Transcript How Changes Occur Naturally in Ecosystems

How Changes Occur Naturally
in Ecosystems
Chapter 3.1
Always Changing...
• Abiotic (non-living) and biotic (living)
factors can change the conditions of
an environment/ ecosystem
• Animals and plants ADAPT in order to
survive in their environments.
• Let’s look at an example (the 3-spine stickleback)
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?
Natural Selection
Species that are best
adapted (fittest) will
reproduce and survive.
Fit doesn’t mean “in shape” but
having characteristics that
give species an advantage!
Famous Example
• Charles Darwin – Galapagos Island Finches
A number of different species have “radiated out” from one common
ancestor to inhabit different niches.
How Ecosystems Change
• Abiotic factors change in an ecosystem
• Biotic factors (who lives there) changes
too
Ecological Succession = changes in
the types of organisms over time
Primary and Secondary
Primary Succession
• Occurs in an area with NO SOIL (ex: bare rock)
How it starts...
• Wind/ rain
carry spores
(lichen) to
rocks
• Lichens
release
chemicals into
rock (obtain
nutrients,
break down
rock)
And then....
• Spores of
plants (mosses)
deposit
• “Pioneer
species” can
survive harsh
conditions.
• Provide food,
water,
nutrients
Climax Community
• This is a “mature” community
• Ex: Boreal forest, grasslands,
rainforest...
• They change too...
– Small disturbances cause these
communities to change (even if they appear
unchanged).
Secondary Succession
• The slow process of plants/
animals inhabiting an area that
was DISTURBED but already
had soil.
• It was once the home of living
organisms.
Faster than Primary succession
(decades to a hundred years)
Why is it faster???
- Because soil with nutrients is already present
• Erupted Aug 27, 1983
• Eruption was heard in Madagascar, Philippines and Australia. Produced
40m waves.
• Eradicated all life on the island
Now a diverse, rich rainforest
HOW NATURAL EVENTS
AFFECT ECOSYSTEMS
Flooding
• Soil erosion, soil pollution if chemicals present in floodwater
Tsunamis
• Wave carries away or destroys plants and animals, salty soil
Drought
• Crop failures, livestock deaths
Insect Infestations
• Ex: Mountain pine beetle, bird and mammal nests lost, forestdependent economies affected