Ecosystems
Relationships and
Populations
Biotic and Abiotic Factors
(Living and Non-Living)
Abiotic Factors
Biotic Factors
ECOSYSTEM
Niche
 Part of the environment that an
organism uses
 ROLE + HABITAT
Warbler Niche
Cape May Warbler
Feeds at the tips of branches
near the top of the tree
Bay-Breasted Warbler
Feeds in the middle
part of the tree
Spruce tree
Yellow-Rumped Warbler
Feeds in the lower part of the tree and
at the bases of the middle branches
Community interactions
Competition
individuals or species trying to use the same limited resource
Competition
 competitive exclusion principle – 2 species cannot occupy
the same niche in the same habitat at the same time
Predator/Prey - +/-the predator catches the prey
- One organism captures and kills another
http://www.wallpaperbase.com/wallpapers/animals/tiger
s/tiger_6.jpg
http://inspectorgadget.files.wordpress.com/2007/12/tiger.jpg
Symbiosis
Two species living closely together
http://sugarmtnfarm.com/blog/uploaded_images/ClownInBubbleAnemone200511-780236.jpg
Symbiosis
a. Mutualism - +/+
both species benefit
Symbiosis
b. commensalism - +/0
– one benefits, the other is not
helped nor harmed
Example – a bird’s nest in a
tree OR barnacles on
whales
Symbiosis
c. Parasitism - +/one species benefits (parasite), one is harmed (host)
Ecological Succession –
natural progression of an environment
1. primary succession – starting where there is no soil
http://www.v-liz.com/galapagos/isabela/puntam~1/lavacac-.jpg
2. secondary succession – where there was
a community, but it has been removed
Climax Community – last stage of succession,
ecosystem has reached equilibrium
Important characteristics of
populations
•geographic distribution –
the area inhabited by a population
•density –
number of individuals per unit area
•growth rate –
depends on birth rate and death rate
•density –
number of individuals per unit area
low density
high density
Exponential growth
ideal conditions
unlimited resources
Growth rate of bacteria
•some bacteria can divide every 20 minutes
•first 20 minutes – there will be two bacteria
•in one hour - there will be 64 bacteria
•in one day – there would be:
4,720, 000,000,000,000,000,000
or
4.72 x 1021
Logistic growth
as resources become limited
•growth rate slows or stops
•carrying capacity is reached
•Carrying Capacity – maximum population size
an area can support
Logistic Growth – S shaped curve, levels off at the Carrying Capacity
Carrying capacity
Time (hours)
Limiting factors
 nutrient
 space
 carbon dioxide level
 density-dependent – competition, predation,
disease, parasitism
 density-independent – weather, human
activities, seasonal cycles
Populations are dependent on Predator/Prey Relationships
Age-structure diagram
 shows number or percentage at each age