Community Interactions AP Biology AP Biology

Community  A division of an ecosystem that describes all of the organisms that live in an area  Focuses on interactions within the community  Establishes a niche – a set of conditions under which an organism exists

Interactions  Focus on resources available in the community FoodWaterSpaceMates Nesting sites Hiding places Light Macro and micronutrients

Limiting Resources  There are only so many resources in a community for all of the organisms  This limits the growth of populations of organisms within this community  It leads to specialized interactions within the members of this community  ( population dynamics)

Interactions  Interspecific – Between different species  Intraspecific – Within the same species

Interaction links and Examples  havior/lycaenids/lycaen2.htm havior/lycaenids/lycaen2.htm havior/lycaenids/lycaen2.htm

Ecological relations( 1)  One organism benefits in a relationship the other is harmed or is eaten Example – predator – prey and parasite = host Rating +/- Lynx and hare – predator and prey Malaria, red blood cell, and human – parasite and hosts

Cyclic predator-prey relationships

Experiment

Experiment( con)

Ecological relations( 2)  Two organisms compete for the same resources. This is known as competition.  Rating -/- or +/- Examples Competition for mates – intraspecific Competition for space – plants – allelopathy Competition for nutrients and space – fungi and bacteria - antibiotics

Mutualism  Both organisms benefit  Rating +/+  Zooxanthellae and coral polyp  Legumes and Rhizobium  Leaf cutter ant and fungal garden  Ant and acacia

Leaf cutter ants and fungal gardens

Ant and the Acacia

Commensalism  One organism benefits – the other is neither harmed or benefits  +/0  Examples – Pinnepidia crab and tube worm

Amensalism  Animals can have a negative effect on the environment  0/-  Animals trampling the grass on the way to the water hole

Contradictions  Not all organisms fit the description exactly  The definition for symbiosis is changing to include only those interactions between organisms of two different species whose metabolism is altered by the interaction

Competition- Interspecific  Allelopathy – How plants guard their space by releasing molecules into the environment that deters other plants from occupying their space  /itc/index.htmlx /itc/index.htmlx /itc/index.htmlx

Intraspecific Competition

Interspecific Competition  Barnacle species on a rocky shore  Establishes zonation of organisms  Niche determined by ability to barnacles to tolerate dehydration

 Competition may restrict species’ ranges.  Two species of barnacles live on North Atlantic seashores, but as adults, one species lives higher in the intertidal zone than the other, with little overlap between the two (a phenomenon called intertidal zonation).  If one of the species is removed experimentally, the vertical range of the other species becomes greater.  The higher-zone barnacle outcompetes the other because it is more hardy when exposed to air; in the lower zone, the other barnacle is able to smother or crush higher-zone intruders.

Barnacle Competition

Batesian Mimicry  Two different species resemble each other. One is unpalatable. The palatable receives the benefit of birds not wishing to eat it because they have eaten the unpalatable one with bad results.

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Keystone Species  keystone.html keystone.html keystone.html  A keystone species is a species whose very presence contributes to a diversity of life and whose extinction would consequently lead to the extinction of other forms of life. Keystone species help to support the ecosystem (entire community of life) of which they are a part.

Succession  Succession begin when an area is made partially or completely devoid of vegetation because of a disturbance. Some common mechanisms of disturbance are fires, wind storms, volcanic eruptions, logging, climate change, severe flooding, disease, and pest infestation. disturbance

Plant Succession

Succession in a Glacial Moraine

Degradative succession  The dead body of an organism is reduced to basic molecules by decomposers  Plants may produce litter  Deciduous trees may produce layer of litter - compost

Coevolution  The changes in one species may affect the changes in another species over time  Adaptations may occur  The organisms can develop a close association  Pollinators and flowers a key example of coevolution

Yucca Moth

Yucca and moth  Female yucca moths only lay their eggs in the ovules of yucca flowers. A female Tegeticula( Yucca moth) lays no more than 5 eggs in the ovules.  After she has laid the eggs she scrapes the pollen from the flower’s anthers and flies to another Yucca where she transfers the pollen and lays 5 more eggs

Island Biogeography  Immigration of mainland species to island – birds flying – other animals and plants and animals drifting on trees or floating on rafts of vegetation in the currents in the ocean ( new plants and animals) Seeds also carried by birds  Isolation of species after immigration  Novel adaptations  New species develop – allopatric speciation  New genetic species

Galapagos

Darwin’s finches and the Galapagos Islands  Pages/DarwinFinch.html Pages/DarwinFinch.html Pages/DarwinFinch.html