Transcript Environmental Biology (Energy Flow)

Environmental
Biology
and Genetics
Energy Flow
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Ecology –
The study of living organisms in
relation to their environment
Organism – Living thing
Habitat – The place where an organism lives
Population – The total number of one type of
organism living in any one habitat
Community – The different populations of plants,
animals and micro-organisms found in
a particular habitat
Ecosystem – A natural biological unit which is made
up of living and non-living parts
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All the energy in an ecosystem comes from the sun
Green plants are able to convert light energy from the
sun into chemical energy (starch) during
photosynthesis
Green plants are called producers because they are
able to produce their own food
Other organisms can not produce their own food, so
must eat (consume) these plants and/or animals
They are known as consumers
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Three types of consumers;
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Herbivores
Carnivores
Omnivores
- Eat only plant material
- Eat only meat (animal) tissue
- Eat both plant and animal tissue
An animal that hunts another animal is called a
predator
The animal being hunted is the prey
Decomposers are micro-organisms ie. Bacteria and
fungi, which get their energy from breaking down
waste materials
Now complete pages 1 and 2 of your sheets. (Use pg 109 of the textbook to help)
Food Chains / Webs
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When an animal eats a plant or animal energy is
transferred from the food to the feeder
The animal that eats the plant at the start of a feeding
relationship is called the primary consumer
(Normally a herbivore may be an omnivore)
If the primary consumer is eaten by a second animal,
this second animal is called the secondary consumer
(may be an omnivore or a carnivore)
Energy transfer continues the whole way along the
feeding relationship. This is known as a food chain.
Food Chains
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A food chain always begins with a producer or
detritus
Eg.
Grass
Rabbit
Fox
(Producer)
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(1st consumer)
(2nd consumer)
The arrows indicate the direction of energy
transfer.
Food Webs
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In nature a food chain rarely occurs in isolation
The producer may be eaten by a number of different animals,
which in turn may be preyed upon by many different predators
(See pg 3 of sheets, pgs 110 – 112 of text )
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Food chains interconnect at many points to form a food web
Look at the following food web and pick out at least 5
different food chains;
Eagle
Fox
Mountain Hare
Merlin
Skylark
Grouse
Moth Larva
Heather
Food Webs
Pick out all the food chains from this web;
Fox
Owl
Frog
Hedgehog
Weasel
Snail
Vole
Rabbit
Primrose
Oak
Energy Loss
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Not all the energy available at each step of the food chain is passed on to
the next step (See sheets pg 4)
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There is a significant energy loss at each step of a food chain
Energy
from
food
100%
90% lost and is
unavailable to
other animals
Some energy
used
Some energy
not used
uneaten
undigested
Lost as
heat
Used for
movement
10% is passed on to
other animals (this
energy is stored in the
tissue of the plant or
animal, until it is eaten)
Pyramid of Numbers
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In most food chains there is a greater number of
producers than primary consumers, and a greater
number of primary consumers than secondary
consumers, and so on
The final consumer is least numerous
This numerical relationship is called a pyramid of
numbers.
As the organism higher in the food chain requires
more food, the level before it in the pyramid is bigger
This is due to a decrease in energy being passed on.
Pyramid of Numbers
Primrose
Snail
Hedgehog
FOX
HEDGHOG
SNAIL
PRIMROSE
Fox
Decreasing
numbers
Decreasing
energy
Pyramid of Numbers
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In some food chains the
producer is a single
large plant and the
pyramid therefore takes
a different form.
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Oak Tree
Caterpillar
Owl
Shrew
Caterpillar
O
T
Shrew
Owl
Pyramid of Biomass
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The biomass of a population is its total mass of
living matter
The biomass at each level of the pyramid
decreases
This can be represented as a pyramid of
biomass
As there are so many organisms at each level
of the pyramid, the weight decreases with the
numbers.
Pyramid of Biomass
Primrose
Snail
Hedgehog
FOX
HEDGEHOG
SNAIL
PRIMROSE
Fox
Decrease in biomass
Pyramid of Energy
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The most reliable
comparison between
organisms found at different
levels of a food chain is in a
pyramid of energy
This is based on
productivity
This is measured as dry
mass per square metre per
year, before being converted
into kilojoules per square
metre per year.
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This type of pyramid will
always take the shape of a
true pyramid, as only a
proportion of energy is
transferred from one level to
the next. (Complete pgs 3-6 of sheets)
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Test your knowledge pgs 113 + 118 of text
Apply your knowledge pgs 119-122 of text
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FOX
HEDGHOG
SNAIL
PRIMROSE
Factors Affecting The Variety of
Species in an Ecosystem
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Species –
A group of living organisms
which are so similar to one
another that they are able to
interbreed and produce fertile
offspring
Biodiversity
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Within an ecosystem there is a variety of habitats
Within each habitat there is a range of populations (plants,
animals and micro-organisms)
As well as being adapted to their habitat, each population is
adapted to a particular ecological niche in the pattern of the
community
As an ecosystem develops over a period of time the range of
habitats and niches it contains increases
This gives rise to a wide diversity of species in every
ecosystem
An adaptation is an inherited characteristic that makes an
organism well suited to survival in its environment
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Some adaptations involve the structure of the organism’s body,
or a behavioural response to a particular environmental stimuli
Adaptation can leave some species unable to cope with
other/different habitats, environmental conditions
This means that some species will only be found in an area
where the conditions are suitable to its survival needs,
influencing its distribution in the ecosystem
A stable ecosystem contains a balance of interdependent
producers, consumers and decomposers
(Complete pgs 7 and 8 of sheets, use pgs 123-128 of text)
Test your knowledge pg 127
Importance of Biodiversity
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1. Could provide us with future life changing
medicines
2. May provide us with a genetic storehouse
in many wild species which could help
humans and plants recover from disease
3. Could provide us with future varieties of
food
4. May add to our education of the nature
around us. (Sheets page 14, see text pgs 139-140)
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Factors such as pollution and grazing reduce
the variety of species in an ecosystem
They act selectively on populations
disadvantaging some species and allowing
others to thrive by eliminating their
competition.
Reduction in Biodiversity
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Human activity can reduce biodiversity through the
destruction of habitats (Pages 8-13, see text pgs 129 - 138), ie;
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Disruption of food webs
Grazing
Pollution – Acid rain
- Sewage
- Thermal pollution
Deforestation
Desertification
Mass extinction
Over-hunting
Habitat destruction
Disruption of Food Webs
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Food webs are generally more stable than food
chains, and can normally withstand small/ temporary
disruptions
If , however an organism is affected by an external
factor, then this will have a knock-on effect in a food
chain
A chain having only a few links will be more
seriously affected than a longer chain
Myxomatosis is an example of an external factor
which nearly wiped out the rabbit population in
Britain
Grazing
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Grazing can be of an advantage to some plant species
and a disadvantage to others
If natural grasslands go un-grazed, some of the
stronger species will thrive on the available resources,
causing other weaker species to die
This reduces biodiversity
If on the other hand, animals are left to over-graze,
this can also lead to a reduction in biodiversity
This is because the plants are not able to grow and
reproduce.
Pollution
Acid Rain
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Caused by the burning of fossil fuels (coal, oil)
Release sulphur dioxide (poisonous gas), damages many plant
species
Ie.different Lichen species tolerate different levels of SO2
pollution
As air pollution increases, the variety of lichen species
decreases
Water and land environments can also be affected by pollution
Ie. a reduction in the number of fish species
Sewage
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Untreated sewage may be released into rivers in
densely populated areas if the sewage works become
overloaded
This provides food for bacteria (which feed on
organic waste)
(Organic waste ie. Dead skin cells, faeces, urine, hair,
plant/animal food waste)
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As sewage bacteria oxygen fish etc.
This could result in loss of clean water species
ie. Loss of species diversity
Thermal Pollution
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Some power stations use local river water to cool their
generators
When the water is returned to the river it is considerably
warmer, and causes thermal pollution
Deforestation
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The complete clearing of vast areas of natural forests
and the failure to plant new forests in their place;
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Loss of regular water flow, so loss of sponge
effect = rivers fail to provide a regular supply
of water for human consumption and irrigation
Loss of rain water from hillsides = flooding of
low-lying downstream areas, cannot be
cultivated
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Erosion of fertile top soil = fertility of hillside
reduced, rivers, lakes, irrigation channels and
dams become blocked, muddy and undrinkable
Less water evaporation into atmosphere =
reduction in rainfall, so drier climate
More CO2 (burning) not removed by
photosynthesis and less O2 = extra carbon
dioxide may add to the greenhouse effect.
Desertification
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Removal of protective shrubs and plants which
act as wind breaks which normally hold the
soil together
Removal causes the soil to dry out and lose
fertility.
Mass Extinction, Over-hunting and
Habitat destruction
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Fossil fuels take millions of years to form, and
are quickly becoming depleted due to over use
As they take so long to form it will take as
long again to form more
Hundreds of birds and animals have become
extinct over the centuries, and many more are
in danger
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Two major contributors are over-hunting and
habitat destruction
Human activities are causing the current wave
of extinction to run at about 400 times its
natural rate.
(See pgs 8-13)
Test your knowledge pg 141 of text.
Behavioural Adaptations
in Animals
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Animals exhibit behavioural responses to their
environment
Behavioural responses/adaptations are of survival
value to the animal
The way an animal responds depends on the
environmental stimulus which it has triggered its
internal receptors
Theses receptors are linked with the sense organs
which in turn communicate with the nervous system
The sense organ detects an environmental stimulus
then transmits nerve impulses through the nervous
system, causing an effector to create a behavioural
response
The effector could be muscles or glands. (See pgs15-17)
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Pg 16/17 Activity 2.1, text pgs 143 - 144
Pg 17/18 Activity 2.2, text pgs 145 -147
Testing your knowledge pg 147 of text.
Competition Between Plants
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If any of the following resources are in short supply
plants will compete with one another for them;
 Light
 Water
 Soil Nutrients
Same species plants will have intense competition for
these resources. (See sheets pgs 19- top 20, text pg 147)
Pg 19 Activity 2.3, text pgs 148 – 149.
Competition Between Animals
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Animals will compete with one another for
resources such as;
Food
 Water
 Shelter
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(See sheets pg 20, text pgs 150 - 152)
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Test your knowledge pg 152 of text.
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Applying your knowledge pgs 153 – 158 of
text
What you should know pgs 158 – 160 of text.