Download 3.1 How Changes Occur Naturally in Ecosystems

3.1 How Changes Occur Naturally in
Ecosystems

Natural selection - process where individuals
with advantages are better able to reproduce
and pass along their traits.
 A salmon with a smaller tail may never have a
chance to spawn because it can’t swim to the
correct location.
Three-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).
The Sticklebacks in the lake adapted!
As the salt water slowly changed to
freshwater, the stickleback adapted.
Now there are marine and freshwater
species.
Marine (left) and freshwater (right) guarding nests...
Question!
Did
the stickleback
adapt to an abiotic or a
biotic change in its
environment?
In the lakes...

Sticklebacks in BC lakes have evolved
into species pairs (one species lives and
feeds at the bottom, the other species
lives and feeds in surface waters)
Bottom dweller
Surface dweller
What differences do you see?
In the lakes...
There are about 6 species pairs of
sticklebacks in lakes around Vancouver Island.
 Recently, 1 species pair or sticklebacks living
in Hadley Lake (Lasqueti Island) has
disappeared

Introduction of
catfish
to the lakes
Question!
Did
the stickleback
adapt to an abiotic or a
biotic change in its
environment?
Example: The Finches of the Galapagos Islands
(off the coast of Ecuador)
Finches: There are 13 species on the island…
 All
the species are
descended from one finch
species on the mainland.
 Each species has unique
characteristics that allows
them to thrive in their own
niche, and not compete with
other finches for resources.

Adaptive radiation - a form
of natural selection when
many different species appear
from one original species.
Famous Example

Charles Darwin – Galapagos Island Finches
A number of different species have “radiated out” from one common
ancestor to inhabit different niches.
ECOLOGICAL
SUCCESSION
Changes in the biotic
characteristics in an
area over time.
Primary
Succession
Secondary
Succession
1) Steps of Primary Succession
a. Starts with bare rock.
b. Wind carries spores of lichens that can survive
on bare rock.
c. Weathering breaks down rock
 soil begins to form
e.
f.
g.
h.

Pioneer species make/improve soil
other plants can grow
animals appear
form a mature
community (stable
and change slowly)
Pioneer Species are the first organisms to
survive and reproduce.

Examples: Lichens and mosses
2. Secondary Succession:


when an area already has soil, but has
had a disturbance like a forest fire or
clearcut.
Happens more quickly
than primary because
there are already
seeds, insects, worms
etc. in the soil.
Disturbances that Might Cause
Secondary Succession

Flooding
– Leads to soil erosion, spread of pollutants and
harmful bacteria associated with sewage
– Climate change and global warming may be
increasing incidents
of flooding.
– A tsunami occurs
when huge waves,
from large earthquakes,
flood coastal areas.

Drought

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, but….
…in our forests there are a lot of old trees, 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.