Download Community PPT

CHAPTER 3
Communities and Ecosystems
Dining In
• 1) Wasps and Pieris
caterpillars form an unusual
three-step food chain
– a) The 4-mm-long wasp
Apanteles glomeratus
stabs through the
skin of a Pieris rapae
caterpillar and lays her
eggs
Dining In
• 1. The caterpillar will be destroyed from
within as the wasp larvae hatch and
nourish themselves on its internal
organs
– b) Ichneumon wasps can detect when a
Pieris caterpillar contains Apanteles larvae
• 1. A female ichneumon will pierce the
caterpillar and deposit her own eggs
inside of the Apanteles larvae
Dining In
Dining In
– c) Finally, yet another wasp, a chalcid, may
lay its eggs inside the ichneumon larvae
• 1. Usually, only the chalcids will emerge
from the dead husk of the caterpillar
Dining In
• 2) A biological community derives its structure
from the interactions and interdependence of
the organisms living within it
– a) Ecosystem functioning depends on the
complex interactions between its
community of organisms and the physical
environment
The Community
• 1) All the organisms in a particular area make
up a community
– a) A number of factors characterize every
community
• 1. Biodiversity
• 2. The prevalent form of
vegetation
• 3. Response to disturbances
• 4. Trophic structure
(feeding relationships)
The Community
• 2) Biodiversity is the variety of different kinds
of organisms that make up a community
– a) Biodiversity has two components
• 1. Species richness, or the total number
of different species in the community
• 2. The relative abundance of different
species
Competition Within Communities
• 1) Interspecific competition occurs between
two populations if they both require the same
limited resource
– a) A population's niche is its role in the
community
• 1. The sum total of its use of the biotic
and abiotic resources of its habitat
• 2) The competitive exclusion principle
– a) Populations of two species cannot
coexist in a community if their niches are
nearly identical
High
tide
Chthamalus
Balanus
Ocean
Low
tide
Competition Within Communities
• 3) Competition between species with identical
niches has two possible outcomes
– a) One of the populations, using resources
more efficiently and having a reproductive
advantage, will eventually eliminate the
other
– b) Natural selection may lead to resource
partitioning
Predation
• 1) Predation is an interaction where one
species eats another
– a) The consumer is called the predator and
the food species is known as the prey
– b) Parasitism can be considered a form of
predation
• 2) As predators
adapt to prey,
sometimes natural
selection also
shapes the prey's
defenses
– a) This process of
reciprocal
adaptation is
known as
coevolution
Eggs
Sugar
deposits
Predation
• 1. Example: Heliconius and the
passionflower vine
– b) Prey gain protection against predators
through a variety of defense mechanisms
• 1. Mechanical defenses, such as the
quills of a porcupine
Predation
• 3) Chemical defenses are widespread and
very effective
– a) Animals with effective chemical
defenses are often brightly colored to warn
predators
• 1. Example: the poison-arrow frog
• 4) Camouflage is a very common defense in
the animal kingdom
– a) Example: the gray tree frog
• 5) Batesian mimicry occurs when a palatable
or harmless species mimics an unpalatable or
harmful one
– a) The mimicry can even involve behavior
• 1. This hawkmoth larva puffs up its head
to mimic the head of a snake
• 6) Müllerian mimicry is when two unpalatable
species that inhabit the same community
mimic each other
– a) Example: the cuckoo bee and the yellow
jacket
Diversity in a Community
• 1) A keystone species exerts strong control
on community structure because of its
ecological role
• 2) A keystone predator may maintain
community
diversity by reducing
the numbers of the
strongest competitors
in a community
– a) This sea star is a
keystone predator
– b) Predation by
killer whales on
sea otters,
allowing sea
urchins to
overgraze on kelp
• 1. Sea otters
represent the
keystone
species
Symbiotic Relationships
• 1) A symbiotic relationship is an interaction
between two or more species that live
together in direct contact
– a) There are three main types of symbiotic
relationships within communities
• 1. Parasitism
• 2. Commensalism
• 3. Mutualism
Symbiotic Relationships
– b) Parasitism is a kind of predator-prey
relationship
• 1. The parasite benefits and the host is
harmed in this symbiotic relationship
• 2. A parasite obtains food at the
expense of its host
• 3. Parasites are typically smaller than
their hosts
2) In the 1940s, Australia was overrun by
hundreds of millions of European rabbits
– a) The rabbits destroyed huge expanses of
Australia
– b) They threatened the sheep and cattle
industries
• a) In 1950, a parasite that infects rabbits
(myxoma virus) was deliberately
introduced to control the rabbit
population
Symbiotic Relationships
• 3) Commensalism is a symbiotic relationship
where one partner benefits and the other is
unaffected
– a) Examples of commensalism
• 1. Algae that grow on the shells of sea
turtles
• 2. Barnacles that attach to whales
• 3. Birds that feed on insects flushed out
of the grass by grazing cattle
– b) Mutualism is a
symbiotic relationship
where both partners
benefit
• 1. Examples of
mutualism
–a. Nitrogen-fixing
bacteria and
legumes
–b. Acacia trees
and the ants of
the genus
Disturbance
• 1) Disturbances include events such as
storms, fires, floods, droughts, overgrazing,
and human activities
– a) They damage
biological
communities
– b) They remove
organisms from
communities
– c) They alter the
availability of
resources
Disturbance
• 2) Ecological succession is a transition in the
species composition of a community following
a disturbance
– a) Primary succession is the gradual
colonization of barren rocks by living
organisms
– b) Secondary succession occurs after a
disturbance has removed the vegetation
but left the soil intact
Talking About Science
• 1) Ecologist Frank Gilliam
is especially interested in
the role that fire plays in
shaping ecosystems
– a) According to Dr.
Gilliam, fire is a key
abiotic factor in many
ecosystems
– b) Grasslands are so
dependent on fire that its
absence is considered a
disturbance
• 2) Following a fire in southeastern pine forest,
the numbers and variety of nonwoody plants
usually increase dramatically
– a) Fire makes more nutrients available to
these plants
Energy Flow and Chemical Cycling
• 1) A community interacts with abiotic factors,
forming an ecosystem
– a) Energy flows from the sun, through
plants, animals, and decomposers, and is
lost as heat
– b) Chemicals are recycled between air,
water, soil, and organisms
A terrarium ecosystem
Chemical cycling
(C, N, etc.)
Light
energy
Chemical
energy
Heat
energy
Trophic Structure
• 1) A food chain is the stepwise flow of energy
and nutrients
– a) from plants (producers)
– b) to herbivores (primary consumers)
– c) to carnivores (secondary and higherlevel consumers)
TROPHIC LEVEL
Quaternary
consumers
Carnivore
Carnivore
Tertiary
consumers
Carnivore
Carnivore
Secondary
consumers
Carnivore
Carnivore
Primary
consumers
Herbivore
Zooplankton
Producers
Plant
Phytoplankton
A TERRESTRIAL FOOD CHAIN
AN AQUATIC FOOD CHAIN
2) Decomposition is the breakdown of organic
compounds into inorganic compounds
– a) Decomposition is essential for the
continuation of life on Earth
– b) Detritivores
decompose waste
matter and recycle
nutrients
• 1. Examples: animal
scavengers, fungi,
and prokaryotes
Food Chains
• 1) A food web is a network of interconnecting
food chains
– a) It is a more realistic view of the trophic
structure of an ecosystem than a food
chain
Wastes and
dead organisms
Tertiary
and
secondary
consumers
Secondary
and
primary
consumers
Primary
consumers
Producers
(Plants, algae,
phytoplankton)
Detritivores
Energy Supply
• 1) Biomass is the amount of living organic
material in an ecosystem
– a) Primary production is the rate at which
producers convert sunlight to chemical
energy
• 1. The primary production of the entire
biosphere is about 170 billion tons of
biomass per year
2) A pyramid of production reveals the flow of
energy from producers to primary consumers
and to higher trophic levels
Tertiary
consumers
10 kcal
Secondary
consumers
100 kcal
Primary
consumers
1,000
kcal
Producers
10,000 kcal
1,000,000 kcal of sunlight
Energy Supply
• 3) Only about 10% of the energy in food is
stored at each trophic level and available to
the next level
– a) This stepwise energy loss limits most
food chains to 3 - 5 levels
• 1. There is simply not enough energy at
the very top of an ecological pyramid to
support another trophic level
Production Pyramid
• 1) The dynamics of energy flow apply to the
human population as much as to other
organisms
– a) When we eat grain or fruit, we are
primary consumers
– b) When we eat beef or other meat from
herbivores, we are secondary consumers
– c) When we eat fish like trout or salmon
(which eat insects and other small
animals), we are tertiary or quaternary
consumers
• 2) Because the production pyramid tapers so
sharply, a field of corn or other plant crops
can support many more vegetarians than
meat-eaters
TROPHIC LEVEL
Secondary
consumers
Primary
consumers
Human
meat-eaters
Human
vegetarians
Cattle
Corn
Corn
Producers
Figure 36.12
Chemicals are Recycled
• 1) Ecosystems require daily infusions of
energy
– a) The sun supplies the Earth with energy
• 1. But there are no extraterrestrial
sources of water or other chemical
nutrients
– b) Nutrients must be recycled between
organisms and abiotic reservoirs
• 1. Abiotic reservoirs are parts of the
ecosystem where a chemical
accumulates
Chemicals are Recycled
• 2) There are four main abiotic reservoirs
– a) Water cycle
– b) Carbon cycle
– c) Nitrogen cycle
– d) Phosphorus cycle
Water
• 1) Heat from the sun drives the global water
cycle
– a) Precipitation
– b) Evaporation
– c) Transpiration
Solar
heat
Water vapor
over the sea
Precipitation
over the sea
(283)
Net movement
of water vapor
by wind (36)
Evaporation
from the sea
(319)
Water vapor
over the land
Evaporation
and
transpiration
(59)
Precipitation
over the land
(95)
Oceans
Flow of water
from land to sea
(36)
Surface water
and groundwater
The Carbon Cycle
• 1) Carbon is taken from the atmosphere by
photosynthesis
– a) It is used to make organic molecules
– b) It is returned to the atmosphere by
cellular respiration
CO2 in atmosphere
Burning
Cellular respiration
Plants,
algae,
cyanobacteria
Photosynthesis
Higher-level
consumers
Primary
consumers
Wood and
fossil fuels
Decomposition
Detritivores
(soil microbes
and others)
Detritus
The Nitrogen Cycle
• 1) Nitrogen is plentiful in the atmosphere as
N2
– a) But plants cannot use N2
• 1. Various bacteria in soil (and legume
root nodules) convert N2 to nitrogen
compounds that plants can use
–a. Ammonium (NH4+) and nitrate
(NO3–)
The Nitrogen Cycle
– b) Some bacteria break down organic
matter and recycle nitrogen as ammonium
or nitrate to plants
• 1. Other bacteria return N2 to the
atmosphere
Nitrogen (N2) in atmosphere
Assimilation
by plants
Denitrifying
bacteria
Amino acids
and proteins in
plants and animals
Nitrogen
fixation
Detritus
Nitrogen-fixing
bacteria in root
nodules of legumes
Nitrates
(NO3–)
Detritivores
Nitrifying
bacteria
Decomposition
Nitrogen
fixation
Ammonium (NH4+)
Nitrogen-fixing
bacteria in soil
The Phosphorus Cycle
• 1) Phosphates (compounds containing PO43-)
and other minerals are added to the soil by
the gradual weathering of rock
– a) Consumers obtain phosphorus in
organic form from plants
• 1. Phosphates are returned to the soil
through excretion by animals and the
actions of decomposers
Uplifting
of rock
Phosphates
in organic
compounds
Weathering
of rock
Phosphates
in rock
Animals
Plants
Runoff
Detritus
Phosphates
in solution
Phosphates
in soil
(inorganic)
Decomposition
Rock
Precipitated
(solid) phosphates
Detritivores
in soil
Ecosystem Alteration
• 1) Experimental studies have been performed
to determine chemical cycling in ecosystems
– a) A study to monitor nutrient dynamics
has been ongoing in the Hubbard Brook
Experimental Forest since 1963
– b) Dams were
built across
streams at the
bottom of each
watershed to
monitor water and
nutrient losses
2) In 1966, one of the valleys was completely
logged
– a) It was then
sprayed with
herbicides for 3
years to prevent
plant regrowth
– b) All the original
plant material
was left in place
to decompose
• 3) Researchers found that the total removal
of vegetation can increase the runoff of water
and loss of soil nutrients
Ecosystem Alteration
• 4) Environmental changes caused by humans
can unbalance nutrient cycling over the long
term
– a) Example: acid rain
David Schindler
• 1) Eutrophication is a process in which
nutrient runoff from agricultural lands or
livestock operations causes photosynthetic
organisms in ponds and lakes to multiply
rapidly
– a) The result is algal bloom
• 2) Algal bloom can cause a pond or lake to
lose much of its species diversity
– a) Human-caused eutrophication wiped out
fisheries in Lake Erie in the 1950s and
1960s
• 3) Dr. David Schindler
is an ecologist who
worked at the
Experimental Lakes
Project in northern
Ontario
– a) He performed
several classic
experiments on
eutrophication that
led to the ban on
phosphates in
detergents
David Schindler
• 4) According to Dr. Schindler, there are three
serious threats to freshwater ecosystems
– a) Acid precipitation
– b) Climate warming
– c) Changes in land use
Zoned Reserves
• 1) The human alteration of ecosystems
threatens the existence of thousands of
species
– a) To slow the disruption of ecosystems,
some nations are establishing zoned
reserves
• 1. These are undisturbed wildlands
surrounded by buffer zones of
compatible economic development
Zoned Reserves
– b) Costa Rica has established eight zone
reserves
• 1. Costa Rica looks to its zoned reserve
system to maintain at least 80% of its
native species
2) On this map, the reserves are shown in
green and the buffer zones in yellow
NICARAGUA
COSTA
RICA
Guanacaste
Caribbean Sea
Llanuras de
Tortuguero
La
Amistad
Arenal
Bajo
Tempisque
Cordillera
Volcanica Central
Pacifico Central
Peninsula de Osa
Pacific Ocean