population ecology ( ch.5)
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Population Ecology(Ch.5)
population
ecosystem
community
biosphere
organism
• Density Independant - Abiotic factors – Amount ofsunlight &
temperature– precipitation / water– soil / nutrients
• Density Dependant -Biotic factors– other living organisms
• prey (food)• competitors• predators, parasites,
disease
Factors that affect Population Size
At risk populations• Endangered species
– limitations to range / habitat, over hunting, fishing– Loss of habitat (clear cutting, development, farming)– Changes in environment, competition. Introduced
species that take over!
Socorro isopod
Devil’s holepupfish
Iriomote cat
Northern white rhinoceros
New Guineatree kangaroo
IiwiHawaiian
bird
Catalina Island
mahoganytree
marking territory = competition
Population Spacing• Dispersal patterns of a population
uniform
random
clumped
Provides insight into the environmental associations & social interactions of individuals in population
Population Size• Changes to
population size• (4 factors)-
– adding & removing individuals from a population
• 1)Birth (B)• 2)Death (D)• 3)Immigration (I)• 4)Emigration (E)
Births and immigration add individuals to a population.
Births Immigration
PopuIationsize
Emigration
DeathsDeaths and emigration remove individuals from
a population.
Age structure• Relative number of individuals of each age
What do these data imply about population growth in these countries?
Survivorship curves
• Generalized strategiesWhat do these graphs tell about survival & strategy of a species?
0 25
1000
100
Human(type I)
Hydra(type II)
Oyster(type III)10
150
Percent of maximum life span
10075
Sur
viva
l per
thou
sand
I. High death rate in post-reproductive years
II. Constant mortality rate throughout life span
III. Very high early mortality but the few survivors then live long (stay reproductive)
Reproductive strategies• K-selected
– late reproduction– few offspring– invest a lot in raising offspring
• Primates (us)• Big mammals
r-selected– early reproduction– many offspring– little parental care
• insects• many plants
K-selected
r-selected
Exponential growth rate (J) curve -• Characteristic of populations without
limiting factors (wide open resources)– introduced to a new environment or rebounding from a
catastrophe
African elephantprotected from hunting
Whooping cranecoming back from near extinction
Introduced (Invasive) species• Non-native species
– transplanted populations may grow exponentially in new area
– May out-compete native species • lack of predators, parasites,
competitors– reduce diversity – examples
• African honeybee• gypsy moth• zebra mussel• purple loosestrife
kudzu
gypsy moth
Zebra mussel, Cane Toad http://www.youtube.com/watch?v=gX1FLXEo96g
ecological & economic damage
~2 months
reduces diversity loss of food & nesting sites
for animals economic damage
Purple loosestrife
1968 1978
reduces diversity loss of food & nesting sites
for animals
The Snakehead • Great Snakehead Problems Snakeheads eat game fish and have no predators so
they can overcrowd a body of water and harm native species. They are adapted to survive in water with little oxygen and can even crawl across land for short distances on their fins, taking in oxygen from a special bronchial adaptation. They will not attack people but may injure anyone stepping on them.
http://www.youtube.com/watch?v=nmU7etSYYqI
K =carryingcapacity
Logistic rate of growth• Can populations continue to grow
exponentially? Of course not!
effect of natural controls
no natural controls
Human population growth
What factors have contributed to this exponential growth pattern?
1650500 million
20056 billion
Industrial Revolution
Significant advancesin medicine throughscience and technology
Bubonic plague "Black Death"
adding 82 million/year~ 200,000 per day!
Is the human population reachingcarrying capacity?
4. Assuming these age structure diagrams describe human populations, in which population is unemployment likely to be most severe in the future?
A. IB. IIC. IIID. No differences in the magnitude of future unemployment
would be expected among these populations.
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