the U.S. is discovered.

Some species have characteristics that make them vulnerable to ecological and biological extinction.

SPECIES EXTINCTION

Figure 11-4

Species vulnerability to extinction

• Low reproductive rate • Specialists • High trophic level • Rare • Commercially valuable • Large territories/migration routes

Causes of premature extinction

Habitat destruction, degradation, and fragmentation Invasive species Population growth Pollution Climate Change Overharvest (HIPPCO)

Reduction in ranges of four wildlife species, mostly due to habitat loss and over-harvesting.

Figure 11-8

Terminology

“From here” • Native (Organisms brought to

a location without the help of man, such as by wind, wave and or birds. )

• Indigenous (Organisms that are native but can be found elsewhere.)

• Endemic (Organisms that are native and can be found ONLY in that location.)

“Not from here” • Non-native • Exotic • Introduced • Alien • Invasive

NON-NATIVE SPECIES Many nonnative species

provide us with food, medicine, and other benefits but a few can wipe out native species, disrupt ecosystems, and cause large economic losses.

Kudzu vine was introduced in the southeastern U.S. to control erosion. It has taken over native species habitats.

NON-NATIVE SPECIES intentionally introduced Purple loosestrife

European wild boar African honeybee

Nutria Hydrilla

NON-NATIVE SPECIES Unintentionally Introduced

Zebra mussel Asian tiger mosquito

Snakehead Fire ant

Beneficial non-natives

• Corn (Mexico) • Oats (Switzerland)

• Wheat (southwestern Asia – Syria, Jordan, Turkey)

• Rice (India/Nepal) • Cattle (Europe)

• Poultry (Asia-India) • Honey bees (Asia/Europe)

Fig. 11-13, p. 236

• Climate similar to habitat of invader

• Absence of predators

on invading species • Early successional systems • Low diversity of

native species • Absence of fire • Disturbed by human

activities

Characteristics of Successful

Invader Species

• High reproductive rate, short generation time (r-selected species) • Pioneer species • Long lived • High dispersal rate • Release growth-inhibiting chemicals into soil • Generalists • High genetic variability

Characteristics of Ecosystems Vulnerable

to Invader Species

How to be a successful invader • Be a pioneer species (lichens, mosses)

• Have a high reproductive rate, short generation time (r-selected

species)

• Have a high dispersal rate

• Have an adaptation that is harmful to other competing organisms (e.g., releasing chemicals into soil that inhibit other plants from growing

• Be a Generalist

• Have high genetic variability

Which ecosystems are vulnerable to invasion?

• Climate similar to habitat of invader

• Absence of predators on invading species

• Low diversity of native species

• Absence of fire

• Disturbed by human activities

Types of Population Change Curves in Nature

• Population sizes may stay the same, increase,

decrease, vary in regular cycles, or change erratically. – Stable: fluctuates slightly above and below carrying

capacity. – Irruptive: populations explode and then crash to a more

stable level. – Cyclic: populations fluctuate and regular cyclic or boom-

and-bust cycles. – Irregular: erratic changes possibly due to chaos or

drastic change.

Types of Population Change Curves in Nature

• Population sizes often vary in regular cycles when the predator and prey populations are controlled by the scarcity of resources. Figure 8-7

PREDATION

ways in which prey species avoid their predators:

– Speed – outer protection – Camouflage – chemical warfare

– warning coloration – mimicry – deceptive looks – deceptive behavior.

Figure 7-8

Speed

Outer Protection

Camouflage

Find the

frogs!

Did you find all

4?

Chemical Warfare

Warning Coloration

Fig. 7-8f, p. 153

Mimicry

Deceptive Looks

Deceptive Behavior

This is a snake caterpillar. It is a

caterpillar that (when threatened) expands

the tail end of its body to resemble a snake

head

Symbiosis

• Parasitism • Mutualism • Commensalism • Ammensalism

Parasites: Mooching

• Parasites do not usually kill their host (at least not quickly) as opposed to predation. – Some parasites live in host (micro-organisms,

tapeworms). – Some parasites live outside host (fleas, ticks,

mistletoe plants, sea lampreys). – Some have little contact with host (dump-nesting

birds like cowbirds, some duck species)

Mutualism: Win-Win Relationship

• Two species can interact in ways that benefit both of them.

Commensalism: Using without Harming

• Some species interact in a way that helps one species but has little or no effect on the other.

Figure 7-10

Ammensalism

• Ecological interaction in which an individual harms another without obtaining benefit

• Red tide, proliferation of algae that can lead to death of fishes and other animals