Download Understanding Populations

Understanding
Populations
Chapter 8
Environmental Science
Population



All the members of a species living in the
same place at the same time
Organisms from the same population breed
with each other, usually not other populations
Three ways to describe populations


Size
Density


Number of individuals per unit area or volume
Dispersion

Distribution or arrangement of individuals within a
given amount of space
How does a population grow?

Growth rate

Change in the size of a population over a given
period of time
Change in
population
size
=
Birth rate
-
Death rate
How fast can a population grow?

Reproductive potential




Maximum number of offspring that each member of a
population can produce
Some species have a higher reproductive rate than others
Biotic potential
 Fastest rate that a population can grow
Reproductive potential increases when individuals:
 Produce more offspring at a time
 Reproduce more often
 Reproduce earlier in life

Bacteria (short generation time), humans (longer generation time)
Exponential Growth

When a population grows faster and faster

Example: Dog gives birth to 6 puppies


Next generation – 18 puppies and so on
Occurs in nature when:


Plenty of food and space
No competition or predators
What limits population growth?

Carrying capacity



The maximum population that the ecosystem can
support indefinitely
Populations may go over this number
Carrying capacity can be estimated, not exact
What limits population growth?

Resource limits

Limiting resource


A resource that is being consumed at the same rate it
is being produced
Example: plant growth limited by…..




Water
Sunlight
Mineral nutrients
Supply of the most limiting resource determines the
carrying capacity of an ecosystem
What limits population growth?

Competition within a population


Species in a population use the same resources
in the same ways (ex. Food)
Indirect competition

Competing for their territory


Area defended by one or more individuals against others
Territories are valuable to an organism




Space
Shelter
Food
Breeding sites
Growth Rate



Math Practice
Page 201
Worksheet
Population Regulation

Density dependent

Deaths occur quickly in crowded populations




Limited resources
Predation
Disease
Density independent


Portion of population will die regardless of density
Possible causes


Severe weather
Natural disasters
Assignment



Page 202
Section 1 Review
# 2-5
How Species Interact with
Each Other

Niche


Unique role of a species within an ecosystem
Includes:




Different from habitat



Species’ physical home
Environmental factors necessary for survival
Interactions with other organisms
Habitat is only a location
Niche is a pattern of how the habitat is used
Can be thought of as a job in an ecosystem
Ways Species Interact

Competition



Different individuals or populations attempt to use
the same limited resource
Can occur within a species or between a species
Indirect competition


Example – one insect feeds on a plant during the day
and another insect feeds on the same plant at night
Adaptations can occur over time to decrease
competition


Using less of a niche than they are capable of using
Similar species will divide up the niche to “share space”
Ways Species Interact

Predation

Predator


Prey



Feeds on another organism
Organism that is fed upon
Organisms can be a predator and the prey
Some predators will only eat specific types of prey
Ways Species Interact

Parasitism

Parasite


Host


Organism that lives in and feeds on another organism
Organism the parasite takes its nourishment from
Examples of parasites



Ticks
Fleas
Tapeworms
Ways Species Interact

Mutualism



Close relationship between two organisms where
both benefit
Example – bacteria in your intestines and you
Commensalism


Relationship where one species benefits and the
other is neither helped nor harmed
Example – Birds nesting in trees (causing no
harm to the tree)
Ways Species Interact

Symbiosis


Relationship where two organisms live in close
association
Coevolution



Relationships may coevolve over time
Can reduce the harm to an organism
Can increase the benefit to an organism
Assignment



Page 209
Section 2 Review
# 1-5
Chapter 8 Review Questions


Pages 211-213
# 5-18, 21-23, 25, 31