ECOSYSTEMS AND
CYCLES
EVERYTHING IS CONNECTED
• Ecology is the study
of the interactions
between living things
and their environment
– Living things are
known as biotic
– Non living things are
abiotic
The environment is organized into 5
layers
• Organism
– Single living thing
• Population
– All the same kind of organism in one
place at one time
• Community
– All the different populations living in
the same place at the same time
• Ecosystem
– The community AND the abiotic parts
of the environment
• Biosphere
– All of the ecosystems throughout the
Earth
LIVING THINGS NEED ENERGY
• The sun is the ultimate source of energy in
almost all ecosystems
• Energy is passed from organism to
organism
• A balanced ecosystem has organisms in
all of the following roles
– Producers
– Consumers
– Decompsers
Producers
• Most producers use sunlight,
carbon dioxide and water to make
food for other organisms through
the process of photosynthesis.
• Plants and algae are main
producers
• A few producers use
“chemosynthesis” where chemicals
in the environment are used to
make food without light
Consumers
• Consumers are organisms that
eat (consume) other organisms
– Herbivores eat plants (primary
consumers)
– Carnivores eat other consumers
(secondary consumers)
– Omnivores eat both plants and
animals (are both primary and
secondary consumers)
– Scavengers feed on the bodies of
already dead animals (secondary
consumers)
Decomposers
• Breakdown the remains
of dead organisms into
simple nutrients (water,
CO2, etc.) and return
them to the soil or
atmosphere
• Bacteria and Fungi are
decomposers
Food chains and food webs
• Both are models that show how energy
moves, in the form of food molecules, from
one organism to the next
– Food chains are simple and show ONE route
for the energy to move
– Food webs are complex and show multiple
(and possibly ALL) paths for the energy to
move like overlapping food chains.
Energy pyramids
• Model that shows
HOW MUCH energy
is at each level of the
ecosystem
• Producers are at the
bottom showing that
the number of
organisms and the
amount of energy are
the greatest there
ENERGY PYRAMIDS – 2
• The herbivores are next
because they get the
energy directly from
producers
• Then carnivores
• Then scavengers
• At each level the number
of organisms decreases
since there is less energy
available to them to
sustain life
Wolves…stay or go?
• One hundred years ago wolves were
eliminated from Yellowstone National Park
• Why would people do this intentionally?
• What would be some advantages or
disadvantages of taking them out?
DISCUSS
Wolves and the energy pyramid
(When reintroduced into Yellowstone)
• Wolves are top carnivores
in the ecosystem
• Reduced the number of
large unhealthy, weak, old
herbivores
• Increased number of
smaller herbivores
• Improved balance of
ecosystem
Types of interactions
• Interactions in the environment
– Limiting factors
• those resources that prevents the population from
getting too large such as food, space, water, and
for plants sunlight.
• Any single resource can be a limiting factor to
population size
– Carrying capacity
• Is the largest a population can be in an
environment.
• Limiting factors determine what the carrying
capacity is.
Types of interactions-continued
• Competition
– Occurs when two or more species try to
use the same limited resource
• Food
• Space
• sunlight
– Can occur between populations of
different organisms or within the same
population
Types of interactions-continued
• Predators and prey
– Predators are carnivores that have developed
adaptations to help them catch other animals to eat
them
•
•
•
•
Vision
Speed
Camouflage
Others?
– Prey are animals that are adapted to survive so that
even though their species is being killed by predators
enough of them survive for their population lives on
•
•
•
•
Vision
Speed
Camouflage
Others?
Types of interactions-continued
• Symbiosis –long term association between two
or more species
– Mutualism – both types of organism benefit
– Commensialism – one organism benefits and the
other organism is unaffected
– Parasitism – one organism benefits and the other is
harmed or killed
• Coevolution – is a long term change that has
occurred because of the close relationship
between two species.
CYCLES OF MATTER
• Matter is anything that has mass and
occupies space
• Certain types of matter is constantly
reused and recycled in nature
• Examples studied in 7th grade:
– Water
– Carbon
– Nitrogen
Cycles in Nature
• Water cycle
– Precipitation – liquid
water falls to earth in
four forms rain, sleet,
snow, hail
– Evaporation – liquid
water becomes
water vapor
– Ground water –
liquid water seeps
into the earth and is
stored under the
ground
Cycles in Nature
• Other processes
– Run-off – water flows
along the ground and
collects in streams,
rivers, lakes, and
oceans
– Transpiration –water
vapor is released from
plants
– Condensation – water
vapor cools, becomes
liquid water
Carbon cycle - part of all living things.
• move carbon from the atmosphere into the organisms and back to
the atmosphere.
– Photosynthesis – plants use carbon dioxide and water to make sugar
( food)
– Respiration – organisms use the food and it is broken down to produce
energy for the organism carbon dioxide and water are released
• Other processes that
put carbon back into
the atmosphere
– Combustion – coal, oil
and natural gas
contains high
amounts of carbon.
When burned carbon
is released
– Decomposition –
breakdown of dead
organisms releases
the carbon stored in
their bodies back into
the environment.
Carbon Cycle
Cycles in Nature
• Nitrogen Cycle –
nitrogen is
essential to life
because it is the
main ingredient
in proteins, which
build muscles
and is in DNA.
• The nitrogen
cycle has two
processes:
– Fixation
– decomposition
Cycles in Nature
Nitrogen cycle – continued
• Fixation – the atmosphere is
78% nitrogen but it is not in a
form organisms can use.
– Nitrogen must be “fixed” so
it can be absorbed by
plants and then passed
onto animals.
– Nitrogen is fixed by
bacteria and lightning
• Decomposition – when
organisms die nitrogen stored
in their bodies is released into
the environment to be used
again
Succession
• Succession is a series of slow gradual,
predictable steps in the development of a
community. There are two types.
– Primary – occurs in an area where there is no soil or
life of any kind. Soil must be formed first so it takes a
VERY long time (hundreds or thousands of years)
– Secondary – occurs in an area where the existing life
had been destroyed by a natural disaster such as a
flood or a forest fire. Soil is already present so it takes
place over a shorter period of time (100 years)