Transcript 5 3 Populations - Ms. Lee`s Classes @ JICHS

Happy Wed!
9/8/2010
(a) State which species of turtle nests in the greatest numbers on Jupiter Island.
(1 mk)
(b) Compare the distribution of nesting in the three species of turtle along the
eastern coastline of Florida. (2 mks)
• (a) loggerheads / Caretta caretta 1
• (b) all three species nest over the same range of
latitudes
on the same beaches/areas;
density of loggerheads is greatest and leatherbacks
is lowest;
similar relative densities/numbers on the different
beaches / latitudes;
all three had most nests on Jupiter;
more loggerheads at northern end of range /(Do not
accept answers giving
around 28 (°N) / on Melbourne;) the range 26–28
or 26–30.)
2 max
I’ll CHECK your
IB Journal on quiz day
for
5.1 and 5.3
Don’t forget...
• “Exercises” ?s as you read or after we’ve
gone over in class
– Make sure you GET IT
• “Practice ?s” @ end of chapter— old
exam ?s
– Studying for quizzes/tests!
5.3
Populations
5.3.1
Outline how population size is affected by natality,
immigration, mortality and emigration.
5.3.2
Draw and label a graph showing a sigmoid (Sshaped) population growth curve.
5.3.3
Explain the reasons for the exponential growth
phase, the plateau phase and the transitional
phase between these two phases.
5.3.4
List three factors that set limits to population
increase.
5.3.1 Factors affecting pop size
5.3.2 Pop
growth
curves
• MODEL
– Change in pop size over time
• Pop expanding into a habitat offering INITIAL
LOW RESISTANCE or LOW LIMITING FACTORS
A-Exp = rapid pop growth rate
B-slowing but still high
C-plateau = pop remains stable w/time;
slight oscillations
5.3.3 Phases of pop growth curve…details!
EXPONENTIAL PHASE
• Low/reduced limiting factors
• Pop expands exponentially into hab. @ 2n
where n= # of generations
• natality + imm. > mortality + emigr.
• Note that it does not mean that death/
emigration= 0 !!!
When do you observe exp. phase in
nature?
Pop of germinating annual plants in new
season
Bacterial pop @ onset of infection
Succession—any species’ pop entering
previously uninhabited area
5.3.3 TRANSITION PHASE
• Resources reduced, become limiting
• Competition…not all survive
– NATURAL SELECTION!
•  lower rate of increase in pop
5.3.3 POPULATION PLATEAU
• Pop remains constant over time/generations
• Natality + imm = mortality + emig
• Pop size determined by CARRYING CAPACITY
of habitat @ that time
What factors affect the rate of growth of a
population?
What factors LIMIT pop growth of a
species?
5.3.4 Factors limiting pop growth
• With unltd resources, pop would keep
increasing…exponentially!
• REALITY CHECK!
• Environmental resistance limits it & determines
carrying capacity
–
–
–
–
–
Shortage of food/prey
Predation, parasitism
Disease
Accumulation of waste
Shortage of space/territory
Food for Thought...