Transcript chapt 16

Chapter 16
Lecture Outline
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16-1
The Nature of Communities
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A community consists of all of the populations of
different species that interact in a particular location.
Before an ecologist can study a community, he must
first define the community boundaries.
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Defining Community Boundaries
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The boundaries of an aquatic community are
naturally defined by the water’s edge.
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All community boundaries are artificial.
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But does the community involve the plants and
animals that live at the edge, or the predators that
enter the area to eat and then leave?
Generated by ecologists for the purposes of
studying the community’s interactions
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Complexity and Stability
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The interactions between species in a
community involve a number of food chains.
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Even though the interactions are complex,
community structure is relatively stable.
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These food chains interconnect as a food web.
Complexity and stability are directly correlated.
More complex communities with more species
that interact are more stable.
Simpler communities that have been influenced
by humans tend to be less stable.
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A Food Web
16-5
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Communities are Dynamic
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Saying that communities are stable does not imply
that they do not change.
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On a large scale they are not changing, but individual
organisms are constantly experiencing change.
Individuals are producing, consuming or decomposing.
Populations are growing and shrinking.
However, if one particular species increases or
decreases significantly, the community as a whole
will be affected.
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Niche and Habitat
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Studying all of the species interactions in a
community at one time is not possible.
Ecologists often focus on the activities and
impact of a few species.
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One element that ecologists focus on is the
specific niche and habitat of individual species.
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The Niche Concept
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An organism’s niche is its specific functional role in
the community.
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The niche of an earthworm
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Involves the organisms impact on the biotic and abiotic
elements of the community
Also involves how the abiotic and biotic elements in a
community impact that organism
Affected by characteristics of the soil (abiotic)
Affects soil composition by transporting minerals, air and
water to deeper regions
Impacts biotic elements since it is food for a number of
different species; serves as a host for various parasites
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The Niche of an Earthworm
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The Niche Concept
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Organisms with broader
niches are more
evolutionarily successful
than organisms with more
narrow niches.
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Understanding the niche
concept is important to
understanding the impact of
a new species on a
community.
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Opossum vs. koala
Cows and dung beetles in
Australia
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The Habitat Concept
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The habitat of an organism is the place or
community where it lives.
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Habitat examples
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Habitat is a part of their niche.
Habitats are described in terms of features of an
organism’s home.
Prairie dogs live in grasslands.
Tuna live in the open ocean.
Cacti live in the desert.
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Kinds of Organism Interactions
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An important aspect of an organism’s niche
is how it interacts with other species in the
community.
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Interactions between species occur when
organisms share a common habitat.
Some interactions are positive, some are negative
and some are neutral.
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Competition
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Occurs when two organisms need a vital resource
that is in short supply
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Intraspecific competition occurs between members
of the same species.
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Pine seedlings competing for sunlight
Interspecific competition occurs between members
of different species.
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Can be food, water, shelter, nesting sites, mates, etc.
Usually harms both organisms to some extent
The most common interaction between species
Cultivated plants and weeds competing for sunlight, water,
space
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Competition
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Competition and Natural
Selection
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In a competitive relationship, usually one of the two
species “wins” the competition.
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Competition is a force for natural selection.
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The winner gains access to the limited resource.
The more similar organisms are, the more intense the
competition will be between them.
The competitive exclusion principle states that no
two species can occupy the same niche at the same
time.
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If two organisms occupy the same niche, the competition
will be so intense that
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One of the two species will become extinct.
One of the two species will evolve to occupy a slightly different
niche.
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Examples of Competitive
Exclusion
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Warblers
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Different species of birds eat flying insects.
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Different species of warblers feed on similar
organisms, but do so in different parts of trees.
Some feed at night, others feed at different
altitudes.
Birds are specialized by the size and kind of
insect eaten.
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Niche Specialization
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Predation
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Predation occurs when one organism is
captured, killed and eaten by another.
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Predators are specially adapted to catch their
prey.
Predation strategies are widely varied.
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The predator is the killer and the prey is killed.
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Chase and kill (leopards, lions, etc.)
Camouflage, wait and strike (frogs, lizards, etc.)
Pounce and kill (spiders)
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Predation
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Predators help control populations of
potentially dangerous organisms.
Populations of prey benefit from predation by
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Controlling population growth
Predators also act as selecting agents by
eliminating less well adapted individuals.
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The Predator-prey Relationship
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Symbiotic Relationships
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Symbiosis means “living together”.
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Include
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Emphasized in interspecific relationships in which
two species live in close physical relationship
Not always positive for both species
Parasitism
Mutualism
Commensalism
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Parasitism
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Involves one organism living in or on another
living organism in order to obtain nutrients
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The parasite benefits and the host is harmed.
Parasites do not kill their host immediately
because they need nutrients from it.
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However, as the parasite drains nutrients from the host,
it is weakened and may die.
Bacteria, viruses, protists, plants, fish, insects,
worms, mites and ticks are common parasites.
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Styles of Parasitism
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External parasites
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Internal parasites
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Live on the exterior of
their hosts
Fleas, ticks
Live inside their hosts
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Parasite Life Cycles
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Parasites have complicated life cycles.
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Many parasites experience different parts of their
life cycles in different hosts.
Some parasites use vectors, organisms that they
infect simply to get to their necessary host.
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Ticks are vectors for the bacterium that causes Lyme’s
disease.
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Lyme Disease—
Hosts, Parasites and Vectors
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Commensalism
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Commensalism is a relationship in which one
organism benefits and the other is not affected.
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Sharks and remora
Trees and epiphytic plants
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Mutualism
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Mutualism is a
relationship in which
both species benefit.
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Usually involves a close
physical association
Bacteria in the guts of
herbivores
Lichens and corals
Flowering plants and
bees
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Types of Communities
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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.
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These conditions include
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Precipitation types and amounts
Temperature ranges
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The Influence of Precipitation
and Temperature on Vegetation
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Biomes of the World
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Temperate Deciduous Forest
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Moderate rainfall spread over the entire year
Relatively long summer growing season
The dominant vegetation is deciduous forest.
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Deciduous trees lose their leaves in the fall.
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Adapted to significant precipitation and short, mild
winters
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Temperate Deciduous Forest
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Spreads from Mississippi River to Atlantic
coast, from Florida to southern California;
found in Europe and Asia
Primary consumers in this community are
leaf-eating insects, squirrels, deer
Secondary consumers are birds
Carnivores include foxes, hawks, and owls
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Temperate Deciduous Forest
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Temperate Grassland
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Also called a prairie
Rainfall is not adequate to support the
growth of trees .
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Dominant vegetation is grasses
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Long periods of time between rainfall
Trees only exist near streams.
Interspersed with wildflowers
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Temperate Grassland
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Primary consumers are large grazing mammals,
small insects and rodents
Carnivores include meadowlarks, coyotes and
snakes.
Birds are merely visitors.
Fires are common during the dry season.
Found between the Mississippi River and the Rocky
Mountains
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Also in Eurasia, Africa, Australia and South America
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Temperate Grassland
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Savanna
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Tropical biomes that have distinct wet and dry
seasons
Found in central Africa, northern Australia, South
America
Dominant vegetation is grasses
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Animals include grazing animals
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Includes some drought-resistant trees
Antelope, wildebeest, zebras, kangaroos, capybara
Termites are common
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Savanna
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Mediterranean Shrublands
(chaparral)
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Located near an ocean
Wet, cool winters and hot, dry summers
Vegetation dominated by woody shrubs
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Can withstand the hot, dry summer by becoming dormant
Fire is common feature
Wide variety of animal life
Not much still in existence because of human activity
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Mediterranean Shrublands
(chaparral)
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Tropical Dry Forest
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Characterized by seasonal rainfall
Heavy monsoons for several months are
followed by extensive dry periods.
Plants have special adaptations for
withstanding drought.
Animals are similar to tropical rain forest, but
not as abundant
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Tropical Dry Forest
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Desert
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Very dry areas where rainfall levels are low and
irregular
Either extremely hot or cold
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Characterized by scattered thorny plants
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Lack leaves as an adaptation to the dry climate
Stems are green and undergo photosynthesis
Many store water in their stems (cacti)
Contains flowering plants, insects, reptiles and
mammals
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Show large daily fluctuations in temperature
These species are active at night and burrow during the day.
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Desert
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Boreal Coniferous Forest
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Also known as
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Long, cold winters
Dominated by evergreen trees
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Northern coniferous forest
Taiga
Adapted to long, cold winters and short growing
seasons
Spruce, firs, pines
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Boreal Coniferous Forest
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Evaporation is low, therefore, this climate is
humid.
Animals include mice, snowshoe hare, lynx,
bears, wolves, squirrels, moose, midges and
flies.
Found in northern regions of the US, and
southern Canada, northern Europe and Asia
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Boreal Coniferous Forest
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Temperate Rainforest
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Wind from ocean brings moister air to the coast
Moisture falls as rain or snow.
Abundant water, fertile soil and mild temperatures
Plants include evergreens like spruce, fir, hemlock.
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As well as deciduous trees such as red alder, maple,
cottonwood
Trees are covered in mosses, ferns, etc.
Found in coastal areas of northern California,
Oregon, Washington, British Columbia and southern
Alaska
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Temperate Rainforest
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Tundra
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Characterized by extremely long, severe winters
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Short growing season (less than 100 days)
Low rainfall
Deep layers of soil remain frozen (permafrost)
Very few animals and plants can survive.
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Short, cool summers
No trees
Plants include grasses, sedges, shrubs, lichen.
Animals include caribou, wolves, fox, snowy owls,
mice, insects.
Found in the extreme north (Alaska)
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Tundra
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Tropical Rainforest
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High temperature
Rainfall everyday
Thousands of plants and animals
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Balsa, teak, ferns
Trees covered with orchids vines and mosses
Tree frogs, bats, lizards, birds, monkeys and insects
Found primarily at the equator
Human clear-cutting, coupled with the excess
rainfall, causes extensive leaching of the soil.
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Tropical Rainforest
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The Relationship Between
Elevation and Climate
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Air temperatures are warmest near the
equator and become cooler toward the poles.
Air temperature decreases as elevation
increases.
Traveling from the ocean to mountain peaks
will lead through the same biomes as
traveling from the equator to the north pole.
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The Relationship Among Elevation,
Latitude and Vegetation
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Major Aquatic Ecosystems
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Can be separated into:
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Also vary in terms of:
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Marine: salt content greater than 35 parts per
thousand
Freshwater: salt content less than 0.5 parts per
thousand
depth of water
how far sun’s rays penetrate water
nature of bottom substrate
water temperature
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Major Marine Ecosystems
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Pelagic—consists of organisms that float or
actively swim in the ocean
Benthic—consists of organisms that live on
the ocean floor
Estruaries—shallow, partially enclosed areas
where water enters the ocean
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Pelagic Marine Ecosystem
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Plankton are so small and weakly swimming
that they are carried by the ocean currents
Phytoplankton carry out photosynthesis
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Majority are bacteria or algae
Commonly found in the upper layer of the ocean,
known as the euphotic zone
Zooplankton are weakly swimming animals
that feed on phytoplankton.
Dependent on material dissolved in the water
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Role of Plankton in Marine
Ecosystems
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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
Material that makes up the ocean bottom is important in
determining the type of community.
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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 which type of benthic community
arises.
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Two Types of Benthic Marine
Ecosystems
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Coral reef ecosystem
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Abyssal ecosystem
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Dependent upon photosynthesis, so found at
shallow depths
Not dependent upon photosynthesis, so found at
great depths
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Coral Reef Ecosystem
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Produced by coral animals that build cup-shaped
external skeletons around themselves
Corals protrude from their skeletons to catch food
and be exposed to sunlight.
While coral animals are not themselves
photosynthetic, they harbor photosynthetic algae.
Coral skeletons provide a surface upon which many
animals live.
Considered one of the most productive ecosystems
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Coral Reef Ecosystem
16-63
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Abyssal Ecosystem
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No light for photosynthesis
Rely on organic material from euphotic zone
All organisms are scavengers, eating
material that drifts their way.
Some animals generate light to aid in their
search for food.
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Estuary
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Shallow, partially enclosed areas where freshwater
meets the ocean
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
Serve to trap river sediments from entering ocean
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Human Impact on Marine
Ecosystems
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Over-fishing has destroyed many traditional
fishing industries.
Estuaries are impacted by the flow of
fertilizer, animal waste and pesticides
downriver.
The use of oceans for transport results in oil
and trash pollution.
Coral reefs are impacted by over-fishing and
siltation from rivers.
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Freshwater Ecosystems
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Amount of salt present is lower than marine
Temperature of water can change greatly
Water is in the process of moving to the ocean.
Oxygen can be in short supply.
Two major types:
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Lakes and ponds: water is relatively stationary
Streams and rivers: water is running downhill
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Lakes and Ponds
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Large lakes are similar to oceans in that there is a deep,
non-photosynthetic zone and a euphotic zone in
shallower regions.
Flowering plants rooted in the bottom are present along
the shore.
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Region with rooted plants is called the litteral zone; region
without rooted plants is the limnetic zone.
Dissolved oxygen is important for the ecosystem.
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Emergent plants have leaves that float on or protrude above
the surface (cattails, water lilies).
Submerged plants stay below the surface (Elodea, Chara).
Oxygen comes from photosynthesis, or by mixing of air into
the water by wave action.
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Lakes and Ponds
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Streams and Rivers
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Since water is moving, plankton organisms
are not as important as attached organisms.
Most algae grows attached to rocks or other
attached surfaces.
It is difficult for photosynthetic organisms to
accumulate nutrients necessary for growth.
Debris is used as a source of food.
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Human Impact on Freshwater
Ecosystems
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Any activity on land eventually affects
freshwater ecosystems because of runoff.
Agricultural runoff, sewage, sediment and
trash all make their way to streams and
lakes.
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Succession
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A climax community is a stable, long-lasting
community.
When communities change from one type to another,
succession occurs.
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Successional stages lead to a climax community.
Primary succession occurs when a community
develops in a previously uninhabited location.
Secondary succession occurs when a community is
disturbed and then has to re-grow.
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Primary Succession
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Relatively rare because there are few areas
that are not already inhabited
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Tops of mountains, newly formed volcanic rock
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Primary Succession
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Pioneer organisms grow first and establish
a pioneer community.
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Bacteria, algae, fungi, and lichens
Lichens are particularly important.
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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.
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Primary Succession
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As soil forms, small plants become
established.
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As larger plants grow, animal consumers
move in.
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This adds more soil.
Introduces shade, smaller plants die out
Succession from this point depends on the
climate.
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Pioneer Organisms
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Primary Succession
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Secondary Succession
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Occurs after a community is altered by a natural or
human-induced disaster
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Soil is already present.
A reservoir of seeds from plants still exists from the
original community.
A pioneer community of weeds appears first.
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Then grasses emerge.
Grasses can support insects, small mammals and birds.
If rainfall is adequate
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Hurricane, fire, abandoned agricultural land
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Shrubs and small trees will begin to grow.
Larger trees will follow and grasses will die out.
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Succession From a Pond
to a Wet Meadow
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Secondary Succession on Land
16-80
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The Impact of Human Activities
on Communities
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Humans have affected almost every
community on earth.
We must analyze the effects of our actions
when we manipulate a community.
Analyzing the impact of human activity on
communities is crucial for the future of our
environment.
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Introduced Species
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Humans have introduced many species into
new communities, both planned and
accidental.
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Agricultural species are almost always introduced
species.
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Accidental introductions significantly alter
communities.
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Cattle have displaced native grazers in the Midwest.
Pigs are destroying natural communities in Hawaii.
Chestnut blight
Fungal disease
Zebra mussels
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Introduced Species
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Predator Control
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Humans have destroyed large predators to
protect livestock.
The absence of predators has led to a
number of problems.
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Deer have become over-populated.
Alligators present problems to pets and children.
Elk and bison populations have increased in
national parks.
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Predator Control
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The Reintroduction of Wolves
to Yellowstone
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Habitat Destruction
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Human activity has destroyed the habitat of
many communities.
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Human activity has impacted certain species
by destroying their habitat.
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Communities with less species diversity are more
fragile and susceptible to damage by human
activity.
The tundra has been severely affected by human
activity.
Whales, condors, eagles, etc.
Converting land to farmland or developing land
destroys habitats.
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Habitat Destruction
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Endangered and Threatened
Species
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Pesticide Use
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Herbicides kill plants; insecticides kill insects.
Continual use of pesticides selects for resistant
organisms.
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Pesticides also kill other valuable organisms.
Natural predators and parasites can kill pests.
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Take longer than pesticides, but do not negatively impact
the community
Integrated pest management
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This makes the pesticides no longer useful.
Involves using pesticides and encouraging the growth of
natural pest enemies
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Pesticide Use
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Biomagnification
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The continual use of chemical pesticides and
fertilizers significantly impact the food chain.
Chemicals ingested by organisms in the lower
trophic levels are passed to successively higher
trophic levels.
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The chemicals accumulate as they are passed to higher
trophic levels.
This can result in the death of secondary and tertiary
consumers.
This is called biomagnification.
DDT, PCBs, dioxins, methylmercury
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Biomagnification of DDT
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