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Populations
Ms. Lowrie
Science 10
Definitions
Community
Ecosystem
Habitat
Population
Species
We will correct them in another order!
Ecosystem
A group of
communities that
share a physical
environment
Including air,
land, water,
living organisms
Species
A group of organisms that can
reproduce only among themselves
Habitat
Characteristics of
the environment
where an organism
lives
Ex: A giraffe’s
habitat is the African
savannah
Population
A group of individuals of
the same species living in
the same area
Ex: A population of giraffes in
eastern Africa OR a population
of giraffes in
southern Africa
Community
Includes all
populations of
organisms in
an area
Ex: A community of giraffe, elephant,
lion, tiger, insect and plant populations
How they all connect:
Species
Populations
How did the killer whale’s feeding
habits affect the sea otter?
Food Chains (#1, a-c)
Draw the ocean food chain (before).
Draw the kelp food chain (after).
How are the two food chains
mentioned in (a) and (b) different?
Killer whale
Seals
Sea Lions
Fish (perch & herring)
Ducks
Sea Gulls
Sea Stars
Kelp
Food Web (d)
Sea Otters
Sea Urchins
Eagles
Mussels
Killer whale
Seals
Sea Lions
Fish (perch & herring)
Kelp
Food Web (simple)
Sea Otters
Sea Urchins
Populations (#1, e-g)
e. Why did killer whales change their
feeding habits?
f. What effects did these changes
have on the ocean ecosystem?
g. What effects did these changes
have on the kelp ecosystem?
Killer whale
Seals
Sea Lions
Fish (perch & herring)
Food Web (#1, f)
Populations (e-g)
e. Why did killer whales change their
feeding habits?
f. What effects did these changes
have on the ocean ecosystem?
g. What effects did these changes
have on the kelp ecosystem?
Killer whale
Sea Otters
Sea Urchins
Kelp
Food Web (#1, g)
Populations
2. Explain how each organism survives
in a food web.
3. Outline how the population size in
each trophic level (feeding level) is
continually adjusted or changing.
Carrying Capacity
Maximum amount of individuals that
an environment can support
Example: Paramecia
Carrying Capacity
4 Factors that affect:
Materials & Energy
Food chains
Competition
Density
Factor: Materials & Energy
Populations are limited by the
amount of abiotic factors available
Such as: sunlight,
water, oxygen, etc.
E.g. Too little sunlight
reduces plant growth
Factor: Materials & Energy
Another example:
Layer of algae on pond blocks sunlight from
reaching organisms at bottom of pond
Factor: Food Chains
Availability of food
If organisms in one trophic level are
affected it will affect organisms in
other trophic levels
E.g. Killer whales
& seaotters
Factor: Competition
Due to the demand for resources
Such as: food, water, mates, space, etc.
Types of Competition
Intraspecific
Between individuals
of same species
Types of Competition
Interspecific
Between individuals
from different species
Factor: Density
More organisms in a space makes it
more difficult to survive
Population Density
Number of organisms that can live
in an area
Population Density
Based on an organism’s need for
space
E.g. Bears & elk need more space than some birds
Factors that Limit Population
Growth
Density-Dependent Factors
Any factor that affects growth that
DEPENDS on the number of
individuals in a population
Examples?
Factors that Limit Population
Growth
Density-Dependent Factors
E.g. competition, disease, parasites,
predation, overcrowding (leads to:
stress, offspring neglect, aggression),
etc.
Factors that Limit Population
Growth
Density-Independent Factors
Any factor that affects growth that
DOES NOT depend on the number
of individuals in a population
Examples?
Factors that Limit Population
Growth
Density-Independent Factors
E.g. extreme weather, earthquake,
volcanic eruption, forest fire, flood,
drought, pollution, etc.
Check Your Understanding
A. How might overcrowding lead to a
reduction in population size?
B. How might an increase in the
population of hawks in an area lead
to an increase in the population of
plants?
Explain the graph:
Any Questions???