Transcript Reproduction and Niches

Reproduction and Niches
ES 100
August 20, 2007
Opportunists vs. Competitors
•
•
•
•
•
•
Do well in variable
climate or with
disturbance
Population boom and
bust cycles
Rapid development
Early reproduction
Small body size
Single reproductive
effort
•
•
•
•
•
•
Do well in stable
climate
Population carrying
capacity
Slow development
Late reproduction
Large body size
Repeated
reproduction
Practical Aspects of r vs. K
Robin
Eagle
Why different life strategies?
•
More ways to live in an environment and
use its resources.
•
Another way to say this: filling niches
•
•
Fundamental vs. Realized niche
Principle of competitive exclusion
What is a niche?
•
A niche is the total of all biotic and abiotic
factors that determine how an organism
fits into its environment.
•
Where and how does an organism live and
function?
•
•
habitat
role in community
Fundamental vs. Realized niche
Fundamental niche:
All possible environmental (biotic and abiotic) conditions
in which an organism can live.
Realized niche:
The actual environmental conditions in which an organism lives.
Success
potential
survival, but
stressed
intolerant
potential
survival, but
stressed
optimum
intolerant
Environmental variable (Temperature, for example)
Niche in n-variable hyperspace
Fundamental vs. Realized Niche
Fundamental niche: where a
species could live
Realized niche: with competition
from other species, where a
species does live
Principle of Competitive
Exclusion
Two species can’t occupy the same niche…
one would out-compete other and drive it to extinction
Niche Partitioning in Animals

Species divide up an apparent niche
Selection minimizes
competition
Two species living
separately.
In a guild, natural
selection minimizes
competition
Disease prevention via C.E.
Convergent Evolution
•Organisms adapt to fill open
niches
•Niches that are separated by
geographic barriers may be
filled by different species
(1 species, 1 niche, 1 location)
•Unrelated species who fill a
similar niche and display
similar form or function
exemplify convergent
evolution
Summary of Today

Life History: Reproductive Strategies



opportunists vs. competitors
Insight into ecosystem management
Life tables

Insights into population dynamics





Vulnerable age stages
Fitness
Generation time
Population trajectories
Niches



Fundamental vs. realized niche
Competitive exclusion principle
Convergent evolution