Lecture 1
Carrying Capacity, Biodiversity, &
Predator/Prey relationships
Lisa Antoniacci Ph.D.
Marywood University
Biology Standards
HS-LS2-1. Use mathematical and/or computational representations to support
explanations of factors that affect carrying capacity of ecosystems at different scales.
[Clarification Statement: Emphasis is on quantitative analysis and comparison of the
relationships among interdependent factors including boundaries, resources, climate, and
competition. Examples of mathematical comparisons could include graphs, charts,
histograms, and population changes gathered from simulations or historical data sets.]
HS-LS2-6. Evaluate the claims, evidence, and reasoning that the complex interactions in
ecosystems maintain relatively consistent numbers and types of organisms in stable
conditions, but changing conditions may result in a new ecosystem. [Clarification
Statement: Examples of changes in ecosystem conditions could include modest biological or
physical changes, such as moderate hunting or a seasonal flood; and extreme changes, such
as volcanic eruption or sea level rise.]
HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human
activities on the environment and biodiversity.* [Clarification Statement: Examples of
human activities can include urbanization, building dams, and dissemination of invasive
species.]
Goals/Agenda
Introductory ecological information related to:
 Carrying capacity
 Biodiversity
 Competition
Activities containing mathematical comparisons of
ecological data related to the concepts above.
What is ecology?
Ecology is the scientific study of the interactions between
organisms and their environment.
a. Interactions determine distribution and abundance
of organisms.
b. Two main themes in ecology are:
- Where do organisms live? & Why?
- How many organisms are present? & Why?
An organism’s environment has both abiotic
and biotic components.
 Abiotic components are nonliving chemical
and physical factors such as temperature,
light, water, and nutrients.
 Biotic components are living factors such
as other organisms.
The Scope of Ecological Research
• Ecologists work at levels ranging from individual
organisms to the planet
• Organismal ecology studies how an organism’s
structure, physiology, and (for animals) behavior
meet environmental challenges
• A population is a group of individuals of the same
species living in an area
• Population ecology focuses on factors affecting
how many individuals of a species live in an area
• A community is a group of populations of different
species in an area
• Community ecology deals with the whole array of
interacting species in a community
• An ecosystem is the community of organisms in an
area and the physical factors with which they
interact
• Ecosystem ecology emphasizes energy flow and
chemical cycling among the various biotic and
abiotic components
Population Dynamics
Three Key Features of Populations
•Size
•Density
•Dispersion
• (clumped, even/uniform, random)
Three Key Features of Populations
1. Size: number of individuals in an
area
Factors that affect Size
Growth Rate: Birth Rate (natality) Death Rate (mortality)
How many individuals are born vs. how
many die
Three Key Features of Populations
2. Density: measurement of
population per unit area or unit
volume
Pop. Density = # of individuals ÷ unit of space
Factors that affect density
1. Immigration- movement of
individuals into a population
2. Emigration- movement of
individuals out of a population
3. Density-dependent factors- Biotic factors in
the environment that have an increasing effect
as population size increases
Ex. Disease, competition, parasites
Factors That Affect Future
Population Growth
Immigration
Natality
+
+
Population
Emigration
-
Mortality
The Fundamental Equation of Ecology
ΔN=B–D+I–E
Change in Number = Births – Deaths +Immigration-Emigration
Three Key Features of Populations
3. Dispersion:describes their
spacing relative to each other
• clumped
• even or uniform
• random
Other factors that affect population growth
Limiting factor- any biotic or
abiotic factor that restricts the
existence of organisms in a
specific environment.
– EX.- Amount of water
Amount of food
Temperature
Other factors that affect population growth
Carrying Capacity- the maximum
population size that can be supported
by the available resources
There can only be as many
organisms as the environmental
resources can support
Carrying Capacity
N
u
m
J-shaped curve
(exponential growth)
Carrying Capacity (k)
b
S-shaped curve
(logistic growth)
e
r
Time
EXAMPLE – BACTERIAL GROWTH PHASES
2 Life History Patterns
• 1. R Strategists






short life span
small body size
reproduce quickly
have many young
little parental care
Ex: cockroaches,
weeds, bacteria
2. K Strategists
 long life span
 large body size
 reproduce slowly
 have few young
 provides parental care
 Ex: humans, elephants
ACTIVITY #1
MINNOWS
ACTIVITY #2
KAIBAB DEER
Handout – examining the Kalibab Deer
population in the early 1900s and
analyzing data by generating graphs of
the data. Discussion of the methods
used to protect the population.
Balancing Predator and Prey interactions:
Predators provide ecological stability by regulating the impacts of
grazing and browsing animals, thus ensuring the overall productivity
of the habitat.
They cull weak, sick, and old prey, thus ensuring the maximum fitness
of elk, deer, antelope, and hares.
They foster biological diversity by “enforcing” ecological boundaries
or preventing what ecologists refer to as “competitive exclusion,” the
tendency of one prey animal to outcompete another.
So-called “apex predators,” the wolves, lions, and tigers are the
Godfathers, as they also control the numbers of “meso predators,”
the coyotes, raccoons, possums, foxes—even domestic cats—which
when left unchecked can do enormous damage to birds and native
rodents.
ACTIVITY #3
DEER/WOLF PREDATION
EXPREIMENT
Handout – examining the the effects of
deer population on an island with the
introduction of wolves.
How imported animals effect ecosystem:
• Imported Naturally
• Imported by Humans
 May be no natural predators so they overpopulate
 May cause competition with native population
 May be detrimental to organisms that live no where else in
the world.
Needs to be balanced with Biodiversity:
See these effects when an aggressive species
provides a novel challenge to the endemic
organisms
Competition
Organisms may compete with each other to capture some
of the limited resources in the ecosystem.
 Interspecies
 Intraspecies
– Competition is thought to be ubiquitous in nature, both
as an agent of natural selection and a factor structuring
communities.
– For competition occur:
• both organisms must use a common resource that is
important to their survivorship and reproduction
• that resource must be limited-use by one individual must
decrease what is available to others in a meaningful way
Competition
• Some possible limiting resources– plants-light, water, nutrients, space, pollinators
– animals-prey, nesting sites, territories, water, host
organisms, space (sessile organisms), mates
(intraspecific only)
Consequences of Competition
• Coexistence
• Exclusion of one species
Exclusion
• The phenomenon of competitive exclusion
was first documented experimentally by the
Russian biologist C. F. Gause.
– Gause’s experiment is now quite famous
– P. caudatum is larger than P. aurellia, but has a
slower reproductive rate. Both species consume
bacteria via a “funnel” lined with cilia.
– Gause grew each species alone, in a culture where
a fixed amount of food (bacteria) was added each
day.
– He then grew the two species together.
ACTIVITY #4
PARAMECIUM COMPETITION
EXPREIMENT
http://www.biologycorner.com/worksheets/virtual_lab_population.html
http://glencoe.mheducation.com/sites/
dl/free/0078757134/383928/BL_04.ht
ml
His result was the
exclusion of P.
caudatum by P. aurellia.
He hypothesized that
the two species
compete for the same
food-ultimately P.
aurellia is ultimately
able to multiply under
conditions where P.
caudatum can no longer
gain enough energy to
divide.
This is called
competitive exclusion
• Gause’s experiment was tremendously influential.
Based on this, and other experiments, ecologists
arrived at the competitive exclusion principle, which
is now firmly established.
– Two species cannot exist on the same limiting resource
indefinitely-ultimately, even a slight reproductive
advantage to one of them will result in their displacing the
other.
– In terms of the niche-if the niches of two species overlap
completely, only the superior competitor can survive.
• Ironically, this experiment gives different results, depending upon
which strains of Paramecium are used-some strains coexist,
presumably by partitioning the limiting resource (bacteria).