1. Succession and Niches

2. Succession
• Definition: Ecological succession is a
process in which communities of
plant and animal species are
replaced in a particular area over
time by a series of different and
usually more complex communities.

3. Succession
• Primary – succession based on
natural development of communities
– Algae, moss, grasses, trees
• Secondary – succession based on
“event”, which usually causes a
return to a state similar to its original
state
– Tree falling, volcano, hurricane

4. Succession
• G.2.7: Outline the changes in species
diversity and production during primary
succession.
– Not very diverse: Lichen pioneer species
– Very diverse: Forest climax community

5. Succession
• G.2.8:Explain the effects of living
organisms on the abiotic
environment, with reference to the
changes occurring during primary
succession.
– Small amount of soil formed by the
lichens is colonized by mosses, which do
not have roots and require little soil
– As the seedless plants live and die
decomposition increases the richness of
the soil
– Grasses can successfully grow

6. Niche
• G.1.5 Explain what is meant by the niche
concept.
• The total of a species’ use of biotic and
abiotic resources is called the species’
ecological niche.
– Habitat
– Feeding relationships
– Symbiotic/other interactions with organisms

7. Niche
• Fundamental niche = where the
species is designed to live the best
• Realized niche = where the species
actually resides because of
competition

8. Niche
• G.1.7: Explain the principle of
competitive exclusion.
• two species competing for the same
limiting resources cannot coexist in
the same place – one must leave or
becomes extinct

9. Interactions
G.1.6:Outline the following
interactions between species (with
examples):
• Competition
• Herbivory
• Predation
• Parasitism
• Mutualism