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Food Web and Food Chain
 Ecology - is the study of the interaction of organisms with one another and their
environments.
 The environment is often divided so that scientist can assess the areas
properly (See Next slide).
 The environments have both Abiotic Factor and Biotic factor the interaction
between them is what makes up and ecosystem.
Biotic- Means Living things
Abotic- Means Non- Living things
Each Organism in environment has both a Habitat and a Niche
Habitat- is an area in an ecosystem where a particular organism lives. This is
usually based on the resources available.
Niche- is the role an organism play's in an environment.
Population Dynamics
Both the environment and the amount of energy in a given ecosystems is limited.
Often when a species has little to no competition, meaning lots of access to
food, exponential growth (making on increase in population size and density)
occurs. During exponential growth the population doubles in size with each
reproductive cycle cause a huge period of time also known as a population
explosion. When the population reaches the limits of the ecosystem, this is
known as an ecosystems carrying capacity. The population must be adjusted due
to the resources cannot support the population. This cause competition between
the organisms and also creates several unique relationships between organisms.
Competition generally acts as a negative feedback interaction for both species
involved. Predation is usually through a system where the population growth
of one species; the predator is favored and the population growth of the other;
the prey is negative; affected.
Competition can often lead to Natural Selection in that the strongest
organisms survive to reproduce. These are the organism that are best suited
to the environment, have the ability to hide from predators, are the strongest
against disease and the best at find food and meeting there nutritional needs.
a. Competition also has benefits to both the predator and the prey
populations. The predator helps keep the population of the prey
below that of the carrying capacity helping to prevent disease and
sickness.
b. When an exotic species is introduced into a food web this puts a
new predator into the system. This could have huge
consequences in the population.
i. For example when a mongoose was introduction to several
Caribbean Island in an effort to control the rat population;
the governments did not see the unintended consequence
that it would have on the rest of the food web. The island
saw the mongoose population explode do to no predator
to keep this species in check. This lead to the island seeing
mass extinction of many native birds, reptiles and small
mammals.
ii. Carrying Capacity – the amount of organisms that an
ecosystem can support based on the resources that the
ecosystem has availed.
iii. Competition – this is where a species or organism must
challenge another species or organism for resources such as
for food water and habitat.
Types of Competition
Symbiosis- Any relationship between organisms that live in the same
ecosystem. There are three different types.
Parasitism
Relationship where one organisms feeds on another.
One organism is harmed or killed and one organism.
Tapeworms
Mutualism
Relationship where both organism benefits
Flowers and Bees
Gopher tortoises
Commensalisms
A relationship where one species benefits and the other is
unaffected
Clown fish and sea anemones
Example diagram
Question you should be able to answer:
What is the Oreo Effect?
What happens if you remove green plants?
What happen if you remove kites?
What happen if you remove the rabbit and mouse?
What happens if habitat is destroyed to a food web?
2. Food Chain- these are a sequence of organisms which have a predator/ prey
relationship. The chain consists of a Producer, a Primary consumer, a Secondary
Consumer and a Decomposer. Consumers are separated into to types Herbivores
and Carnivores.
3. Components of a Food Chain
i. Producers – are the plant life in an ecosystem. The total amount of
energy that flows through and ecosystem depends on the amount of
energy that is fixed by the producers.
ii. Herbivores- role in the ecosystem is to convert the stored energy in
plants (producers) tissue into animal tissue. With out this step there
could be no higher levels in the food chain. Most of these organisms
have high bacteria counts in their digestive systems in order to deal
with the large quantities of digestible fiber.
iii. Carnivores – eat herbivores or each other. First level carnivores eat
only herbivores while 2nd level carnivores have the ability to also eat
other carnivores. Usually 2nd level carnivores have adapted hunting
skills and are considered very intelligent.
iv. Decomposer- is also known as the final consumer. Their role is to
breakdown plant and animal biomass after it has expired. This
releases the nutrients and minerals that are contained in the
carcasses for future use. There are two types of decomposer.
Food Web
This is looking at the ecosystem as a whole. Food webs show the connections to organism
and what they eat
Refresher of the player in a Food Web
Producer
Plants
Autotrophic- gets energy from the sun
(100% energy efficient)
Consumers- Heterotrophs must obtain food from other sources
First Order Consumer or Primary Consumers
Eats plants only
Also known as Herbivores
Second order or Secondary Consumers
Larger animals which eat Primary Consumers
Also know as Carnivores
Other consumers
Omnivores - eats both plants and animals
Scavengers- eats dead and dying organism
Decomposers- organisms which brake down dead matter into simple compounds.
Arrows in a food web point in the direction that energy flows.
Ex. From Above: The energy from the green plant energy flows into the Rabbit and
the Goat after they eat the green plants.
Food webs are complex but often there is a central player known as a Key Stone
Species that in one way or another count on this central player. The removal or
decrease in the population of that organism will greatly impact the food web and
most of the other organism populations suffer.
Human Impact: Pesticides, Herbicides, Extinctions, over Development: All possible used in
application and system question- if more detail needed ask.
Energy Pyramid
The Energy pyramid show how energy moves throughout the varying levels in a food chain.
Producers are considered to be 100% energy efficient. This is because plants make
sugar for energy production in the process of photosynthesis. This set of organism
makes up the largest biomass (Living Material) on the planet.
Herbivores have to move for food, this make them less efficient that plants in that
they must burn energy to get energy. When looked at Herbivores are considered to
be 10% efficient. Like energy efficiency the amount of organism or Biomass
decrease do to the nutritional needs.
Carnivores are the least energy efficient and often require large hunting area, speed
and other adaptations in order for them to meet all nutritional requirements.
Carnivores are the least efficient at 1%. Like energy efficiency the amount of
organism or Biomass decrease do to the nutritional needs.
Human Impact: The food webs and energy pyramid are disturbed with any of the
following
Invasive species- impacts the food chain and population numbers
Extinction – food chain impact the other organism in the area-Keystone
species.
Habitat loss- No homes mean lower numbers of critical foods.
Population Density
Measurement that determines how crowded a population is. This is usually
done for one species at a time but if it is part of a Field Experiment several
populations can be looked at.
Number of individuals / unit of volume
This can only be an estimate because there is no way of counting every
organism in a population. In order to get a population density number you
must take multiple sample of the area in question and count the individuals
that are visible.
This is how close the individuals of a population are to another individuals of
the same species
POPULATION DISPERSION
Dispersion- two types
Even dispersion - animals or plants have antisocial behaviors
Organisms want to be apart. Often seen in birds and gulls.
Clumping dispersion - grouping organism in a pack, very social behavior.
Often seen in fish, lion, elephants ect.