3.1 How Changes Occur Naturally 3.1 How Changes Occur Naturally in Ecosystems in Ecosystems

Natural selectionNatural selection - process where - process where individuals with advantages are better individuals with advantages are better able to reproduce and pass along their able to reproduce and pass along their traits.traits.

A salmon with a smaller tail may never A salmon with a smaller tail may never have a chance to spawn because it can’t have a chance to spawn because it can’t swim to the correct location.swim to the correct location.

Three-Spine SticklebackThree-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 The Sticklebacks in the lake adapted!adapted!

As the salt water slowly changed to As the salt water slowly changed to freshwater, the stickleback adapted.freshwater, the stickleback adapted.

Now there are Now there are marinemarine and and freshwater freshwater species.species.

Marine (left) and freshwater (right) guarding nests...

Question!Question!

Did the stickleback Did the stickleback adapt to an adapt to an abioticabiotic or or a a biotic biotic changechange in its in its

environment?environment?

In the lakes...In the lakes...

Sticklebacks in BC lakes have Sticklebacks in BC lakes have evolved into evolved into species pairsspecies pairs (one (one species lives and feeds at the species lives and feeds at the bottom, the other species lives and bottom, the other species lives and feeds in surface waters)feeds in surface waters)

Bottom dweller

Surface dweller

What differences do you see?

In the lakes...In the lakes... There are about 6 species pairs of There are about 6 species pairs of

sticklebacks in lakes around Vancouver sticklebacks in lakes around Vancouver Island. Island.

Recently, 1 species pair or sticklebacks Recently, 1 species pair or sticklebacks living in living in Hadley Lake (Lasqueti Island) Hadley Lake (Lasqueti Island) has has disappeareddisappeared

Introduction of catfish to the lakes

Question!Question!

Did the stickleback Did the stickleback adapt to an adapt to an abioticabiotic or or a a biotic biotic changechange in its in its

environment?environment?

Example: The Finches of the Galapagos Example: The Finches of the Galapagos Islands (off the coast of Ecuador) Islands (off the coast of Ecuador)

Finches: There are 13 species on the Finches: There are 13 species on the island…island…

Provincial Exam QuestionProvincial Exam Question

All the species are All the species are descended from one descended from one finch species on the finch species on the mainland.mainland.

Each species has unique Each species has unique characteristics that allows characteristics that allows them to thrive in their own them to thrive in their own niche, and not compete with niche, and not compete with other finches for resources.other finches for resources.

Adaptive radiationAdaptive radiation - a form - a form of natural selection when of natural selection when many different species many different species appear from one original appear from one original species.species.

Famous ExampleFamous Example Charles Darwin – Galapagos Island Finches Charles Darwin – Galapagos Island Finches

A number of different species have “radiated out” from one common ancestor to inhabit different niches.

Provincial Exam QuestionProvincial Exam Question

ECOLOGICAL SUCCESSION

Changes in the biotic characteristics in an

area over time.

Primary Succession

Secondary Succession

1) Steps of 1) Steps of Primary Primary SuccessionSuccession

a.a. Starts with bare rock. Starts with bare rock.

b.b. Wind carries spores of Wind carries spores of lichenslichens that can that can survive on bare rock.survive on bare rock.

c.c. WeatheringWeathering breaks down rock breaks down rock

soil begins to soil begins to formform

Pioneer SpeciesPioneer Species are the first are the first organisms to survive and reproduce.organisms to survive and reproduce.

Examples: Lichens and mossesExamples: Lichens and mosses

e.e. Pioneer speciesPioneer species make/improve soil make/improve soil f.f. other plants can grow other plants can grow g.g. animals appearanimals appearh.h. form a mature form a mature

community (stablecommunity (stable and change slowly)and change slowly)

2. 2. Secondary SuccessionSecondary Succession::

when an area already has soil, but when an area already has soil, but has had a has had a disturbancedisturbance like a forest like a forest fire or clearcut.fire or clearcut.

Happens more quickly Happens more quickly

than primary because than primary because

there are already there are already

seeds, insects, worms seeds, insects, worms

etc. in the soil.etc. in the soil.

Secondary SuccessionSecondary Succession

Provincial Exam QuestionProvincial Exam Question

Disturbances that Might Cause Disturbances that Might Cause Secondary SuccessionSecondary Succession

FloodingFlooding– Leads to soil erosion, spread of pollutants Leads to soil erosion, spread of pollutants

and harmful bacteria associated with and harmful bacteria associated with sewagesewage

– Climate change and global warming may Climate change and global warming may be increasing incidents be increasing incidents of flooding.of flooding.

– A tsunami occurs A tsunami occurs when huge waves,when huge waves,from large earthquakes,from large earthquakes,flood coastal areas.flood coastal areas.

DroughtDrought

Insect infestationInsect 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, in our forests there are a lot of old trees, the climate is warming, and the bugs are not the climate is warming, and the bugs are not dying in the winter.dying in the winter.

Pine beetle has blue stain fungus in its Pine beetle has blue stain fungus in its mouthparts, which it transmits to the trees mouthparts, which it transmits to the trees (symbiotic relationship).(symbiotic relationship).Fungus slows down resin production on trees Fungus slows down resin production on trees so the beetle can eat the tree more easily.so the beetle can eat the tree more easily.

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