ECOLOGY. Features that determine the future of a population: Population size- the # of individuals...
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Transcript of ECOLOGY. Features that determine the future of a population: Population size- the # of individuals...
ECOLOGY
Features that determine the future of a population:
• Population size- the # of individuals in a population
• Population density- the # of individuals in a given area
• Dispersion-the way individuals are arranged in space
A population refers to all the members of one species, in one place at one time.
How members of a population are arranged in a given space.
DISPERSION:
Patterns of dispersion Individuals in a population may be
distributed according to 3 basic patterns of dispersion– Random– Uniform (also known as Even)– Clumped
Random Dispersion
Scattered, not uniformWhy?
Environment is uniform Individuals are solitary
They live independently
Pine trees in a random distribution
Uniform Dispersion
About equal distance apart, forming a patternWhy?
Resource competition
Birds in an even distribution
Clumped Dispersion
Grouped in some places, absent in others irregular pattern
Why? Resources are patchy Search for food
Buffalo in a clumped distribution
Why do you think scientists study
population dispersion? How individuals are arranged within a population can affect...
Reproduction
Protection(from
predators)Hunting patterns
(if carnivorous)
Can you name the 3 patterns of dispersion?
Clumped
Uniform
Random
Scientists study the population density because it helps determine how the individuals of a population interact.
Reproduction
Protection
Eating patterns
Social hierarchies, if any
Which population of wildebeest has the greatest population
density?
An extremely dense population of wildebeest:
Modeling Population growth
Population success = reproduction of species
We can study how and why the number of individuals change over time
Populations grow when more individuals are born than die in a given period. A simple population model describes the growth rate as shown:
(r) = birthrate – death rate
A small # of the youngest-decrease
Middle age population is constant, secure, not changing
The older population decreases, faster
Describe what is happening to the population in this graph
AGE
# o
f In
div
idu
als
Exponential Growth
Exponential growth-the rate of population growth stays the same and the population size increases steadily.
This model displays a J-shaped curve which indicates a steady increase of population size.
What if the population size kept growing and growing and...
carrying capacity (K)- the population size that an environment can sustainWhat factors do you think contribute to an environment's carrying capacity???
Resources that are limited because the rate at which
they become depleted depends on the density of the
population that uses them.
Food WaterShelter
LOGISTIC GROWTH MODEL
Once again, exponential growth is a steady increase in the population size.
Now we must consider the carrying capacity (K) and density-dependent factors when modeling population growth.
logistic model- a population model in which exponential growth is limited by a density-dependent factor. This model considers carrying capacity.
LOGISTIC MODEL
Factors that do not depend on the size of the population, but can affect it nonetheless.
Weather
Climate
Remember...
(r)= rate of growth, birthrate – death rate
(K)= carrying capacity, the population size an environment can sustain
There are 2 types of populations, (r)-strategists and (K)-strategists
r-strategist: Species that grow exponentially when the environment allows for it. Results in temporarily large populations.
When the environmental conditions are no longer suitable for the species, the population size quickly decreases.
K- strategists- organisms that grow slowly. Population sizes are usually small and kept near the carrying capacity of their environment.
K-strategists are characterized by a long life span, a slow maturing process, and reproduction late in life.