http://www.epa.gov/region5/superfund/ecology/images/fishcartoon.gif

http://www.uark.edu/depts/agripub/Publications/Agnews/mosquito.jpg

http://www.mark-ju.net/wildlife/images/monkey03.jpghttp://www.dimijianimages.com/Aggression-defense-page4/vultures.jpg

Ecosystem Interactions&

Factors that affect populations

What is a population?

• A group of members of the same species that live in the same area.

• The size of any population is constantly changing.

• WHY?Limiting factors - an environmental factor that

prevents an increase in the number of organisms in a population or prevents them from moving into new habitats

Limiting Factors that affect populations in ecosystems:

2 types:1) Abiotic

- a) resources available- b) climate- c) natural and human disturbances

2) Biotic - a) competition among organisms- b) predation- c) cooperation and symbiosis- d) presence of disease

ABIOTIC:WHAT IS A RESOURCE?

Anything needed by an organism for life

Examples:

_____________________________Nutrients, water, sunlight/energy, space

ABIOTIC:What are examples

of climate?• temperature, humidity, atmospheric pressure, wind, rainfall

These in turn can cause/contribute to some natural disturbances like:

storms, droughts, fires

ABIOTIC:What are examples of human

disturbances?

• logging• development and construction

BIOTIC:What is competition?

• interaction between 2 or more organisms competing for the same resource in a given habitat

• Can occur between members of same species- Example: male mountain goats compete to determine who will mate and produce offspring

• Members of different species may compete for the same resources- Example: raccoons and ravens might both try and feed on eggs from the same nest of a common bird

BIOTIC:Competition

• For similar species to live together in the same area, they must have slightly different niches.

WHAT CAN ORGANISMS COMPETE FOR?

- All the abiotic factors!

- Mates!

COMPETITION

FOOD

Organisms in an ecosystem have to compete with each other for available resources.

http://www.harcourtschool.com/glossary/science/images/gr3/community3.jpg

http://www.knology.net/~sgoswald/Eating.jpg

COMPETITIONOrganisms in an ecosystem have tocompete with each other for available resources:

http://www.dpiw.tas.gov.au/inter.nsf/Images/LBUN-5K538R/$File/fox_adultandcub.jpghttp://www.gdccc.org/Records/EOY2004/NSEOY.htm

shelter

COMPETITIONOrganisms in an ecosystem have tocompete with each other for availableresources:

space/territory

http://www.rilanationalpark.org/gr.phtml?dir=../../pictures/in_text&img=/65_1180.jpg

http://www.elise.com/weblog/photos/prairie-dogs.jpg

Prairie dogs - 5 to 35 per acreMountain lion- 1 male per 50-300 sq. mi

COMPETITIONOrganisms in an ecosystem have tocompete with each other for availableresources:

LIGHT

http://vilenski.org/science/safari/cellstructure/chloroplasts.htmlhttp://www.csjbacau.ro/gallery/images/Beech%20Tree%20Forest%20in%20Slanic%20Moldova.jpg

COMPETITIONOrganisms in an ecosystem have tocompete with each other for availableresources

mates

http://www.wasatchcomputers.net/gallery/elk_fight.jpg

http://www.biocrawler.com/w/images/thumb/3/34/200px-Peacock_courting_peahen.jpg

BIOTIC:What is predation?

• when one organism hunts and kills another organism for food

Prey animals are well adapted to avoid being eaten. Some examples include:

- Physical attributes: speed, mimicry- Physical defences: camouflage, quills (porcupine)- Chemical defences: odour (skunk), ink spray

(octopus), etc…

Mimic Octopus (2:59 min): http://www.youtube.com/watch?v=H8oQBYw6xxc

PREDATIONOrganisms in an ecosystem that

capture and eat other organisms to supply their energy needs

http://personal.ecu.edu/wuenschk/rabbit-wolf.gif

http://www.aphis.usda.gov/lpa/pubs/images/wspred_6.jpg

BIOTIC:What is cooperation?

- between SAME kind of organisms- live together and help each other

What is symbiosis?• Between 2 DIFFERENT species • live in/on or near a member of another

species

COOPERATIONSame species live together in groups

EX: herds, packs, colonies, families, etc

http://www.kenyatravelideas.com/african-elephants.htmlhttp://www.sphoto.com/medium/meercats37.jpghttp://people.uleth.ca/~d.rendall/groom4.jpg

Share food & childcare responsibilitiesGroom each otherTake care of sick

COOPERATIONSame species live together in groups

EX: herds, packs, colonies, families, etc

Hunt in packs

Provide protection

http://www.knology.net/~sgoswald/Eating.jpghttp://rosswarner.com/zebras1.jpg

3 KINDS of SYMBIOSIS

1)______________________Both organisms benefit

2)______________________One organism benefits;Other is neither harmed nor

helped

3)_____________________One organism benefits;Other is harmed in some way

MUTUALISM

COMMENSALISM

PARASITISM

Bed bugs (2:10 min): http://www.youtube.com/watch?v=WfKCcSPCOQo

1) MUTUALISM“Good for me - Good for you”

Birds eat parasites living on the hides of giraffes and rhinos while enjoying protection from predators. Groomed animals lose their pests.

http://www.imbt.org/science.htm

http://www.hugheshome.net/jon/africa02/images/rhino_bird_JPG.jpg

1) MUTUALISM “Good for me - Good for you”

Insects transfer pollen between plants as theygather nectar for food.

http://www.yksd.com/DistanceEdCourses/YKSDbiology/lessons/SecondQuarterLessons/Chapter5/5-5/images/3-way-mutualism.jpg

http://www.providence.edu/bio/faculty/adams/LECTUREProvCollegeMutualism.html

MUTUALISM cont’d “Good for me - Good for you”

Clown fish gets protection from enemies by hiding out in poisonous sea anemones

http://www.zahnersatz.com/english/library/symbiosis.jpg

Sea anemone gets scraps of leftover food dropped by fish

2) COMMENSALISM“Good for me - Doesn’t bother you”

http://www.geology.wmich.edu/gillespie/g322/Chapters/C16shark.gif

Pilot fish receive scraps of food dropped by shark;Shark is neither harmed nor helped

COMMENSALISM cont’d“Good for me - Doesn’t bother

you”

http://www.abyssal.com/meeks/images/hermit_crab.jpg

Hermit crabs make homes in shells abandoned by snails;Snail is not harmed by crab

3) PARASITISM“Good for me - Hurts you”

Barnacles are crustaceans that attach to the surface of whales and feed on their skin and fluids; Whale is harmed

http://www.geology.wmich.edu/gillespie/g322/Chapters/C16parasitism.whale.gif

PARASITISM cont’d“Good for me - Hurts you”

Tick feeds on dog’s blood; Dog has discomfort, can get diseases/infection from bite

http://www.dogbreedinfo.com/guineafowltickphotos.htm

PARASITISM cont’d“Good for me - Hurts you”

Tapeworms absorb food by living inside host intestine; host is harmed

http://www.biology.ucok.edu/AnimalBiology/Platyhelminthes/tapeworms.jpg

INTERDEPENDENCE

All living and non-living things in an

ecosystem are interconnected and changing

even one thing impacts the whole ecosystem.

When one tugs at a single thing in nature, he finds it attached to the rest of the world. 

~John Muir, naturalist, Sierra Club founder

• Have you ever wondered why we don’t see millions of mice running around when we look out the window if they reproduce so quickly?

• The environment can only support a maximum number of individuals because of limited resources

Characteristics of a Population:• As a population grows, each individual gets a

smaller share of the resources in the area.• If resources are scarce, some organisms will

starve and populations will decrease.• The organisms become stressed. Some die,

others aren’t able to reproduce.• This may lead to fewer births and more

deaths. Eventually, the number of births = number of deaths

• The population is in EQUILIBRIUM

REMEMBER: EVERYTHING IS CONNECTED !

•A decrease in the prey population means some predators will starve.•Fewer predators mean prey population will increase.

•Increase in prey means more food for predators.•Predator population will increase until there is not enough food . . . and the cycle repeats itself.•Rabbit/Wolf simulation: http://www.shodor.org/interactivate/activities/RabbitsAndWolves/

BIOLOGY; MIller and Levine; Prentice Hall; 2006

Carrying Capacity• Carrying Capacity is the

maximum number of individuals an ecosystem can support without reducing its ability to support future generations of the same species

• The population overshoots the carrying capacity before it is reached

• If a population exceeds carrying capacity for a long time, it usually harms its environment.

• For an ecosystem to be sustainable, none of the populations in the community can exceed its carrying capacity by very much or for very long.

• GOAL OF SUSTAINABILITY:meet the needs of the present generation without affecting the ability of future generations to meet their needs

Human Population Growth

Questions:

1) What does the following graph suggest about our population growth rate in the

future? Discuss each line.

Questions:

2) Brainstorm reasons why the human populations seems to be growing exponentially, even after analyzing the previous graph.

(You may use ideas from the Bill Nye video on Populations.)

Questions:3) a. Finish sketching in the following curve based on the

general graph showing a population reaching carrying capacity.

b. If this were a graph of the Earth’s population, estimate the following: i) overshoot population

ii) carrying capacity population