Download Section 13.2: Biotic and Abiotic Factors

Section 13.2: Biotic and Abiotic
Factors
Biology
Objectives
 Define and give an example of biotic and abiotic
factors.
 Outline the importance in biodiversity in the health of
an ecosystem.
 What is a keystone species and how does it affect its
ecosystem? Give an example.
Ecosystems
 Include living and nonliving components
 Biotic Factors: living things, such as plants and
animals, that each play a particular role in the
ecosystem
 Abiotic Factors: Nonliving things, such as moisture,
temperature, wind, sunlight, and soil, which
determine what living things can survive in a
particular environment
Caribbean Sea Ecosystem
 Observation: More fish in coral reefs near marshes than out to sea
 Biotic Factors: Fish, mangrove trees, other plants within marsh
 Abiotic Factors: Oxygenation in mud, salinity of ocean, tidal
changes
 The mangrove trees protect newly hatched fish, who when they
mature swim to the reefs
 The ability of the mangrove tree to survive is greatly affected by the
ocean, and the fishes survival is dependent upon the mangrove tree’s
survival
Example
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What is our ecosystem?
Biotic Factors?
Abiotic Factors?
How could each of these things affect the overall
health of our ecosystem?
Ecosystems Are Always Changing
 Ecosystems can look similar from one year to the next, but they are
actually quite dynamic
 The amount of precipitation can change the dominant plant
species, which can change the communities composition (the
number of plants is similar, but the species is different)
 This can change the animals that get their food from this area
 As these cyclic changes occur, an ecosystem falls into balance,
which is called an approximate equilibrium
 What changes occur in our ecosystem, and what is our
approximate equilibrium?
One Factor Can Affect Change
 The change of a biotic or abiotic factor can affect
all of the organisms in an ecosystem
 Changes that can affect an ecosystem:
 Biodiversity
 Keystone Species
Biodiversity
 Biodiversity: Assortment, or variety, of living things in
an ecosystem
 Rainforest: high level of biodiversity, which accounts for
more than 50% of the plant and animal species on the
planet
 Amount of biodiversity depends on many factors,
including moisture and temperature
Keystone Species
 Complex ecosystems are dependent on very few
important parts of the web, that when disturbed can
have a significant effect on the health of the
ecosystem
 A species that has an unusually large effect on its
ecosystem
 Example: Beavers
Beavers
 Beavers fell trees to construct dams
 Change free-flowing streams into ponds, wetlands & meadows
 Changes to the ecosystem:
 Wider variety of fish in still water of pond
 Attraction of birds that eat the above fish
 Insects are attracted to the pond, which brings insect eating birds
as well
 Waterfowl nest near the pond, which brings in prey animals that
eat the eggs
 Beavers can greatly change their environment, and the loss of
them can severely impact the ecosystem
Sea Otters
 Sea Otters are also a keystone species, because they
eat sea urchins
 Sea urchins, if allowed to populate the ocean without
a predator, eat all of the available kelp
 The loss of kelp means less food for crabs, snails, and
geese
 It also means that species of fish that hide in the kelp
from predators are heavily eaten and their numbers
drop dramatically, further upsetting the ecosystem
Outputs
1. We live in the Sonoran
Desert. Name three
biotic and abiotic
factors.
2. Compare with your
neighbor and write
down one biotic and
abiotic factor that you
did not have.
3. Hummingbirds are a
keystone species in the
Sonoran Desert. Give 3
reasons why you think
this is.