1. 5-3 How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
Concept 5-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

2. Communities and Ecosystems Change over Time: Ecological Succession
The types and numbers of species in biological communities can ________________ over time in response to changing environmental conditions…
Fires, volcanic eruptions
Climate change
Clearing of forests to plant crops
The normally gradual change in species composition in a given area is called ___________________ ______________________
change
ecological
succession

3. Communities and Ecosystems Change over Time: Ecological Succession
Two main types of ecological succession…depending on the conditions present at the _______________ of the process
___________________ ecological succession
______________________ecological succession
beginning
primary
secondary

4. Some Ecosystems Start from Scratch: Primary Succession
Primary Succession – the gradual establishment of biotic communities in _______________ areas where there is…
__________________ in terrestrial ecosystems
No _________________________ in aquatic ecosystems
Takes hundreds to ________________ of years
Need to build up soils/sediments to provide necessary _________________
lifeless
No soil
bottom sediment
thousands
nutrients

5. Lichens and mosses - _____________ species pioneer
Balsam fir, paper birch, and white spruce forest community
Figure 5.19: Primary ecological succession: Over almost a thousand years, these plant communities developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in northern Lake Superior. The details of this process vary from one site to another. Question: What are two ways in which lichens, mosses, and plants might get started growing on bare rock?
Jack pine, black spruce, and aspen
Heath mat
Small herbs and shrubs
Lichens and mosses
Exposed rocks
Time
Fig. 5-19, p. 119

6. Locations where primary succession would occur?
Bare rock exposed by a retreating ________________
Newly cooled _______________
An abandoned __________________ or parking lot
Newly created shallow ________________ or reservoir
glacier
lava
highway
lake

7. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (1)
Secondary Succession – occurs when a series of communities or ecosystems with different species develop in places already ___________________ soil or bottom sediment
Begins in an area where an ecosystem has been __________________, removed, or destroyed, but some soil or bottom sediment remains
containing
disturbed

8. Locations where secondary succession would occur?
Abandoned __________________
_______________ or __________ forests
Heavily _______________ streams
________________ land
Because some soil or sediment is present, new vegetation can begin to germinate, usually within a few ______________
farmland
burned
cut
polluted
flooded
weeks

9. Mature oak and hickory forest
Figure 5.20: Natural ecological restoration of disturbed land: This diagram shows the undisturbed secondary ecological succession of plant communities on an abandoned farm field in the U.S. state of North Carolina. It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here. See an animation based on this figure at CengageNOW. Questions: Do you think the annual weeds (left) would continue to thrive in the mature forest (right)? Why or why not?
Mature oak and hickory forest
Young pine forest with developing understory of oak and hickory trees
Shrubs and small pine seedlings
Perennial weeds and grasses
Annual weeds
Time
Fig. 5-20, p. 120

10. Secondary Ecological Succession in Yellowstone Following the 1998 Fire
Figure 5.21: These young lodgepole pines growing around standing dead trees after a 1998 forest fire in Yellowstone National Park are an example of secondary ecological succession.
Fig. 5-21, p. 120

11. Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2)
Primary and secondary succession are important natural __________________
Tend to increase biodiversity
Increase species _____________ and interactions among species
Both types of succession are examples of ________________ ecological ____________________.
Primary and secondary succession can be ______________ by
Fires
Hurricanes
Clear-cutting of forests
Plowing of grasslands
Invasion by nonnative species
services
richness
natural
restoration
disrupted

12. Science Focus: How Do Species Replace One Another in Ecological Succession?
Three factors affect the how and _______ of succession
Facilitation – one set of species makes an area suitable for species with _______________ niche requirements
Ex: Lichens help to build soil
Inhibition – some early species _______________ the establishment of and growth of other species
Ex: black walnut trees release toxic chemicals that reduce competition from other plants
Tolerance – late stage plants are largely ____________ by earlier stage plants
Young shade-tolerant trees does not compete with taller, older tree
rate
different
hinder
unaffected

13. Succession Doesn’t Follow a Predictable Path
Traditional view of succession
Succession proceeds in an ____________ sequence along an expected path until a certain stable type of __________________________ occupies an area
Balance of nature or permanent _________________
Current view of succession
Ever-_____________ mosaic of patches of vegetation
Mature late-successional ecosystems
State of continual disturbance and change
orderly
climax community
equilibrium
changing

14. Living Systems Are Sustained through Constant Change
The ability to respond to change provides us with _________________ – or the capacity to withstand external ______________ and disturbance
Inertia, or __________________ - ability of a living system to survive _______________ disturbances
______________ diverse areas have high persistence
Resilience - ability of a living system to be _________________ through secondary succession after a more _________________ disturbance
Grasslands can recover quickly after a fire
stability
stress
persistence
moderate
highly
restored
severe

15. Does a tropical rainforest have high or low resilience?
Does a tropical rainforest recover quickly after it is cut down or burned?
Does a tropical rainforest have high or low resilience?
No..the soil loses nutrients quickly
Low resilience

16. Three Big Ideas
Certain interactions among species affect their use of _________________ and their population sizes.
There are always _____________ to population growth in nature.
Changes in environmental conditions cause communities and ecosystems to _____________ alter their species composition and population sizes (ecological succession).
resources
limits
gradually

17. Review Questions
What are some of the main differences between primary and secondary succession?
Does a grassland have high persistence (inertia) or high resilience?
No soil or bottom sediment
Soil present
Hundreds to thousands of years
New growth in a few weeks
Pioneer species
High resilience – recovers well