LECTURE 6: MACROECONOMIC INTERDEPENDENCE (I) Interdependence: Y depends on Y*.
10 Interdependence
-
Upload
sureshthevan -
Category
Documents
-
view
221 -
download
0
Transcript of 10 Interdependence
-
7/27/2019 10 Interdependence
1/5
- GCSE Bitesize - Interdependence
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependencerev_print.shtml[10/21/2013 8:15:20 PM]
Science
Interdependence
Food chains show the feeding relationships in a habitat.
Pyramids of biomass are charts that show the mass of
iving organisms at each step in a food chain. Energy is lostmoving up in a food chain, and this l imits the length of the
chain. Parasites live off a host organism. Mutualism is
where species work together for mutual benefit.
Food chains
A food chain shows who eats what in a particular habitat. For
example, grass seed is eaten by a vole, which is eaten by a
barn owl. The arrows between each item in the chain always
point from the food to the feeder. This is the direction in which
energy flows in the food chain.
Food chains always start with producers, which are almost
always green plants. The other organisms in the food chain are
consumers they all get their energy and biomass by
consuming (eating) other organisms.
Most food chains are quite short, and they rarely consist of more
than four steps. This is because a lot of energy is lost at each
step. After about three steps, very little energy is still available
Food chain
-
7/27/2019 10 Interdependence
2/5
- GCSE Bitesize - Interdependence
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependencerev_print.shtml[10/21/2013 8:15:20 PM]
for use by living organisms. This also explains why there are few
organisms at the top of food chains, compared with those lower
down.
Energy transfer
Energy is transferred along food chains from one stage to the
next. But not all of the energy available to organisms at one
stage can be absorbed by organisms at the next one. The
amount of available energy decreases from one stage to the
next.
Some of the available energy goes into growth and the
production of offspring. This energy becomes available to the
next stage, but most of the available energy is used up in other
ways:
energy released by respiration is used for movement and
other life processes, and is eventually lost as heat to the
surroundings
energy is lost in waste materials, such as faeces
All of the energy used in these ways returns to the environment,
and is not available to the next stage. The animation shows how
the level of available energy goes down as it is transferred
through a temperate forest food chain.
Most food chains are pretty short. There are rarely more than
four stages, because a lot of energy is lost at each stage.
Pyramids of biomass
Biomass means the mass of living material at a stage in a food
chain. The biomass goes down as you go from one stage to the
next, just like the amount of energy.
Pyramid of biomass
A pyramid of biomasspyramid of
biomass: a diagram to illustrate
-
7/27/2019 10 Interdependence
3/5
- GCSE Bitesize - Interdependence
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependencerev_print.shtml[10/21/2013 8:15:20 PM]
Parasit ism and mutualism
Parasitism
Parasites are organisms that live on or in a host organism. The
parasite benefits from this arrangement, but the host suffers as
a result. Fleas are examples of parasites. They live on the skin
of other animals and suck their blood: this feeds the flea but
weakens the host.
A tapeworm lives inside another
animal, attaching itself to the hosts
gut and absorbing its food. The host
oses nutrition, and may develop
weight loss, diarrhoea and vomiting.
Parasites do not usually kill the host
because this would cut off their food
the amount of biological material
within a food chain or web is a
chart, drawn to scale, showing
the biomass at each stage in a
food chain. The bars become
narrower as you reach the top.
This pyramid of biomass is for the
food chain:
oak tree caterpillar blue tit
sparrowhawk
Note that you do not need todraw the organisms. But you
must draw your pyramid of
biomass to scale. Each bar should be labelled with the name
of the organism.
A tapeworm
-
7/27/2019 10 Interdependence
4/5
- GCSE Bitesize - Interdependence
//www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependencerev_print.shtml[10/21/2013 8:15:20 PM]
supply.
Other examples of parasites are:
headlice - they bite other animals such as humans in
order to feed off their blood
mistletoe - the roots of mistletoe grow into the veins of
the host tree to absorb nutrients and minerals.
Mutualism
Some organisms rely on the presence of organisms of a
different species. For example, oxpecker birds eat ticks and
arvae infesting the skin of buffalo and other large animals. For
this reason oxpeckers are called a cleaner species. This is an
example ofmutualism - both species benefit from the
arrangement.
Lichens are another example of mutualism. They are formed by
algae and fungi living together. Algae can photosynthesise and
make food, which is shared by the fungus. The fungus in turn
shelters the algae from a harsh climate.
Other examples of mutualism include:
'cleaner' fish - these feed off the dead skin and parasitesof larger fish such as sharks This provides the cleaner
fish with food and keeps the larger fish clean
chemosynthetic bacteria in deep sea vents - these use
chemicals from tubeworms in order to get substances to
make food. In return the tubeworms feed off substances
made by the bacteria.
Nitrogen-fixing bacteria Higher tier
Peas, beans and clover are leguminous plants. They have
colonies of nitrogen-fixing bacteria in nodules attached to their
roots. The plants gain nitrates from the bacteria, and the bacteria
gain sugars from the plants. This is another example of
mutualism.
-
7/27/2019 10 Interdependence
5/5
- GCSE Bitesize - Interdependence
// bb k/ h l / bit i / i / d l/ bl i i t/i t d d i t ht l[10/21/2013 8 15 20 PM]
Now try a Test Bite.
Back to Revision Bite
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependence/quiz/q30777943/http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependencerev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependencerev1.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/problems_in_environment/interdependence/quiz/q30777943/