OPTION G
G 1, G 2, G 3
SL TOPICS
G1 Community ecology
Abiotic factors that effect distribution of plant species
Discuss how each factor affects plants species
• Temperature (determines plant communities, desert plants show specific
adaptations)
Why does temperature affect plants distribution?
• Water (determines plants species desert plants?)
Why does water determine plants species in an ecosystem?
• Light
Why does light affect plants distribution?
• Soil pH
How does pH of soil and water affect plants? Acid rain?
• Salinity
Effect of salt on plants? Link osmosis. Halophytes live in salt marshes.
• Minerals
Why are minerals important for plants? pH and mineral uptake
relationship?
Discuss how each factor affects animals species
• Temperature:
How does temperature affect animals distribution?
Cold blooded and warm blooded animals?
Thermoregulation adaptations?
• Water
Animals adaptation to desert? For habitat or
reproduction
• Breeding sites
Many animals need special breeding sites. Salmon
• Food supply
Many animals have special diet. Humming birds eat
nectar. Panda bears?
• Territory
Some animals need special territory. Ex. Tigers
Ecological Sampling
• What is a sample?
– “A portion, piece, or segment that is representative of
a whole”
• Why do we sample?
– it is usually impossible to measure the whole
One big assumption…
• That the sample is representative of the whole
• It is necessary to take enough samples so that
an accurate representation is obtained
• It is important to avoid bias when sampling
Sampling Methods
• Transects and Quadrants
– Plants and Non-motile animals
• Lincoln Index
• Capture –Mark- Recapture
– Small animals
• Aerial observations
– Large trees and animals
Sampling along Transects
• Samples taken at fixed intervals
• Set up along an environmental gradient (e.g.
high to low on a mountain)
Line transect method
• A measured line laid across the area in the
direction of the environmental gradient
• All species touching the line are be recorded
along the whole length of the line or at specific
points along the line
• Measures presence or absence of species
Belt transect method
• Transect line is laid out and a quadrant is placed
at each survey interval
• Samples are identified and abundance is
estimated
– Animals are collected
– For plants an percent coverage is estimated
• Data collection should be completed by an
individual as estimates can vary person to
person
Quadrats
• Used to measure coverage and abundance of
plants or animals
• A grid of known size is laid out and all the
organisms within each square are counted.
Lincoln Index
• Capture-Mark-Recapture
– Animals are captured,counted, tagged and released.
– After a period of time another capture occurs.
– Previously tagged animals are counted and unmarked
organisms are marked.
– Abundance is calculated using the following formula:
n 1 x n2
n3
n1=total marked after catch 1
n2=total marked after catch 2
n3=total caught in catch 2 but
marked in catch 1
Measurements
• Sampling methods measure
–
–
–
–
–
Density
Coverage
Frequency
Biomass
Diversity
Density (D)
• The number of individuals per unit area
– D=ni/A
– Eg. 10 dandelions/m2 ni=number of individuals for
species i
• Relative density i (Rdi)A=the area sampled (could
volume V)by the sum of all
– The Density of species be
i, Dthe
i, Divided
the densities of the other species sampled
– Rdi=Di/S D
– Eg. 10/5+8+16
Coverage (C)
• The proportion of ground that is occupied or
area covered by the plant/species
– Ci=ai/A
• Relative coverage
ai=the area covered by
species
i divided by the sum
– The Coverage of species
1, Ci,
total area
total of the coverage ofA=the
the other
species sampled
Frequency (f)
• The number of times a given event occurs
– Eg. the number of quadrants that contain maple trees
as a ration of all the quadrants
– fi=ji/k
• Relative frequency
ji=number of quadrants with
species i
– The frequency of species i relative to the sum total of
k=total number of quadrants
the frequencies of the other
species found
Biomass (B)
• Can be calculated by measuring the mass of the
individuals per unit area
– B= S W/A
– More appropriate measure than density or frequency
when
• Number of individuals in hard to determine
• Photosynthesis and carbon fixation, energy and nutrient
transfer are more dependent upon biomass than the total
number of individuals
Biomass Measurement methods
• Fresh or wet weight
– Used when organisms are alive
• Dry weight
– Used when the water content varies greatly
– Oven dry at 105oC to remove water
• Ash-Free Weight
– Used when inorganic content varies greatly
– Oxidize at 500oC until only inorganic ash remains
Diversity
• The measure of variety of an ecosystem
• Consists of 2 components
– The number of different species or the richness of
species in a specific area
– The relative abundance of the individuals of each
species in a specific area
Simpson's Diversity (D)
• Measures species richness
D=N(N-1)
S n(n-1)
D=Diversity
N=total number of organisms of all
species found
n=number of individuals of a
• If D is high the area
may be a stable ancient site.
particular species
• Low D may suggest pollution, recent colonization, or
agricultural management
Random sampling and quadrat methods,
See the worksheet
• Use of a transect
• See the worksheet
INTERACTION BETWEEN BIOTIC FACTORS
1- Symbiosis
a. Mutualism
b. Commensalism
c. Parasitism
2- Competition
3- Feeding relationship
a. herbivory (grazing)
b. predation
Symbiosis: is a long term interaction between
two species which live in or on..
• Mutualism describes any relationship
between individuals of different species where
both individuals benefit.
• lichen: algae and fungi, legumes and nitrogen
fixation bacteria
• anemone hermit crab
Mutualism: Lichen
Lichen
Commensalism
• Commensalism describes a relationship
between two living organisms where one
benefits and the other is not significantly
harmed or helped.
Commensalism
Barnacles adhering to the skin of a whale or shell of a
mollusk
Parasitism
• A parasitic relationship is one in which one
member of the association benefits while the
other is harmed
Feeding relationship
• Producers: produce organic molecules by
photosynthesis or chemosynthesis
• Consumers: feed on other organisms.
– Herbivores: eat plants. They are primary
consumers
– Carnivores: they eat meat. They can be secondary,
tertiary consumers.
– Omnivores: they eat both meat and plant.
Scavengers
It is a carnivorous feeding behaviour in which a predator
consumes corpses that were killed by by other animals. It is
part of decomposition. Well known scavengers include
vultures, burying beetles, blowflies, yellowjackets, and
raccoons
Detritivores: Animals which primarily consume
dead plants. Organisms such as termits,
worms in soil are examples.
Decomposers: fungi and bacteria that obtain
their nutrients and energy mainly by feeding
on dead organisms by digesting them outside
of the cell.
Feeding relationship
Prey- predation
Competition
Interspecific
competition:
Competition
between two
different species.
Why?
• Intraspecific competition: competition
between the members of the same species.
• Why do they compete?
WHAT IS NICHE?
NICHE describes;
• where the organism lives
• how it lives
• how it interacts with other member of the
community
Fundamental and Realized Niches
Fundamental niche: is the niche that an organism
could potentially occupy.
Realized niches: is the proportion of the
fundamental niche that actually occupied by the
organisms. In other words it is the actual mode of
existence, which results from its adaptations and
competition with other species.
The Competitive Exclusion Principle
KEY POINTS
• For any given species a niche is precise and
cannot be occupied by more than one species.
• When the niches of two different species
overlap, competition takes place for the
resources.
• The stronger species exclude the weaker one
Parasitism: ectoparasite sheep thick
Mutualism : Fungus takes sugar and amino acids from root and it gives
ions to the root
Biomass
Biomass is the total weight (or volume, or
energy equivalent) of living organisms in a
given area (e.g. a quadrat).
(kJ m−2 yr−1).
Productivity of an ecosystem
• Primary productivity, the production of new
organic matter by green plants (autotrophs)
6CO2 + 12H2O ----------- C6H12O6 + 6H2O +6O2
Photosynthesis
• Secondary productivity, the production of
new organic matter by consumers
(heterotrophs).
Both primary and secondary productivity can be
divided into gross productivity and net
productivity.
1- Gross productivity is the total gain in organic
matter (biomass) or energy per unit area per
unit time.
2- Net productivity is the gain in energy or
biomass per unit area per unit time that
remains after deduction due to respiration.
Gross production – respiration = net production.
Values are in KJm -2 yr -1
Net Productivity (NP) of Carnivores
12
Respiration and other losses
Calculate W,X,Y
and Z
Carnivores
Z
Consumed by carnivores
Y
Decomposers & other losses
320
NP of herbivores
400
Respiration & other losses
HERBIVORES
X
Consumed by herbivores
W
Decomposers & other losses
32000
NP of Producers
2.00 x 107
40000
360,000
1.96 x 107
400,000
PRODUCERS
Source: M01 IB Examination
So how are gross and net
productivity related ?
Net productivity = Gross productivity - Respiration Energy
or using symbols:
NP = GP - R
This equation applies to animals too, but more on that
later…..
The productivity of a plant is called:
PRIMARY PRODUCTIVITY
because plants are the first or primary organisms in the
food web
So what about animal productivity?
• Animals must eat other organisms to obtain energy, unlike
plants which photosynthesize
• Animals may eat plants or animals or both
• Not all the energy in food is absorbed (assimilated) into an
animal’s body
• Unassimilated food is ejected as faeces or droppings
So gross productivity = food assimilated
or gross productivity = food eaten - energy in faeces
What about net productivity for an animal
(secondary consumer)?
• Gross secondary productivity =
Energy in eaten food - energy in faeces
• As well as keeping themselves alive, animals must use
energy to move and keep warm - plants need rather less
energy- but in the end it, as in plants, it all turns to heat
• Net secondary productivity (NSP ) =
food eaten - faeces - respiration energy
so NSP = GSP- R (just like plants)
?
NPP versus NSP
PRODUCTIVITY OF ECOSYSTEMS
The following data were collected in a study of secondary
productivity in a population of woodlice. Some of the
woodlice produced offspring during the experiment.
Source: IB Examination Paper 1 May01
Estimated Dry Mass at start of
experiment (g)
Estimated Dry Mass
at end of experiment (g)
Adult woodlice
1.53
1.59
Young woodlice
-
0.63
22
19.45
-
0.84
Food (dead leaves)
Fecal matter
ANSWER
1. What is the Gross Productivity (g) of this
population over the period of the
experiment?
2. What is the Net Productivity (g) of this
population over the period of the
experiment?
ANSWER
1. What is the Gross Productivity (g) of this
population over the period of the experiment?
Answer: GP = Food Eaten – Fecal Loss
GP =
(22 - 19.45) – 0.84
GP = 1.71
2. What is the Net Productivity (g) of this
population over the period of the experiment?
Answer: NP = Biomass (dry mass)
NP = 1.59 – 1.53 + 0.63
NP = 0.69
DETERMINING PRIMARY PRODUCTIVITY:
THE LIGHT BOTTLE-DARK BOTTLE METHOD
The light bottle-dark bottle method can be
used to estimate the rate of photosynthesis,
the amount of caloric energy stored in the
carbon compounds that are formed.
What does this method measure?
• This method compares the oxygen changes
that occur in plankton communities contained
in light bottles with those occurring in dark
bottles during a specified period of time.
What happens in the light bottle
• In the light bottle, oxygen is being produced
during photosynthesis by the phytoplankton in
the water and oxygen is being consumed by
plant and animal respiration.
What happens in the dark bottle
• In the dark bottle, only respiration is occurring
because there is no light present for
photosynthesis to occur.
How can we measure the biomass at
different trophic levels?
• find the dry mass of a representative sample
(at least) of each type of organism by heating
weighted sample at 70-80 °C .
• This technique kills many animals which is not
ethical. Instead of dry mass measurement
method, fresh mass can be used to estimate
biomass of the trophic level. It is less accurate.
Ecological productivity by the fresh- water community
at Silver Springs, Florida
Biomass expressed in terms of energy content (kJ m–2 yr–1)
Trophic level
Matter retained
lost respiration
Exported due
to herbivory or
predation by
organisms of
next trophic
level
________________________________________________________________________
Producers
1695
50112
35263
Primary consumers
6506
27154
1602
Secondary consumers
192
1322
88
Tertiary consumer
33
54
Calculate net productivity of the primary consumers by using data above.
Gross PP= 35263+50112+1695= 87070 kJm−2yr−1.
Net PP= 87070- 50112 = 35263
• The gross production by the primary
consumers (herbivores that eat producers –
the green plants) was the biomass that is
recorded as exported by the primary
producers, that is 35 263 kJ m−2 yr−1.
• The respiratory loss by the primary consumers
was 27 154 kJ m−2 yr−1. So the net production
by the primary consumers was (NSP):
• 35263 − 27154 = 8109kJm−2yr−1.
• Calculate net production by the secondary
and the tertiary consumers of the fresh-water
community at Silver Springs
SUCCESSION
Succession, a sequence of communities develops with
time by a process known as ecological succession.
OR
Succession is the directional and cumulative change in
the types of species that occupy a given area through
time.
Primary succession and secondary
succession
• Primary succession: When the succession
sequence starts on entirely new land without
established soil, then the process is known as
a primary succession. Ex: at river deltas, at
sand dunes, from cooled volcanic lava,
• Secondary succession: A succession that starts
from existing soil is known as a secondary
succession. Ex: after forest fire, human
destruction
Succession
Primary succession
Secondary succession
What is the difference between the two?
Succession could be…
• Primary
1o Succession
• Primary begins when
new territory is formed
devoid of life.
• The pioneer species are
adapted to life without
soil and in the case of
lichens, produce it by
decomposing rock.
• Plants cannot grow
Succession involves:
-colonization, establishment, extinction
• Succession stops when species composition
changes no longer occur with time, and this
community is said to be a climax community.
Stages
• Most successions contain a number of stages that
can be recognized by the collection of species that
dominate at that time
• These stages are called seres or seral stages
Succession could be…
• Secondary
• Secondary Succession begins when an area is made
devoid of vegetation because of a disturbance
• disturbances are fires, wind storms, volcanic
eruptions, logging, climate change, etc..
Succession in terrestrial environments
Source
http://www.physicalgeography.net/fundamentals/images/succession.gif
How does primary succession affect species diversity
and production of an ecosystem?
• Intially, Biomass and
productivity of the community
increases.
• This, in turn, provides food for a
larger community of consumers.
• As succession continues, the
diversity of species in the
community increases.
• As the system approaches its
climax, the rate of increase in
net productivity of the plants is
consumed by its own
heterotrophs.
• In a climax community, the
system comes into equilibrium
and reaches peak energy
efficiency.
How do living organisms affect abiotic factors during
primary succession?
• Role of lichens?
• Role of producers?
• Role of decomposers?
Major biomes
• desert
• grassland
• shrubland (chaparral, matorral, maquis and
garigue, dry heathlands, fynbos)
• temperate deciduous forest
• tropical rainforest
• tundra.
PROJECT PRESENTATION
How do rainfall and temperature affect the distribution
of biomes?
G3 Impacts of humans on ecosystems
Calculate the Simpson diversity index for two local
communities. G.3.1
Analyze the biodiversity of the two local communities
using the Simpson index. G.3.2
• http://www.biologycorner.com/flash/mark_re
cap.swf
Discuss reasons for the conservation of biodiversity
using rainforests as an example. G.3.3
• Rainforests cover almost 2% of the Earth’s
land surface,
• habitats for almost 50% of all living species.
• It is the case that tropical rainforests contain
the greatest diversity of life of any of the
world’s biomes.
Read page 622-623 and discuss why
rainforests should be conserved.
Alien species (introduced species, invasive species)
• Alien species are introduced plants and
animals that have been accidentally or
deliberately transferred from habitats where
they live, to new environments where the
abiotic conditions are also suitable for them.
• the rabbit (Oryctolagus sp.)
• Japanese knotweed (Fallopia japonica)
• American grey squirrel (Sciurus carolinensis)
Discuss the impacts of alien species on ecosystems. G.3.5
• Japanese knotweed (Fallopia japonica)
deliberately introduced into northern Europe
in the early nineteenth century as an
ornamental plant for garden ponds and lakes;
• American grey squirrel (Sciurus carolinensis)
accidentally introduced into Britain in the
nineteenth century.
•
Outline one example of biological control of invasive
species. G.3.6
• the rabbit (Oryctolagus sp.) deliberately
introduced from Europe, into Australia, and
the myxoma virus disease of rabbits, from
South America, introduced as a biological
control;
The role of ozone layer
+ UV light
O2 ⎯⎯⎯⎯⎯→O·+O·
+ UV light
O·+O2 ⎯⎯⎯⎯⎯→O3
• In the stratosphere, CFCs are exposed to high levels
of UV light, and are broken down. Highly reactive
chlorine atoms are then released, and these break
down ozone molecules in a cyclic reaction:
• O3 + Cl· ⎯⎯⎯⎯⎯→ ClO + O2
• ClO + O· ⎯⎯⎯⎯⎯→ Cl· + O2
Physical change: effects of ultraviolet (UV) radiation on
living things
• Mutation in all organisms
• Skin cancer