Bottom-Up & Top-Down Models of Community Organization
Community Organization
In governments, communities are generally organized in a top-down or bottom-up fashion. Either you're a proponent of the 'trickle-down effect' or of grassroots organization. Similarly, in nature, communities may be organized in a bottom-up or a top-down model. What do these models represent? Well, for one thing, it has nothing to do with voting or your political beliefs, since these are models of a more natural rather than human understanding.

An error occurred trying to load this video.
Try refreshing the page, or contact customer support.
You must cCreate an account to continue watching
Register to view this lesson
As a member, you'll also get unlimited access to over 84,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.
Get unlimited access to over 84,000 lessons.
Try it nowAlready registered? Log in here for access
BackResources created by teachers for teachers
I would definitely recommend Study.com to my colleagues. It’s like a teacher waved a magic wand and did the work for me. I feel like it’s a lifeline.
You're on a roll. Keep up the good work!
Just checking in. Are you still watching?
Yes! Keep playing.Bottom-Up
Let me pose a little simple scenario for you so you can begin mulling over the two models, the first one being the bottom-up model. Let's say there is some grassland and some deer. The grass, G, provides food for the deer, D. In the bottom-up model, we can say that the flow of influence on community organization goes in one direction, G to D, meaning it flows from a lower trophic level (grass) to a higher one (deer). From the bottom to the top, bottom-up. What this means is that if there is more grass, then deer will increase in number, or biomass, the total mass of living matter in a certain region. However, because the flow of G to D is unidirectional, the abundance of deer will not change the abundance of grass in such a model.
Okay, that was a simple example. Let's solidify our understanding of the bottom-up model with a more complex example. Let's say the soil contains nutrients, N, that helps the grass, G, grow. This, in turn, controls the number of deer, D and this, in turn, controls the number of predators, wolves, W. In the bottom-up model, our flow of influence is thus N to G to D to W. This means that if we want to alter this bottom-up community structure, we have to change the biomass at lower trophic levels in order to affect the higher trophic levels. If we increase the abundance of N, then G should increase and, theoretically, so should D and then W. However, if you decrease W, this should not effect lower trophic levels.
Top-Down
All of this stands in contrast to the top-down model of community organization, where the flow of influence goes in the opposite direction. That is to say, W to D to G to N. If we increase the number of wolves, more deer are eaten. This means more grass can grow since less of it is being eaten by a fewer number of deer. However, this also means nutrients decrease because of the abundance of grass growing and utilizing those nutrients. The top-down model of community organization has been used by ecologists to alter an ecosystem's characteristics. This is called biomanipulation. One example of this is the use of the top-down model to improve water quality without the use of chemicals. For example, to manage the occurrence of detrimental algal blooms, ecologists can remove fish from the ecosystem. This means zooplankton density will increase and this will, in turn, decrease the algal population. That's because fish eat zooplankton that, in turn, graze on algae.
Lesson Summary
I don't think that algae would be voting for the top-down model of natural government. The top-down model basically says that the influence on community structure flows from the top, the predators, down to the herbivores, then the vegetation, and finally the nutrients. Bottom-up model says that the influence on community organization flows from the nutrients, to the vegetation, then the herbivores, and finally the predators. So, if there's more vegetation then higher trophic levels, like that of herbivores, should increase in biomass, the total mass of living matter in a certain region, as a result.
To unlock this lesson you must be a Study.com Member.
Create your account
Register to view this lesson
Unlock Your Education
See for yourself why 30 million people use Study.com
Become a Study.com member and start learning now.
Become a MemberAlready a member? Log In
BackResources created by teachers for teachers
I would definitely recommend Study.com to my colleagues. It’s like a teacher waved a magic wand and did the work for me. I feel like it’s a lifeline.
Bottom-Up & Top-Down Models of Community Organization
Related Study Materials
- Glencoe Chemistry - Matter And Change: Online Textbook Help
- Chemistry: Credit Recovery
- Fundamental Chemistry
- 8th Grade Earth Science: Enrichment Program
- Remedial Earth Science
- Natural Sciences for Teachers: Professional Development
- Astronomy for Teachers: Professional Development
- Physical Science: Credit Recovery
- Remedial High School Physical Science
- AP Chemistry Textbook
- Honors Chemistry Textbook
- Microbiology Textbook
- AP Biology: Homeschool Curriculum
- Middle School Physical Science: Homeschool Curriculum
- Biology: Credit Recovery
Browse by Courses
- Top-Down Processing: Examples & Definition
- Bottom-Up Processing in Psychology: Examples & Definition
- Bottom Up & Top Down Teaching Strategies
- Bottom-Up Estimating: Definition, Disadvantage & Examples
- Top-Down Estimating: Advantages & Disadvantages
- Bottom-Up Approach to Reading Instruction
- Top-Down Budgeting: Definition, Process & Advantages
- Top-Down & Bottom-Up Approaches to Implementing Change
- Bottom Up Budgeting: Definition, Process & Advantages
- Top-Down & Bottom-Up Estimating Techniques in Project Management
- Attention and Top-Down vs. Bottom-Up Processing
- How to Evaluate Assessment Instruments & Their Results
- Modular Arithmetic & Congruence Classes
- Perfect Numbers & Mersenne Primes
- Math for Long-Term Financial Management
Browse by Lessons
Explore our library of over 84,000 lessons
- Create a Goal
- Create custom courses
- Get your questions answered