Adapted ESS presentation to support IB Biology Option G

1. G1: Community ecology
Option G: Ecology
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2. Biotic Factors = A living,
biological factor that may
influence an organism or
ecosystem, eg predation,
parasitism, disease, competition.
Abiotic Factor = A non-living,
physical factor that may
influence an organism or
ecosystem, eg temperature,
sunlight, pH, salinity,
precipitation.
Biotic Factors
Producers
Consumers
Detrivores
Decomposers
Interactions
Competitors
Parasites
Pathogens
Symbionts
Predators
Herbivores
Atmosphere
Wind speed
Humidity
Light intensity
Precipitation
Temperature
Water
ph and salinity
Dissolved Nutrients
Dissolved Oxygen
Disolved nutrients
Soil
Available nutrients
Moisture
pH
Structure
Temperature
G1: Community Ecology
G.1.1-2: Factors that affect the distribution of animal
and plant species
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3. Abiotic Factors affect animal and plant species, but also
interact and change with time themselves
E.g. Temperature depends upon:
solar radiation, wind speed, time of year, time of day,
altitude and aspect
Temperature affects:
water loss, respiration, photosynthesis
Changes in temperature affect:
relative humidity and evaporation from soils and water
surfaces
G1: Community Ecology
G.1.1-2: Factors that affect the distribution of animal
and plant species
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4. Biotic and Abiotic factors vary both between and within ecosyetems
G1: Community Ecology
G.1.1-2: Factors that affect the distribution of animal
and plant species
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5. Tropical Rain Forests
Dominant Species
Trees and Vines
Floral community
Highest Biodiversity of all Biomes
Faunal community
Very High biodiversity, mammals,
bird, amphibians and arthropods
Soil Community
Very rich in decomposer species
The Biotic Part
0
6.5
13.0
19.5
26.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Temperature
0
75
150
225
300
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rainfall
G1: Community Ecology
G.1.1-2: Factors that affect the distribution of animal
and plant species
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6. Abiotic conditions
within an ecosystem Humidity: 67%
Light: 70%
Humidity: 75%
Light: 50%
Humidity: 80%
Light: 12%
Humidity: 85%
Light: 6%
Humidity: 90%
Light: 1%
Humidity: 98%
Light: 0%
G1: Community Ecology
G.1.1-2: Factors that affect the distribution of animal
and plant species
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7. What about these two
ecosystems?
G1: Community Ecology
G.1.1-2: Factors that affect the distribution of animal
and plant species
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8. Niche
A species’ share of a
habitat and the resources
in it.
An organism’s ecological
niche depends not only on
where it lives but on what
it does.
G.1.5:The Niche concept
G1: Community Ecology
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9. Niche
the niche is defined by where the
species lives in the ecosystem/
habitat
how the species obtains its food/
nutrition
the interactions with other species
in the ecosystem/ relationships
G.1.5:The Niche concept
G1: Community Ecology
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10. Competition
All the organisms in any ecosystem have
some effect on every other organism in
that ecosystem.
Also any resource in any ecosystem
exists only in a limited supply.
When these two conditions apply jointly,
competition takes place.
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G1: Community Ecology
G.1.6: Interactions between species

11. Competition
Competition between members of
the same species:
INTRASPECIFIC COMPETITION
Just like a boxing match?
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G1: Community Ecology
G.1.6: Interactions between species

12. Competition
In a Gannet colony on an oceanic
outcrop, as the population grows,
so the pressure for good nesting
sites increases
This can affect the number of eggs
that each female can successfully
hatch, and so affects the birth rate
of the population as a whole.
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Density Dependent
G1: Community Ecology
G.1.6: Interactions between species

13. Competition
Some species deal with
intraspecific competition by
being territorial.
Red Deer stags fight to hold a
territory
Some birds sing to hold one
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G1: Community Ecology
G.1.6: Interactions between species

14. Competition
Or through display such as in this
bird of paradise or peacocks all of
which use bright feather displays
to attract a mate.
Energy investment in a large tail
feather is a trade off against
reproductive success
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G1: Community Ecology
G.1.6: Interactions between species

15. Competition
Intraspecific
competition leads to
logistic population
growth
0
175
350
525
700
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Population growth over time
Population
Time
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G1: Community Ecology
G.1.6: Interactions between species

16. Competition
Competition between members of
different species:
INTERSPECIFIC COMPETITION
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G1: Community Ecology
G.1.6: Interactions between species

17. The balance between the population
size of a prey species and that of its
predator.
Populations of predators and prey are
linked.
Include both carnivore and herbivore
relationships.
Predator Prey relationships
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G1: Community Ecology
G.1.6: Interactions between species

18. When the interaction involves animals
preying on other animals, then this is
termed - PREDATION
Predator Prey relationships
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G1: Community Ecology
G.1.6: Interactions between species

19. When the interaction involves animals
preying plants, then this is termed -
HERBIVORY
Predator Prey relationships
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G1: Community Ecology
G.1.6: Interactions between species

20. Predator Prey relationships
0
20
40
60
80
1900 1905 1910 1915 1920
Snowshoe Hare Lynx
Year
Numberofpelts(1000s)
Prey population
grows
Prey population falls
Predator population
falls
Predator population
grows
More food
More huntingLess hunting
Less foodMore food
More huntingLess hunting
Less food
G1: Community Ecology
G.1.6: Interactions between species

21. Special case of predation;
the main difference being
that the predator (parasite)
coexists with the prey
(host), rather than killing it.
Parasitism
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G1: Community Ecology
G.1.6: Interactions between species

22. Endoparasite - lives
inside the body of the
host
Parasitism
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G1: Community Ecology
G.1.6: Interactions between species

23. Ectoparasite - live on
the body of the host.
Parasitism
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G1: Community Ecology
G.1.6: Interactions between species

24. Competition
The amount of competition depends
on how much each species need for
the resource overlaps:
Species 2Species 1
Resource Overlap
Species 2Species 1
Resource Overlap
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G1: Community Ecology
G.1.7: Competitive exclusion

25. Competition
Interspecific competition
may result in a balance, in
which both species share
the resource.
But with the population
size of each species
reduced compared to
without competition
0
200
400
600
800
1,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Species1
Species2
Carrying Capacity -Theoretical Maximum Population Size
Intraspecific Competition Greater than
Interspecific Competition
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G1: Community Ecology
G.1.7: Competitive exclusion

26. Competition
The other outcome is that
one species may totally
out compete the other.
This is the principal of
competitive exclusion
0
150
300
450
600
750
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Species1
Species2
Carrying Capacity -Theoretical Maximum Population Size
Interspecific Competition Greater than
Intraspecific Competition
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G.1.7: Competitive exclusion
G1: Community Ecology

27. Competition
In a woodland plant
species compete for light
Trees should be able to
out compete any smaller
plants
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G1: Community Ecology
G.1.7: Competitive exclusion

28. Competition
In deciduous woodland snowdrops,
primroses and bluebells get around
this problem
They cary out their life cycle when the
bigger trees and shrubs have no or few
leaves
In spring
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G.1.7: Competitive exclusion
G1: Community Ecology