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Ecology
All Materials © Cmassengale
Ecology is the study of interactions between organisms (biotic part) and their
nonliving environment (abiotic factors)
Biotic factors includes plants, animals, fungi, & microorganisms. They may be
producers, consumers, or decomposers.
Abiotic factors include climate, soil, temperature, water, air, sunlight, humidity,
pH, and atmospheric gases.
Habitat is the place a plant or animal lives, while its niche is its total way of life.
Life is organized into levels:
Organism (any single living thing)
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Population (members of the same species living in one place)
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Community  (all the populations living in a defined area)
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Ecosystem the Community living in a similar habitat, ecosystems consist of both
biotic and abiotic components
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iomes Ecosystems covering a wide area with similar climates and organisms
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iosphere all the living and nonliving things on Earth
Producers:
Make their own food through photosynthesis or chemosynthesis. Autotrophic
Includes: plants, algal, protists, and some bacteria
Consumers
Can not and do not make their own food. Need to eat something that is an autotrophe or eat something
that ate an autotrophe.
May be herbivoures, feed only on plants, carnivores feed only on meat or omnivores feed on plants and
animals.
Decomposers:
Break down dead plants and animals into their inorganic component part to be
Recycled (nutrients) in the soil for producers to use. Called detritivores and include bacteria, fungus and
mold.
Sunlight is the ultimate energy for all life on the surface of the planet and the upper regions of the oceans.
But only producers can get their energy from sunlight and convert it into a biological storage form of
glucose.
a food pyramid is divided into tropic levels- these are feeding levels of producers and
consumers in an ecosystem. Each tropic level is all the biomass that supports the
levels above it.
1st tropic level are the producers that use sunlight directly or in deep marine
environments the chemotrophes bacteria that feed on methane or sulfur compounds.
2nd tropic leve includes herbivores that feed on the plants directly or the organisms in
the deep chemotrophe sink areas feed on the bacteria.
The higher tropic levels 3rd and 4th in some cases are the carnivores that feed on level
2, 3 and sometimes 4.
Food Chains and Food Webs:
Chains show who eats whom in an ecosystem in a single organism to single organism passage of
energy
Webs are made up of several food chains and the interconnections, showing that organisms have
more than one food source in the ecosystem.
Always begin with the producers, and their initial energy source.
Producers store energy in the chemical bonds of the food, glucose, they make
Stored energy is passed to consumers when they eat the producers or other consumers
Someenergy is lost at each tropic level as heat when chemical bonds are broken or lost if the
consumer can not digest the stored form.
Both energy and nutrients must move through the ecosystem.
Populations
Populations (included in Biome Project)
• A population is a group of individuals of a species that live together and influence each
other’s survival
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Populations have several properties that can describe them
 population range is the area throughout which a population occurs
 population distribution is the pattern of spacing of individuals within that range
 population size is the number of individuals in the population
 population density is the population size that occurs in a given area
 population growth describes whether a population is growing or shrinking, and
at what rate
 No population occurs in all habitats worldwide
Most species have relatively limited geographic ranges
 Each population has its own requirements that determine where it can live and
reproduce temperature, humidity, food
 Ranges may expand or contract in response to environmental change
Altitudinal shifts in population ranges in the mountains of southwestern North
America
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Population Distribution
Populations may be distributed randomly, uniformly, or clumped
Random spacing occurs when individuals do not interact strongly with one another or
with nonuniform aspects of their environment
 not common in nature
Uniform spacing often results from competition for resources
 territories provide exclusive access to resources such as food, water, refuges, and
mates
Clumped spacing occurs in response to uneven distribution of resources in their
immediate environments
 social interactions also can lead to clumped distributions
 common in nature
Dispersal mechanisms to colonize new areas may occur through
 water
 wind
 transfer from an animal traveling between locations
Humans have altered population ranges of organisms by altering the environment
Humans have served as an agent of dispersal for many species
Population Growth
Critical properties of any population include
 population size - the number of individuals in the population
 population density - the number of individuals that occur in a unit area
 population growth - capacity to grow
A population’s growth rate is the difference between the birth and death rates, corrected
for movement of individuals into (immigration) or out of (emigration) the population
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when a population’s growth rate remains constant, the population experiences
rapid growth called exponential growth
 in natural populations, exponential growth only prevails for short periods, such as
when an organism reaches a new habitat
Exponential growth in a tree population
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A population ultimately stabilizes at a certain size, called the carrying capacity
 the carrying capacity is defined as the maximum number of individuals that an
area can support
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No matter how rapidly populations grow, they eventually reach a limit imposed by
shortages of important environmental factors
 at this point, the population begins to experience logistic growth
Most natural populations exhibit logistic growth
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Logistic growth can best be represented by a sigmoid growth curve or S curve
 growth is rapid at first when the population is small, then tapers off at an
increasing rate as population size approaches carrying capacity
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Logistic growth is characteristic of most biological populations
Compare the two growth curve types
The Influence of Population Density
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Many factors act to regulate the growth of populations in nature
 density-independent effects
• these effects regulate population growth regardless of population size
• for example, weather effects or geological events (i.e., volcanoes)
 density-dependent effects
• the effect that these factors have on population growth depends on
population size
• these effects grow stronger as the population size increases
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In natural systems that are exploited by humans, the aim is to maximize productivity by
exploiting the population early in the rising portion of its sigmoid growth curve
 commercial fisheries, for example, attempt to operate so that they harvest a
population near its point of maximal sustainable yield
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ii.
iii. Introduction—hierarchy activity
iv. Richness/evenness-- Bird Island activity
v. Density dependent/independent factors – Dominos Demo
vi. Population growth curves
vii. carrying capacity
Communities (included in Biome Project)
viii. Interactions (symbiosis, predator/prey, competition, keystone species,
etc.)—Soaring Eagle lab
ix. Succession
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Community refers to the species that occur at any given locality
 communities can be characterized by either their constituent species (a
list of all species present in the community) or by their properties, such
as primary productivity
 interactions among community members govern many ecological and
evolutionary processes
• for example, predation, competition, and mutualism affect the
population biology of a particular species, as well as the way in
which energy and nutrients cycle through the ecosystem
• Coevolution is the adaptation of a species to the other organisms in its
community
 examples of coevolution include
• plants and animal pollinators
• predator-prey interactions
• symbiotic relationships
Pollination by bat
Coevolution and Symbiosis
 Symbiosis means “living together”.
– Describes situation in which members of two species live in close
physical relationship
– Not always positive for both species
• In a symbiosis, two or more kinds of organisms live together in often elaborate
and more or less permanent relationships
 there are three major kinds of symbiotic relationships
• mutualism
• commensalism
• parasitism
• Mutualism is a symbiotic relationship in which both species benefit
The pistol shrimp defends the coral, which he calls home—an example of
mutualism
– Commensalism is a symbiotic relationship that benefits one species but
neither hurts nor helps the other. Example Sharks and remora
– Trees and epiphytic plants.Oxpeckers eat insects off an impala—an
example of commensalism
Parasitism is a symbiotic relationship in which one species benefits while the
other is harmed
 Involves one organism living in or on another living organism in order to
obtain nutrients
– The parasite benefits and the host is harmed.
– Parasites usually do not kill their host immediately because they need
nutrients from it.
 However, as the parasite drains nutrients from the host, the host is
weakened and may die.
– Bacteria, viruses, protists, plants, fish, insects, worms, mites, and ticks
all have species that are parasites.
– There are more parasitic species than nonparasitic species in the world.
 Internal parasites
– Live inside their hosts
– Tapeworms, bacteria, protozoa
 External parasites
– Live on the exterior of their hosts
– Fleas, ticks
 There are even parasitic plants
– Indian pipe
Examples
Mosquito: Females ingest blood for the protein. Male mosquitos ingest plant juices.
Dirofilaria immitis: Heartworm of dogs, whose adults reside in the right side of the heart.
• Predation is the consuming of one organism by another
 in nature, predators often have large effects on prey populations
• population cycles may be, in some situations, stimulated by
predators
• a classic example is the “10-year cycle” of the snowshoe hare,
Lepus americanus, that appears to be under the influence of food
plants and predators
 under laboratory conditions, predators may exhaust their prey species
and then starve
prey predator cycles
 Predation occurs when one organism is captured, killed, and eaten by another.
– The predator is the killer and the prey is killed.
– Predators have evolved specific methods for capturing prey.
 Chase and kill (leopards, lions, etc.)
 Camouflage, wait and strike (frogs, lizards, etc.)
 Use tools to capture and kill (spiders and webs)
Affects on Prey
 Prey populations are controlled by predators.
 Predators act as selecting agents on prey populations by eliminating less welladapted prey individuals.
 Predators remove sick and injured prey, which can control the spread of disease
in the prey population.
• Predator-prey interactions are an essential factor in the maintenance of
communities that are rich and diverse in species
 predators prevent or greatly reduce competitive exclusion by reducing
the number of individuals of competing species
• Plants have evolved many mechanisms to defend themselves against predators
 Physical defenses: spines, thorns, prickles
 Chemical defenses: chemicals that make the plants toxic to herbivores
• some herbivores have, as a result, evolved a tolerance to these
chemicals and may use them for their own defense
 many animals have defensive coloration
• aposematic coloration is a warning coloration that is
characteristic of animals that use poisons
• cryptic coloration is color that blends in with surroundings
Ecological Succession
 A climax community is a stable, long-lasting community.
 When communities change from one type to another, succession occurs.
– Successional stages lead to a climax community.
 Primary succession occurs when a community develops where non-previously
existed.
 Secondary succession occurs when a community is disturbed and regenerates.
• Succession is the orderly replacement of one community with another
 primary succession
• occurs on bare, lifeless substrates, such as those left behind when
a glacier retreats or when a volcanic island emerges
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• pioneering community is the first to become established
Pioneer organisms grow first and establish
a pioneer community.
 Bacteria, algae, fungi, and lichens
 Lichens are particularly important.
• Combination of algae and fungi
• Able to grow on bare rock
• Capable of photosynthesis and can form new organic matter
• Small consumers can eat lichen.
• Breaks down rock and liberates minerals
• Soil begins to form.
As soil forms, small plants become established.
 This adds more soil.
As larger plants are established smaller plants die out.
 Shade from tall plants makes it difficult for shorter plants to survive.
Succession from this point depends on the climate.
Each stage in plant succession is accompanied by specific kinds of animals
 secondary succession
• occurs after an already established community has been disturbed
Occurs after a community is altered by a natural or human-induced disaster
 Hurricane, fire, abandoned agricultural land
Soil is already present.
A reservoir of seeds from plants still exists from the original community.
A pioneer community of weeds appears first.
 Then grasses emerge
 Grasses can support insects, small mammals, and birds.
If rainfall is adequate
 Shrubs and small trees will begin to grow.
 Larger trees will follow and grasses will die out.
Three main elements that must move through an ecosystem:
Water
Carbon and
Nitrogen
The follow up 4th is phosphorous
Water or Hydrologic Cycle:
Cells are 70-90$ water, water is needed for metabolic processes serving as a
solvent in biological organisms as we understand them, water is the most
important element for terrestrial organisms because they loose water to the
surrounding environment- desiccation or drying out.
Steps in the water Cycle:
Evaporation
Transpiration
(water loss from lakes, rivers, oceans...)
(water loss from plant leaves)
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Condensation
water vapor forms clouds or fog
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Precipitation
Water returns to the surface of the Earth in the form or rain, sleet, snow…
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Surface Runoff
returns water to the surface or to ground water.
USGS water cycle http://water.usgs.gov/edu/watercycle.html
Carbon Cycle:
Consists of photosynthesis, cellular respiration and decomposition
Begins with producers taking carbon dioxide from the air to use during photosynthesis to make
glucose.
The carbon dioxide in the glucose is used during cellular respiration to make ATP the energy of
biological work and CO2 is made as a waste product.
Decomposing plants and animals return carbon to the soil and air.
Carbon Cycle Steps:
Plant leaves take carbon dioxide from air
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plants convert carbon dioxide into carbohydrates – glucose and store it as starch or use to make
their structures- grow- as cellulose.
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plants and animals release carbon dioxide back into the air during cellular respiration
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Decomposers return carbon products to the soil and water to be reused by producers.
Nitrogen:
Needed by all organisms
Used to make proteins & nucleic acids (DNA & RNA)
Air made up of 80% nitrogen
Only Cyanobacteria & Rhizobium bacteria can use nitrogen directly from the
air (nitrogen fixation)
Bacteria found in the soil & on the roots of legumes (beans, peas ...)
Steps in the Nitrogen Cycle:
Cyanobacteria & Rhizobium take nitrogen from air
(nitrogen fixation)
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Convert Nitrogen gas into ammonia
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nitrifying bacteria in the soil convert ammonia into nitrates
plants can use the nitrates to make proteins
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Consumers eat the plants an get the proteins containing nitrogen
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Decomposers break down dead organisms and return the nitrogen to the air and
soil called ammonification
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anaerobic bacteria (work without oxygen present) in the soil release nitrogen
from the nitrates into the air, called denitrification.
 The world can be subdivided into different types of communities called
biomes.
 Biomes are particular communities or organisms that are adapted to a
particular set of climate conditions.
– These conditions include
 Precipitation types and amounts
 Temperature ranges
The Influence of Precipitation and Temperature on Vegetation
Three main types of ecosystems:
Terrestrial (land)
Freshwater (rivers, ponds, lakes ...)
Marine (oceans & seas)
Terrestrial ecosystems are divided into 7 biomes with similar climates &
organisms
Seven Terrestrial Biomes:
Tropical Rain Forest (jungle)
Savanna (tropical grasslands)
Deserts
Grasslands
Deciduous Forest
Taiga (coniferous forest)
Tundra
Tundra:
Cold & dark most of the year
Includes the arctic
Permafrost is the top layer of soil that thaws & in which plants grow
No trees, but sedges & grass, mosses, & lichens
Many migratory animals
Lemmings & ptarmigans are year round residents
Approximately 20 cm annual rainfall
Taiga:
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Coniferous forest
Extends across northern Eurasia & North America
Contains conifers or evergreens (spruce, cedar, fir, pine ...)
Needle like leaves withstand weight of snow
Bear, deer, moose, wolves, mountain lions ...
Sequoia or redwood (largest conifer) grows here
Bristle cone pine oldest living conifer found here
Temperate Deciduous Forest:
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South of taiga in North America, eastern Asia, & Europe
High annual rainfall (75-150 cm)
Moderate temperatures
Well-defined seasons of about equal length
Trees loose leaves in winter (deciduous)
Show stratification (plant layers):
1. Canopy - broad leaf deciduous trees forming uppermost layer
2. Under story - shrubs
3. Forest Floor - herbaceous plants
Songbirds, deer, rabbits, foxes, squirrels, frogs 7 toads, lizards ...
Tropical Rain forest:
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Near equator
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Warm climate (20 -25 degrees C)
Plentiful rainfall (190 cm/year)
Contains the greatest diversity of plants & animals
Insects, monkeys & apes, snakes, tropical birds, leopards...
Animals & plants brightly colored
Poor soil for agriculture
Grasslands:
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Mostly grasses with a few trees due to less rainfall
Moderate climates
Good for agricultural crops
Grazing & burrowing animals dominate
Also called prairies
Savanna:
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Tropical grasslands
Warm climate & rainy season
Antelope, zebra, lions, wildebeests, hyenas, elephants...
Suffer from floods & drought
Deserts:
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Low annual rainfall
Subject to strong winds
Days usually hot & nights cold
Sahara desert is without vegetation
Succulents such as cacti & other water storing plants
Most animals nocturnal
Lizards, snakes, roadrunners, insects, tarantula, hawks, rodents, coyotes...
Aquatic Biomes:
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May be freshwater or saltwater
Wetlands near oceans have brackish water (mixture of fresh & salt waters)
Part of the part water or hydrologic cycle
Often polluted by man's activities
Lakes & Rivers:
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Freshwater
Oligotrophic lakes are nutrient poor (catfish, carp...)
Eutrophic lake are nutrient rich (trout, bass...)
Deep lakes have layers or strata where different plants & animals live
Phototropic organisms in upper layers for light
Estuary at mouth of river contains brackish water
Ocean Zones:
Major Marine Ecosystems
 Pelagic—consists of organisms that float or actively swim in the ocean
 Benthic—consists of organisms that live on the ocean floor
 Estuaries—shallow, partially enclosed areas where freshwater enters the ocean
– Brackish
Pelagic Marine Ecosystem
 Plankton are so small and weakly swimming that they are carried by the ocean currents.
 Phytoplankton carry out photosynthesis.
– Majority are bacteria or algae
– Commonly found in the upper layer of the ocean, known as the euphotic zone
– Dependent on material dissolved in the water
 Zooplankton are weakly swimming animals that feed on phytoplankton.
 Larger animals (fish, shrimp, etc.) feed on zooplankton.
Benthic Marine Ecosystems
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Consists of organisms that live on ocean floor (whether attached or not)
Photosynthesis by seaweed can occur in shallow regions.
Food sinks to bottom from upper water layers
Material that makes up the ocean bottom is important in determining the type of
community.
– Sand makes it difficult for plants to attach, but is good for crustaceans.
– Mud provides suitable habitat for rooted vegetation, and burrowing organisms
that filter feed in the water above the mud.
– Rocky surfaces provide a good substrate for large algae and a variety of animals.
 Temperature also affects the type of benthic community that is present.
Two Types of Benthic Marine Ecosystems
 Coral reef ecosystem
– Dependent upon photosynthesis, so found at shallow depths
 Abyssal ecosystem
– Found on the bottom at depths below the euphotic zone
– No photosynthesis
Estuary
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Shallow, partially enclosed areas where freshwater meets the ocean
Sediments from rivers accumulate in estuaries.
Saltiness changes with the ocean tides and the flow of the rivers.
Organisms are specially adapted to these conditions.
Phytoplankton and algae provide photosynthetic activity which supports the ecosystem.
Important as nursery sites for fish and crustaceans
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Intertidal zone
1. Along shoreline
2. Wave action
3. Lots of light so many producers
4. Starfish, sand dollars...
Neritic Zone
1. Ocean water above continental shelf
2. Coral reef found here
3. Surrounds continents & receives light in upper layers
Oceanic Zone
1. Beyond continental shelf
2. Deepest area (up to 7 miles)
3. Bottom doesn't receive light so animals adapted to darkness (many
produce their own light, feed on other animals...)
4. Deepest area called abyss
5. Upper area gets light & called the photic zone (lots of seaweed here)
6. Floaters called plankton (microscopic organisms)
7. Swimmers such as fish called nekton
8. Bottom dwellers called benthos