Environmental Science
Chapter 5, Section 1 Outline Notes
Quick Summary: Chapter 5 provides an overview of ecosystem dynamics. Section 1 concentrates on
distinguishing between habitat and niche, discusses how changes in the abiotic/biotic factors could lead to a
species’ demise. Section 2 expands on the concepts of evolution and adaptation. Section 3 discusses
population dynamics; their capacity for growth and the limiting factors that prevent infinity.
Section 1: Habitats and Niches
I.
Niche
A. What is a Niche?
1. Definition ­ the role of an organism in the ecosystem
2. Identified by the organism’s actions, i.e. what the organism does {aka job} within its
environment/habitat/ecosystem.
B. Characteristics
1. Habitat
a) Location, a species’ physical home
b) The place in an ecosystem where the organism lives
c) F ­ W ­ S ­ S + E
2. Environmental Factors necessary for survival
a) Biotic (living) Factors ­ food source, predators
b) Abiotiv (non­living) Factors ­ temperature, sunlight, water availability, time of
day/night
3. Ways in which species interact
a) Competition
(1) Key Concept: NO TWO SPECIES CAN OCCUPY THE SAME NICHE
(2) Why?: They will compete for the same resources leading to generally
negative effects.
(3) When they overlap, what occurs?
(a) Answer: Competitive Exclusion
(b) Competitive Exclusion may cause …
(i)
Extinction of a population
(ii)
Eviction of a population
(iii)
Reduced survival rates for both species
b) Predation
(1) Definition: an interaction where organisms feed on one another
(a) Predator ­ an organism that actively hunts other organisms
(b) Prey ­ an organism that is hunted
II.
Niche Diversity
A. What is it?
1. Definition ­ the number of different niches in an ecosystem
2. Largely determined by abiotic factors
a) Temperature, Moisture, pH
(1) Marsh ­ fairly constant physical environment → fewer niches
(2) Desert ­ fairly variable physical environment → greater niches
3. Can also be determined by biotic factors
a) Predators and Prey
(1) Predators increase niche diversity by decreasing prey species which in
turn increases resources for other species.
(2) Cyclic → this predator/prey relationship has an ebb and flow to it
(a) Canadian Lynx ­ vs ­ Snowshoe Hare **
B. Keystone Predator
1. Definition ­ a predator that promotes a great niche diversity in its habitat
2. Examples
a) Sea Star in tidepools
b) Gray Wolves in Yellowstone **