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ECOLOGY
Chapter 4
Ecology
Ecology is the
study of the
interactions
between living
things and their
environment.
The Biosphere
The biosphere is
the part of the
planet (air, water,
soil) in which life is
found.
Population
A population is all
the members of the
same species in an
area.
Community
A community
contains many
different populations
in an area (animals,
plants, fungi, microorganisms).
Ecosystem
An Ecosystem is a group of clearly
distinguished organisms that interact with
their environment as a unit.
Habitat
A Habitat is the place
in which an organism
lives.
Examples: Hedgerow,
Forest.
4 Environmental factors affecting
distribution of organisms
1.
2.
3.
4.
Abiotic Facrors
Biotic Factors
Climatic Factors
Edaphic Factors
Abiotic Factors (Non-Living)
• Altitude
• Aspect
• Steepness
• Currents
• Exposure
Biotic Factors (Living)
•
•
•
•
•
•
•
Food
Competition
Predation
Parasitism
Pollination
Seed Dispersal
Human activity
Climatic Factors (Long-term weather)
• Temperature
• Rainfall
• Humidity
• Day length
• Light intensity
• Wind
Edaphic Factors (Soil)
• pH
• Particle size
• Organic matter
• Water/air/mineral content
Aquatic (Water) Habitats have several
problems compared to terresterial habitats.
• Light may not penetrate
• Currents move organisms
• Wave action moves and damages
organisms
• Salt content (salinity) means organisms
adapt to freshwater or saltwater
• Oxygen is in lower concentration
The Sun is the main source of energy for
the planet. Energy flows in one direction
from the sun to producers to consumers.
• Producers are autotrophic
(they make their own food).
• Primary consumers feed on
producers. They are
herbivores (plant eaters).
• Secondary and tertiary
consumers feed on animals.
They are carnivores (meat
eaters)
A food chain
A food chain is a list of
organisms in which each
organism feeds on the next
member.
A grazing food chain
starts with a producer.
Each feeding stage is a
trophic level.
Usually the number of
organisms decrease as go
move up a trophic level. A
foodchain is limited in length
by the loss of 90% of the
energy at each trophic level.
Energy Flow – About 90% is lost
at each link in a food chain.
The Pyramid of Numbers
A pyramid of numbers is a representation of
the numbers of organisms at each trophic levels
A Food Web
A food web is a series of interlinked food chains
Niche
A niche is the role
an organism plays
in the community.
Organisms with
identical niches will
compete with
each other.
Energy flows through the ecosystem,
whereas nutrients (minerals) are recycled.
The carbon cycle and nitrogen cycle must
be studied for this course.
In The Carbon Cycle
• Carbon dioxide is
removed from the
environment by
photosynthesis in
plants.
• Carbon dioxide is
returned to the
environment by:
• Respiration in plants,
animals and microorganisms.
• Decay caused by
microorganisms.
• Combustion.
• Weathering.
Role of micro-ogganisms in the Nitrogen Cycle
Type
Location
Acts on
Product
Nitrogen fixing
Free in Soil or in
nodules in
legumes
N2gas
Nitrates (NO3)
Soil
Dead organic
matter
Nitrogenous
waste (e.g.
ammonia)
Nitrifying
Soil
Nitrogenous
waste (e.g.
ammonia)
Nitrates
Denitrifying
Soil
Nitrates
N2 gas
Bacteria and
Fungi of Decay
3 ways Humans affect ecosystems
Pollution
Conservation
Waste Management
Pollution
Pollution is any
undesirable
change in the
environment
caused by
pollutants.
E.g. CFC’s cause ozone depleation.
D
A
C
B
Say what A, B, C & D stand for
in the nitrogen cycle? (20)
Ecological pyramids
•Include pyramids of numbers, mass or energy.
•Allow different communities to be compared
according to different trophic levels.
•They indicate that the number of organisms
falls as you ascend each pyramid.*
•The body size of the organisms increases as
you ascend each pyramid.*
Pyramid of numbers are limited because:
•The size of the organisms can change the standard shape.
•It may not be possible torepresent large numbers of organisms correctly.
Population
A population is all the members of
the same species in an area.
The factors that control the numbers
in a population act mainly on the
birth and death rates.
Factors controling population include competition,
predation, parasitism and symbiosis.
Competition
Competition occurs when two or
more organisms seek a scarce
resource.
Intra-specific competition takes
place between members of the
same species.
Inter-specific compeittion takes
place between different species.
Competition reduces
population numbers
The 2 main types of competition are:
Contest Competition where one
organism gets the resource while
the second is left without.
Scramble Competition which
means that all of those competing
get some (but often not enough) of
the resource.
Predation
Predation is the catching,
killing and eating of
another organism. A
predator catches, kills and
eats other organisms (prey
Predation initially increases
the number of predators
and decreases the number
of prey.
The numbers of predators
and prey often show repeated
cycles of rising and falling
numbers.
Parasitism
A parasite is an organism that
feeds from and harms another
organism.
Exo- or ectoparasites live on the
outside of the host.
Endoparasities live inside the host.
Parasites sometimes reduce the numbers in a population,
but often have little effect on the host numbers.
Symbiosis
Symbiosis (Mutualism) occurs
when two organisms from a different
species live in close association for
the benefit of at least one of the
organisms.
Population dynamics
Population dynamics refers to
factors that cause changes in
population numbers.
Predator-Prey numbers interact due to:
Availability of food, which increases predator
numbers when high but reduces them when low
Concealment, which means that some prey survive by
hiding from predators
Movement of predators, which means that move to
new areas when prey numbers are low.