Ecosystems continually
change over time
Chapter 3 – Science 10
Ecosystems continually change
▪ 3.1 How Changes Occur
Naturally in Ecosystems
Natural
Phenomena
▪ 3.2 How Humans Influence
Ecosystems
▪ 3.3 How Introduced Species
Introduced
Species
Human
Activities
Affect Ecosystems
Ecosystems
Change and
Species
Adapt
Natural Selection
▪ When an organism is born, it belongs to a species, but it also
is born with unique characteristics.
▪ Sometimes, these unique characteristics give organisms an
advantage within their niche. For example, a salmon with a slightly
larger tail may be able to swim a little faster or a little farther in a
river.
▪ Natural selection is the process where individuals with
advantages are better able to reproduce and pass along their
traits.
▪ Those with unfavourable characteristics have less chance to
reproduce and pass along their traits.
▪ A salmon with a smaller tail may never have a chance
to spawn because it cannot swim to the correct location.
A salmon with a large tail may be able to
swim faster and farther.
3.1 How changes occur naturally in ecosystems
▪ Natural Selection
▪ Change is possible in living things
▪ Adaptive Radiation
▪ Different species have “radiated” out from a common ancestor to inhabit different niches.
▪ Lake Victoria Cichlid
Cichlid – an example of adaptive radiation
Galapagos Finches & Charles Darwin
Natural Selection
▪ Natural selection is the process that enables organisms to change in
response to changes in abiotic and biotic components of an
ecosystem.
Adaptive Radiation
▪ Adaptive radiation is the change from a common ancestor into a
number of different species that can inhabit different niches.
http://www.youtube.com/watch?v=AMtT5_AQmLg
How ecosystems change over time:
Ecological Succession
▪ A connection with Chapter 12: Mt. St. Helens
▪ http://www.youtube.com/watch?v=BaRAGzjSkzo
Ecological Succession
▪ Two types:
▪ Primary Succession
▪ Occurs in an area where NO SOIL exists
▪ Slow
▪ First organisms to appear are called pioneer species
▪ Lichens, mosses etc…
▪ Secondary Succession
▪ After a disturbance in an area that already had soil and organisms
▪ Fire, floods, building a road through a forest etc…
▪ Much faster than primary succession
Primary Succession: Mature Community
▪ From Bare Rock to Mature Communities
▪ A mature community is also called a climax community but a mature
community is a preferred term because forests are constantly
changing.
▪ A forest is an example of a mature community.
Primary Succession: Pioneer Species
▪ Pioneer Species take advantage of bare rock.
▪ Pioneer species decay and create soil.
▪ Pioneer species provide food for other organisms, introducing new animals to
the community.
▪ New plants take over the new soil area until….
▪ The next species succeeds the previous species and so on until a
mature community is established.
Primary Succession: hundreds of years
Secondary Succession: tens of years
http://www.youtube.com/watch?v=V49IovRSJDs
How natural events affect ecosystems
▪ Natural events can change the abiotic and biotic conditions of an
ecosystem
▪ Some examples:
▪
▪
▪
▪
Flooding
Tsunamis
Drought
Insect infestations
Flooding
▪ Can cause soil erosion and wash away nutrients
▪ Can cause the spread of disease in human populations
▪ Bacteria and toxins polluting the water supply
▪ Climate change
▪ May be causing increase around the world
Tsunamis
▪ Huge rapidly moving ocean wave
▪ Caused by earthquakes or underwater
volcanic eruptions *Ch. 12/13
▪ Salt water kills the plants on shore
*remember the NaCl lab?
Drought
▪ Below average precipitation
▪ Crop failure, animal death
▪ Made worse from climate
change
Insect Infestation
▪ Insect infestations
▪ Many insects play important roles in their ecosystems.
▪ Even insects that appear destructive, such as the
mountain pine beetle, actually play a role in the
renewal of the forest.
▪ The beetles have a symbiotic relationship
with a species of fungus that inhibits the
trees’ ability to use resin for protection.
▪ However, when normal conditions are changed, infestations can occur.
▪ Trees can be stressed from overcrowding drought or animal grazing and do
not resist the insects as effectively.
▪ A warmer climate and lack of forest fires allows the insects to spread much
more effectively than in the past.
▪ Not only are the trees affected, but so is the entire forest ecosystem, as
well as any human industries relying on the forest.
Mountain pine beetle.
Insect Infestation
▪ Mountain pine beetle example:
▪ Forests are no longer exposed to sustained periods with temperature
below -30°C
▪ Climate change
▪ Too many beetles attack stressed out trees.
▪ A fungus symbiotic with the beetle is passed from tree to tree.
▪ Blue stain fungus prevents the tree from making protective resin and destroys
tissues
▪ Trees die!
▪ Many habitats are destroyed for organisms depending on the trees.
Insect Infestation: Mountain Pine Beetle
http://www.youtube.com/watch?v=anxJsQ7GEV4