Transcript Subtopic (b) How it works

Sub topic (b)
How it
works
Ecosystems
• Examples of ecosystems
include a woodland, ocean ,
desert, moorland etc..
• The main parts of an
ecosystem are the habitats,
animals and plants
woodland
ocean
desert
Parts of an ecosystem
• Habitat – the place
where an organism
lives
• Population – a group
of organisms of one
species
• Community – all the
organisms living in a
habitat
• Ecosystem – all the
living things and
their environment
Producers
• Plants harness the sun’s
energy in photosynthesis
• We call plants producers
because they trap light
energy from the sun and
convert it into chemical
energy during
photosynthesis.
• Consumers eat other
organisms
• Many animals eat only
plants -they are
herbivores. We also call
animals that eat plants
primary (first)
consumers
• The next group, called
the secondary consumers
are carnivores or
omnivores. They eat
primary consumers
Consumers
A Basic Food Chain
Plants absorb light from the sun,
which is turned into chemical
energy to grow. We call these
producers.
The herbivores eat the plants, they
are called Primary consumers.
Secondary consumers eat or
prey on primary consumers. They
can also be called predators
Food chain
• A food chain is a diagram which shows how energy flows
from producers through primary consumers to secondary
consumers in a natural ecosystem
• The arrows in a food chain diagram indicate the direction
of energy flow
• As energy flows along a food chain 90% is lost as the
animal uses energy for heat and movement.
oak tree
producer
mouse
primary
consumer
weasel
owl
secondary consumers
Food web
• Food chains rarely occur
in isolation
• Normally a producer is
eaten by several
herbivores
• Each herbivore is preyed
upon by several
predators
• A food web is a diagram
which shows a system of
interconnecting food
chains.
Woodland
Web
1
•diagram of interconnecting food chains.
1.
What is a food web?
2.
Name the producer?
Green plant
3.
From this food web write
down
a)
a complete food chain with 4
organisms
b)
a complete food chain with 5
organisms
c)
Name two herbivores?
beetle, grasshopper, snail
d)
Name a primary consumer?
beetle, grasshopper, snail
4. Name a secondary
consumer?
Woodland web 2
shrew, spider, wood mouse, owl
5. Name two prey animals
shrew, spider, wood mouse, beetle, grasshopper, snail
6. Name two predators
shrew, spider, wood mouse, owl
7. Name two animals which
are both predators and prey
shrew, spider, wood mouse,
8. Which animal will be least
numerous?
owl
Removal of species from a food web (C)
1. Predict and explain the effect of removing the holly leaf
miner from this food web on
a)
Pigeon population
Pigeons increase as they have
more food (holly leaf) to eat
b)
Blue tit population
Blue tits decrease as they have less
food (holly leaf miner) to eat
2.
Predict and explain the effect
of removing blue tits on
a) Sparrow hawks
Sparrowhawks decrease as they
have less food (blue tit) to eat
b) Woodpeckers
Woodpeckers stay the same as they have more insects to eat
but less blue tits to eat
• As energy flows along a
food chain there is a loss of
energy at each level
• 90% of the energy is lost as
heat and movement
• Only 10% is converted into
stored energy of an
animal’s body tissues meat ( muscle)
• Only this stored energy is
available for the next level
Energy transfer
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Food Pyramids
Food pyramids are diagrams which give us an idea of how
much energy is available at each level in a food chain.
There are two types;
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Pyramid of Numbers
Pyramid of Biomass
A Pyramid of Numbers shows the number of living things at each
level in a food chain.
A Pyramid of Biomass shows the total mass ( weight) of living
material at each level in the food chain.
A Pyramid of Biomass is the more accurate way of displaying how
much energy is available at each level because it takes into account
the fact that sometimes a very large organism, containing lots of
energy, may have lots of smaller ones living on it whose combined
energy is less.
To draw a pyramid you may sometimes be given figures but they are not
necessary. You only have to be aware that the greatest mass/numbers
will always be at the start of a food chain and least will be at the end.
For example :
For the food chain
lettuce
rabbit
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fox
The Pyramid of Numbers is;
fox
least numbers
rabbit
lettuce
greatest numbers
For some food chains the pyramid of numbers can look a bit strange
and this makes it an inaccurate representation of the available
energy.
For example,
chain;
rosebush
bird
ladybird
greenfly
rose
bush
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For the food
greenfly
ladybird
bird
This pyramid looks strange
because there is only one
large rosebush in the food
chain but there are
hundreds of tiny
greenflies living on the
rosebush
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The Pyramid of Biomass for the same food chain would look like
this;
bird
smallest combined
mass
ladybird
greenfly
rosebush
greatest combined
mass
This is because the combined mass, and therefore energy, of
all the rose bushes in the area is greater than that of the greenfly,
which in turn is greater than that of the ladybirds which is greater
than that of the birds.
This makes the Pyramid of Biomass a more accurate
representation of the energy available.
• A population is a group of
living things of the same type
e.g. sparrows, foxes, daisies
• The size of a population
changes from time to time
• How big a population gets
depends on the number of
births (birth rate) and the
number of deaths (death rate)
• A population gets bigger if the
birth rate is greater than the
death rate (A - B)
• A population will remain stable
if the birth rate equals the
death rate (C)
• A population gets smaller if the
birth rate is less than the death
rate (D)
Population growth
Growth limiting factors
• As a population grows its
growth usually slows down
due to growth limiting factors
• There are many ways in
which population growth is
slowed down
• The main limiting factors are
• Lack of food – weaker
individuals die due to
competition
• Lack of space –
overcrowding makes it
easier for disease to spread
• Disease- kills weaker
animals
• Predators- eat lots of them
Population Graph
• Under ideal conditions a
population will grow
slowly at first as
reproduction is just
beginning A
• Growth rate rapidly
increases due to high BR
and low DR (no limiting
factors) B
• Finally several
generations will be alive
and all reproducing - the
population size rises
almost vertically in a
population explosion C
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• Competition occurs
when organisms have
the need for the same
resources
• Animals compete for
resources which are
in short supply e.g.
food, water, shelter
• Any animal that fails
to get the minimum
requirements will die
• Only the best
competitors survive
Competition
Competition between plants
• In plant communities,
competition is mainly for
light
• Light
• Water
• Soil nutrients
soil nutrients
water
Effects of competition
• Red squirrels are
losing habitats in
competition with grey
squirrels
• Gannets which don’t
get a nesting site will
not mate
• Plants which don’t get
enough sunlight will
be stunted or yellow
Recycling ( Nutrient Cycles )
The ______
bodies and ______
waste products of organisms have important
nutrients
_______ locked up inside them.
These important nutrients include ______
carbon and _______.
nitrogen
In nature these nutrients are ________.
recycled
Without recycling these nutrients would not
___ be available to new
living members of the community.
Recycling involves the _____
decay of dead bodies and waste
bacteria
products by microscopic decomposer
__________ organisms ( _______+
fungi
____ ).
Clover – a leguminous plant
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root nodules
The recycling of nitrogen
The circulation of nitrogen is called the ________
Nitrogen _____.
cycle
Nitrogen cycle
Atmospheric
nitrogen
Denitrifying
Lightning
bacteria
storms
Soil nitrates
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Nitrogen-fixing bacteria
(in root nodules)
absorbed
Plant protein
through roots
Nitrifying bacteria
nitrites
eaten
Animal
protein
death
death
Faeces +
dead remains
Nitrifying
bacteria
Ammonium
compounds
Decomposers
(bacteria+fungi)
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Bacteria in the soil require ________
oxygen for __________.
respiration
In the _______
absence of oxygen, nitrates are ________
used up and not
replaced.
Also in the absence of oxygen, ___________
Denitrifying ________
bacteria break
nitrogen ____
gas which is released into the
down soil nitrates to _______
atmosphere
__________.
Nitrogen can enter the cycle in other ways.
Nitrogen
fixing ________
bacteria in the root nodules of leguminous
________ ______
plants change atmospheric nitrogen gas into nitrates.
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Also, during ______________
lightning storms the energy generated during a
combine forming
flash causes nitrogen and oxygen to ________,
oxides
of nitrogen
dissolve in rain water to form
________________which
then ________
nitrates
______.
An _______
artificial way is to add a chemical _______.
fertiliser