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Chapter 21
On the Tracks of Wolves and Moose
Young Gray Wolf-Romeo
• Every summer and a few weeks in winter,
scientist investigate the Isle Royale’s pack of
wolves and herd of moose
• Studies for almost 50 years, it is the longestrunning predator prey study in the world.
– Scientists would like to understand the dynamic
fluctuations of the wolves and moose.
– They are trying to learn about ecology
Ecology
• Ecology is the study of the interactions
between organisms, and between organisms
and their nonliving environment (land, water,
etc.)
– The Isle Royale is a great place to study ecology
– Uninhabited by humans, protected national park,
undistributed by hunting, logging, settlement
– No other predators or prey on the island
– Island just the right size to study ecology
Ecology
• Ecologists can study
organisms at a
number of levels:
the individual, the
population, the
community, and the
ecosystem.
Ecology
• At the individual level, ecologists can study
how an individual organisms fares in its
surroundings.
Ecology
• At the population level, ecologists study a
group of individuals of the same species living
and interacting in the same region.
Ecology
• At the community level, ecologists study
interacting populations of different species.
Ecology
• At the ecosystem level, ecologists study all the
living organisms in an area and the nonliving
components of the environment with which
they interact.
Ecology
• Ecology is a multidisciplinary science. It draws
not only on many areas of biology but also on
many other branches of science, including
geography and meteorology as well as
mathematics.
Distribution patterns
• Moose are relatively solitary creatures
– Random dispersion of individual roaming moose
on the island.
– Hard to count for research studies.
– One type of distribution pattern
Moose
• The distribution pattern, or the way that
organisms are distributed in geographic space,
depends on resources and interactions with other
members of the population.
– For moose, being solitary may help protect them from
predation – harder to see in forest
– A truly random distribution is rare in nature
– Resources may be unevenly distributed, etc.,
– Distribution pattern are different for wolves and
moose- wolves clump
Distribution patterns
• Distribution patterns generally reflect behavioral or
ecological adaptations. Three different types:
Distribution patterns
• A random
distribution may
allow
individuals to
maximize their
access to
resources.
Distribution patterns
• A clumped
distribution may
result when
resources are
unevenly
distributed across
the landscape, or
when social
behavior dictates
grouping.
Distribution patterns
• Uniform
distribution
usually results
from territorial
behavior.
Moose
• Few Moose swam to Isle Royale in 1900
• Moose population exploded on the Isle Royale
due to abundant food supply and no natural
predators
• By 1920, more than a 1000
• Rapid increase in growth rate
Population growth
• The growth rate of a population is the difference
between the birth rate and the death rate of a given
population.
Population growth
• Ecologists describe two general types of population
growth: exponential growth and logistic growth.
Population growth
• Exponential growth is the unrestricted growth
of a population increasing at a constant
growth rate.
• When a population is growing exponentially, it
increases by a certain fixed percentage every
generation. Increase 20% each year, for
example
Population growth
• Unrestricted growth is rarely, if ever, found
unchecked in nature.
• As populations increase in numbers, various
environmental factors such as food availability
and access to habitat limit an organism’s
ability to reproduce.
Population growth
• When populationlimiting factors slow
the growth rate, the
result is logistic
growth―a pattern
of growth that starts
rapidly and then
slows.
• Disease, food
limitation
Population growth
• Eventually, after a period of rapid growth, the
size of the population may level off and stop
growing.
• At this point, the population has reached the
environment’s carrying capacity ―the
maximum number of individuals that an
environment can support given its space and
resources.
Population growth
• Carrying capacity places an upper limit on the
size of any population;
• No natural population can grow exponentially
forever without eventually reaching a point at
which resource scarcity and other factors limit
population growth.
Population growth
• Ecologists use a
variety of data to
monitor the health of
populations.
– Moose dropping
– Moose bones
– Wolf scat
– Urine –soaked snow
Population growth
• Population density is the number of
organisms per given area. Wolves kill moose
– As the population density of a species increases,
individuals of that species may face food
shortages.
• This is an example of a density-dependent
factor―a factor whose influence on
population size and growth depends on the
number and crowding of individuals in the
population.
Population growth
Biotic refers to the living components of an
environment. Not all density-dependent
factors are biotic.
– Food, predators, diseases
• Nonliving, or abiotic, factors like weather and
habitat can also influence population size in a
density-dependent manner.
Population growth
• Density-independent factors take a toll on the
population no matter how large or small the
population is.
• Most, but not all, density-independent factors
are abiotic.
Chapter 22
What’s Happening to Honey Bees?
Honey Bee’s
• Bee’s help farmer’s pollinate local crops
– Almonds to melons
• Colony collapse disorder (CCD)- what
happened to the bees?
• Several beekeepers reported 30-90% loss of
bee colonies
• Over 3 million honey bees have been wiped
out
• What is happening to the honey bees????
Bees
• Loss of agricultural crops
• Affect on health and diversity of ecosystems
that rely on bees for services
• Pollination of flowering plants depends on
insects.- bees
– 75% of the 250,000 species of flowering plants
depend on insects
– Bees are the most important
Community Ecology
• Bees are keystone species
• A keystone species plays a central role in
holding a community together because other
species depend on it. The removal of a
keystone species has a dramatic impact on the
community.
• A community is a group of interacting
populations of different species living together
in the same area.
Community Ecology
• Bees are a
keystone
species. Many
of the crops that
we rely on for
food, fuel, and
fiber rely on
bees for their
pollination and
reproduction.
Crops
• In US more than 100 different crops relay on
honey bee pollination
• 15 billion annually
Flowering Plant Reproduction Relies
on Pollinators
• Flowering plants use their flowers and nectar
to attract pollinators for pollination – the
transfer of pollen (small, thick-walled plant
structures that contain cells that will develop
into sperm) from male to female plant
structures so that fertilization can occur.
Flowering Plant Reproduction Relies
on Pollinators
• The male flowering plant reproductive organ,
called a stamen, consists of a stem-like
filament topped with a pollen-saturated
anther.
• When a bee lands on or brushes against an
anther during her pursuit of nectar and pollen,
her furry body picks up pollen grains.
Flowering Plant Reproduction Relies
on Pollinators
• As the bee continues to forage, she carries the
pollen to the female reproductive organ of the
flower – the pistil.
• The pistil is topped with a sticky “landing pad”
called a stigma.
• When a bee lands on the stigma, pollen grains
are deposited, and from there travel down a
tube-like style into the ovary, where they
fertilize the egg.
Flowering Plant Reproduction Relies
on Pollinators
• A fertilized egg
will eventually
develop into an
embryocontaining seed,
while the
surrounding
ovary eventually
becomes the
fruit.
Food Chains
• Keystone species play a crucial role in food
chains – the linked sequences of feeding
relationships in a community in which
organisms further up the chain feed on those
below them.
Food Chains
• The base of the
food chain is
composed of
producers –
autotrophs that
obtain energy
directly from the
sun and supply
it to the rest of
the food chain.
Food Chains
• Consumers – heterotrophic organisms that eat
the producers or eat other organisms lower on
the chain to obtain energy – are found higher
on the food chain.
Food Chains
• Predation is an interaction between two
organisms in which one organism (the
predator) feeds on the other (the prey).
Herbivory is predation on plants, which may
or may not kill the plant preyed on.
Food Chains
• As consumers prey on organisms below them
in the chain, energy is transferred up the chain
through what are known as trophic levels
(feeding levels, based on positions in a food
chain).
Food Chains
• Not all of the energy stored in a lower level
makes it to the level above it; at each step,
much of this energy is lost from the chain.
• Energy is lost as??
• Only about 10% of the energy at the lower
level is passed from one organism to the next
organism in the chain.
Food Webs
• The food-chain concept is an
oversimplification.
• Many organisms are omnivores (that is, they
eat both plants and animals) and so occupy
more than one position in the chain.
• The result is a complex, intertwined food web
of feeding relationships in a community.
Symbiotic Relationships
• Parasitism is a type of symbiotic relationship
in which one member benefits at the expense
of the other.
Symbiotic Relationships
• Mutualism is a type of symbiotic relationship
in which both members benefit.
Symbiotic Relationships
• Commensalism is a type of symbiotic
relationship in which one member benefits
and the other is unharmed.
Competing for Resources
• An ecological
niche includes
the space,
environmental
conditions, and
resources
(including other
living species)
that a species
needs in order
to survive and
reproduce.
Competing for Resources
• When two or more species rely on the same
limited resources – that is, when their niches
overlap – the result is competition.
• Competition tends to limit the size of
competing populations and may even drive
one out.- extinction
Competing for Resources
• The competitive
exclusion principle
is the concept that
when two species
compete for
resources in an
identical niche,
one is inevitably
driven to
extinction.
Competing for Resources
• Very few species share exactly the same niche,
so different species may find a competitive
balance by resource partitioning.
Humans Impact Other Species
• Human
development
and
agriculture
have altered
and decreased
habitat for
other species.
What is killing the honey bees?
• CCD
• Pesticides, stress, nutrition, parasites, viruses
• Some believe we suffer from NDD or nature
deficit disorder
• People need to take more time to understand
where their food comes from.
• Haagen-Dazs