Ecosystems Continually Change

Over TimeChapter 3

(pages 106 -161)

Volcanic island; distributed around the equator in the Pacific Ocean (isolated)

2 seasons: worm and dry

Finches (birds): There are 13 species on the island

primary food source: seeds

Galapagos Islands

3.1 How Changes Occur Naturally in Ecosystems

A. How Organism ChangeQ: How do these changes occur?Adaptation Characteristics that allow organisms to better

survive and reproduce (3 types, chapter 1)Q: What if there is new environment? (eg.

Forest fire)? Speciation or extinction Natural selection Evolution The process in which, over time, the best-adapted

members of a species will survive and reproduce

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.

Activity 3.1A 5 min Page 109. DO “What to do”- “Mouth”

and “eyes” Match structural adaptation with

correct advantage to the environment.

Question: Which is more rapid:Change from bare rock to a mature forest or A burned down forest to an established forest?Why?

Ecological succession: changes that take place over time in the types of organisms that live in an area

Ecological Succession

Primary Succession

•Occurs in an area where no soil exists such as bare rock

• Takes a long time to complete ->up to several hundred years

1) Steps of Primary Successiona. 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

Pioneer Species are the first organisms to survive and reproduce.

Examples: Lichens and mosses

d. Pioneer species make/improve soil; Insects and microorganism move in when soil forms

e. As soil builds, other plants can grow (wildflowers and shrubs take root);

More types of insects and microorganisms move in

f. animals appear; tree seeds are transported to

the area by birds or other animals Trees must be tolerant of lots of sunlight eg. Deciduous forest.

g. Trees such as coniferous trees germinate and eventually shade out the deciduous trees

I. A mature community form (stable and grows slowly.)

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.

Read page 115-117 Complete “How natural events affect

ecosystem” check at the end of the class

HW. Read page 3.2 complete “Human

influence Ecosystem handout” Pg 121 Q 2-5, 6, 9,11,