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Title: IB Biology SL - Ecology and Conservation
Description: A summary of chapter 9 (pages 423-493) "Ecology and Conservation", option C in the new curriculum (2015). Based on the new SL Biology book.
Description: A summary of chapter 9 (pages 423-493) "Ecology and Conservation", option C in the new curriculum (2015). Based on the new SL Biology book.
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IB Biology 4A
Option C: Ecology and Conservation
New Syllabus
p
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1: Species and communities
Limiting factors affect the distribution of species in a community
The distribution of a species depends on both biotic and abiotic factors
Biotic factors
-‐ living organisms in the ecosystem
-‐ inter-‐relationships between organisms
Abiotic factors
-‐ light (length and intensity)
-‐ water availability
-‐ temperature
-‐ salinity of soil or water
-‐ soil conditions
-‐ atmosphere
The distribution of species depends on their tolerance of limiting factors
Shelford’s law of tolerance
The levels of one or more chemical/physical factors determine the abundance and distribution
of a species in a ecosystem
...
Limits of tolerance and zones of stress: an animal example
The red kangaroo in Australia
-‐ distribution has been stable for over a century
-‐ distribution reflects interaction of temperature and precipitation
-‐ lives in hot interior of Australia (desert/savannah)
-‐ possesses certain adaptations that increase its tolerance to high temp
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423-‐493
Keystone species
Definition
a species that is not necessarily abundant but exhibits a strong control over the structure of a
community
Removal Experiment
-‐ way to determine whether an organism is a keystone species
-‐ sea star (Pisaster ochraceous) and mussel (Mytilus californianus)
-‐ sea star was removed from interdial area
-‐ mussel able to take over rocks and exclude algae and others from zone
-‐ sea star limited number of mussel
-‐ without sea star, diversity declined rapidly
-‐> sea star = keystone species: had control over diversity of community
Each species plays a unique role within a community
The unique role that a species plays in the community is called a niche
...
Spatial habitat
Area inhabited by any particular organism
For example: leopard frogs (Rana pipiens) live in the ponds of Indiana (USA) dunes, burrowed in
the mud between the grasses on the edge of the pond
...
a
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Interactions with other species
Competition
When two species rely on the same limited resource , one species will be better adapted to
benefit from the resource
Example 1:
-‐ USA: coyotes (Canis latrans) and red foxes (Vulpes vulpes)
-‐ both predators that eat small rodents and birds
-‐ coyotes inhabit grassland communities, red foxes inhabit edges of forests/meadows
-‐ forests removed (farmland) -‐> habitat of red fox overlapping with the one of the coyote
-‐ the two species are competing for a smaller food supply
-‐> the one less adapted is likely to become extinct
Example 2:
-‐ UK coastal dunes: natterjack toad (Epidalea calamita) and common toad (bufa bufa)
-‐ disturbance of the dune area limits the habitat available to both toads
Herbivory
A primary consumer (plant eater) that feeds on a producer (plant)
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423-‐493
Predation
Consumer (animal: predator) eating another consumer (animal: prey)
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Example 1:
-‐ Canadian lynx (Lynx Canadensis) and arctic hare (Lepus arcticus)
-‐ lynx preys on hare
Example 2:
-‐ blue heron (Ardea Herodias) and frogs in the pond of sand dune ecosystems in the USA
-‐ blue heron preys on frogs
Parasitism
A parasite lives on or in a host and depends on host for at least part of its life cycle
...
Example 1:
-‐ Plasmodium causes malaria in humans
-‐ reproduces in the human liver and red blood cells
-‐ Part of the life cycle of Plasmodium takes place in body of Anopheles mosquito
-‐ mosquito transmits malaria parasite from one human to another
Example 2:
-‐ Leeches (Hirudo medicinalis, live in ponds) and humans or other mammals
-‐ puncture skin of host and secrete enzyme into wound to prevent clotting
-‐ can ingest several times their weight in blood
Mutualism
Two species live together and both benefit from the relationship
...
It states that no two species in a
community can occupy the same niche
...
Example
-‐ two different species of Paramecium: P
...
caudatum
-‐ when each species grown in separate culture, they did equally well
-‐ when cultured together with a constant food supply, P
...
aurelia out-‐competed P
...
It is the potential mode of existence, given the adaptations of the species
...
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IB Biology 4A
Option C: Ecology and Conservation
New Syllabus
p
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The observer
moves along a fixed path to count the occurrences of that population among the path
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423-‐493
C
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5-‐20% of the Sun’s energy is trapped by
plants (producers) and transferred to the primary consumer
...
Energy is lost as heat as
it moves from producer to primary consumer to secondary consumer etc
...
When an organism dies, its body is
decomposed and the energy is transferred to decomposers
...
The width
of the block indicates how
much energy it contains
...
Gross production
the total amount of energy trapped in the organic matter produced by plants per area per time in
kilojoules: kilojoules per metre squared per year (kJ m-‐2yr-‐1)
Net production
the gross production minus the energy lost through respiration (kJ m-‐2yr-‐1)
Biomass
dry weight of an organism, measured in grammes per metre squared per year (g m-‐2yr-‐1)
-‐> actual weight of organism includes large parts of water -‐> needs to be removed and the dry
weight measured
Calculating gross production and net production
Gross production – respiration = net production
Pyramids of biomass
Biomass is lost during respiration
at each trophic level
...
Both are excreted and
the biomass of glucose is lost
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423-‐493
Difficulties of classifying organisms into trophic levels
A food web gives a true but complicated picture of what is being eaten in an ecosystem
...
Typically, the organisms at higher and higher trophic levels are
increasingly more efficient
...
Conversion ratio in sustainable food production
The feed conversion ratio (FCR) is a measure of the efficiency of an animal’s ability to convert
feed mass into increased body mass
...
The FCR shows us how much
energy is being lost durinf the transfer from plant to animals, as seen with energy pyramids
...
It’s the
reason why some species gradually replace other species in one particular area
...
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IB Biology 4A
Option C: Ecology and Conservation
New Syllabus
p
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The type of stable community is predicted by climate
...
If a climax community is extensive and well developed, it’s called a
biome
...
Certain species are found in
one type of biome and not in others
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423-‐493
Tundra
-‐ high elevations with low temperatures and low precipitation
-‐ plants and animals are adapted to a cold and dry environment
Coniferous forest
-‐ high elevations with less cold temperatures and slightly more rainfall
-‐ ground freezes during some months of the year
-‐ coniferous trees adapted for conserving water when its frozen
-‐ animals have heavy coats of fur in winter but lose some in the summer
Temperate forest
-‐ lower elevations, temperature warmer, more water available
-‐ plants and animals must be adapted for a wide range of conditions
-‐ summer: warm, lots of water / winter: cool, water might be unavailable because frozen
-‐ trees will lose leaves in winter to reduce water loss
Desert
-‐ low elevations with warm temperatures and little precipitation
-‐ plants and animals have specific adaptations to survive in this extremely hot and dry biome
Tropical forest
-‐ low elevations with warm temperatures and very high moisture
-‐ extremely productive
-‐ high primary productivity due to combination of high temperatures and high rainfall
Gersmehl diagrams
Another way of describing energy flow and
nutrient recycling within the main ’stores’ of
an ecosystem
...
Included in diagram:
-‐ input (eg nitrogen, oxygen, carbon)
-‐ output (eg loss of nutrients by leaching)
-‐ flows (eg from biomass to litter)
An example of humans interfering with nutrient cycling
Collapse of marine fisheries as a result of overfishing and habitat loss -‐> affected nutrient cycling
-‐ fish recycle nutrients (esp
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A closed ecosystem
Most ecosystems are open
...
No natural system
on Earth is considered to be a closed system, but the entire planet can be considered ‘almost’
closed (large amounts of light energy enter earth and eventually return to space as heat, but no
matter is exchanged)
...
In a CES, waste products made by a species must be used by at least one
other species and converted into eg oxygen, food and water -‐> involves at least one autotroph
and sunlight must be available
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423-‐493
C
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-‐> environmentally friendly alternative to chemical control
-‐> but there’s always a risk when introducing a new organism into a ecosystem
Introduced alien species can become invasive
Introduction of cane toads (Bufo marinus) into Australia in the 1930’s
-‐ cane toad imported from Hawaii + released in Queensland to control beetle pests of sugar cane
-‐ larvae of the beetle eat roots of cane and the plants die
-‐ cane toad was being used to control beetle infestations of sugar cane crops in Hawaii
-‐ toads released in Queensland without risk assessments being done
-‐ rapid growth of toad population but no effect on beetles whatsoever
-‐> toads had found other food sources
-‐> cane toad pest
Competitive exclusion can affect endemic species
-‐> no two species can occupy the same niche
Example: Small skinks in Australia
-‐ disappeared when cane toads introduced
-‐ both species are insectivores -‐> skinks outcompeted by toads due to voracious appetite of toad
Absence of predators can affect endemic species
-‐ cane toads are extremely poisonous (glands behind ears contain toxic substance)
-‐ predator species in Australia affected by eating cane toads
-‐ turtles at risk since able to eat cane toads large enough to kill them with toxic
-‐ lizards die after eating cane tiads
-‐> absence of successful predator is significant factor in the population explosion in Australia
Kudzu: an introduced alien species
-‐ Kudzu introduced from Japan to USA as an ornamental plant to solve problem of soil erosion
-‐ grows rapidly -‐> grows in many conditions, crushes other plants
-‐ recognized as pest weed
Biomagnification
Process, in which chemical substances become more concentrated at each trophic level
...
After ingestion, they’re stored in
fatty tissues of the consumer
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423-‐493
-‐ some chemicals deliberately put into environment to kill insect pests
-‐ dichlorodiphenyltrichloroethane (DDT) is one of those pesticides
-‐ when first used not known that it doesn’t break and can persist for decades in environment
-‐ DDT commonly sprayed on plants and eventually entered water supply
-‐ absorbed by microscopic organisms (zooplankton) -‐> eaten by small fish -‐> large fish -‐> osprey
-‐> DDT built up in fatty tissues
Consequences of biomagnification
-‐ first sign of problem with DDT: decline in number of predator birds
-‐> eggs of birds easily cracked (mother sitting on them cracked them)
-‐ discovery: DDT building up in the tissue and interfering with calcium needed for shells
-‐> DDT banned in USA
-‐ bird population began to recover
DDT also affects humans:
-‐ eat fish containing DDT
-‐ DDT stored in fat -‐> level of DDT in breast milk 6x higher than level in blood of mother
The trade-off between DDT pollution and malarial parasite control
Malaria is the most deadly vector-‐borne disease in the world
...
DDT pollution
DDT is a persistent organic pollutant
...
DDT levels in human blood have declined sharply and DDT has
disappeared from the breast milk of nursing mothers
...
-‐ IRS used in houses = DDT found in breast milk
-‐ no IRS = hundreds of mosquitoes enter house
-‐ health officials would like to use DDT but donor governments refuse to allow DDT spraying
Macroplastics in the marine environment
Macroplastics are pieces of plastic bigger than 5 mm and can pose a serious threat to marine
wildlife
...
-‐ amount and distribution in marine environment has steadily increased over past 20 years
-‐ act like sponges and soak up toxic chemicals in marine environment
-‐ large surface area -‐> plenty for chemicals to stick to
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IB Biology 4A
Option C: Ecology and Conservation
New Syllabus
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Attempts to eradicate them:
Example: Black striped mussel, Australia
-‐ multiplied fast and tucked to ships -‐> threat to tropical waters -‐> damage to pearl industry
-‐ eradication: poured chemicals into the sea -‐> death of all organisms
Example: Oriental fruit fly, Japan
-‐ larvae ate fruit -‐> damaging crops
-‐ eradication: sterile insect release (SIR): released sterile males, eggs not viable
Analysis of data illustrating the cause and effects of biomagnification
Bioaccumulation is the net accumulation over time of POPs or heavy metals within an organism
from both biotic and abiotic sources
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423-‐493
C
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They’re called
indicator species
...
The number of organisms in
each group is multiplied by a factor that is determined by how sensitive the organism is to
pollution
...
The more
sensitive organisms are in the sample, the higher the quality of the water in the river/stream
...
Richness and evenness are components of biodiversity
Biodiversity can be described in two ways: evenness and richness
...
25%)
-‐ analyze squares
-‐ process data: calculate mean number of organism in subsample
-‐ mean number * number of squares = estimated population in field
Management of conservation areas
On order to maintain beauty & diversity in a nature reserve, it is important to manage it
efficiently
...
Restoration
-‐ attempts to return the land to its natural state
-‐ requires managers to use active management techniques (eg cutting, burning, replanting)
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IB Biology 4A
Option C: Ecology and Conservation
New Syllabus
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-‐ maintain habitat
-‐ remove invasive species
-‐ defend against predators
-‐ maintain large area -‐> maintain large population -‐> maintain large genetic diversity/gene pool
If the population and/or the gene pool is too small or the destructive forces (eg invasive species)
cannot be controlled, in situ conservation is no longer enough
...
Captative breeding
-‐ increase reproductive output
-‐ secure survival of offspring in zoos: generates new funds
Artificial insemination
take semen from male and place it into female body
Embryo transfer
transfer embryo to a surrogate mother: in vitro fertilisation to increase offspring
Cyrogenics
sperm, egg cells, embryos frozen for future use
Human-‐ raising
Human-‐raising when mother can’t/doesn’t care for young
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IB Biology 4A
Option C: Ecology and Conservation
New Syllabus
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Helena Boxwood
-‐ extinct in its natural habitat, St
...
Latitude gradient
effect of climate on species diversity
-‐> the farther away form equator, the fewer species can be found
Elevation gradient
effect of altitude on species richness
-‐> increase in altitude = increase in species richness -‐> reaches mid-‐point bulge -‐> declines
Area effect
effect of area on species richness
-‐> the larger the area, the more species it can support
The impact of edge effect on diversity
Edge effect describes what occurs at habitat boundries where two bordering communities
influence each other
Title: IB Biology SL - Ecology and Conservation
Description: A summary of chapter 9 (pages 423-493) "Ecology and Conservation", option C in the new curriculum (2015). Based on the new SL Biology book.
Description: A summary of chapter 9 (pages 423-493) "Ecology and Conservation", option C in the new curriculum (2015). Based on the new SL Biology book.