Download 8.L.3 – Understand how organisms interact

8.L.3 – UNDERSTAND HOW
ORGANISMS INTERACT
8.L.3.1
Explain how factors such as food, water, shelter,
and space affect populations in an ecosystem.
Ecosystems

Complex interactive systems
 Consist
of:
 Abiotic
Factors: Physical components of the environment
 Biotic Factors: Biological communities

Species  Populations  Communities 
Ecosystem  Biosphere
 Species:
groups of the same organisms
Ecosytems

Dynamic
 Their




characteristics vary over time
If there is a disruption to a physical or biological
component, a population shift can happen
Biodiversity: variety of species found in Earth’s
ecosystems
Population: group of organisms belonging to the
same species that live in a particular area
Population Density: the number of individual
organisms living in a defined space
Factors Influencing an Ecosystem

Density-Dependent
Competition (for food, water, shelter, space)
 Predation, parasitism, disease



Density-Independent

Mostly abiotic, human factors, natural disasters


Ex: Weather Changes, Pollution, Fires
Abiotic


Triggered by crowding
Ex: Water, nitrogen, oxygen, salinity, pH, soil nutrients,
temperature, amount of sunlight, precipitation
Biotic

Bacteria, Fungi, Plants, Animals
8.L.3.2
Summarize relationships among producers,
consumers, and decomposers; including positive
and negativeconsequences
Interactions between organisms




Generate stability within the ecosystem
Facilitate or restrain growth
Enhance or limit the size of populations
Change both the biotic and abiotic characteristics
Stable Ecosystems


Ecosystem: a community (all organisms in area) and
the abiotic factors that affect them
Stable Ecosystems:
 Population
numbers fluctuate at a predictable rate
 Supply of resources of the physical environment
fluctuates at a predictable rate
 Energy flows through the ecosystem at a constant rate
over time
Stability of Ecosystems

Predation: an interaction between species in which one
species (the predator) eats the other (the prey)


Helps regulate the population
Competition: a relationship that occurs when two or
more organisms need the same resource at the same
time
Can occur between the same organism or different
organisms that share the same niche
 Niche: the role of an organism in its environment including
type of food it eats, how it gets food, how it interacts with
other organisms

Stability of Ecosystems


Symbiotic Relationship: exists between organisms of two
different species that live in direct contact, where the
relationship between the two usually helps each other
Types:

Parasitism: one organism benefits at the expense of the other
organism


Mutualism: where both organisms benefit


Ex: Tapeworms, heartworms, fleas
Ex: Pollenation, Anemone fish and Anemones
Commensalism: where one organism benefits without affecting
the other

Ex: Remora sharks, which eat leftover food from a whale and "hitch a
ride"
Examples
8.L.3.3
Explain how the flow of energy within food webs
is interconnected with the cycling of matter
Energy in Ecosystems



The SUN is the ultimate source of energy
Energy is transferred by producers into chemical
energy by photosynthesis
Food provides molecules that serve as fuel and
building material for all organisms
 Proteins

The amount of matter remains constant, though its
form and location changes
Food Chains/Webs/Pyramids


All of the above are models of how energy and
matter are transferred between producers and
consumers
Each level of the transfer of energy in a food chain
is called a Trophic Level.
Trophic Levels

Level 1

Consists of producers

Capture the suns energy


Level 2

Primary Consumers

Eat green plants and are called herbivores.


Ex: Green plants, phytoplankton
Ex: Grasshoppers, rabbits, zooplankton
Level 3+

Consumers


Consumers that eat Primary Consumers are called carnivores.
Consumers that eat both Producers & Primary Consumers are called
omnivores.

Ex: Humans, wolves, frogs, minnows
Food Web

Represents many interconnected food chains,
describing the many paths energy can take through
an ecosystem
Ecological Pyramids

Energy Pyramid
 Represents
the energy available for each trophic level
in an ecosystem

Number Pyramid
 Represents
the number of individual organisms
available for energy at each trophic level

Biomass Pyramid
 Represents
the total mass of living organic matter at
each trophic level
Energy Pyramid
Number Pyramid
Biomass Pyramid