Chapter+4+Evolution,+Biological+Communities+and+Species+Interactions

Chapter 4 textbook Powerpoint [|chapt04_lecture.pdf]

4.1 Evolution

 * __Allopatric and Sympatric Speciation__**

__Allopatric-__ In allopatric speciation, new species are created when members of one original species are __geographically isolated__. They begin to develop new traits, which are passed down because they do not breed with the original species.

__Sympatric-__ When new species arise from a common ancestor because of a genetic variation and __behavioral barriers__ that isolate the organism’s reproduction, though they are in the same location as the original species.

**Resource Partitioning vs. Niche Specialist**
 * Partitioning can allow several species to utilize different parts of the same resource and coexist within a habitat
 * Species specialize over time in order to gain access to the resources they need. This is one way to reduce competition because different species share resources. Therefore more species can survive.


 * Niche specialists have narrow ecological niches and very specific needs in terms of resources and habitats. They don’t compete as much as other species because they don’t require the same resources as them.


 * Partitioning can cause species to specialize in the area of the habitat where they find resources and the type of resources that they rely on. This can cause species to evolve in such a way that they become niche specialists, and are less resilient to environmental changes.

A niche specialist is an extreme example of resource partitioning.

Directional Selection - Certain genes or traits are distributed mroe than others in a population. Many birds have mutations of their beak but mosty mutation result in one general shape/size. Stabilizing Selection - Less genetic variation within a population. Birds of a population lose a trait all together (short legs). Disruptive Sleection - One trait will be distibuted to the extreme. Birds gain extremelty long wing spans or relaly short wing spans.


 * Competitive exclusion || BOTH || Resource partitioning ||
 * No two species can occupy the same niche || Process of niche evolution || Several species can use the same resource but different parts of it ||
 * More efficient one in using available resources excludes the other || Diversity depends on niches || Can coexist in the same habitat ||
 * One species per niche || Genetic variation depends on competition || Multiple species per niche = more diversity ||
 * More competition = “fittest” passes down best genes to offspring ||  || Less competition = less genetic variation ||
 * No time for production because busy competing, but more genetic variation because they push each other to evolve more ||  || More time to reproduce the same species when less competition ||

4.2 Relationships

 * barnacle ws: [|competition.pdf]
 * snake hawk relationships ws:[|analyzing relationships.pdf]
 * reading and question ws: [|brood parasitism article.pdf]
 * Lynx Hare Ws: [|what goes up must come down.pdf]
 * Sea otter, Kelp, Orca --> Which is the keystone in this community - or is there a keystone set of organisms?

4.3 Properties of Communities
> || Species complexity ||  ||   ||   || > || Resilience ||  ||   ||   || > || Stability ||  ||   ||   || > || Edge effect ||  ||   ||   || > || ecotones ||  ||   ||   ||
 * Community Structure
 * || Pond || Stream || Swamp ||

4.4 Community Change

 * Primary succession WS: [|primary succession.pdf]
 * Secondary Succession WS: [|secondary succession.pdf]
 * Aquatic succession WS: [|succession in a water community.pdf]