REMEMBER
Ecological Niches
• all the physical, chemical and biological factors
that a species needs in order to survive and
reproduce in an ecosystem
• Also the role played by an organism in the
community
• In order to fully understand the ecological niche of a species, you must study many aspects of the species' life. It is important
to know where it lives (its habitat), what species it feeds on, which species it competes with, its predators, how and when it
reproduces—even where it leaves its wastes for decomposition. It is also important to know its physical and chemical niche,
that is, its body temperature, the chemicals it can and cannot tolerate, among other factors, as well as its effect on the
abiotic parts of the environment.
• The niche of an organism determines its
habitat.
• Each animal having its own ecological niche
diminishes competition among species
• Information about ecological niches helps
humans to manage species resources and to
predict the effects of either adding or
removing a species from an ecosystem
• The giant panda obtains 99% of its food by
eating bamboo plants.
• Starlings and house sparrows introduced in
North America have displaced native species
such as bluebirds from many areas because of
their aggressive behaviour.
Mechanisms of Population
Equilibrium
1. Abiotic and Biotic Limiting Factors on
Populations
- chemical or mineral availability, climate and
energy supply
- Predation, parasites, competition
2. Increasing Population Density
- Territoriality - mark and defend a territory in an
effort to ensure successful breeding.
- Sometimes brings about changes in behavior.
When rats are overcrowded, they often do not reproduce. In a study of blowflies, the population seemed to be self-
governing, regulating its own population. At high densities, the competition between flies was so severe that egg
production decreased and fewer offspring were born. The population dropped and egg production began again.
- Animals feeding on plant species tend to keep
their numbers stable (like predator/prey)
Ecological Succession
http://www.youtube.com/watch?v=k03
vxRYsJ4Y&feature=related
http://www.teachertube.com/viewVide
o.php?video_id=182733
• The repeated replacement of one community
by another
• As this continues, species diversity, population
numbers, ecological niche availability, biomass
and plant and animal size all increase.
• Energy is used more efficiently and food webs
become more complex.
• All of this adds to the complexity of the
ecosystem.
• takes a long period of time for this to happen
• The ecosystem will eventually reach a stable,
self-sustaining, mature community where
change is very slow. This is the climax
community.
• Although very stable, they are eventually
destroyed by accident (a forest fire, for
example) or by deliberate actions (cutting
down a pine forest, for example)
Primary Succession
• occurs in an area where no living organisms
previously existed = no soil
• Examples - rock or mud exposed by a
retreating glacier or mud slide, newly exposed
sand dunes, cooled volcanic lava and surface-
mined areas from which all topsoil has been
removed.
• Weathering of rock provides place for first life
called pioneers (lichen, moss, ants…)
• An example of primary succession is that which occurred over many regions of southern Canada after the
most recent glacier retreated. First, the retreating glacier exposed the bare rock of the highlands. Wind,
rain and frost weathered the rock surface and cracks became filled with water, which slowly dissolved
minerals in the rock. These minerals were able to support lichens, which grew on the rocks. Gradually the
lichens covered the rocks, dissolving additional minerals from the lichens as they themselves died.
Decomposer organisms then moved in. Soil particles blown by wind became trapped in the debris. Pioneer
mosses invaded at this stage and then ants, spiders and mites followed. This collection of plant and animal
species is called the pioneer stage of succession.
• They die, decomposers add them to soil,
bigger plants grow, repeat…
• Eventually there are mature trees, etc
Secondary Succession
• Secondary succession occurs after a
community is either partly or completely
destroyed as with fire, disease or even a clear-
cut hillside or abandoned field = soil there
• Same last steps