principles of ecology chapter 2. introduction: what is ecology? the scientific study of...
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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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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