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Unit 6 Study Guide: Ecology
- Ecology - Study of how living things interact
with each other and with their environment.
- Biotic factors – all the living things that affect
an ecosystem
- Abiotic factors – non-living things that affect
an ecosystem
- Population – group of same species that breed
and live in the same area
- Community – all the different living
populations in the same area
- Ecosystem – all the living (biotic) and nonliving (abiotic) factors in an area
- Biome – environment defined by it’s climate
and the biological communities
- Biosphere – the Earth
- Producers – organisms that make their own
energy (autotrophic)
- Consumers – organisms that consume other living things for energy (heterotrophic)
- Herbivore – consumer that eats plants
- Carnivore – consumer that eats animals
- Omnivore – comsumer that eats both plants and animals
- Decomposer – consumer that breaks down living/dead organic matter
- Detritivore – consumer that eats decaying organic matter and feces
- Trophic Level – energy level or step in a food chain/web
- Succession – series of predictable changes in a community over time.
- Symbiosis – two organisms living together in a close relationship
- Mutualism – symbiosis in which both organisms benefit
- Commensalism – symbiosis in which one organism benefits and the other gets no
benefit and is not harmed either
- Parasitism – symbiosis in which one organism benefits (parasite) and one is harmed
(host). The parasite usually lives in or on the host
- Predation – when one organism kills and eats another
- Competition – occurs two individuals try to use the same resource at the same time and
place
- Niche – an organisms way of life and role in an ecosystem. Includes all the biotic and
abiotic factors that a specific organism needs to live.
- Immigration – occurs when individuals move IN to a population
- Emigration – occurs when individuals leave/move OUT of a population
- Exponential growth – “J-curve” – very fast, non linear growth
- Logistic growth – “S-curve” – very fast growth followed by stable population
- Carrying capacity - highest number of individuals that an ecosystem can support
- Limiting factor – anything causing a population to stop growing/decrease in size
- Density dependent – limiting factor that depends on population size and density
- Density independent – limiting factor that affects populations equally regardless of size
or density
Unit 6 Study Guide: Ecology
MAJOR CONCEPTS
The ecological levels of organization from smallest to largest are:
Individual < Population < Community < Ecosystem < Biome < Biosphere
Energy Flow
Energy in an ecosystem flows in only one direction from the lowest trophic level to the
highest trophic level.
- Only 10% of the energy in one trophic level is transferred to the next
highest level
- Nutrients (such as carbon, water and nitrogen – not energy) flow through an
ecosystem in a circular cycle
Producers make up the lowest trophic level in a food chain or web. Consumers make up the
trophic levels above that. Each step in the food chain is a different trophic level.
- Every consumer depends on lower trophic levels for energy.
- Producers get their energy from the sun
Community Interactions
Symbiotic relationships occur when two species live together in a close relationship.
There are three types (defined above). You should also know the following chart:
Mutualism
Commensalism
Parasitism
Organism A
Organism B
+
+
+
0
+
–
Draw a ‘+’ if the organism benefits.
Draw a ‘–’ if the organism is harmed
Draw a ‘0’ if the organism does not benefit AND is not harmed
Competition occurs when two organisms try to use the same resource at the same time and
place. There are two types:
1. Interspecific competition – competition between 2 members of different species
2. Intraspecific competition – competition between 2 members of the same species
Predation occurs when one organism kills and eats another.
Predators kill and eat other organisms
Prey get eaten.
Unit 6 Study Guide: Ecology
Ecological Niche
A niche is an organism’s role/job and way of life in an ecosystem.
It includes everything the organism does or needs to live.
Examples: what it eats, predators, when/how it reproduces, what biome it
lives in, what habitat it lives in, what climate it lives in
Producers – make their own food (autotrophic)
Consumers – Must eat others to obtain food (heterotrophic)
There are Primary consumers, secondary consumers, tertiary consumers,
and quaternary consumers. This just means that they are further up the food
chain. For example, tertiary consumers eat secondary consumers. Secondary
consumers eat primary consumers.
Decomposers – Eat at every level of the food web. They break down organic matter into
usable nutrients for producers and the cycle begins again. (examples are
mushrooms, soil bacteria, and some worms/beetles/insects.
Population Ecology
Population Growth
Four (4) factors affect population growth:
Birth rate, Death rate, Immigration, and Emigration
There are two (2) types population growth:
1. Exponential growth = J-curve
Very fast growth, occurs when resources are very abundant
2. Logistic growth = S-curve
Fast growth followed by plateau.
This is what population growth tends to look like in nature
Unit 6 Study Guide: Ecology
Carrying Capacity and Limiting Factors
Carrying Capacity describes the maximum number of individuals that an ecosystem can
support. On the graph on the opposite page this point is represented by the letter K.
Carrying capacity is limited (made smaller) by limiting factors
Limiting factors are things that cause a population to stop growing or get smaller. There are
two(2) types of limitng factors:
1. Density-dependent – affected by population size and density
Greater effect on large/dense populations
Usually are biotic factors (e.g. competition, predation, disease)
2. Density-independent – not affected by population size/density
Affect all size/density populations equally
Usually are abiotic factors (e.g. natural disaster, weather)
Predator-Prey populations
Look at the graph for hare and lynx populations in your notes
1. Predators cause the population of prey to decrease.
2. When population of prey falls, predator population decreases after.
3. Decrease in predators causes the population of prey to increase.
4. When population of prey rises, predator population increases after.
This interaction between predator and prey, where the population sizes cycle back and
forth in reaction to each other is called dynamic equilibrium.