The Biosphere
Standard Grade Biology
What is an ecosystem, population,
community, habitat?
What is an Ecosystem?
Investigating an Ecosystem
3 Stages
• Collecting and counting samples of
organisms
• Correct identification of organisms
• Measuring the physical conditions
present in the environment
State a way of measuring biotic factors in
an area and state possible errors and
ways to overcome them.
What is the definition of abiotic and give
some examples of abiotic factors.
Abiotic factors
(Non living factors which affect the organisms living in a
particular place)
•
•
•
•
•
pH
Moisture
Light intensity
Temperature
Oxygen concentration etc
List some ways of measuring abiotic
factors, state possible errors and ways of
overcoming them.
Sources of Error
Effect of Abiotic Factors
• Green plants need light for
photosynthesis and will not grow where
light levels are low
• Most organisms will not survive
extremes of temperature, enzymes will
not function at low temperatures and
are denatured at high temperatures
• Water freezes at 0ºC and living
processes depend on liquid water.
Biotic factors
(Presence of Living Factors)
• Presence or absence of predators
• Competition
• Consumers
Be able to make and use branched keys
and paired statement keys.
Keys
What is a producer? Consumer? Herbivore?
Carnivore? Omnivore?
Food and Energy in an Ecosystem
• What always comes at the start of a food
chain?
• What do the arrows in a food chain
represent?
Food chains
• From the following food web pick out 3
food chains.
Food Webs
• In what ways is energy lost along a food
chain?
• If a population is increasing, what do you
know about the birth rate and the death
rate?
• List 3 things that can limit the growth of a
population.
Population Growth
• Populations grow when the birth rate
is greater then the death rate.
• Populations stop growing when growth
limiting factors come into play:lack of space (prevents breeding),
disease, shortage of water or food,
predators, build up of toxic waste.
• Where on the following graph is death rate
and birth rate equal?
Population Growth Curve
a.
b.
c.
d.
Growth in numbers is slow as individuals grow in size
As individuals mature and reproduce the rate of increase in numbers is at
a maximum
As food begins to run out and waste (toxins) build up the rate of
population growth slows down
Birth rate = Death rate, numbers are steady
World Population
• List 5 factors that limits population growth.
Pyramids
Pyramid of Numbers
• What does a pyramid of biomass
represent?
Pyramid of Biomass
• What do animals compete for?
• What do plants compete for?
Competition
• Animals compete for food, water,
shelter, space (territory), mates
• Plants compete for light, space, water,
minerals.
Effects of competition
• The stronger competitor gets all the
food and the weaker competitor can die
out.
• The stronger competitor can also die
out if it runs out of food, water, space
or toxic waste builds up.
• What do plants use nitrogen to make?
Nitrogen
• Nitrogen is a nutrient
• It is used to make protein by animals
+ plants
• It is constantly recycled in the nitrogen
cycle
• The nitrogen cycle is possible because
of the action of bacteria.
• Draw the nitrogen cycle. Include:
nitrification, denitrification, nitrogen
fixation, decomposition, excretion, eating.
Core Nitrogen Cycle
• Go over the full version in your notes.
Dead plants,
animals
Urine &faeces
Plants make
protein
Ammonium
Compounds
Plants absorb
Nitrates through
their roots
Nitrites
Nitrates
• Why are some plants able to fix nitrogen
gas from the air?
Nitrogen Fixing Bacteria in the root Nodules of Peas, Beans and
Clover
Recycling of nutrients
• overview
Death + excretion
Nutrients in
living
organisms
Absorption
by living
things
Nutrients in dead
bodies + waste
Nutrients freed and
in environment e.g
in soil
Decomposition by
bacteria + fungi
Types of bacteria
• Nitrogen fixing (root
nodules of peas, beans
,clover)
• Fix nitrogen gas from air into
nitrates
• Nitrifying (soil)
• Change ammonia into nitrites
and nitrites into nitrates
• Denitrifying (soil)
• Change nitrates back to
nitrogen gas
• Decomposers (bacteria and
fungi)
• Bacteria + fungi which
decompose dead plants +
animals into ammonia
• Draw a diagram of the carbon cycle.
Include: fossilisation, burning, respiration
and photosynthesis.
• What is an indicator species?
Indicator species
A species whose presence or absence tells us about the
conditions present in the ecosystem
• Mayfly + stonefly - found in
unpolluted water
• Sludge worms + rat tailed maggots
- can be found in polluted water
• Lichens found in areas with low levels
of air pollution
• How does sewage kill fish?
• Give 4 sources of pollution.
• Name the 4 main areas affected by
pollution.
Control and Management
• Give an example of poor management of
resources by humans and give a possible
solution.
Management of Resources
• The earth’s
resources will not
last forever
• Solutions must be
found to halt and
then reverse damage
Poor
Management
Possible Solution
Overfishing
in North Sea
Larger mesh in nets
allows small fish to
escape
Fishing quotas
Destruction
of
rainforests
Managed timber
production
Efficient food
production
Overgrazing
leading to
desertificati
on
Overuse of
chemicals
Changing farming
practices (crop
rotation, natural
fertilisers)