Biological Communities in the World Around Us

Big Idea #4Interactions

Chapter 54 : Community Ecology

What is a biological community?• A group of

populations of different species living close enough to interact

• Biome = community with a characteristic climate

Think outside the box…

• What are the members of this community?• Are you a biological community?

Interactions within a community (54.1)

• Competition– Intraspecific– Interspecific:

• competitive exclusion

• Predation– Including Herbivory

• Symbiosis– Mutualism– Commensalism– Parasitism

Competitive Exclusion Principle defines an organisms niche

• How might this play out in the human body? What conditions in the human body cause a different member of the community to be successful?

Also important…

• Dominant Species: usually most abundant…what if they change?

• Keystone Species: not usually abundant…why might you start seeing them?

• Ecosystem engineers: foundation species…drives change in other species.

Succession

• Changes in community composition– Primary Succession– Secondary Succession

Does ecological succession occur when you take antibiotics?

• How might this change impact the human body? (27.5)

Nitrogen cycling in a biological community• What types of organisms play a critical role? (27.5)• How might changing the members of the community

affect nitrogen cycling? • What events might cause succession/change?

How can succession be measured?

• Species biodiversity is used to characterize a community---so-called “climax communities” have stable, distinctive organisms

• Higher biodiversity = greater succession• The impact of events on a community may be

evaluated by studying changes in biodiversity

Shannon Diversity Index

• The biodiversity of an area can be calculated using the equation: H = -(pAln pA + pBln pB+ pCln pC….)

• Higher values of H indicate greater biodiversity

• We will practice using this equation in a separate activity

• See 54.2 Example two forest communities.

What’s this all got to do with cheese?

• Cheese is the scaffold for a microbial community – a microbiome.

• The process of making cheese involves an understanding of biology.

New England Cheese Economy

• From these Chronicle clips, appreciate an understanding of why biologists (yes…ones at that big University in Cambridge, MA) might be interested in the cheese making process.

• Part 1:http://www.wcvb.com/chronicle/Vermont-s-Cheese-Trail-Part-1/-/12523032/13392120/-/ute169/-/index.html

• Part 2:http://wedgeintheround.com/2012/11/11/vermonts-cheese-trail-part-2-chronicle-wcvb-home/

• Part 3:http://www.wcvb.com/chronicle/Vermont-s-Cheese-Trail-Part-3/-/12523032/13392188/-/13v2y1t/-/index.html

Experimental Design

• Experimental Question:– How can humans impact the microbial community

growing on cheese?

What background do you need to know?

• How is cheese made?• What types of conditions is cheese cultured

under?• What types of bacteria usually grow on

cheese?

Designing an experiment

• What is an independent variable?– What could be an independent variable in this

lab…what do you need to know?!?!• What is a dependent variable?– What qualitative results might you observe?– Is there a quantitative dependent variable that

would be appropriate to this lab?