Transcript Interactions Among Species

Interactions Among Species
Section 2.2
Ecological Niche
 the role or “job” that an organism has in its ecosystem
 the organism’s way of life
 includes:
 habitat
 resource consumption
 interactions with other species
 ecological “services” provided – how it contributes to
function and sustainability of the ecosystem
No two species occupy the same exact
ecological niche.
Example: Big brown bat, Eptesicus fuscus
 Lifestyle: nocturnal
 Habitat: roosts in hollow trees, and man-made structures;




hibernates in caves
Range: North, Central, and South America
Diet: insects
Predators: cats, snakes, raccoons, owls
Ecological Service: regulating insect populations
All of these factors
together make up the
big brown bat’s niche.
Types of Species Interactions
 predation
 competition
 interspecific
 intraspecific
 symbiosis:
 mutualism
 parasitism
 commensalism
Predation
 occurs when one organism (the predator) feeds on
another (the prey)
a) Classify the lynx and hare in this photo as either predator or prey
b) From the graph: What happens to the lynx population when the hare
population increases?
Predator-Prey
interactions influence
the size of both
populations.
 Bottom-Up Population Regulation
 fluctuation in a resource at the base of a food chain
affects the animals at the higher trophic levels.
 Top-Down Population Regulation
 fluctuation in animals at higher trophic levels causes a
change at lower trophic levels
Scenario
a) DDT causes a decrease in hawk populations. Lizards,
rabbits, and snake populations grow.
a) Abundant rainfall creates favourable growing conditions
for grass. Populations of consumers grow.
a) Rabbit birth rates are higher than normal. More grass
gets eaten, but hawks also have more to eat.
Type of
regulation
Competition
 occurs when individuals compete with the same
limited resource
 food, shelter, water, mates
Two types:
 interspecific – Two different species compete
 intraspecific – Individuals of the same species
compete
 Observation: As population of female song sparrow grows,
the number of eggs laid decreases.
 Hypothesis: Competition reduces the reproductive output
(by limiting energy available for reproduction).
 Prediction: If birds are experimentally provided with food,
no decrease in number of eggs laid will be observed.
 EXPERIMENTALLY-SUPPORTED
Making connections:
 Is competition a biotic or abiotic factor?
 Is competition density-dependent or independent?
 What type (interspecific vs. intraspecific) of
competition was described in the previous example?
Competition can influence the niche an organism
occupies.
 Organisms have to share available resources.
 Their realized niches are smaller than their potential niches.
Example: Brook stickleback & Nine-spined stickleback
 similar habitat
 similar diet
 similar lifestyle
similar niche
How does competition affect the habitat of brook
sticklebacks?
Scenario 1:
Only brook
sticklebacks present:
The brook sticklebacks
are found at all levels
of the lake
Scenario 2:
Nine-spined
sticklebacks also
present:
The brook sticklebacks
are only found at
bottom of the lake
Competition for resources requires that the organisms
share in order to co-exist in the same space.
Symbiosis
 Symbiosis is a type of interaction where members of
two species live together in close physical
association.
 can be further classified based on nature of
interaction:
 mutualism
 parasitism
 commensalism
Mutualism
 both organisms benefit from the relationship
Examples:
A. Bees and flowers – Bees receive food (nectar), and
flowers are pollinated.
B. Gut bacteria and humans – Bacteria break down food
molecules so that humans can absorb nutrients.
Parasitism
 one organism benefits
while the other is harmed
Examples:
 tapeworms in human intestines
 fleas live on animals
http://www.youtube.com/watch?v=XuKjBIBBAL8
Commensalism
 one organism benefits,
while the other is not affected in any way
Example:
 Remora sharks use a special
disk on their heads to attach to
other animals, and “hitch rides”
http://www.youtube.com/watch?v=9z3pqp12UEg
Homework
 Handout
 Pg. 64 #2, 5, 6, 7