Chapter 4 - Ecosystems and Living Things
Vocabulary for Study
| Animalia Eukaryote Prokaryotes Protista Plantae Fungi Lichens Chloroplasts Mitochondria Symbionts Symbiosis |
Parasitism |
Realized niche |
Pioneer Community |
Lecture Notes
Ecosystems and Living Things
I. The niche concept
Remember the definition of a community: an assortment of different species living together in the same general environment.
Some examples of communities:
A prairie
A forest
A decaying acorn
Every member of the community has a job to do in the community (and by extension the ecosystem). Leads to the recognition of . . .
THE ECOLOGICAL NICHE
A. Fundamental (or Theoretical) Niche - the role or job that a species is capable of doing.
B. Realized Niche - the role or job that the species eventually performs, usually more limited than the fundamental niche. Examples of the anoles: genus AnolisAnole is pronounced: A-no-le
1. The native Carolina Anole and the introduced Cuban Anole have overlapping niches.
2. One or both must "shrink" their niche so that the competition for a resource (in short supply) is reduced (see the diagram, Fig 4-8). This has led to the concept of. . .
1. Role of Competitive Exclusion Ecological theory holds that no two species can occupy or fulfill the same niche. Adapted by J. H. Zar, Dean of the NIU Graduate School, from On beyond Zebra, by Dr. Seuss:
On Competition. . .
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Let us consider the African Nutches
Who live in small caves, knows as Nitches, for Hutches.
These Nutches have troubles, the biggest of which is
The fact there are many more Nutches than Nitches.
Each Nutch in a Nitch knows that some other Nutch
Would like to move into his Nitch very much.
So each Nutch in a Nitch has to watch that small Nitch
Or nutches who haven't got Nitches will snitch.* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Competition - two organisms [species] aim to use the same resource. Particularly evident when that resource is in short supply.
2. Role of Limiting Factors - "Law of the Minimum" - the well-being of each organism or population is limited by whatever essential factor (resource) is in shortest supply or in toxic abundance. Could also be stated: populations flourish where the resources to which they are adapted are in greatest abundance. OVERHEAD
3. Results of introduction of exotics (example: the Zebra Mussel) You have already been informed of a few introduced species of a local nature.
II. Coevolution
Coevolution: the more or less simultaneous evolution of two species as a result of interdependencies.
A. Plant-Pollinator Relationship - easy to perceive
1. Examples are numerous
2. Dahlia
3. Silphium: Prairie-dock Compass Plant Flowers earlier Flowers later In lower places In higher places Easterly Westerly Identical Karyotypes - Chromosomes Identical Glycosides - Biochemical make-upB. So how can these two species look so different yet hybridize?
1. Flowering period
2. Pollinator activity
3. Ecological separation
4. Geographic distribution
5. Result of mowing
6. Presence of Italian Honey Bee
III. Symbiosis - manifestations of coevolution
Evolution - Descent with modification resulting in new taxa.
Coevolution - Two taxa develop interdependencies or interactions
A. Mutualism - both partners benefit from the association
1. Humming Birds & Columbines
2. Lichens - Fungi and algae
3. Termites and bacteria
4. Dandelions and ChemlawnB. Commensalism - one partner benefits, the other neither benefits nor has a cost
1. Many epiphytes - Vines in our woodlands
2. Barnacles on whales
3. Remoras on sharks - get a free ride and share in the shark's meal - may slow down the shark but insignificantlyNote: Remoras were once thought to be able to delay ships to which they attached. "mora" in Latin means delay
C. Parasitism - one organism benefits, the host may suffer---even severely. Not to be confused with predation.
1. Dwarf Misteltoe
2. Common Misteltoe - traditional Christmas decoration1. Inserts haustoria in host
2. Derives some of its nourishment
3. "River Blindness" - Schistosomiasis
4. Extreme parasitism that brings on death of the host is called a Pathogen. Example: Dutch Elm Disease - a fungusExample: Lyme Disease - a bacterium called Spirocheate
V. Community Change - Ecological Succession
Ecological Succession: the orderly change in community composition (species profile) over time.
Most easily observed in the vegetation.
Three attributes:
1. Orderly
2. Variable in rate
3. Continuous ± indefinitely
A. Primary Succession -
1. Takes place in a new area
2. No organisms previously existed
3. No soil exists
4. Proceeds very slowly
5. Seldom observedExamples:
1. Volcanoes
a. Pico Paricutin
b. Krakatoa2. Rock outcroppings
3. Gravel deposits from glaciers
B. Secondary Succession -
1. Takes place in an old area (formerly occupied)
2. Organisms previously inhabited the site
3. Soil is usually present and may be very well developed
4. Proceeds at a fast rate - comparatively
5. A familiar kind to us - we can observe it ± everywhere
C. "Old Field Succession"
1. A common form of secondary succession
2. Takes place in abandoned agricultural land
3. Activates the existing seed bank of weed seeds.
D. Successional sequence - sere in 2° succession
1. Pioneer community
a. Pioneer species
b. Examples:1) Path Rush
2) Giant Foxtail2. Climax community
a. Climax species
b. Examples:1) Sugar Maple
2) Red Oak
3. Seral or successional communitya. Seral stage
b. Seral species1) Horeseweed
2) Box-elder
3) Brambles4. Sub-climax - a seral stage that is well-defined in some seres.
For example: The Oak-Hickory stage is a subclimax to the Beech-Maple climax in eastern USA forests.
a. Oaks and hickories are shade intolerant
b. Sugar Maple and American Beech are shade tolerant
V. Five developments common to most seres (see also diagrams on following page):
1. Increase in species diversity
2. Increase in biomass
3. Increase in structural complexity - greater range of life-forms (see following pages)
4. Trend toward metabolic stability
5. Development toward mesophytic conditionsa. The Principle of Mesophytism: all succesion proceeds toward a mid-point on a moisture gradient. Ponds get drier, dunes get more moist.
b. Mesophytic conditions are the most moist that can be maintained over a long period.
VI. Life Forms of organisms: some principal categories
I). PLANTS:
A. Herbaceous plants - those that are green and do not develop woody parts.
1. Annuals - live for one season; must be replanted from seed the following season. examples:
Tomatoes
Petunias
Snap-dragons
Pumpkins (an herbaceous vine)2. Perennials - regrow each season from roots, crowns, tubers, or other underground storage organs. Above ground parts wither and die at the end of the season. Old stalks may remain standing but no longer possess the ability to come to life. examples:
Tulips
Milkweeds
Most ferns
Dandelions3. Biennials - produce only leaves the first season. Overwinter as a taproot (like a carrot). Regrow the second season, produce flowers, then die. Must then be restarted from seed. Examples:
Carrots
Parsley
Beets
(Note: these vegetables are grown as annuals because we harvest their roots and normally do not permit them to complete their life cycle except to derive a crop of seeds.)B. Woody plants - those that have overwintering above-ground parts (stems). Regrow from buds that occur in the notch of leaves and produce lateral branches.
1. Shrubs
2. Trees
3. Woody vines
II).ANIMALS
There is not the same kind of convenient classification of animals into "life forms" corresponding to the sort of ordering done for plants. Rather, animals, from fruit flies to elephants, are generally thought of in terms of their food gathering habits: