Class notes
Class notes Ecology (BIO1006)
- Course
- Institution
Class notes for first year Ecology module
[Show more]
Seller
Follow
eleanorton
Content preview
25/10/2018 ecology lecture ten – communitiesA community is a unit of the natural world comprising assemblages of different species, in different
proportions and doing different things. Populations of different species interacting in the same area.
- A community is comprised on individuals living in populations
Interspecific competition affects community composition and structure for example the competitive
exclusion principle.
Competition may not be apparent:
- If competition only occurs rarely eg at high population densities
- If population densities are low due to other factors
- Species may coexist even where competition is intense due to a patchy habitat
- Past competition has resulted in niche differentiation
- Unsuccessful competitors are extinct
Predation affects competition:
- Predator-mediated coexistence: predation can increase or decrease species richness,
predator may reduce density of competitors, when there is no competitive dominance,
predation can decrease species richness, if the preferred prey in a community is dominant,
selective predation increases species richness
- If population densities are low, due to other factors, competition will not be apparent.
Rabbits are broadly generalist grazers. Grazing keeps aggressive, dominant grasses in check
and greater plant diversity arises. If grazing pressure is removed then plant diversity declines
Population dynamics: predator and prey populations fluctuate independently (Lotka-Volterra model)
For example the snowshoe hare and lynx. The hare population follows an 8-11 year cycle that is
tracked by predators such as the lynx.
Declines in hare abundance due to low birth weight, low growth weight, low survival. Plants respond
to heavy grazing by producing toxins and remain unpalatable for 2-3 years.
Keystone species – species that are critical to the community and determine community structure ie
top predators and pollinators. Keystone predators can reverse the outcome of competitive
interactions.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller eleanorton. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.22. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52355 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now