BIG IDEA: All organisms interact
with living and nonliving things in
their environments
30.1 Organisms and their
Environments
Ecology is the study of how organisms
interact w/ their environments.
 Population= a group of individuals in a
single species living in a specific area
 Community= all of the organisms w/in a
specific area
 Ecosystem= biotic (living) and abiotic
(nonliving) organisms w/in a given area
1. An ecologist studies how hyenas and cheetahs compete
for food, Is this a study at the population, community,
or ecosystem level?
Community, 2 different species being
compared
2. An ecologist is interested in counting how many
mountain lions live in a certain park. Is this a study at
the population, community, or ecosystem level?
Population, looking at 1 species, in a
specific area
30.2 Species interactions in
Ecological Communities
Food chains/webs- show who eats whom
Bottom= producers, species that make their own
food (usually plants)
Primary consumers eat the producers
(Top)Secondary consumers eat the primary
consumers (carnivores)
Decomposers consumer dead organic matter
Other species interactions:
Competition occurs any time 2 species in a community
compete for the same resource, and there is a limited
supply of resource
-Competition can cause evolution
Niche is the total set of biotic and abiotic resources
w/in a community (sunlight, water, food, space)
Symbiosis: individuals of 2 species that live in
close proximity
1. Parasitism: Good for 1 species, harmful to the
other (+/-)
2. Commensalism: Good for 1 species, no effect on
the other (+/0)
3. Mutualism: Both species benefit (+/+)
Illinois invasive species
Invasive species: a species that has moved from it’s
original home to a new area, causing lots of damage
Compete w/ native species for resources. Decrease
natural diversity, increases cost of food an lumber
production
Ex’s: Bush honeysuckle, Garlic-mustard,
Asian carp
30.3 Energy Flow in Ecosystems
Biomass is the amount of organic matter in an
ecosystem
-Only ~10% of energy at one level of a food
chain gets passed to the next level of the food
chain.
Ex: producer= 10,000 kg of biomass (trees/grass), there
would be 1000kg of primary consumers (like zebras), and
100kg of secondary consumers (lions)
10,000 𝑘𝑔
= 1,000 𝑘𝑔
10
1,000 𝑘𝑔
= 100 𝑘𝑔
10
The other 90% of energy?
Not every organism on one level is eaten, energy
lost in maintenance, growth, and feces
When energy is converted from one form to another
some energy is converted into heat
30.4 Kinds of ecosystems
There are 8 major types of ecosystems
(biomes)
-The type of biome found in a certain place
depends mainly on climate (determines
what plants/animals will thrive
1. Tropical forests: near equator, warm,
large biodiversity, lots of rain, poor soil.
Destroyed for timber/agriculture
2. Temperate forests: areas w/ 4 seasons, leaves
change color and fall. Fertile soil (chopped down
for farming)
3. Coniferous forests: Long, cold winters, dry,
ground covered by pine needles. Threatened by
logging.
4. Tundra: Extreme cold, permafrost
(permanently frozen soil) above topsoil, low
biodiversity
5. Savanna: Tropical grasslands, long dry season,
animals prevent overgrowth
6. Temperate grasslands: very good soil, 4 seasons,
don’t become forests b/c seasonal drought, fire,
and grazing
7. Chaparral: Mild, rainy winters, hot dry
summers. Drought, fire
8. Desert: Extremely dry (can be hot OR coldAntarctica). Organisms have adaptations to
survive extreme dry conditions
Aquatic ecosystems
Freshwater: Still water of lakes/ponds, and flowing
water of rivers, streams. Have adaptations depending
on environment
Saltwater: Many different species, at the surface,
bottom, and in-between of ocean. Photic zone=closer
to surface. Aphotic=bottom, no sunlight
Plankton- float in water, and go wherever current takes
them (Ex: Microscopic organisms)
Vs.
Nekton- organisms that swim through the water (Ex:
fish, whales, sea turtle)
Materials Cycling in Ecosystems
Geochemical cycles move different substances from the
biotic to abiotic world
Water- evaporates from water source condenses in
clouds precipitates to land, runs off back  ground water
Carbon- Found in atmosphere  plants/other organisms
back to abiotic world from cellular respiration
Nitrogen: bacteria convert atmospheric N2 can be used by
living organisms
30.5 Change in an Ecosystem
Ecological succession describes how the community of
species living in an ecosystem changes over time
o Primary succession: colonization of bare land with no
soil
o Secondary succession: when existing life in a habitat is
destroyed, but soil remains.
Succession ends when stable population forms
All ecosystems experience change, smaller disturbances
are more frequent
30.6 Population Studies
4 Factors determine population size:
1. Birth rate
3. Immigration rate
2. Death rate
4. Emigration rate
Exponential growth occurs when the population
grows @ a fixed rate for a certain amount of time
-Populations that undergo exponential growth usually
cycle w/ growth to crashing (resources run out!)
Logistic growth shows a slow climbing
population as it approaches carrying capacity
(max # a habitat can support). Stable populations
30.7 Human Population Growth
Current population: ~7.2 billion people
 Growth was exponential in recent decades, but is
now slowing down
 We learn how population is growing from age
structure