By the end of section 3.1 you should be able to understand the following:

Over time, and many generations, organisms change along with the biotic and abiotic factors in their environments through the process of natural selection.

In natural selection, the best-adapted members of a species survive, grow strong and reproduce more easily than the rest of that species.

In ecosystems, ecological succession (primary succession and secondary succession) also occurs, as changes tend to favour certain ecological conditions over others as an ecosystem matures.

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.

3.1 How Changes Occur Naturally in Ecosystems

Example: The Finches of

the Galapagos Islands (off the coast of Ecuador)

There are 13 species of finches on the island… http://science.discovery.com/videos/1

00-greatest-discoveries-shorts-natural-selection.html

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.

Ecological Succession

(Changes to the biotic characteristics in an area)

Primary Successio

n

Secondary Successio

n

Natural Changes to Ecosystem

Life Without People

1) Steps of Primary Succession

Starts with bare rock.

Wind carries spores of lichens that can survive on bare rock.

Weathering breaks down rock - soil begins to form

Pioneer Species are the first organisms to survive and reproduce. e.g. Lichens and mosses

1) Steps of Primary Succession

Pioneer species make/improve soil

other plants can grow

animals appear

form a mature community (stable and change slowly)

p. 112,113

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.

FloodingLeads 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.

Disturbances that Might Cause Secondary Succession

Disturbances that Might Cause Secondary Succession

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.