ECOLOGY
Biosphere and Its Units
ECOLOGY
The study of the relationships between
organisms and their environment.
Not just related to pollution
Unifying factor is adaptation.
Biosphere and Its Units
Biosphere
Area of earth where life exists
Most on or within a few meters of earth's surface.
Some found 8 km high and some found 8 km
below ocean surface.
Smaller ecological units
Population - all members of a species that live in
same area and make up a breeding group
Group of deer in a forest, trout in a lake.
Community - All populations in an area
Biosphere and Its Units
ECOSYSTEM
An ecological unit that includes all interacting parts of an
environment in an area.
Abiotic Factors
Nonliving components of an ecosystem.
Biotic Factors
Living components of an ecosystem.
Biosphere and Its Units
Biosphere and Its Units
Biosphere and Its Units
ABIOTIC FACTORS
Nonliving components of an ecosystem.
Light, precipitation, temperature, slope/drainage of
land, soil chemistry, and atmosphere.
Abiotic factors may interact
Stream flooding results in deposition of sediment
Changing of river courses
Creation of mountains or islands by volcanoes
Landslides removing soil.
Biosphere and Its Units
BIOTIC FACTORS
Living components of an ecosystem.
Plants, animals, protists, microorganisms
Living things may interact
Predation – predator kills prey for food.
Symbiosis – relationship between two
organisms
Usually beneficial to one organism.
Biosphere and Its Units
Abiotic and biotic factors may also interact
Affect each other.
Climate/soils determine type of plants in
area; determines animals of area.
Plants replenish oxygen - photosynthesis
Overgrazing can result in loss of soil.
Ecosystem Structure
HABITAT
Place where an organism lives - "home"
Provides food and shelter.
Habitats may overlap
NICHE
Role or occupation; everything organism does in its habitat
Organisms way of life
includes habitat, feeding habits, reproductive behavior, and all
other biological aspects of the organism.
No two organisms can occupy the same niche
Habitats overlap, niches do not.
Ecosystem Structure
Trophic Levels
Energy enters an ecosystem from the sun.
Energy flows between organisms when one
organism eats another.
Trophic Level is defined by the relationship
between what organism eats and what eats it.
The feeding level in an ecosystem.
Comes from Greek that means "food"
Ecosystem Structure
Trophic Levels
Producers
Autotrophic organisms that make their own food
using solar or chemical energy
Consumers
Heterotrophic organisms that feed on producers
either directly or indirectly for their energy.
Decomposers
Organisms that breakdown organic material and
return it to the environment for use by producers
Heterotrophic organisms.
Ecosystem Structure
PRODUCERS
Autotrophic organisms that make their own food using solar or
chemical energy.
Plants, algae, and photosynthetic bacteria
Manufacture all organic nutrients for ecosystem
Also called primary producers.
Occupy the First Trophic Level
Primary Productivity of an ecosystem - rate at which solar energy is
converted into organic compounds
Gross Primary Productivity - total amount of energy produced,
includes energy used by plant for own respiration
Net Primary Productivity - rate at which plants store energy
not used in plant respiration.
Ecosystem Structure
Ecosystem Structure
CONSUMERS
Heterotrophs that feed on producers either directly or
indirectly for their energy.
Primary Consumer - feeds on producers
Secondary Consumer - feeds on a primary consumer.
Consumers may be classified on basis of food type
Herbivore - eats primary producers; "Plant eater"
Carnivore - eats other consumers; "meat eater"
Omnivore – eats both primary producers and
consumers;
Scavenger - feeds on organisms that recently died.
Ecosystem Structure
Ecosystem Structure
Ecosystem Structure
DECOMPOSERS
Breakdown organic material and return it to environment
for use by producers
Heterotrophic organisms.
Process called Decay
Includes bacteria, mold, mushrooms
Types
Saprophytes - obtain their food from dead organisms
or the waste products of living organisms
Ex - molds, mushrooms
Parasites - obtain their food from living organisms
Ex - athlete's foot
Ecosystem Structure
Ecosystem Structure
Energy Flow
Energy flows in various patterns in ecosystem.
Total energy of one trophic level never flows to
next level
Food Chain - specific sequence where organisms
obtain energy and organic materials from one
another.
Food Web - interconnected food chains formed
due to the complex relationships
Ecosystem Structure
Ecosystem Structure
FOOD CHAIN
Producer
Primary Consumer
Secondary Consumer
Scavenger
Grass
Deer
Puma
Vulture
Ecosystem Structure
FOOD WEB
Hawk
Snake
Mouse
Lizard
Bird
Grasshopper
Rabbit
Grass
Ecosystem Structure
Ecological Pyramids
Complexities of ecosystem are graphed to show
the relationship between trophic levels
Primary producer at the base with consumer
levels above it.
Common pyramid models
Energy Pyramid
Numbers Pyramid
Biomass Pyramid
Ecosystem Structure
ENERGY PYRAMID
Shows that energy is lost at each level
Each organism in a given trophic level uses
some of energy to carry on its own life
functions.
Always a loss of energy as heat in any
system of energy transfer.
Never inverted.
Ecosystem Structure
Ecosystem Structure
NUMBERS PYRAMID
Shows number of organisms at each level
Usually an increase in the size of the
organisms with each level
Normally producer organisms are most
numerous; may be inverted
Single tree may support thousands of
insects and birds
Ecosystem Structure
Ecosystem Structure
BIOMASS PYRAMID
Amount of matter that can be supported at
each trophic level.
Biomass is the total dry weight of organisms in
the ecosystem.
Ecosystem Structure
BIOGEOCHEMICAL CYCLES
Process where inorganic materials move from
atmosphere or soil to living things and back
Also called Nutrient Cycles.
Water Cycle
Nitrogen Cycle
Oxygen-Carbon Cycle
Ecosystem Structure
WATER CYCLE
Movement of water from atmosphere to the
earth and back again.
Precipitation - movement of water to earth from
atmosphere
Evaporation - way most water lost from earth's
surface to atmosphere.
Transpiration - loss water by green plants through
their leaves.
Ecosystem Structure
NITROGEN CYCLE
Process by which nitrogen passes from the atmosphere to
organisms and back again
Four major processes
Nitrogen Fixation - bacteria convert nitrogen gas into
ammonium compounds; live in roots of legumes
Ammonification - bacteria break down nitrogencontaining amino acids from animal wastes and dead
organisms to form ammonia compounds
Nitrification - Bacteria oxidize ammonia compounds to
produce nitrates and nitrites
Denitrification - anaerobic bacteria break down nitrate
releasing nitrogen gas back into the atmosphere
Ecosystem Structure
OXYGEN-CARBON CYCLE
Involves processes of photosynthesis and
respiration
Photosynthesis removes CO2 from atmosphere
and fixes it as glucose and releases O2
Respiration removes O2 from atmosphere and
CO2 is released.
Normally processes balance each other.
Levels of O2 and CO2 remain fairly constant
Ecosystem Structure
Since about 1850's fossil fuels consumption has increased
Fossil fuels represent stored carbon compounds
Combustion of the fuels has increased the CO2 level of
the atmosphere.
Increased levels of CO2 increase the atmosphere’s
ability to trap heat.
Greenhouse Effect - an increase in atmospheric
temperature due to heat being trapped by the
atmosphere.
Can change climates and habitats
Should be called Global Warming
Terrestrial Biomes
BIOME
Large area identified by the presence of
characteristic plants and animals.
Commonly identified by dominant plant life.
Don't have definite boundaries
Usually have characteristic rainfall and
temperatures.
Terrestrial Biomes
POLAR BIOMES
Surround North and South poles
Receive very little precipitation - fresh water scarce
Soil is sparse, low in nutrients, frozen much of the year
Temperature range - -40o C to 4o C
Receive virtually no sunlight for half the year.
Arctic Polar Biome
Lies over Arctic Ocean
Plants - Some flowering plants, mosses, lichens,
Animals - Gulls, Walruses, polar bears along Arctic coast.
Antarctic Polar Biome
Lies over landmass of the Antarctic continent.
Plants - lichens, mosses, 3 types of flowering plants
Animals - small insects, seals, whales, penguins.
Terrestrial Biomes
TUNDRA
Treeless biome blanketed by snow in winter that forms continuous
belt across northern North America, Europe, and Asia
Tundralike regions may also exist on mountains above treeline
Highest point at which trees grow.
Characterized by a Permafrost
Surface soil thawed for only about 8 weeks
During thaw patchwork of shallow pond, bogs, and soggy soil
Climate - cold and dry
Plants - mosses, lichens, dwarf woody plants – No trees
Animals - Insects, ducks, geese, predatory birds, musk ox, caribou,
lemmings, and weasels
Terrestrial Biomes
CONIFEROUS FOREST
Biome dominated by conifers
Long, cold winters and short cool summers.
Nutrient poor soils; usually acidic.
Animals - moose, bear, lynx
Northern parts of Europe, Asia, and North America
Three subdivisions
Taiga
Coniferous Belt
Southern Pine Forests
Terrestrial Biomes
DECIDUOUS FOREST
Characterized by trees that lose their leaves in the fall.
Definite seasons; temperate region
Stretch across eastern U.S., much of Europe, part of
Asia, South America, Africa, and Australia
Precipitation evenly distributed over the year;
Rainfall - 75 to 125 cm per year; moderately rich soil
Dominant trees - birch, beech, maple, oak, hickory,
elm, sycamore, willow, and cottonwood.
Animals - white-tailed deer, black bear, raccoons,
squirrels, hundreds of bird species
Terrestrial Biomes
GRASSLAND
Dominated by grasses
Cover about one-fourth of earth's land surface
Found in variety of temperature ranges
Rainfall - 25 to 75 cm per year.
Animals - bison, antelope, elephants, giraffes, kangaroos
Soil usually very rich
Various names
Prairie - North America
Steppes - Asia
Pampas - South America
Veldt - Africa
Terrestrial Biomes
DESERT
Dry areas - rainfall averages <25 cm per year
Organisms are adapted to harsh conditions
Plants have deep root systems, some store water,
thickened stems and branches.
Temperatures may vary greatly - hot days/cold nights
Plants - cactus, sagebrush, creosote, some annuals.
Animals - camel, jackrabbits, many reptiles, scorpions,
Kangaroo rats
Terrestrial Biomes
RAIN FORESTS
TROPICAL RAIN FOREST
Found near equator
Abundant rainfall and sunlight - 200 to 225 cm per year.
Supports many plant species - growth rate is rapid
Soil is thin, moist, very low in nutrients.
Removal of vegetation results in loss of soil
Animals - insects, parrots, toucans, apes, monkeys, predatory cats
TEMPERATE RAIN FOREST
Moderate temperatures and high humidity
West coast of North America from California to Alaska.
Plants - redwood, Sitka spruce
Animals - deer, elk, rodents
Aquatic Biomes
MARINE BIOME
Earth's oceans and associated areas
Divided into 3 areas
Ocean
Intertidal zones
Estuaries
Aquatic Biomes
OCEAN
Covers 70% of earth
Water contains about 3.5% salt
Divided into two zones
Pelagic Zone - open ocean
Neritic Zone - out over continental shelf
Oceanic Zone - over deep water of open sea.
Benthic Zone - ocean bottom
Divided according to light penetration
Photic Zone - light penetrates
Aphotic Zone - light doesn't penetrate
Aquatic Biomes
INTERTIDAL ZONES
Area between high tide and low tide lines
Organisms adapted to periodic air exposure
Animals - crabs, clams, mussels, shorebirds.
Aquatic Biomes
ESTUARY
Biome between freshwater and marine biomes
Region where rivers/streams flow into the sea
Subject to the oceanic tides
Tidewater regions
Organisms subject to changing environment.
Animals - shrimp, oysters, clams, crabs, many
fish, numerous birds.
Aquatic Biomes
FRESHWATER BIOME
Characterized by low levels of dissolved salts
Separated into 2 categories
Lakes and Ponds
Eutrophic Lakes - rich in organic matter /vegetation
Oligotrophic Lakes - water with little organic matter.
Rivers and Streams
Bodies of water that flows down a slope
Gradient is key abiotic factor
Steep gradient - fast flow
Low gradient - slow flow.
Animals - fish, muskrats, otters, ducks, loons, numerous insects
Biotic Relationships
COMPETITION
Use or defense of a resource by one individual that
reduces the availability of that resource to other
individuals
May complete for habitat or food
Individuals in nature that don't retain access to
prime habitat may be less successful in their
struggle to survive and reproduce.
Types
Intraspecific Competition
Interspecific Competition
Biotic Relationships
INTRASPECIFIC COMPETITION
Competition between members of same
species
Example - lions fighting to mate
Individuals best adapted, survive and pass
genetic material on at a greater rate.
Driving force of evolution.
Biotic Relationships
INTERSPECIFIC COMPETITION
Competition between organisms of different species.
Not as intense - members aren't competing for exactly
the same materials
Deer and rabbits grazing in an open meadow
Competitive Exclusion Principle
When 2 or more species compete for the very
same resource, all but one will eventually fail
2 competitors can’t coexist on same limiting
resource.
Biotic Relationships
PREDATION
Consumer hunts/feeds on another consumer.
Predator - the hunter
Prey - the hunted.
Helps maintain an ecological balance or natural
equilibrium in an ecosystem
Predator and prey numbers graphs show max
of prey followed by a max of predators.
Snowshoe hare and lynx populations
Biotic Relationships
SYMBIOSIS
Biological relationship where 2 dissimilar
organisms live together closely
Interaction affects survival of one or both
Types
Parasitism
Commensalism
Mutualism
Biotic Relationships
PARASITISM
Symbiotic relationship where one organism
obtains nutrition from another organism
One benefits; other harmed
Parasite - organism that benefits
Host - organism that provides food; harmed.
Good parasite doesn’t kill its host quickly.
Ex - athlete's foot; ticks/mites; tapeworms
Biotic Relationships
COMMENSALISM
Form of symbiosis in which one organism benefits
and the other neither benefits nor suffers harm
Host is not harmed.
Epiphytes - type of plant that grows on other
plants; Orchids - orchid roots absorb air
moisture, tree - high place for light.
Barnacles on whales - barnacle benefits,
steady food supply, whale not harmed.
Biotic Relationships
MUTUALISM
Symbiosis where both organisms benefit
Bacteria in digestive tract of cattle
Lichens
Termites
Rhythmic Patterns
Activities of many organisms tied to cycles of time.
Rhythmic because they are regular and predictable.
Adaptation that often limits competition
Allow species to occupy the same habitat but to
utilize resources at different times.
Owls hunt mice - night
Hawks hunt mice - day.
Rhythmic cycles may be linked to variations in:
Length of daylight
Temperature
Hormone levels
Rhythmic Patterns
CIRCADIAN RHYTHMS
Cycles occurs about every 24 hours; means "about a day"
So-called biological clock; not sure where control center is located
Have investigated whether human rhythms are controlled by
sunlight, other physical factors, or some internal physiological
mechanisms
Humans keeps regular cycle between 22 - 26 hours in dark rooms.
Nocturnal - active mainly at night
Diurnal - active during the day
Examples
Morning Glories
Marine zooplankton
Humans
Rhythmic Patterns
ANNUAL RHYTHMS
Any physiological/behavioral pattern that recurs yearly
Many reproductive cycles tied to annual rhythms
Female bears give birth during winter
Nesting of ducks in spring /summer
Production of flowers/pollen at particular time
Seasonal Changes
Hibernation
Estivation
Rhythmic Patterns
HIBERNATION
State of severely reduced physiological activity in winter.
Allows active creatures to survive when extremely cold
and food scarce.
Breathing slow/irregular, blood pressure drops, and
body temperature drops.
Animals that hibernate
Bats, chipmunks, woodchucks, many reptiles
and amphibians.
Some animals go into a deep sleep, not hibernating
Bears, opossums, skunks
Rhythmic Patterns
ESTIVATION
Annual rhythm characterized by severely reduced
physiological activity in summer.
Escape from hot temperatures/dry conditions
May last for days, weeks, or months
Animal usually buries self in mud.
Animals that estivate
Frogs, toads, box turtles, some mice
Rhythmic Patterns
MIGRATORY RHYTHMS
Seasonal movement of some species from one community
or biome to another called Migration
Allows use of nutrients, habitats, and climatic conditions
only available during a particular season.
Some movements may cover long distances
Arctic tern breeds in N. Atlantic; migrates to Antarctic
Monarch Butterflies from Canada/northern U.S. to
Mexico
Mountain dwelling animals may migrate vertically
Bighorn sheep/elk move up slopes of in summer and
down in winter.
Rhythmic Patterns
TIDAL or LUNAR RHYTHMS
Tides due to gravitational pull of moon and sun on earth’s
oceans
High tides - about every 12.5 hours.- low tide in between.
Activities of intertidal organisms affected by the rise/fall of tides.
Barnacles - shell closed during low tide to prevent drying.
Many fish feed in tidal pools at high tide, leave as tide
recedes
Grunion Reproduction - with high tides of spring/summer
Male fish come ashore, followed by females
Eggs laid/fertilized/buried in sand
Fry carried to sea about 10 days later.
Succession
Gradual, sequential replacement of
populations in an area by other populations.
Organisms change their environment in ways
that make it less favorable to themselves and
more favorable for other organisms
Changes in abiotic factors may lead to changes
in the ecosystem
Succession
Stages of Succession
Pioneering Stage
Pioneer Species - first species to colonize a new habitat
Stabilize and enrich soil.
Serial or Developmental Stage
Intermediate communities of area.
Crowd out pioneer species, shade out smaller species;
further stabilize and enrich soil
Climax Community
Community that remains stable if the area is undisturbed.
Abiotic factors usually determine climax community
Succession
Types of Succession
PRIMARY SUCCESSION
Sequential replacement of populations in an area that
has not previously supported life.
Usually occurs in areas where bare rock has been
exposed.
Lichens are the pioneer organisms
Helps begin soil formation
As soil established larger plants may inhabit the area.
Eventually a climax community will be reached.
Process is very slow - may require hundreds of years.
Succession
Types of Succession
SECONDARY SUCCESSION
Community development in an area where a prior
community was removed.
Usually associated with some type of natural disaster.
Soil still present - grasses usually pioneer species.
Re-establishes the original community.
Progresses more rapidly than primary succession
Usually requires about a hundred years.
Old Field Succession
Population replaced on abandoned farm fields.
Succession
LAKE SUCCESSION
Transformation from crystal clear bodies of water to dry land
Involves process of Eutrophication
Increase in nutrients in an environment.
Young lakes called Oligotrophic
low in nutrients relatively few organisms
As nutrients and silt flows into the lake the water becomes murkier.
Sediment accumulates around roots of cattails and rushes at edge of lake
Lake Biomass increases
Aquatic arthropods and fish populate the lake.
Sediment begins to fill lake, becoming eutrophic
Lake becomes filled with rich sediment it becomes a marsh, then a
swamp, and finally dry land
Can proceed through stages to become dense forest.
Population Changes (Growth)
Growth of a population - due to births and immigration
Immigration - moving of individuals/organism to area.
Population increase in size.
Decrease of a population - due to deaths and emigration.
Emigration - moving of organisms/individuals from area.
Size of the population decreases.
Change in population size expressed as mathematical formula:
Change = (Births + Immigrants) - (Deaths + Emigrants)
Climax communities, birth and death rates remain about same
Developing communities populations may change in size
Population Growth
An increase in a population
POPULATION GROWTH RATE
Change in the number of individuals in a population over time:
Growth Rate = Change in Number of Individuals / time
BIOTIC POTENTIAL of a population
Rate a population grows if all survive and reproduce at maximum
Biotic potential usually never reached - limiting factors.
Food supply
Available space
Predation
Accumulation of wastes
CARRYING CAPACITY - population size environment can support.
Population Growth
GROWTH CURVES
A graph showing the number of individuals in
a population over time
Types of Growth Curves
J - SHAPED CURVE
S - SHAPED CURVE
Population Growth
J - SHAPED CURVE
LAG PHASE - period when there is little or no
increase in a population
Limited number of females reproducing
EXPONENTIAL PHASE - population increases so
rapidly that number of individuals doubles in a
specific time interval
Doubles in shorter periods of time
Population Growth
S - SHAPED CURVE
Exhibits lag & exponential phases
Doesn't increase as rapidly.
Leveling off represents a period of relative
stability after the lag and exponential phases.
Leveling gives indication of carrying capacity
Stabilization Phase – remains level
May get curve that declines after leveling off
Associated with bacterial/fungal cultures.
Population Growth
Limits to Growth
POPULATION DENSITY
Number of individuals per unit of area
Density = Individuals / Area
Low density may result in population dying
High population density
Protects individuals in the population
Population Growth
DENSITY-DEPENDENT FACTORS
Factors that affect populations in different
ways depending on population density
Usually biotic
Food Availability controls population size
Factors include availability of space and light,
disease, number of predators, and parasitism
Population Growth
DENSITY-INDEPENDENT FACTORS
Factors affect populations regardless of
population density.
Usually abiotic
Temperature, rainfall, wind speed, etc.
Human Populations
Survival rate of humans has increased due to
domestication of crops and animals
Provided humans with stable food supply.
Human Populations
Human Population Growth
From about 6000 B.C. to A.D. 1800
Number of humans in world increased steadily
Lag phase of J - shaped curve
About mid 1800's
Dramatic increases - entered exponential phase
Increased food production, rise of industry, and
better medicine
Life expectancy became longer.
Eventually will be limited by same density dependent
factors that limit other populations.