PRINCIPLES OF ECOLOGY

Chapter 2

Introduction: What is Ecology? The scientific study of interactions

among organisms and their environments Shows relationships between living and

nonliving parts of the world Scientists obtain data through observation

and controlled experiments

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Aspects of Ecological Study

Biosphere = the portion of Earth that supports life Interactions between living and non-living things Abiotic factors = nonliving parts of the

environment Determine which species live in a particular

environment (deserts, grassland, forest, tropical forest, tundra,

freshwater, saltwater) Ex: air currents, temperature, moisture/water, light, soil

Biotic factors = living parts of the environment All living organisms affect other organisms (food,

shelter, reproduction & protection) Ex: plants, animals, decomposers

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Levels of Organization Scientists study interactions among

organisms at different levels:1. Organism – one species

A zebra What does it need to survive?

2. Population – a group of the same species A herd of zebras Competition for resources

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Levels of Organization, cont.

3. Community –interacting populations in an area zebras, giraffes, lions, trees, grass changes in one population affect the other

populations

4. Ecosystem – interactions between the community and nonliving surroundings African grassland Three major kinds of ecosystems:

Terrestrial = land Freshwater = ponds, lakes, streams Saltwater (marine) = oceans

5. Biome6. Biosphere

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Organisms in an Ecosystem Habitat = the place where

an organism lives Several species may share one

habitat Niche = the role and

position a species has in its environment – how it survives & reproduces Unique strategies for finding

food & shelter Example: bird beaks –

adapted for different foods or feeding strategies

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Beak Variations in Finches7

Biodiversity

the number of different species that live in a certain area

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How Organisms Get Energy

All organisms need energy to survive

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Autotroph

Two types of Organisms

Autotrophs – use energy from the sun (photosynthesis) or chemicals (chemosynthesis) to produce their own food Also called producers – they produce usable

energy Examples: plants, some bacteria

Heterotrophs – organisms that must eat to obtain energy Also called consumers – they must consume food

to get usable energy Examples: all animals, some bacteria,

decomposers

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Kinds of Heterotrophs

Herbivores – feed on autotrophs such as plants, seeds, or algae Insects, deer, rabbits,

squirrels, bees, elephants

Carnivores – feed on other heterotrophs Lions, coyotes, sharks Scavengers eat

carrion & refuse (leftovers from carnivores) Ants, beatles, vultures

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Kinds of Heterotrophs

Omnivores – feed on animal and plant materials Humans, raccoons,

opossums, bears Decomposers –

break down dead organisms & recycle nutrients Fungi & bacteria

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Matter & Energy Flow in Ecosystems

The food you eat contains matter (carbon, nitrogen, oxygen, hydrogen, etc) and energy

Energy moves ONE WAY – it cannot be recycled

Food chains – simple models used to show the movement of energy through an ecosystem

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Food Chains

Energy moves from autotrophs to heterotrophs, eventually to decomposers

Arrows indicate the direction of energy transfer

Example: Algae fish bird The algae is an autotroph. Energy is

transferred to the fish when it eats the algae, then to the blue heron when it eats the fish

Most food chains have no more than five links because the amount of energy decreases at each level.

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Trophic Levels

Represent a feeding step in the passage of energy Many species may occupy one trophic level

Food webs express all the possible feeding relationships at each level in a community More realistic than a food chain because most

organisms depend on more than one food source

Food webs represent a network of food chains – overlapping & interconnected

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Sample Food Web:

Autotrophs

1st order heterotrophs

2nd order heterotrophs

3rd order heterotrophs

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Ecological Pyramids

Food chains, food webs, and ecological pyramids show how energy moves in only ONE direction through an ecosystem

10% rule – only about ten percent of the energy at one trophic level is passed on to the next (the rest is used for life processes)

Types of Pyramids: Energy Pyramid Pyramid of Numbers Biomass Pyramid

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Energy Pyramid18

Nutrients in the Biosphere

Nutrients differ from energy in two ways: It is not lost after being used, it will not

produces a product such as heat for the environment

Passes from one organism to another in a continues cycle that has no beginning or end

Water Cycle

Consists of three process: Evaporation Condensation Precipitation

Nitrogen Cycle

Nitrogen fixation – convents atmosphere N2 to ammonium (NH4) and nitrate (NO3)

Autotrophs will absorb and convert to organic materials

Heterotrophs will consume in foods

Carbon Cycle

Autotrophs uses CO2 gases from the atmosphere to use in photosynthesis

Non-photosynthetic organism give off CO2

COMMUNITIES & BIOMES

Chapter 3

Living in a Community

Limiting Factors Environmental factors that affect

an organism’s ability to survive Any biotic or abiotic factor that

restricts the existence, population, reproduction, or distribution

Food, predators, competing species, temperature, rainfall, light, soil

Changes in one population may affect others in the community

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Ranges of Tolerance

Tolerance = the ability of an organism to withstand changes in biotic & abiotic factors Organisms must stay within their

tolerance range Examples: people and temperature;

plants & water May affect population size

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Succession: changes over timeSuccession = the orderly, natural

changes and species replacements that take place in the communities of an ecosystem

Occurs in stages May take centuries Two types:

Primary Succession Secondary Succession

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Primary Succession The colonization of new sites

Avalanche, volcano eruption, volcanic island Pioneer species = first species in an area

Lichen grows on rocks, breaking them down and producing soil

Climax community = a stable, mature community that undergoes little or no change in species

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Secondary Succession

The sequence of community changes that takes place after a community is disrupted Natural disasters (hurricane, fire), human actions Occurs in areas that previously contained life

Takes less time than primary succession

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Biomes

Is a major type of ecosystem with its own temperature ranges, rainfall amounts, and types of organisms

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Aquatic Biomes

Marine (Salt Water) Location: Oceans, Estuaries, Photic Zone (with

light), & Aphotic Zone (without light) Types of Organisms: Kelp, Whales, Dolphins,

Sharks, Tuna, Crabs, Shrimp, Lobsters, Salmon, Eels, Plankton

Freshwater Location: Wetlands, Rivers, Streams, Ponds,

Lakes, & Creeks Types of Organisms: Algae, Muskrats, Ducks,

Geese, Fish, Pike, Carp, Bass, & Catfish

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Land Biomes

Tundra Taiga Temperate Forest Grassland Desert Tropical Rain Forest

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POPULATION BIOLOGY

Chapter 4

Population Growth

Population Growth = an increase in the size of a population over time

Populations grow exponentially The rate increases because the

total number of reproducing individuals is increasing

As the population grows larger, it reproduces faster

Patterns of population growth Depend on environmental

conditions Example: Elephants vs.

mosquitoes

Stages of Population Growth

1. Beginning growth

2. Rapid growth

3. Leveling off

4. Carrying capacity

5. Fluctuations

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2

3

4

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Limits to Population Growth (abiotic)

Populations cannot grow indefinitely Carrying Capacity = the number of

organisms that an environment can support

Two kinds of limiting factors: Density-dependent factors

disease, competion, parasites, food Bigger influence if population is large

Density-independent factors Temperature, storms, floods, drought,

habitat disruption Affect all populations

Limits to Population Growth (biotic)

Predation Predators usually catch and eat

the young, old, sick, or injured individuals of a population

Competition When population numbers are

large, organisms must compete for resources

when the demand exceeds the supply, the population decreases

Crowding & Stress Individuals may become more

aggressive, decreased parental care, decreased fertility, decreased resistance to disease

As a result, the population decreases

Symbiosis

Other interaction between species

Occurs when two species live in close contact with each other for a long period of time

Host – is the species that is being used

Symbiot – is the species that is acting on the host

Symbiosis Mutualism

Both individuals benefit from each other

+ +

Parasitism One benefits the other is

harmed + --

Communalism One benefits the other is

not affected + 0

Amensalism One will stop the growth

of another without being affected by it

0 --

Human Populations Demography (demographics) =

study of human populations Several factors affect human

population: Birth rates Death rates Age structure – helps to predict if a

population is growing rapidly Immigration – movement into a

population Emmigration – movement out of a

population

Age structure

Demographers collect data on age structures of different countries

Tracking data allows scientists to make predictions about population growth

BIOLOGICAL DIVERSITY & CONSERVATIONChapter 5

Biological Diversity Biodiversity = the variety of life in an area

The number of species that live in a certain area Terrestrial biodiversity increases as you move

closer to the equator Canada = 163 mammal species United States = 367 Mexico = 439

The greatest biodiversity is found in warm areas such as tropical rain forests and coral reefs

Larger islands have more biodiversity than smaller islands with the same climate

Importance of biodiversity

Organisms are adapted to live together in communities If one species is lost, it affects the populations of

other species Life depends on life

Animals cannot exist without plants Many plants cannot exist without the animals that

pollinated them Decomposers recycle nutrients and get rid of dead

and decaying material Biodiversity brings stability to an ecosystem

A pest or parasite may destroy a farm, but not a forest.

Importance to people Humans depend on other organisms

Oxygen supplied by plants Diversity of foods to eat

Biodiversity is useful to humans Making new food crops Improving people’s health

Loss of biodiversity

Extinction = the disappearance of a species when the last of its members dies Almost 40 species of plants and animals in the

United States have gone extinct since 1980 Threatened = When the population of a

species begins to decline rapidly Ex. African elephants have decreased in number

due to hunting Endangered = when a species’ numbers

become so low that extinction is possible Ex. California condor, Florida manatees, bald

eagle, Sumatran tiger, Galapagos tortoise, etc.

Threats to Biodiversity Complex interactions among

species make ecosystems unique and species well adapted to their habitats Changes to habitats put

organisms in danger of extinction

Most common threats to biodiversity Habitat loss Damage to habitats Pollution Introduction of exotic species

Habitat Changes The biggest threat to biodiversity is habitat loss Habitat fragmentation = the separation of

wilderness areas from other wilderness areas Ex. Building a freeway, clear-cutting forest trees, etc.

Habitat degradation = damage to a habitat by pollution Air pollution Water pollution Trash Acid precipitation

Habitat changes can change climate Edge effect = conditions along the boundaries of

an ecosystem

Strategies of Conservation Biology Conservation Biology is a new field that

implements plans and methods to protect biodiversity Resource conservation Conservation biologists study law, politics,

sociology, economics, and ecology

Legal Protection of Species

President Nixon signed the US Endangered Species Act into law in 1973. It is illegal to harm any species on the endangered

or threatened species list. Federal agencies cannot fund any project that

would harm these animals Cannot change an ecosystem where

endangered or threatened species live Other countries have established similar laws

International trade is controlled regarding certain species

Preserving habitats

National Parks & Preserves Protecting whole communities and ecosystems is the

best way to protect the organisms that live there. Ex. Yellowstone, Yosemite, etc

Park rangers are hired to manage the parks and ensure protection of organisms

Sustainable use = allowing people to use the resources without damaging the ecosystem

Habitat corridors = natural strips that allow the migration of organisms from one area to another Prevents isolation and habitat fragmentation

Reintroduction programs The release or organisms into an area where

their species once lived Organisms are captured and bred, then returned to

the wild Most successful when organisms are transported to

new, sustainable habitats Ex. Brown pelican, gray wolf, panda breeding

program, etc Captivity = an organism that is held by people

Zoos & aquariums Animals kept in captivity may lose the necessary

behaviors to survive in the wild