Ecology
Yr 12 Revision
Revision 1
Species Interactions
Year 12 Biology
Ecology
Can be studied by:
• Populations: single spp in a habitat
• Communities: all spp in an area (a group of
populations)
• Ecosystems: includes living and non-living
factors.
Factors that affect organisms
• Abiotic (not living):
– Temperature (dormancy, hibernation,
migration)
– Light (day length, photosynthesis)
– Salinity (freshwater vs marine)
– Oxygen (aerobic vs anaerobic)
– pH (soil and water)
– Humidity (invertebrates need damp skin)
– Water flow
Factors that affect organisms
• Biotic (living):
– Competition (inter and
intra) for food, mates,
territory
– Parasitism
– Predation
– Mutualism
– Commensalism
– Disease
Species Interactions
• “How species interact with each other and
their physical environment.”
• “A behaviour that changes the fitness of a
participating agent.”
Mutualism
• Mutualism involves an intimate
association between two species
that offers advantages to both.
• For example:
– birds pollinating plants while getting
nectar
– Cleaner fish getting food
Commensalism
• In commensal
relationships two species
form an association where
one organism benefits
and the other is neither
harmed or helped.
Competition
• Competition is the endeavor of 2 or more
organisms to gain the same particular thing.
• Competition occurs when resources are limited
• Leads to a reduction in
the survivorship, growth,
and/or reproduction of
the competing individuals.
• Inter & intra
Parasitism
• Parasitism is a common
exploitative relationship in
plants and animals.
• The parasite exploits the
resources of the host (e.g. food,
shelter, warmth) for its own
benefit.
• The host is harmed but usually
not killed
• For example caterpillar host to
wasp larvae.
Predation
• This is an interaction where one
species eats another.
• Predator vs. Prey
• This can include both animalanimal, and animal-plant
interactions
Amensalism
• One disadvantaged, other
unaffected
• The bread mould Penicillium is a
common example. Penicillium
secrete penicillin, a chemical that
kills bacteria.
• A second example is the black
walnut tree, which secretes a
chemical that harms or kills
some species of neighbouring
plants, from its roots.
Species Interactions
Type of Interaction
Mutualism
Commensalism
Competition
Predation, Parasitism,
Herbivory
Amensalism
Sign
+/+
+/0
-/+/0/-
Effects
both species benefit from
interaction
one species benefits, one
unaffected
each species affected
negatively
one species benefits, one is
disadvantaged
One species is
disadvantaged/one species
unaffected
Old Exam Questions 07
•
Honeydew excreted by phloem-sap-sucking scale insects (Ultracoelostoma sp.)
living on the bark of beech (Nothofagus) trees plays an important role in
ecosystem processes in native New Zealand beech forests. The only part of the
insect normally visible is a long white hair, ending with a drop of honeydew
obtained from the phloem. This provides food for honeyeaters such as bellbird, tui,
stitchbird, and kaka. Last century, the German wasp Vespa germanica was
accidentally introduced to New Zealand. The wasp thrived on the honeydew of the
beech forests. The German wasp has since been joined by an even more
aggressive species – the common wasp Vespa vulgaris.
(a) Name and describe each of the following relationships:
(i)
The relationship between the scale insect and the beech tree.
Name of relationship:
Description:
(ii)
The relationship between the wasp and the scale insect.
Name of relationship:
Description:
Old Exam Question 05
• The New Zealand mistletoe, Peraxilla tetrapetala, is a semi-parasitic plant that
gains water and nutrients from its host plant, which remains unharmed.
Mistletoe flowers provide birds with fruit and nectar. Parasitic insects live inside
leaf tissue in growths called galls.
For the mistletoe flowers to be pollinated, they need to be opened by native birds
such as the tui and the bellbird or a tiny native bee. The pollen is then
transferred to the next flower that the birds or bee visits. Introduced animals
have not yet learned how to open the mistletoe flowers, so cannot act as
pollinators. Un-pollinated flowers will not produce seeds.
(a) Name and describe two different interspecific relationships involving the mistletoe.
Relationship 1:
Relationship 2:
(b) Explain how the mistletoe is affected by the other species in each of the relationships given in your
answer to part (a).
Relationship 1:
Relationship 2:
http://www.nzqa.govt.nz/nqfdocs/ncea-resource/schedules/2005/90461-ass-05.pdf
Biozone
• Refer to Page 111 – 119
• Complete for homework, if not already done
in class during the year
Revision 2
Niche
• Niche The limits, for all important environmental
features, within which individuals of a species can
survive, grow and reproduce.
• Ecological niche
The 'occupation' or 'profession' of an organism or
species.
Eg
–
–
–
–
–
Herbivore/carnivore/omnivore?
Where it lives?
Adaptations?
Life history?
Feeding behaviour/times
Gause’s Principle or Competitive
Exclusion Principle
• Gause's principle The idea that if two competing
species coexist in a stable environment, then they
do so as a result of differentiation of their
realized niches; but if there is no such
differentiation, or if it is precluded by the habitat,
then one competing species will eliminate or
exclude the other.
• “No two species can occupy the same ecological
niche in the same habitat for an indefinite period
of time”
Example:
• Flax looper caterpillar adult
• Flax notch caterpillar, adult
• Resource partitioning The differential use by
organisms of resources such as food and
space.
Example 2:
• Different beak lengths allow estuarine birds to
specialise on prey living at different lengths.
Adaptations
• Changing to suit their
environment – increases
chances of survival and
reproduction
• Behavioural: What they do
• Structural: Their physical
characteristics
• Physiological: A Response to a
specific external stimulus in
order to maintain balance
Behavioural/Structural/Physiological?
•
•
•
•
•
•
Tanning skin in response to sunlight?
Hibernating over winter?
Callused skin in response to regular contact?
Beak of bird adapts to task?
Bird calls or signals?
Thick fur of a polar bear?
Behavioural/Structural/Physiological?
• Tanning skin in response to sunlight? P
• Hibernating over winter? B
• Callused skin in response to regular contact? P
• Beak of bird adapts to task? S
• Bird calls or signals? B
• Thick fur of a polar bear? S
Food and Feeders
• Autotroph An organism that is independent of
outside sources for organic food materials and
manufactures its own organic material from
inorganic sources.
• Heterotroph An organism with a requirement
for energy-rich organic molecules (animals,
fungi and most bacteria).
Food Chain
• A group of organisms interrelated by the fact
that each member of the group feeds upon on
the one below it.
• All must begin with a producer. (autotroph)
Food Web
• A complex of interrelated food chains in an
ecological community.
Question
• What would happen if all of
the rats were killed?
• Who would it affect?
• Predator/ Prey?
Trophic Levels
• Trophic level Position in the food chain
assessed by the number of energy-transfer
steps to reach that level.
Energy Flow
• Energy is passed on through trophic levels.
• At each link energy is lost and only 10% of the
energy is passed on.
• This is why most food chains are only about 4
links long, too much energy is lost
• Energy flow can be affected by blocking a link.
Eg by overfishing, pollution, drought,
removing predators…..all of which upset the
balance
Old Exam Question 2005
• The sand scarab beetle lives in amongst pïngao and marram
grass and eats the roots. The scarab beetle is active during
the night and during the day it burrows deep into the sand.
The female deposits large numbers of eggs singly amongst
the roots of marram grass and pïngao.
• (c) Describe THREE aspects of the ecological niche of the
sand scarab beetle.
• (d) Describe ONE behavioural adaptation of the scarab
beetle and explain how this enables the sand scarab beetle
to survive in the dune environment.
• schedules/2005
Old Exam Question 2004
• Revegetation consisted of planting native trees,
particularly nectar-producing and berry-producing
species, in and around existing forest remnants to
gradually replace grassland and bracken fern with
forest.
• (d) What is the trophic level of nectar-feeding and
berry-feeding birds?
• Reports/2004
Revision 3
Community Patterns
• Species are not distributed randomly across a
community. Their distribution forms patterns
in a response to change in environmental
conditions.
• These include:
– Zonation
– Stratification
– Succession
Zonation
• When a species distributions fall into ‘bands’ or
‘zones’ across a habitat.
• Intertidal
Oceanic
Vertical vegetation
Zonation Continued……
• Zonation results from a constant change or
gradient of some environmental factor across the
environment. Eg tidal movement, temperature,
light
• Species can only tolerate
certain environments
Stratification
• This results from decreasing light intensity as
layers of vegetation filter out light.
Stratification Continued……
• Different layers possess different physical
conditions eg humidity, light intensity, wind,
temperature
• Consumer species usually establish separate
communities at each level eg kokako live in
canopy layers whereas fantails inhabit lower
layers.
Succession
• Succession The non-seasonal, directional and
continuous pattern of colonisation and
extinction on a site by populations.
Succession Continued…….
• Pioneer species are species which colonises previously
uncolonised land, usually leading to ecological succession.
These species are usually annuals, disappearing after the
second year when perennials take over.
• Annual –Completes life cycle in 1 year (Seed => death)
• Perennial – Flowers once per year and dies back in colder
seasons. Lives longer than just 1 year.
• Climax community The presumed endpoint of a
successional sequence; a community that has reached a
steady state.
Old Exam Questions 2005
QUESTION ONE: SANDY BEACHES
• Pïngao is a native coastal sand dune plant that traps
wind-blown sand in its leaf bases and root system. Pïngao
stabilises sandy coasts and creates a habitat in which
other native coastal plant species can settle and grow.
The first plants that grow are low lying ground covers,
then shrubs and later coastal trees including pöhutukawa
and püriri.
(a) Give the term for this change in coastal plants
over time from pïngao to pöhutukawa.
Continued……
• Marram grass is often found growing in the
same habitat as pïngao. Marram grass grows
more vigorously than pïngao under the same
conditions. Marram grass traps sand more
efficiently and has a root system that grows
more vigorously.
• (b) Explain the effect marram grass will have
on pïngao growing in the same area of a sand
dune.
• schedules/2005
Old Exam Question 2006
• QUESTION TWO: FOREST COMMUNITIES
• Below is a diagram showing the distribution of plant
species relative to drainage.
• (a) Give the term to describe the distribution pattern in
this community.
• (b) Explain why the distribution of the plant species in this
community shows this pattern.
• (c) Describe stratification.
• (d) Discuss how the canopy trees affect the abiotic factors
and the other species present in the forest.
• schedules/2006
Biozone
• Refer to page 91-97
• Complete for homework, if not already done
in class during the year
Quiz
• Ecology Quiz
Revision 4
Nutrient Cycling
• Only plants have the ability to capture the energy
of sunlight and change it into chemical energy.
(Photosynthesis)
• Oxygen is a waste product of PHS which is very
important to all aerobic organisms
• The glucose that is made is passed from one thing
to another through the food chain.
• The glucose can be stored by the plants as:
Starch, fats, proteins, vitamins.
Energy Flow
• Energy is passed on through trophic levels.
• At each link energy is lost and only 10% of the
energy is passed on.
• This is why most food chains are only about 4
links long, too much energy is lost
• Energy flow can be affected by blocking a link.
Eg by overfishing, pollution, drought,
removing predators…..all of which upset the
balance
Carbon Cycle
• Carbon is a key compound in carbohydrates,
fats, and protein. It is transferred between
organisms through consumption.
• The carbon cycle mainly involves the exchange
of carbon dioxide, and oxygen between plants
and animals during photosynthesis and
respiration.
Carbon Cycle
Nitrogen Cycle
• The Nitrogen cycle is used to produce protein,
which forms tissue structures and controls
body processes.
Nitrogen Cycle
• Plants produce protein from combining
carbohydrate (from PHS) and nitrate ions
(from soil).
• Then animals can eat the plants to obtain
protein.
• Nitrogen in the atmosphere must be
converted into nitrogen compounds by
lightening (from atmosphere), bacteria or
legumes (in soil).
Phosphorus Cycle
• Phosphorus is used by organisms in respiration, to produce
protein, and in bone formation in animals.
• This nutrient is most like if any to be in short supply within an
ecosystem as it is ‘locked up’ in bones, clay soils, sedimentary
rocks, and corals which don’t easily decompose.
• NZ’s agriculture relies on phosphate fertilisers for good soils,
as we export produce which removes tonnes of phosphorus
from our country.
• However phosphate ions are present in soils which are taken
up by plants/animals and returned to the soil by
decomposers.
Phosphorus Cycle
Similarities between cycles
• All rely on autotrophs to absorb nutrients to
pass on to consumers.
• All elements are returned to the environment
to become available to autotrophs again.
• The same decomposers are common to all
cycles.
Old Exam Question 2005
QUESTION THREE: FOOD WEBS
Below is a model of the movement of carbon through the organisms in a
food web in a sea area south of New Zealand.
The numbers in the figure below are the amounts of carbon transferred
between organisms (millions of tonnes / year). Net primary
production (phytoplankton growth) in this area generates organic
matter containing about 115 million tonnes of carbon each year.
(a)Describe how energy enters this food web.
(b)Explain why the amount of carbon transferred between organisms
decreases as the trophic level increases in the food web.
(c) Discuss the possible effects on this food web if commercial fishers
increase the number of squid they catch in this region. Use
information from the diagram to support your answer.
schedules/2005
Old Exam Question 2006
QUESTION FOUR: MATERIALS IN A COMMUNITY
Energy and nutrients are important materials in a
community.
1. Compare and contrast the movement of energy
and nutrients in communities. You may use
diagrams in your answer.
schedules/2006
Biozone & Meg Bayley
• Refer to Page 27 – 42 Meg Bayley
• Refer to Page 103-110 Biozone
• Complete for homework, if not already done
in class during the year