1. System Responses to
Natural Disturbances

2. Let’s look at an example (the 3-spine stickleback)
Always Changing...
Animals and plants ADAPT in order to survive in their environments.
Let’s look at an example (the 3-spine stickleback)
Originally an ocean-dweller (only lived in salty ocean waters)
- 13,000 years ago, the glaciers around BC retreated and some
ocean water became lakes (freshwater).
Another adaptation is that one species lives and feeds at the bottom, the other species lives and feeds in surface waters

3. “Survival of the Fittest”
Natural Selection
“Survival of the Fittest”
Species that are best adapted (fittest) will survive and reproduce.
Fit doesn’t mean “in shape” but having characteristics that give species an advantage!

4. Properties of Individuals of a Population
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.
salmon with a slightly larger tail may be able to swim a little faster and feed easier

5. Famous Example Charles Darwin Galapagos Island Finches
14 species have “radiated out” from one common ancestor, but they occupy different niches

6. Adaptive radiation describes the type of natural selection where many different species appear from one original species

7. Natural selection rests on 5 indisputable facts:
Organisms produce more offspring than can survive.
Competition for Resources
Individuals vary in their characteristics.
Survival of the Fittest, i.e. which variation makes them best suit for their survival in their environment
Many characteristics are inherited by offspring from their parents.

8. Ecological Succession
The gradual replacement of one plant community by another through natural processes over time

9. Primary
Succession

10. Primary Succession may take thousands of years
begins in a place without any soil
i.e. barren habitats
(rock, sand, clay, ice)
e.g. Sides of volcanoes
PIONEER SPECIES - first organism to survive and reproduce in an area
Wind and rain carries spores of
lichens to these areas. Lichens and the
forces of weather and erosion help break down rocks into smaller pieces

11. 2. When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

12. 3. Soil improves, plants are able to grow and animals begin to appear….
Simple plants like mosses and ferns can grow in the new soil
The soil layer thickens, and other larger plants begin to take over and cycle continues…
5. This stage can last for hundreds of years, until a mature community eventually forms.

13. Mature communities are called climax communities which are a group of stable plants and animals which appear to be unchanging over long periods of time.
Does not always mean big trees
Grasses in prairies
Cacti in deserts

14. Secondary Succession

15. Secondary Succession Takes about hundred years
Begins in a place that already has soil and was once the home of living organisms
Occurs after a major disturbance
e.g. after forest fires
Process is faster and has different pioneer species (grass/dandelions) than primary succession

16. Natural Events Affect Ecosystem
- Natural disasters are changes which are so great they may cause damage to the shape of the land
- including drought, tsunamis, infestations, flooding, and diseases

17. Flooding –when volume of water exceeds the ability of the water body to contain it

18. Tsunamis
Huge, rapidly moving ocean wave

19. Drought - below average amount of precipitation in an area over a period of month or years.

20. Insect infestation
Most insects are helpful, but when normal conditions change, infestations can occur.
Example: Mountain Pine Beetle:
Usually it is not a problem…it helps remove old trees
HOWEVER, the climate is warming, and the bugs
are not dying in the winter.
Pine beetle has blue stain fungus in its mouthparts, which it transmits to the trees (symbiotic relationship).
Fungus slows down resin production on trees so the beetle can eat the tree more easily.