Chapters 3-6:
Ecology
Ecology
• study of interactions that take place
between organisms and their
environment
Biosphere
• Part of the Earth that holds all living things
• Air, land, and sea
• Living things affected by nonliving and
living things
• Abiotic factors
– Nonliving parts of an environment
– Temperature, moisture, light, soil…etc
• Biotic factors
– All living organisms that inhabit an environment
– Plants, other animals
– Depend on others directly or indirectly
• Food, shelter, reproduction, protection
Levels of Organization
• Organisms make up  population
– Group of organisms of the same species
– Interbreed and live in the same area
– Can compete for food, water, mates
• # of populations make up 
community
–Made up of interacting populations
–Change in a population can affect
entire community
• Populations + abiotic factors make up
 ecosystem
– Terrestrial (land): forests, meadows
– Aquatic (water): oceans, lakes, ponds,
rivers
• Niche: all the ways and
• Habitat: place
adaptations a species
where an organism
uses in its environment
lives
• How it meets its
• Can change or
needs for food,
disappear
shelter, survival,
because of
reproduction
natural and
– Biotic + abiotic parts
human causes
of the environment
Predation
• consumers
• Eat plants and
animals
• Eat prey (animals
that predators eat)
• Fight for survival
Symbiosis
• Relationship where there is a
close and permanent
association between different
organisms
• Means “living together”
• 3 kinds
Mutualism
• Both species benefit (+,+)
Commensalism
• one benefits and the other does
not benefit or is harmed (+,o)
Parasitism
• one benefits and the other is
harmed (+,-)
How Organisms Get Energy
• Sun is the ultimate form of
energy and source for energy
• Producers: autotrophs
–Uses light to make own food
(photosynthesis) and energy
• Ex: grass, trees, green algae
Consumers
• Heterotrophs
• Eat other organisms to get
energy
• CANNOT make its own food
Herbivores
• Only eat plants
Carnivores
• Only eat animals
Omnivores
• Eat both plants and animals
Scavengers
• Eat on dead organisms
Decomposers
• break down and
release nutrients
from dead
organisms
Flow of Matter and Energy
• You consume matter when you eat
food
–Carbon, nitrogen, other elements
• Energy flows through levels of the
entire ecosystem
–Only some energy is transferred
from 1 energy level to the next
Food Chains
• show how matter and
energy move through an
ecosystem
– Nutrients and energy
move from autotrophs
to heterotrophs and
then decomposers
– Ex: grass  rabbit 
wolf
– Arrows indicate the
direction energy is
transferred from one
organism to the next
Ecological Pyramid
• shows how energy
flows through an
ecosystem
– Energy that is
transferred from
one trophic level
to the next is
only 10%
Trophic Level
• A feeding step in passing of energy
and materials
Heterotroph
Heterotroph
Herbivore
Autotroph
Food Webs
• all the possible relationships at each
trophic level of a community
Chapter 3-6 Review #1:
1. Which of the following types of heterotrophs eat
other animals?
a. omnivores & carnivores c. carnivores only
b. herbivores & omnivores d. carnivores & herbivores
2. Which of the following types of heterotrophs
would bacteria and fungi be classified as?
a. detritivores b. herbivores c. carnivores d. decomposers
3. What is the one-way flow of energy in an
ecosystem called?
a. food chain b. energy pyramid c. food web d. biomass
pyramid
4. What is each step in a food chain or food web
called?
Limiting Factors
• Affect an organism’s ability to survive in its
environment
• Ex: water, food, predators, temperature
• Density-dependent: disease, competition,
parasites, food
– Depend on the density of a population
• Density-independent: affects all populations
regardless of their density
– Temperature, storms, floods, drought, and
habitat disruption
Succession
• Natural changes and species replacement that takes
place in communities in an ecosystem
– Occurs in stages
• Primary succession
– Colonizing bare land where there are no
organisms
– Pioneer species: 1st species in an area
Climax Community
• Stable, mature community that
has little or no changes in
species
Secondary Succession
• Changes that occur when existing
community is disrupted by natural
disasters or human actions
Biomes
• Large group of
ecosystems that share
the same type of climax
community
• Terrestrial or aquatic
– Aquatic: marine,
estuaries, freshwater,
swamps
– Terrestrial: tundra,
taiga, desert,
grassland, rain forest,
temperate forest
Population Growth
• Organisms can
grow exponentially
• Exponential
growth: as a
population gets
larger, it also
grows faster
– J-shaped curve
(diagram):
• Growth will be limited at some point by
limiting factors
• Food availability, disease (ex: AIDS,
influenza, TB, Dutch Elm disease,
Pfiesteria), predators, lack of space
• Results in an S-shaped curve
• Diagram:
• Carrying capacity: the number of organisms of
a species that an environment can hold
Define these terms:
• Birth rate
• Death rate
• Emigration
• Immigration
• Zero population growth
Biological Diversity
• Biodiversity: the variety of species in a specific area
• Loss of biodiversity is increasing
• Extinction: disappearance of a species when the
last organism dies
• Ex:
• Endangered species: # of species become low that
can lead to extinction
• Ex:
• Threatened species: population likely to become
endangered
• Ex:
Cycles in Nature
• Matter is constantly being
recycled
Water Cycle
• Water evaporates from lakes and oceans to
become water vapor in the air
• Water vapor in the air condenses to form
clouds
• More water condensation leads to
precipitation, falling as rain, ice, or snow
back to the ground
• Cycle repeats constantly
• Problems with the cycle:
Carbon Cycle
• Starts with autotrophs
– Makes carbon molecules from CO2
during photosynthesis
• Heterotrophs feed on autotrophs,
getting those carbon molecules
• Release CO2 back into the
atmosphere
Problems with Cycle
• Global Warming:
–Greenhouse effect
–Gases that lead to global warming
Nitrogen Cycle
• Lightning and some bacteria convert nitrogen in the air
into a usable form
• Plants use nitrogen to make proteins
• Herbivores eat plants
– Convert nitrogen-containing plant proteins into animal
proteins
• Humans eat plants
– Convert animal proteins to human proteins
• Excess nitrogen in animals released in urine
– Returned to water or soil
• Nitrogen molecules return to the soil when animals die
– Re-used by plants
– Bacteria put nitrogen back into the air
Phosphorous Cycle
• All organisms need phosphorus for
growth and development
• Plants get phosphorus from the soil
• Animals get phosphorus by eating
plants
–Decompose when they die,
returning phosphorus to the soil
Problems:
• Eutrophication
Impact of Human Activities on
the Environment
• Population growth
• Pollution
• Global warming
• Burning fossil fuels
• Habitat destruction
• Introducing nonnative species
Chapter 3-6 Review #2:
1. A lone elephant joining another herd of
elephants is an example of
a. emigration
c. immigration
b. parasitism
d. exponential growth
2. What term is used to describe a species
whose population is rapidly shrinking and
might disappear completely?
a. endangered
c. extinct
b. threatened
d. invasive