Lecture 1Carrying Capacity, Biodiversity, & Predator/Prey

relationships

Lisa Antoniacci Ph.D.Marywood University

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.]

Biology Standards

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.]

Introductory ecological information related to: Carrying capacity

Biodiversity

Competition

Goals/Agenda

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

Growth Rate: Birth Rate (natality) - Death Rate (mortality)

How many individuals are born vs. how many die

Factors that affect Size

Three Key Features of Populations

2. Density: measurement of population per unit area or unit volumePop. Density = # of individuals ÷ unit of space

1. Immigration- movement of individuals into a population

2. Emigration- movement of individuals out of a population

Factors that affect density

3. Density-dependent factors- Biotic factors in the environment that have an increasing effect as population size increases

  Ex. Disease, competition, parasites

Immigration

Emigration

Natality MortalityPopulation+

+

-

-

Factors That Affect Future Population Growth

The Fundamental Equation of Ecology

Δ N = 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 foodTemperature

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

Other factors that affect population growth

Carrying Capacity

Carrying Capacity (k)

Nu

m

b

e

r

Time

J-shaped curve (exponential growth)

S-shaped curve (logistic growth)

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 #1MINNOWS

ACTIVITY #2KAIBAB 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.

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.

Balancing Predator and Prey interactions:

ACTIVITY #3DEER/WOLF PREDATION

EXPREIMENTHandout – 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

CompetitionOrganisms 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

• Some possible limiting resources-– plants-light, water, nutrients, space, pollinators– animals-prey, nesting sites, territories, water, host

organisms, space (sessile organisms), mates (intraspecific only)

Competition

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 #4PARAMECIUM COMPETITION

EXPREIMENT

http://www.biologycorner.com/worksheets/virtual_lab_population.html

http://glencoe.mheducation.com/sites/dl/free/0078757134/383928/BL_04.html

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).