Transcript Primary Succession

SUCCESSION
How do habitats change over time?
Primary Succession
• Succession is the gradual, sequential changing of an
area.
• The habitat changes until the “climax community” is
formed.
• Climax Community – Stable, mature ecosystem.
Stays the same a long time.
Ex – Forest, prairie
Primary Succession
1) Occurs in areas that have no soil
2) No plants or animals in the area
3) 1st inhabitant is called a “pioneer species” – it
is usually lichen.
 Lichen are small and fast growing
Primary Succesion
4) Soil is slowly formed and new plants/
animals gradually move into the area
5) Can occur because of a volcano or a new
island forms or an icecap recedes
Primary Succession
Secondary succession
1) Occurs in an area that has soil
2) Is usually the result of some disruption to a
previous community. (fire, flood, etc…)
3) Happens quicker than primary succession.
Secondary Succession
DO NOW: What kind of factors govern
population size? What variables do
scientists use to describe
populations of animals?
Factors Governing Changes
in Population Size
• Four variables
– births, deaths,
immigration and
emigration
• Population Change =
(births + immigration) –
(deaths + emigration)
OBJ 9.2
Age Structure Stages
• PREREPRODUCTIVE AGE
- Not mature enough to reproduce
• REPRODUCTIVE AGE
- Capable of reproducing
• POSTREPRODUCTIVE AGE
- too old to reproduce
LIMITING FACTOR
OBJ 9.3
DEFINITION: anything that tends to make it
more difficult for a species to live and grow, or
reproduce in its environment
ABIOTIC
- temperature
- water
- climate/weather
- soils (mineral component)
BIOTIC
- competition: interspecific and intraspecific
- predation/parasitism
- amensalism
- mutualism
LIMITS TO POPULATION GROWTH:
Resources & Competition
Biotic potential: capacity for growth
Intrinsic rate of increase (r): rate at which a population
would grow if it had unlimited resources
Environmental resistance: all factors that act to limit the
growth of a population
Carrying Capacity (K): maximum # of individuals of a
given species that can be sustained indefinitely in a given
space (area or volume)
Fig. 9-3 p. 166
Exponential and Logistic Growth
EXPONENTIAL GROWTH-J
shaped curve
LOGISTIC GROWTH-S
Shaped Curve
-Population w/few resource
limitations
- Rapid exp. growth followed by
steady dec. in pop. Growth
w/time until pop. Size levels off
Natural Population Curves
OBJ 9.7
Fig. 9-7 p. 168
• STABLE
– pop. Size fluctuates above or below its carrying
capacity
– Stable population size
– EX: undisturbed tropical rain forests
• IRRUPTIVE
– pop. Growth occasionally explodes to a high peak then
crashes to stable low level
– EX: Algae, insects
• CYCLIC
– Fluctuations occur in cycles over a regular time period
– EX: Lynx & snowshoe hare
• IRREGULAR
– No recurring pattern in changes of population size
1
Do Now: In population ecology, what does each graph represent? What
“letter” curve are they? What kind of species’ growth would be indicative of
each graph? What does “K” represent in the second graph? What happens if
growth goes above the “K” line?
The Role of Predation in
Controlling Population Size
 Top-down control
- lynx preying on hares
periodically reduce the hare
pop.
OBJ 9.8
 Bottom-up control
- the hare pop. may cause
changes in lynx pop.
Fig. 9-8 p. 168
OBJ 9.10
Reproductive Patterns and Survival
 r-selected species vs. K-selected species
Fig. 9-10 p. 170
Survivorship Curves
OBJ 9.11
•Shows the % of members in a pop. Surviving at different ages
LATE LOSS-TYPE I
-High survivorship to certain age; then
high mortality
-EX: elephants, rhinos, humans
CONSTANT LOSS-TYPE 2
-Fairly constant death rate at all ages
-EX: songbirds
EARLY LOSS-TYPE 3
-Survivorship is low early in life
-EX: annual plants, bony fish sp.
Fig. 9-11 p. 171
Population Density Effects
OBJ 9.6
 Density-independent controls
- floods, hurricanes, unseasonable weather, fire,
habitat destruction, pesticide spraying, pollution
- EX: Severe freeze in spring can kill plant pop.
regardless of density
 Density-dependent controls
- competition for resources, predation, parasitism,
infectious diseases
- EX: Bubonic plague swept through European cities in
14th century