Download population - Northwest ISD Moodle

Check on your plants, make observations for today.
BECAUSE our plants are progressing a little slower than they should, make another
data table…hopefully next week our plants will be where they need to be in order to
move to the next step in this lab.
This is 4/19/17, Day 19 since we planted them.
Bell-ringer 4/20
1. What is the difference between innate and
learned behavior?
2. How does altruistic behavior lead to survival
and reproductive success?
GET OUT YOUR ECOLOGY READING
ECOLOGY
The study of organism interactions with each other and with their environment.
Each level of organization emerges from the processes of the level below it.
organism
population
A group of organisms
of the same species
that are in the same
area at the same time.
community
ecosystem
biome
How are populations structured?
Organisms
enter a
population
in one of
two ways…
Organisms
leave a
population
in one of
two ways…
Population Density:
Population Dispersal
The number of
individuals per unit area
in a population.
The pattern of spacing
among individuals in a
population.
Not static- changes as individuals
are added or removed.
Population Growth
Exponential Model:
-Measures population increase under ideal conditions.
-Increase at a constant rate, resulting in a ‘J’ shaped curve
when plotted over time.
-Rarely occurs in nature for long, but can be characteristic
of populations introduced to new environments or
rebuilding from a catastrophic event.
- Studying this reveals the capability of growth and
conditions which this type of growth may occur.
Population Growth
Logistic Model:
-Takes into account that as populations increase, resources become
more limited.
- Each population has a carrying capacity: maximum population
size that a particular environment can sustain.
S-Curves
• Limiting factors are any
biotic or abiotic factor that
can Limiting
determine
Common
Factors the carrying
capacity of a population in a
given area.
• Density-dependent
• Density-independent
Density-Dependent Factors
• Limiting factors that depend on population size
• Density-dependent factors become limiting only when population
density reaches a certain level
• So as a population’s density increases, these are
mechanisms that slow or stop growth by decreasing
birth rates or increasing death rates.
Examples:
Competition for resources
Predation
Space
Contagious disease
Density-Independent Factors
• Limiting factors that affect populations regardless of their size
Examples:
Natural disasters
Unusual weather (drought)
Human activities
(damming rivers/cutting forests)
In nature, there is a trade-off in populations
between reproduction and survival.
Populations based on Survivor Rates
• K-selected species
• Operates in populations living at densities near the
limit imposed by their resources (carrying capacity, K)/
competition among individuals is stronger.
• Few offspring per pregnancy (less offspring per capita)
• Invest a lot in raising offspring (higher survival rates)
• Primates/Elephants
• Coconut/Brazil nut trees
K-selected
Populations based on Survivor Rates
• r-selected
• Operates in populations that are well below carrying
capacity or individuals face little competition.
• These maximize ‘r’- the per capita rate of increase
• many offspring
• little parental care
•
•
•
•
insects
Many plants
Algae
bacteria
r-selected
Human Population Growth
• About 500 years ago, the human population began growing
more rapidly because of agriculture and industry.
• With these advances, the human population experienced
exponential growth
• That growth rate is slowing….
This
decrease in
growth rate
is not
uniform
across the
globe….
As countries
industrialize,
changes can be
seen in birth and
death rates.