SNC1D
Biology Unit
Introduction to Ecology
All living things need energy. Where does it come from?
Important Terms in Ecology
Ecology:
The scientific study of patterns of distribution and abundance of organisms and their
interactions with the environment.
Organism:
an individual animal, plant, or single-celled life form. Different kinds of organisms are called
species.
Population:
the number of organisms of the same species that live in a particular geographic area at the
same time, with the capability of interbreeding.
Community: an interacting group of various species in a common location.
Ecosystem:
The combination of the living (biotic) and non-living (abiotic) things in an area. In other words, a
community of organisms together with their physical environment of any size or scale.
Aquatic ecosystems are underwater (fresh or salty)
Marine ecosystems are in salt water (the oceans)
Terrestrial ecosystems are on land. They are often divided into categories called biomes.
Ecosystems with higher biodiversity tend to be more stable with greater resistance and resilience
in the face of disturbances, disruptive events.
Examples of parts of an ecosystem:
Abiotic Factors – Not Alive
air, water, rocks, minerals, nutrients,
pollutants, weather, climate.
Biotic Factors – Alive
microbes (bacteria, archea, protists,
viruses), fungi, plants, animals.
Read pgs. 7-9, Do Learning Check #1-4
SNC1D
Biology Unit
Understanding an Organisms Place in an Ecosystem
Habitat:
The specific place and conditions required for a particular community or organism to live.
Eg. The habitat for deer may be a forest with access to grassland
Niche:
The specific role that a species or population plays in an ecosystem. It describes how that species
interacts with all of the biotic and abiotic factors in an ecosystem.
Eg.
Deer are herbivores that feeds mostly on grass. They feeding patterns, wastes and
herd movements helps maintain grasslands. They are important prey for top predators
like coyotes and wolves.
The Earth’s Four Spheres (see pg 13)
The earth can be subdivided into 4 major “spheres” in order to make it easier to study. All four spheres
interact with each other and all of them contain major stores of minerals and nutrients such as carbon,
nitrogen and phosphorus in various forms.
ATMOSPHERE
Thin layer of gas surrounding the Earth. It is a complex layered
mixture of different gases
HYDROSPHERE
All of the water on Earth. More than 90% of the water on Earth is
in the oceans (salt water)
LITHOSPHERE
All of the land on Earth. This covers about ¼ of the earth’s surface
BIOSPHERE
Sum of all of the world’s ecosystems. The “zone of life” on Earth
SUSTAINABILITY - The theme of much of modern ecology
Energy and matter flow through ecosystems from one organism to another. In order to be alive, all
organisms must consume resources and energy for themselves. If a resource is used at a rate faster
than it can be replaced, then it will deplete over time and may eventually run out. This would mean that
the resource is NOT sustained into the future.
To be sustainable means to meet your needs today without depleting resources that are
necessary for future generations.
To be truly sustainable might also mean maintaining a surplus of resources so that nature can respond
to changes and to recover from disasters and periods of stress (eg. multi-year droughts)
The choices you makes and the lifestyle you live today affects your future and the future of others.
SNC1D
Biology Unit
Energy Flow Through Ecosystems
Nearly all living things on Earth get their energy either directly or indirectly from the sun.
Tracking what happens to this energy as it moves through ecosystems can help us understand key
patterns in nature.
Primary Producers:
Herbivores
Carnivores
Plants, algae, cyanobacteria
Flow of energy
•
The sun’s energy is captured (fixed) in the chemical reaction of PHOTOSYNTHESIS.
Photosynthesis
Cellular
Respiration
carbon dioxide + water
6 CO2
+ 6 H2O
glucose (sugar) + oxygen
C6H12O6
glucose (sugar) + oxygen
+
6 O2
C6H12O6
+
6 O2
•
photosynthesis traps solar
energy into the chemical bonds
of glucose.
•
Glucose acts as a kind of solar
battery. The energy stored in
glucose can be released and
used in a chemical reaction that
breaks it back apart into carbon
dioxide and water. This reaction
is called CELLULAR RESPIRATION
•
Glucose is also used by plants as
the main component of their
physical bodies. In this way
energy and carbon are stored in
the bodies of plants.
carbon dioxide + water
6 CO2
+ 6 H2O
SNC1D
Biology Unit
FOOD CHAINS:
Grass → Grasshopper → Frog → Snake → Hawk
How the amount of photosynthesis affects ecosystems:
more photosynthesis = more production of sugar and oxygen = more biomass and biodiversity
less photosynthesis = less production of sugar and oxygen = less biomass and biodiversity
•
•
•
Ecologists can use food chains to group organisms based on feeding relationships (“who eats who”)
A food chain lists JUST ONE series of organisms in an ecosystem in order of their eating relationships.
The arrows in a food chain show the direction of movement of energy from one organism to
another.
Autotroph:
Any organism that makes its own food.
Autotrophs in a food chain are referred to as the producer (or primary producer)
Heterotroph: Any organism that cannot make its own food. They must eat other organisms.
Heterotrophs in a food chain are referred to as consumers.
Consumers can be sub-categorized based on what they eat
Herbivores exclusively eat producers
Carnivores exclusively eat other consumers
Omnivores eat a variety of foods that include both producers and consumers
Detritivores / Decomposers / Scavengers consume food that is already dead and decaying
Does every organism fit into a food chain?
Decomposers, like earthworms, snails, bacteria and fungi, may
act anywhere or even at every stage of a food chain. Their niche
is to eat and break down dead and decaying matter. The left
over waste when decomposition is done is called soil. The
process of decomposition returns nutrients into the soil and
makes them available for others to use them again. Nutrients are
recycled through decomposition.
The quality of soil will depend on materials were decomposed
and on which decomposers were involved. Good quality soil is
important for ecosystem health because it holds the moisture,
gases, and nutrients needed for most producers to grow. Over
time, soil can even transform into different abiotic forms such as
clay, rock, or fossil fuels.
SNC1D
Biology Unit
Trophic Levels
Organisms at the same level of a food chains are grouped into a trophic level. There are five main
trophic levels within a food chain. The first contains the producers, while the rest are consumers. The
2nd trophic level contains the herbivores, the 3rd and 4th contain omnivores and carnivores, and the 5th
contains the top predator. Decomposers feed at all levels and don’t formally fit into the trophic level
system.
THE “10% RULE”
Only about 10% of the energy from one trophic level
is available for use at the next higher level.
•
•
Most of the energy derived by an organism is either used by the organism, or lost to the
environment as heat.
Organisms use energy to digest food, grow, move, warm their bodies, reproduce, think and to
perform a host of other metabolic functions. Some parts of food can’t be digested.
The amount of energy which is actually available to the next trophic level is highly variable depending on
which organisms are involved. The 10% rule is mostly a reminder that it is only a very small amount.
•
Some important challenges of food chains:
o they tend to over simply relationships in nature and over-emphasize the importance of the
niche of the organisms represented
o they do not account for ecological importance of organisms beyond feeding relationships.
SNC1D
Biology Unit
How do trophic levels relate to the
sustainability of meat as a food source?
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FOOD WEBS:
•
•
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Feeding relationships in nature are much more complex than food chains show.
Energy usually flows through several food chains within an ecosystem.
Ecologists sometimes try to make more realistic and complete pictures of the feeding relationships in
a whole ecosystem using food webs.
•
Some important challenges of food webs:
o they can become very complex and yet, they rarely include all organisms in an ecosystem
o can be difficult to apply the trophic level system. Organisms may fit into more than one
trophic level in different food chains within the same food web
o The relationships in nature are too complex to make accurate predictions from a food web
about what would happen to an ecosystem if species were removed or introduced.
o Watch this video: https://www.youtube.com/watch?v=ysa5OBhXz-Q&feature=emb_logo
SNC1D
Biology Unit
Food Chain Practice Questions
Frog
Red-tailed Hawk
Berries
Starfish
Otter
Deer
Zooplankton
Snail
Mouse
Turtle
Blue Jay
Bald Eagle
Perch
Kelp
Raccoon
Sardine
Bacteria
Moth
Snake
Ant
crayfish
Pike
Maple tree
Squirrel
Grass
Shelf mushroom
Bat
Rabbit
Leaves
Fox
Salmon
Flower
Clams
Mayfly
Krill
Algae
Grasshopper
Bass
Wolf
Algae
Bee
Dolphin
Dragonfly
Shrimp
Seal
Phytoplankton
Nuts
Butterfly
Shark
Bear
Whale
Spider
Eel
Owl
Answer the following questions on a separate page
1. Use the list of organisms above to write out the following food chains:
a. Write a terrestrial food chain consisting of 4 trophic levels
b. Write an aquatic food chain consisting of 5 trophic levels
c. Write a food chain that is partially aquatic and partially terrestrial
2. Use the food chain below to answer the following questions
Grass → Cow → Bot fly → Spider → Bat
a.
b.
c.
d.
Name the secondary consumer. Name the producer.
How many trophic levels are there in this food chain?
List all of the consumers present.
What would happen to the spider population if a drought caused a lot of grass to die?
3. “All organisms derive their energy from the sun”. Explain this statement in your own words. Describe the
relationships between producers and consumers and how this relates to photosynthesis and cellular
respiration.
4. What is compost, how does it relate to decomposers, and why is it so good for plants?
5. Using the concept of trophic levels explain why it takes much more land to produce meat than it does to
produce vegetables. (use the 10% rule)
6. It is becoming more and more common to raise fish, including salmon in fish farms (aquaculture). Salmon
are carnivorous fish. Why is it not energy efficient to farm salmon? (use the 10% rule)
SNC1D
Biology Unit
Food Web Practice Questions
Follow up Questions (answer on a separate page)
Refer to the three food webs on the following pages to answer these questions:
1) Compare food webs to food chains. Explain 2 advantages and 2 disadvantages for each.
The purpose of the following two questions is to emphasize how unpredictable changes are to ecosystems when species are
added or removed. The only prediction you can make for certain is that if there is less primary production at the bottom of the
food chain, all subsequent trophic levels will be depleted.
2) In Food Web #1, imagine that humans began to fish the forage fish in order to feed livestock.
Make and explain two different predictions about what could happen to the population of salmon.
Your prediction could be that it goes up, down, or stays the same.
3) In Food Web #2, imagine if humans sprayed insecticide on the plants.
Explain each of the following predictions about what could happen to the population of each of the
snowshoe hares. Note that insecticide kills ONLY insects.
(a) The snowshoe hare population is unaffected.
(b) The snowshoe hare population goes up. (offer at least two DIFFERENT explanations)
Food Web #1
SNC1D
Biology Unit
Food Web #2
SNC1D
Biology Unit
Look at this complex food web for fun!