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Science 1206
Unit 01 Section 02 – Lesson 01
Ecology
In this lesson you will:
•
define ecology and ecosystem
•
distinguish between biotic factors and abiotic factors and describe examples
to illustrate each
•
explain how abiotic factors affect the sustainability of the ecosystem
•
describe examples to illustrate biotic interactions
•
describe ways that organisms respond to changes in environmental
conditions
•
describe symbiotic relationships including: mutualism, commensalism,
parasitism, and predation
•
describe trophic structure in terms of food chains and food webs
•
explain how biotic and abiotic factors affect ecological interactions and the
distribution of organisms
• Ecology
– is the scientific study of the interactions of organisms and
their environment.
– Interactions of organisms and their environment refers to the
way the organism affects the environment as well as how the
environment affects the organism
• Ecosystem
– is a community of organisms and the physical environment in
which it lives.
– When an ecologist studies the organisms living in a forest and
includes a study of the physical factors that affect the
organisms in the forest, then the ecologist is studying an
ecosystem.
– Example
Examples:
• Abiotic factors are the nonliving factors which affect life in any ecosystem.
– Space
• All organisms require enough space or territory to insure
adequate resources to food, water, shelter, and mates.
– Temperature
• Environmental temperature affects biological processes and
the ability of most organisms to regulate their temperature.
– Oxygen
• Most living organisms require oxygen for cellular respiration,
which is a process that releases energy from food.
– Sunlight
• Sunlight is the ultimate source of energy for all photosynthetic
organisms which in turn provide the resources for other living
things (in most ecosystems).
– Water
• Water (humidity) is necessary for all life. The ability to find
water, to maintain water balance, and to conserve water help
determine the habitat range for each species.
– Inorganic and Organic Soil Nutrients –
• Inorganic soil nutrients
– include minerals such as phosphates,
nitrates, potassium, magnesium and
– a host of other minerals derived from rocks.
• Organic nutrients
– include organic compounds in humus which promote the
growth of bacteria, fungi, and a host of other organisms
beneficial to the soil.
• The physical structure, water holding potential, pH, and
nutrient level of soil limit the distribution of plants and in turn
the animals that inhabit a terrestrial region.
• The composition of the substrate in a stream affects the
chemistry of the water above and in turn affects plant and
animal life living there. the type of substrate also influences
what animals can attach to or burrow in (especially in the
intertidal zone).
Biotic factors
• refer to the living environment and
include all other organisms that
interact with the individual both of
the same species and all other
species.
• Biotic factors also includes
– decomposing animals and
plants (detritus)
– Disease
– predator/prey interactions
– Competition
– symbiotic relationships
(symbiosis).
• Detritus
– refers to decomposing plant and animal materials including
their dead bodies as well as their wastes.
– Bacteria and fungi living in the ecosystem help to break down
the materials within the detritus and recycle these materials
back to the plants.
• Disease
– is the result if infection by fungi, bacteria, virus, and other
pathogens.
– Disease is an important biotic factor because disease tends to
reduce the number of organisms within the community.
• Predator/prey interaction
– is another important biotic factor which helps to limit the size
of populations within an ecosystem.
– There is a balance between the number of predator and prey
in any ecosystem.
• Competition
– is a struggle for survival that occurs between two organisms
either of the same or different species.
– Competition tends to limit the size of the population keeping it
in balance with the available resources.
Symbiotic relationships:
•
Symbiotic relationships are biotic relationships in which two different
organisms live in close association with each other to the benefit of at
least one.
•
There are five types of symbiotic relationships including:
1.
2.
3.
4.
5.
Mutualism
Commensalism
Parasitism
Parisitoidism
predation.
1.
Mutualism
–
mutual benefit to both of the organisms
in the relationship.
• Ex: hummingbird and flower
2.
Commensalism
–
one organism benefits from the
relationship but the other organism
seems to neither be harmed nor
benefited.
• example to illustrate commensalism
is the beaver and the fish.
• Finding Nemo!
–
Clownfish live within the waving
mass of tentacles of sea anemones;
Because most fishes avoid the
poisonous tentacles, the clownfish
are protected from predators.
3. Parasitism
one organism benefits and the other is
harmed.
• The organism that benefits is called
the parasite, the organism that is
harmed is called the host.
• Some parasites only cause slight
damage to their host, while others
kill them.
•
Ex: tapeworms
4. Parisitoidism
– is similar to parasitism. One
organism benefits but the other is
eventually killed - a sort of slow
death.
•
An example of parisitoidism is
when a female wasp stings a
spider causing paralysis but not
death. The wasp then lays a single
egg on the spider. When the egg
hatches into a larva, it slowly eats
the body of the spider eventually
killing it - but slowly.
5.
Predation
•
•
is where the interaction is
beneficial to one species
and detrimental to the
other.
This is not always
considered a symbiotic
relationship, although it is
quite similar to parasitism,
except for the degree of
harm to the host or prey.
With predation, the prey is
killed.
•
An example of predation
is when a lion kills a zebra
and eats it as its source of
food.
Trophic Structure:
•
Trophic structure
–
refers to the feeding relationships within the ecosystem.
–
five trophic levels
1.
2.
3.
4.
5.
–
primary producers
primary consumers
secondary consumers
tertiary consumers,
decomposers (also known as detritivores).
The various organisms that comprise each of the trophic levels
determines the flow of energy and the cycling of materials within the
ecosystem.
–
Feeding relationships are generally viewed as a food web
consisting of all the possible food chains that exist within the
ecosystem.
–
Since the primary producers are the only photosynthetic
organisms, they determine the amount of energy (trapped from
the sun) that can be passed up through the food web.
–
The detritivores enable the recycling of materials and are therefore
the organisms that are the foundation for biogeochemical cycling.
1. Producers or Autotrophs
–
green plants, that produce their own food.
–
They make organic compounds (food such as
sugar) from inorganic compounds (carbon
dioxide and water) by photosynthesis.
–
The ultimate source of energy for life on
Earth is the sun.
•
•
•
Solar energy is trapped during the process of
photosynthesis and converted into a chemical
form that we normally call food.
The materials within the food are recycled.
They pass from the producers to the
consumers and finally are recycled back to
the producers by the action of the
decomposers.
Energy, unlike the materials, is not recycled.
• As the food is passed through the
food web, most of the energy is lost.
– Pyramid of energy - about 10% of
the energy stored in one trophic
level (such as producers) is actually
transferred to the next trophic level
(for example the herbivores).
– Which means that 90% of the
energy is lost.
– Eventually there is so little energy
remaining in the top trophic level
that no higher trophic level can be
supported.
– This should explain why there are
fewer fourth order consumers in an
ecosystem as compared to
the primary consumers.
HOW?
2. Consumers or Heterotrophs
–
Organisms that obtain nutrients from
other organisms.
–
They cannot make their own food so they
must obtain it ready made.
–
Two types of carnivores.
1.
Predators - hunt and kill other animals for
food.
2.
Scavengers - are animals that feed on the
dead bodies of other organisms.
3. Decomposers
– are organisms of decay.
– These are also called saprobes.
– They are generally fungi or bacteria
that break down the complex
compounds in the remains of dead
animals and plants, producing
simple substances that can be used
again by the producers.
– Decomposers are therefore very
important because they recycle
materials within the ecosystem.
– The decomposers are the final
consumers in any ecosystem
• Herbivores
– are animals that feed only on plants.
– Rabbits, cattle, horses, sheep
• Carnivores
– are animals that feed on other animals.
– Some carnivores may be predators (such as lions, hawks, and
wolves who attack and kill their prey and feed on their bodies) and
some may be scavengers (they feed on dead animals that they
find).
• Omnivores
– These are animals that feed on both
plants and animals.
– Examples of omnivores are humans
and bears.
• Saprobes
– Organisms that get nutrients by
breaking down the remains of dead
plants and animals, or their wastes.
– Examples of saprobes are bacteria and
fungi.
– Saprobes are also known as
decomposers are an essential
component of any ecosystem. Their
main role is to recycle nutrients in dead
organisms and their wastes.
– Without the decomposers to recycle
nutrients, there could be no life since
plants would run out of nutrients.
Review
•
•
Read 1.12 "Roles in Ecosystems" on pages 40-44.
Answer questions 1-4 from "Understanding Concepts" and
"Exploring" on page 44.