1. What Shapes an Ecosystem? Ch. 4-2
Ecology Notes 4
What Shapes an Ecosystem?
Ch. 4-2

2. 1. Symbiotic Relationships
SYMBIOSIS – Biological relationship where 2 organisms live in close association. There are 3 main types:
PARASITISM – Parasite benefits from host and host is harmed
Example: LEECHES ON HUMAN SKIN
COMMENSALISM - One organism benefits and the other is not harmed
Example: REMORA EATING PARASITES OFF SHARKS
MUTUALISM – Both organisms benefit from an association
Example: CLOWN FISH & SEA ANEMONE (clown fish live in the anemone and in return frighten off organisms that may harm the anemone)

3. Clown Fish & Anemone 

4. 2. Predation PREDATION – a predator captures and eats prey
PREDATOR – captures, kills and consumes another organism
PREY- organism that is eaten
PREDATION IS DIFFERENT FROM PARASITISM
Parasites seek to use their hosts as long as possible (goal is not to kill, just use)
Predators remove prey immediately from an ecosystem

5. Predation Drives Evolution
Predators adaptations
locate & subdue prey
Prey adaptations
elude & defend
Predation provides a strong selection pressure on both prey & predator
horns, speed, coloration
spines, thorns, toxins
Predation provides a strong selective pressure on prey populations. Ay feature that would decrease the probability of capture should be strongly favored.

6. Defense Mechanisms
Camouflage
whipporwill
frog
lizard
lizard
toad

7. Warning “Aposematic” Coloration
Bright warning to predators

8. Mimicry green parrot snake hawkmoth larvae
Palatable or harmless species mimics a harmful model
green parrot snake
Hawkmoth larva puffs up to look like poisonous snake
hawkmoth larvae

9. Mimicry
Monarch male
poisonous
Viceroy male
edible

10. 3. Competition
Competition – The “FIGHT” for an area’s resources. There are 2 types:
INTERSPECIFIC – members of two different species compete
Example: TWO TYPES OF BIRDS EATING THE SAME BUGS
INTRASPECIFIC – members of the same species compete
Example: 2 STUDENTS VYING FOR A PARKING SPOT
A NICHE reduces competition
All organisms have different ways of life. A species’ individual lifestyle is its niche (role in the environment).

11. The 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

12. 3. Competition Niche Overlap
When organism niches overlap, competition occurs
An organism will either evolve or die to reduce competition
COMPETITIVE EXCLUSION– one species competing for a limited resource is removed from a community due to its inability to compete with other species
Natural Selection favors the evolution of differences between competitors
CHARACTER DISPLACEMENT– evolution of niche differences or physical variations that lessen competition
Example: Galapagos finches living on the same island have different shaped beaks so all access different food sources
RESOURCE PARTITIONING – Use of only part of a resource so as to avoid competing with an organism in need of the same thing
Example: The text discusses 3 species of warbler that eat the same things but feed in different regions of a tree.

13. Niche & Competition Competitive Exclusion
No two similar species can occupy the same niche at the same time

14. Symbiosis
mutualism
+/+
commensalism
+/0
predation
+/-
competition
-/-

15. 4. Properties of Communities
SPECIES RICHNESS – the number of types of species in an ecosystem
Indicates ecosystem health when high
High biodiversity also increases the chance that life will continue in an ecosystem even after some type of disaster
Two Distinct Patterns
HIGH RICHNESS CLOSER TO THE EQUATOR
The theory suggests that more organisms exist in tropical habitats because they are stable in temperature
Tropical habitats are also “younger” and probably have not been impacted as severely by past Ice Ages
SPECIES AREA EFFECT
Larger land areas support higher numbers of species
Habitat destruction decreases the diversity of species in an area

16. 4. Properties of Communities
SPECIES DIVERSITY – the abundance of each type of species in an ecosystem
Indicates the importance of a particular species
High numbers of a particular organism suggests that it performs an important function for the ecosystem
COMMUNITY STABILITY - Stability of a community is its resistance to change.
High species richness suggests greater INTERDEPENDENCE of organisms
Increased links between organisms equals increased reliance and increased stability of an ecosystem

17. 5. Ecological Succession
SUCCESSION – the gradual growth and re-growth of an ecosystem
Disturbances in an ecosystem affect its growth patterns and development
As an ecosystem recovers from a disturbance it experiences recognizable sequences of re-growth.
There are 2 main types of succession:
PRIMARY SUCCESSION – development of a community that has never been inhabited before
PIONEER SPECIES – The first species to inhabit an area
SECONDARY SUCCESSION – re-growth of a community following natural disaster or human interference
CLIMAX COMMUNITY – a community having successfully gone through stages of succession to reach a stable endpoint
A Climax Community remains constant for a long period of time…at least it hopefully should!

18. Primary Succession pioneer species compete well in high sunlight
lichens & mosses
grasses
more shade tolerant species
climax forest
shade tolerant species
stable community
bushes & small trees
trees

19. Secondary Succession
burning releases nutrients formerly locked up in the tissues of tree
the disturbance starts the process of succession over again