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Transcript of Ecology
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ECOLOGY
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Ecology is the scientific study of:
organisms in relation to their environment
this includes the relationship of organisms with:
organisms
each other
non-living components of their environment
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Temperature affects distribution of vegetation on earth
Polar Temperate Tropic
Polar
TropicTemperate
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Predator & Prey interactions
control each other’s population size
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Biotic factor living organismse.g. predators, competitors,
parasites
Abiotic factor non-living factors which
influence organisms e.g. light, temperature,
soil, rainfall
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Habitat is the particular locality in an environment
in which an organism lives
FOOD
SPACE
WATER
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Examples of habitat:
soil burrows (earthworms)
rock pools (limpets, barnacles, top shells)
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Population
is the group of individuals of the same species living in a particular area at the same time
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Community includes all the
populations of all the species within an ecosystem
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Ecosystem is a natural unit composed of living and non-
living components whose interactions result in a stable self-perpetuating system
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Or more simply, an ecosystem
is a community of organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system
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Examples of
ecosystems
pondsan oak treea fielda rockpoolthe sea
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Competition for resources can be between individuals of the:
same species Intraspecific competition
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Competition for resources can be between individuals of the:
different species
Interspecific competition
Camels, goats and sheep compete for
food.
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Question: SEP, 2007
a) Distinguish between intraspecific and interspecific competition. (2)
b) Explain why intraspecific competition is likely to be more intense than interspecific competition. (1)
Members of a species use the same resources but different species use different resources.
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c. i) List TWO resources that animals compete for. (2)
space, food, water,mate
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ii) List TWO resources that plants compete for. (2)
Space, light, water, ions in soil, carbon dioxide
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d) What is the effect of competition on the growth of a population? (1)Reduces the growth rate of a population.
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Question: MAY, 2008
Before 1859 there were no wild rabbits in Australia but
in 1859 some domestic rabbits escaped from their
pen, when it was swept away by a flood. These rabbits ran wild and bred at such a rate that parts of Australia soon became overrun with them. The following graph shows
how the population of rabbits increased with time.
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a. Describe and explain the growth of the rabbit population at stages 1, 2 and 3. (12)
STAGE 1:Slow increase in population.Few individuals able to reproduce.Rabbits need to acclimatise. STAGE 2:Rapid increase in population.Many individuals able to reproduce.Resources are abundant.
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a. Describe and explain the growth of the rabbit population at stages 1, 2 and 3. (12)
STAGE 3:Population stable.Resources become limited and can support a certain number of individuals.
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b. Discuss the effect of the observed growth rate of rabbits on agricultural activity in Australia. (2)Rabbits fed upon crops and caused damage to agriculture.c. Suggest how the observed growth rate of rabbits affected the natural ecosystem in Australia. (2)Many wild plants were eaten leading to loss of plant species, more soil erosion as soil was no longer covered by vegetation.
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An ecosystem consists of three nutritional groups:
a) PRODUCERS
b) CONSUMERS
c) DECOMPOSERS
–autotrophic plants
–heterotrophic organisms, mainly animals
– saprophytic bacteria & fungi– break down dead matter to
return nutrients to the soil
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Question: SEP,2012
Distinguish between producers and consumers.(4)
Question: MAY,2011
Distinguish between a community of plants and a population of plants. (2)
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Niche is the role or job of an organism within the
community
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Food chains
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Food chains show: the movement of food energy from one
organism to the next
PRODUCER PRIMARY CONSUMER
SECONDARY CONSUMER
TERTIARY CONSUMER
1st Trophic level
2nd Trophic level
3rd Trophic level
4th Trophic level
Trophic level = feeding level
Top carnivore
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Ecosystem: Field
hawk sparrow rcaterpilla leaves
Ecosystem: Oak tree
Ecosystem: Freshwater pool
thrush larvaeinsect oak tree
le waterbeet tadpolealgae
ladybird aphid grass
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FOOD WEBS are made up of many food
chains linked together give a more complex
picture of how animals feed
are more stable than food chains
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In the food web shown:
1. There are …… primary consumers.
2. The top carnivore is the ……… .
5
owl
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3. Suppose all the woodmice died from a poison,
i) the acorn would (increase / decrease).
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3. Suppose all the woodmice died from a poison,
i) the acorn would (increase / decrease).
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3. Suppose all the woodmice died from a poison,
i) the acorn would (increase / decrease).
ii) the weasel would (increase / decrease).
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3. Suppose all the woodmice died from a poison,
i) the acorn would (increase / decrease).
ii) the weasel would (increase / decrease).
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4. Draw a food chain with 5 links from this food web.
5. In this food web, the shrew can be either a ………………. or a ……………….. consumer.
owloak leaf greenfly ladybird shrew
secondary tertiary
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Question: MAY, 2004
The following organisms can be found in the same habitat:
weasel, rabbit, greenfly, green plant, caterpillar, small bird and ladybird.
Construct a food web to include all the organisms found in the list above.
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green plant
ladybird
rabbit greenfly caterpillar
weaselsmall bird
weasel, rabbit, greenfly, green plant, caterpillar, small bird and ladybird
Weasel eats small mammals & birds.
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Three types of pyramid:
a) Pyramid of Numbers b) Pyramid of Biomass c) Pyramid of Energy
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a) Pyramid of Numbers
shows the total number of individuals at each trophic level
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a) Pyramid of Biomass
indicates the weight of all individuals at each trophic level
biomass is the weight of living material
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Draw a pyramid of numbers & of biomass for this food chain:
Pyramid of Numbers
Rosebush Aphid Ladybird
Pyramid of Biomass
RosebushAphid
Ladybird
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Question: SEP, 2012From the food web write a food chain including four trophic levels. (2)
[Any food chain as long as 4 trophic levels are present]
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b) In the space below draw a pyramid of numbers for the food chain you answered in ‘a’. (In your diagram label each trophic level).
(3)
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a) Pyramid of Energy
shows the transfer of energy from one trophic level to the next
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90% loss in energy at EACH trophic level
Pyramid of Energy
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Energy is lost in:1. excretion2. moving about3. keeping the
body warm4. egestion5. respiration
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Question: SEP, 1996
Give a reason why the number of trophic levels seldom exceeds 5. (1)
Great (90%) losses in energy at every trophic level.
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Question: SEP, 1996
Approximately what percentage of all the energy present at one trophic level is transferred to the next higher trophic level? (1)
Only 10% of the energy is transferred to the next trophic level.
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Question: MAY, 1999
Why is energy not recycled in ecosystems?(1)
Lost as heat to the surrounding environment.
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Compare flow of energy & flow of nutrients in ecosystems:
Flow of ENERGY is LINEAR but flow of NUTRIENTS is CYCLIC.
SUNLight
energy
Bioticcomponent
Heat
energy
Abioticcomponent
nutrients
ENERGY FLOW
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SHORTENING THE FOOD CHAIN the shorter the food chain, the more people
can be fedREASON: the 90% ‘wastage’ of energy that occurs between each trophic level is cut down
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Why do leaves look green?
Green light is reflected by the leaf.
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ENERGY FLOW THROUGH PRODUCERS
Only 1% of the light falling on a leaf is used in photosynthesis. What happens to the rest?
30% evaporates water from plant
20% is reflected from plant
40% warms up soil, air and vegetation [transmitted]
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The chemical energy built by the plant is
used by the plant for:1. Respiration2. Growth
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The energy used for: respiration :
is not available for the next trophic level
growth:is passed on the next trophic level
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ENERGY FLOW THROUGH CONSUMERS
over half of the energy in the grass the cow eats, is passed out of the body in faeces
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Absorption by living
things
Decomposition by bacteria and fungi
NUTRIENT CYCLING
Excretion and death
Nutrients in living
organisms
Nutrients in environment available for
use
Nutrients in dead bodies and waste
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all living things need carbon to make: carbohydrates fats proteins
The Carbon Cycle
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Processes that :
1. Respiration2. Decomposition3. Combustion
1. Photosynthesis
CO2 in air
0.03%ADD: REMOVE:
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The Carbon Cyclecarbon dioxide
gas
carbon compoundsin animals
carbohydrates ingreen plants
carbo n co mpo u nd sin de ad o rg an ic matte r
(hu mus)coal
death fossilisationdeath
photosynthesis
plantrespiration combustion
animalrespiration
animalnutrition
decay
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1) More fossil fuels are being burnt than in the past.
2) Large areas of forest are being removed and so less CO2 is removed from the air.
The average CO2 concentration in the air is increasing. Give two reasons for this.
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How can the greenhouse effect be:1) an advantage to plants? Plants grow more as photosynthesis increases due to a higher temperature.
CO2 is a greenhouse gas: causes warming of atmosphere
2) a disadvantage to plants? More chances to wilt as more water is lost by evaporation.
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plants & animals need nitrogen to make: proteins
The Nitrogen Cycle
Nitrogen 78%
plants cannot use atmospheric nitrogen
Gases in air.
From where do plants get the nitrogen they
need?
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From the SOIL Mention THREE ways by
which these ions can end up in the soil.
2. Burning fossil fuels (generates nitric oxide)
1. Erosion
3.
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Processes that :
1. Lightning2. Nitrogen-fixing
bacteria3. Nitrifying bacteria
1. Absorption by plants2. Leaching3. Denitrifying bacteria
Nitrates in soil
ADD: REMOVE:
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The Nitrogen Cycle
NITROGEN(in the air)
Nitrogen-fixing bacteria
Denitrifyingbacteria
SOILNITRATES
lightning
Plant protein
Animal protein
AMMONIA
Dead organisms and faeces
NITRITES
Nitrifyingbacteria
Nitrifyingbacteria
taken upby plants
decompositionexcretion
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LIGHTNING causes N2 & O2 to combine at high
temperatures and nitrogen oxides form these oxides are washed into the soil
by rain where they form nitrates
Process that add nitrates to soil
O2 & N2: most abundant gases in air.
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NITROGEN-FIXING BACTERIA absorb nitrogen gas from the air and ‘fix’ it into a
form which the plant can use to build protein
change nitrogen gas into ammonium compounds
Root nodule full of bacteria.
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NITROGEN-FIXING BACTERIA live:
Root nodules
1) freely in the soil e.g. Clostridium2) in the root nodules of leguminous plants
(e.g. peas, beans, clover) e.g. Rhizobium
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Mutualism: is the relationship between nitrogen fixing
bacteria and leguminous plants
Plant gains:Ammonium compounds
Bacteria gain:1. Food2. Shelter
carbohydrate
N
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SYMBIOSIS: is a relationship between two organisms
MUTUALISM: is a type of symbiosis is a close relationship between two different
organisms where both benefit from each other
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When leguminous plants decay: the nitrogen which the bacteria have fixed
goes into the soil where it can be used by plants
Nitrogen-fixing bacteria are very useful because they increase the amount of useful
nitrogen compounds in the soil.
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Leguminous plants:
1.can live in soils poor in nitrates
2.are used in crop rotation to increase nitrates in soil
Clover
Beans
Peas
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NITRIFYING BACTERIA change ammonia into nitrites and then into
nitrates this is called nitrification ammonia is present in:
dead remains animal waste
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Production of nitrates from organic nitrogen involves decay and nitrification
nitrate
nitrite
ammonia
Organic nitrogen in dead bodies or
animal wasteDecay
Nitrification
Nitrification
Nitrobacter
Nitrosomonas
Bacillus
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1) Absorption by plantsroot hairs provide a large
surface area for absorption
salts are absorbed by: diffusion active transport
Three processes remove nitrates from the soil
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2) Leachingis when salts are lost
from the soil and reach the groundwater
Nitrates
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3) Denitrifying bacterialive in water-logged soilcarry out denitrification by changing
nitrates into nitrogen gase.g. Pseudomonas
Why do farmers dig up the land?To improve drainage and aeration
thus denitrification does not occur.
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Distinguish between nitrification and denitrification. (5)
Nitrification is carried out under aerobic conditions but denitrification under anaerobic conditions.In the process of nitrification, ammonia is converted into nitrites and then into nitrates.In denitrification, nitrates are converted into nitrogen gas.
Question: SEP, 2011
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The Water Cycle
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Question: SEP, 2011
During a fieldwork activity a biology student used a pitfall trap for sampling animals.The diagram above shows the pitfall trap.a) List ONE advantage and ONE disadvantage of this method. Advantage: cheap; easy to set up; no maintenance needed; animals remain alive (1) Disadvantage: animals eat each other; flooding of pitfall trap if it rains (1)
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The photo below shows a student using another sampling technique.
The photo below shows a student using another sampling technique. a) Name the piece of apparatus being used to
sample plant density and diversity in the field. (1)Quadrat
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The following photo shows three biology students during fieldwork in a woodland area.
Explain why the sampling equipment shown in the diagram cannot be used for animals. (1)
Animals move out of the quadrat and so cannot be counted.
Question: SEP, 2013
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