Chapter 14: Interactions in the Ecosystem

Niche versus Habit?• Habitat – describes all of the abiotic and biotic factors in

the area where an organism lives• Niche– All the biotic and abiotic factors that a species

will need to survive and reproduce• Includes–Food–Abiotic conditions–Behavior

Habitat versus Niche

What kind of interactions can organisms in the same community have ?

Think of how you interact with people you know. What kind of interactions are they?FriendshipCompetitorEnemyNo relationship

1. Competition– Two organisms fight for the same limited

resources• Food• Space• Mates• Oxygen and Sunlight

Community Interactions

2. Predator – Prey Relationship– One species captures and feed on another– What happens when the prey population increases to

the predator population? – What happens when the predator population

increases to the prey population?• The two are directly proportional to each other

It increases also

It decreases and then the prey decrease

3. Symbiosis– Close relationship between two or more

organisms of different species which interact with each other

a) Mutualism– Both benefit from the interaction

b) Commensalism– One organism benefits from the relationship

and the other is unharmed

c) Parasitism– One organism benefits and the other is harmed

Carrying CapacityIs the maximum number of

individuals of a particular species which the environment could support

When year did the population first reach carrying capacity?

What is the carrying capacity for this population size?

What is your prediction for population size immediately following WWII?

~1850

~1.6 million people

It will decrease

What ecological factors limit population growth?

1. Density- Dependent limiting factors– Limiting factors that are affected by the

population’s size• Competition – limited resources causes a

struggle for survival (Darwin!!)• Predation – as the predator’s population

increases, the prey population decreases• Parasitism and disease – the three things that

control a population’s size are war, disease and famine!! (Malthus!!)

2. Density – Independent limiting factors– Factors in the environment that limits a

population’s growth that have nothing to do with the size of the population• Weather• Natural disasters• Human activity

Density dependent or density independent factors?

1. Competition between members of population.

2. Predation.3. A hurricane drowning many earthworms

4. Disease5. Burning of a forest6. A very cold winter

Density Dependent

Density Dependent

Density Dependent

Density IndependentDensity Independent

Density Independent

What follows the Natural Disaster?

• Succession– A sequence of biotic changes that regenerates a

damaged community or a bare, new area– What follows a forest fire?– What happens after a volcano?– What occurred after the asteroid hit the earth?

Primary Succession starts from bare rock• Pioneer species are the first to inhabit the area– Lichens and mosses• Break down minerals in rock to allow for soil to build up• Soil gets thicker and now grasses can start to grow.• Next comes small shrubs then trees• Final community is the CLIMAX community which are large

trees like Oaks and Pines

Pioneer species

Climax species

• Usually occurs in areas that have been disturbed– Bulldozed or cleared area– Fire– Flood– Hurricane

Secondary Succession starts from soil

Pioneer species

Climax species