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G1: Community ecology
Option G: Ecology S
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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 FactorsProducers
ConsumersDetrivores
Decomposers
InteractionsCompetitors
ParasitesPathogensSymbiontsPredators
Herbivores
AtmosphereWind speed
HumidityLight intensityPrecipitationTemperature Water
ph and salinityDissolved NutrientsDissolved OxygenDisolved nutrients
SoilAvailable nutrients
MoisturepH
StructureTemperature
G1: Community Ecology G.1.1-2: Factors that affect the distribution of animal and plant species
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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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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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Tropical Rain Forests
Dominant SpeciesTrees and Vines
Floral communityHighest Biodiversity of all Biomes
Faunal communityVery High biodiversity, mammals, bird, amphibians and arthropods
Soil CommunityVery 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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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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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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NicheA 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 S
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Nichethe 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 S
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CompetitionAll 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
CompetitionCompetition 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
CompetitionIn 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
CompetitionSome 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
CompetitionOr 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
CompetitionIntraspecific 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
Popu
latio
n
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G1: Community Ecology G.1.6: Interactions between species
CompetitionCompetition between members of different species:
INTERSPECIFIC COMPETITION
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G1: Community Ecology G.1.6: Interactions between species
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
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
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
Predator Prey relationships
0
20
40
60
80
1900 1905 1910 1915 1920
Snowshoe Hare LynxYear
Num
ber o
f pelt
s (1
000s
)
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
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
Endoparasite - lives inside the body of the host
Parasitism
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G1: Community Ecology G.1.6: Interactions between species
Ectoparasite - live on the body of the host.
Parasitism
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G1: Community Ecology G.1.6: Interactions between species
CompetitionThe 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
CompetitionInterspecific 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
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600
800
1,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Spec
ies
1Sp
ecie
s 2
Carrying Capacity -Theoretical Maximum Population Size
Intraspecific Competition Greater than Interspecific Competition
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G1: Community Ecology G.1.7: Competitive exclusion
CompetitionThe other outcome is that one species may totally out compete the other.
This is the principal of competitive exclusion
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150
300
450
600
750
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Spec
ies
1Sp
ecie
s 2
Carrying Capacity -Theoretical Maximum Population Size
Interspecific Competition Greater than Intraspecific Competition
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G.1.7: Competitive exclusion
G1: Community Ecology
CompetitionIn 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
CompetitionIn 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
