Equilibrium in the Biosphere
Week 2
Bio 20 Cyber High
Ecology
Study of the interactions between
organisms and their physical
environment and with each other.
Biosphere
the part of the earth that is inhabited by
organisms.
3 parts:
1 Lithosphere
Land
2 Hydrosphere
water
3 Atmosphere
The gasses that surround the Earth.
Living vs. Non-living
There are two factors which
make up the biosphere.
 Biotic Factors
Living components of the biosphere
plants and animals…
 Abiotic Factors
Non-living components
of the biosphere
minerals, water, weather...
Interactions Within the
Biosphere
 Abiotic vs Biotic
 When a non-living factor affects a living factor.
 i.e. The weather affecting a living organism
 Biotic vs. Biotic
 When a living factor affects another living factor.
 i.e. Two organisms fighting for the same food.
 Biotic vs. Abiotic
 Abiotic vs. Abiotic
Levels of Organization
Cell
Levels of
organization
Tissue
Organ
System
Organism
Population
Ecosystem
Biome
Biosphere
Community
Hierarchical Levels within the
Biosphere
Biosphere
Ecosystem
Community
Population
Organism
World
Lake or River
Lots of different species of
organisms
Lots of same species of fish
Fish
Important Definitions
Population: group of individuals of the same:
species, place & time
Community: populations of all species in an area
Ecosystem: community and its biotic and abiotic
factors
 Interactions
Biome: large scale ecosystems
 Can be found around the world  tundra, grassland
General Terms
Autotroph
Producer
Photosynthesis
 Light energy used to make organic compounds
(glucose)
 Done by chloroplast containing organisms (plants,
algae)
Chemosynthesis
 Energy released by chemical reactions to make a
sugar
 Oxidizing hydrogen sulfide or methane
 Done by bacteria in extreme environments (deep
sea vents, hot springs)
More General Terms
Heterotroph
Consumer
 A Primary consumer eats a producer
 A Secondary consumer eats a primary consumer
 A Tertiary consumer eats a secondary consumer…
More General Terms
Herbivore
An organism that only eats plants.
 Rabbit, squirrel
Carnivore
An organism that only eats animals.
 Wolf, Lion, Tyrannosaurus Rex
Omnivore
An organism that eats both plants and
animals.
 Bear, Human
More General Terms
Scavenger
An organism that feeds on dead organisms
or the wastes of organisms.
 Vulture, Seagull,
Decomposer
An organism that breaks down organic
wastes and the remains of dead organisms
into simpler compounds such as:
 carbon dioxide
 ammonia
 Water
Input energy
Biogeochemical
Ecosystems are
OPEN SYSTEMS.
Energy and matter
can flow in and out
of system
Cycles
Energy Lost
Food chains
Food Chain
 A linear illustration that represents the step sequence of who
eats whom in the biosphere.
 used to show:
energy transfers
 Two Types
 Grazer: plant, herbivore, carnivore
 Detritus: organic waste, scavengers,
decomposers
Food chains
Characteristics:
 Energy is transferred from organism to organism
 Each time energy is transferred about 90% is lost
as heat or used for life processes
 Lost as heat during cellular respiration, stored in an
unusable form, metabolized by the organism itself
for ATP to live
Food Chain
 Note that:
 the arrow points at the
eater
 the arrows separate
trophic (eating) levels
Trophic Levels
 Trophic level: how far an organism is from the
original energy source
 Plants – first trophic level
Original energy is from the sun
 When an organism is ingested by another, energy
is transferred
 Plant – mouse – owl
 Producer – primary consumer – secondary
consumer (top carnivore)
 T1 – T2 – T3
Food Webs
 What would happen if we relied on deer for our food?
 In reality, a consumer relies on more than one food source
 If one source is scarce, consumer can eat more of
something else
 Food web:
 a series of interlocking food chains
 more accurately represents energy pathways
who eats whom… really
Food Web
 ABCD represent
different trophic
levels.
 Level D represents
the decomposers
Laws of Thermodynamics
Biosphere requires a
constant flow of energy
Energy flows one way
through the biosphere
following basic scientific
principles called the laws of
thermodynamics
Laws of Thermodynamics
First Law
Energy can be changed in form,
but not created or destroyed.
(Law of conservation of energy)
Energy input = Energy Output
Second Law
Any energy change results in loss of
energy as heat
Energy input  desired energy +
waste energy
Energy Flow
 About 10% of the energy is transferred from one trophic
level to the next.
 During any change, some of the energy is lost
as waste energy or heat.
 Applied to an ecosystem, as energy flows
through the community there is energy loss at
each trophic level.
 Much of this loss is in the form of heat which is
lost when food molecules are broken down in
the cells.
 There would be less energy loss in the
community if consumers only fed on producers
Ecological Pyramids
 Ecological pyramids illustrate the energy loss through the
trophic levels
 Solar radiation transformed in plants
 Plants create chemical energy
 Plant eaten by consumer
 Energy lost at each transformation
 Higher trophic level = less energy available
 Number of trophic levels limited b/c of loss of energy
Ecological Pyramids
In ecological pyramids,
Base -the producer populations
Next Level - the primary
consumers
Higher levels and above -the
secondary, tertiary etc.
Ecological Pyramids
 Three types:
 Numbers: total number of organisms in each
trophic levels
 Biomass: mass of dry tissue of organisms at
each trophic level
shows how mass decreases as you move up
the food chain
 Energy: based on energy produced at each
trophic level
Energy Pyramids
Pyramid of Numbers
Pyramid of Biomass
Human Interference in
the Ecosystem
Pesticides
used to kill pests
mosquitoes - malaria
pesticides in food chain
accumulate at each level
causes loss of diversity.
 Example
 DDT: dichloro diphenyl trichloroethane
 developed as a biological weapon in WWII
 1950’s - used as a pesticide for insects
 DDT also affects human populations
 found in breast milk
 came from sprayed crops
animals that ate crops
 Banned in Canada and US in 1970’s
 Not banned in other areas - Mexico, Central
America
 Continues to be produced as a cheap pesticide
in poorer nations
Biological amplification
Pesticide concentration builds up
at the top level of the pyramid
toxins accumulate in fatty tissue
not released in wastes
Magnifies each time you move up
higher trophic level - higher
concentration