Transcript Communities - REVISION-IB2

5.1: Communities
Topic 5: Ecology & Evolution
Miss Friedman
5.1.1: Definitions
Ecology
The study of the relationship between living
organisms and between those organisms and their
environment
Ecosystem
A community and its abiotic environment
Population
A group of organisms of the same species who live
in the same area at the same time
5.1.1: Definitions
Community
Populations of different species in the same area
which are interacting
Species
A group of organisms which can interbreed and
produce fertile offspring
Habitat
Location within which a species normally lives
5.1.2: Autotrophs &
heterotrophs
Autotroph
Heterotrop
h
Producer
An organism that
synthesises its organic
molecules from simple
inorganic molecules
consumer Obtains organic
molecules from other
organisms
5.1.3: Consumers, detritivores,
saprophytes
Consumers
An organism that ingests other organic matter that is
living or recently dead
Detritivores
An organism that ingests non-living organic matter
Saprophytes
An organism that lives on or in non-living organic
matter, secreting digestive enzymes into and
absorbing the products of digestion
5.1.4: Food chains
► Food
chains show a simple linear flow of
“who eats who”
► Therefore shows the energy flowing through
the links in the chain
Questions to consider!
How is energy lost in the chain?
Why are big, dangerous predators so rare?
5.1.5: Food webs
►A
diagram that shows how food chains are linked
together into more complex feeding relationships
Advantages over food chain
o Shows much more complex interactions between species
within a community/ecosystem
o More than one producer supports a community
o A single producer is a food source for many primary
consumers
o A consumer might have a number of different food sources
on the same/different trophic levels
o A consumer can be an omnivore, feeding as a primary
consumer but also as a consumer at higher tropic levels
5.1.6: Trophic level
► The
tropic level of an organism defines the
feeding relationship of that organism to other
organisms in a food web
Autotraph
Hetertroph
Hetertroph
heterotroph
Producer
Primary consumer
Tropic level 1
Tropic level 2
Secondary consumer Trophic level 3
Tertiary consumer
Trophic level 4
5.1.7: Determining tropic levels
in food chains/webs
► Assign
tropic
levels to the
food web on
the right!
5.1.8: Constructing a food web
► Producers
are usually shown at the bottom
► Use full name of organisms
► Arrows show the movement of matter &
energy
5.1.9:Light & food chains
► Sunlight
is the source of energy for most
communities, both aquatic and terrestrial
► Very few communities deep in the ocean
use geothermal energy
5.1.10: Energy flow in Food
chain
a) Not all solar energy will come into
►
►
►
►
►
contact with chlorophyll and will
therefore not be trapped in the
synthesis of organic compounds
b) Photosynthesis
c) Consumers feeding and passing on
energy in the food
d) Loss of energy as heat from
respiration
e) death and the consumption of
dead organisms by detritivores. Or as
food not assimilated because of
incomplete digestion.
Energy Loss
► loss of energy in undigested food
which will then be used by
saprophytes/ decomposers
► loss of heat energy in the reactions of
respiration
► ultimately all energy will be lost has
heat
5.1.11: Efficiency of energy
transformations
► When
energy is
changed from one
form into another, it
is never 100%
efficient
► Approximately only
10-20% of the
energy on one
trophic level will be
assimilated at the
next higher trophic
leve
►l
5.1.12: Shape of energy
pyramids
►A
pyramid of energy is a graphical
representation of the amount of energy of
each trophic level in a food chain
► The units are kJ/m2/yr
► The narrowing shape illustrates the gradual
loss of energy processing along the links of a
food chain to higher trophic levels
5.1.13: Energy and matter in
ecosystems
► Energy
is NOT recycled through the ecosystem
► Energy is constantly received from the sun and
constantly radiates out in the form of light & heat
► Matter IS recycled
► The process of recycling nutrients requires energy
5.1.14: Decomposers
► Two
main groups are detritivores (e.g.
earthworms, dung beetles) and saprotrophs (e.g.
fungi, bacteria)
► Decomposition is a complex process and serves
many functions; formation of soil, recycling of
nutrients, reduction of high energy carbon
compounds
► Organic molecules are oxidized to release nitrogen
in the form of nitrate, nitrite, and ammonia
► Oxidation of organic compounds provides energy for
saprophyte but returns matter to abiotic
environment
Q. Outline the process of decomposition
by saprotrophs
► Decomposition
is a biological process begins
with the secretion of extra-cellular digestive
enzymes. These enzymes are produced by
the saprophytic bacteria and fungi were
they secrete the enzymes onto the dead
organism and the enzymes hydrolyse the
biological molecules of which the dead
organism is composed into soluble
molecules that will then be absorbed by the
fungi or the bacteria.