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The Biosphere
What is Ecology?
Ecology –
the scientific study of interactions among
organisms and between organisms
and their environment, or surroundings.
• Biotic – living
• Abiotic – non-living
Both biotic and abiotic factors shape an
ecosystem
Ex: Affect of drought on skunk population
Biosphere – the combined portions of the planet in which
all of the life exists, including land, water,
and air, or atmosphere. It extends from
about 8 km above Earth’s surface to 11 km
below the ocean surface.
Levels of Organization
To understand relationships within the biosphere,
ecologists ask questions about events and organisms
that range in complexity from a single individual to the
entire biosphere.
Levels of Organization
Species - a group of organisms so similar to one another
that they can interbreed and produce fertile
offspring.
Populations – groups of individuals that belong to the
same species and live in the same
area.
–These clams
that live near
an ocean vent
constitute a
population
Communities – different populations that live together in
a defined area.
Levels of Organization
Ecosystem – a collection of
all organisms that live in a
particular place, together with
their nonliving, or physical,
environment.
Biome – a group of ecosystems
that have the same climate and
similar dominant communities.
Biosphere – the region of the
Earth that supports life
Ecological Methods
Regardless of the tools they use, scientists conduct
modern ecological research using three basic
approaches: observing, experimenting, and modeling.
All of these approaches rely on the application of
scientific methods to guide ecological inquiry.
Energy Flow
Sunlight is the main energy
source for life on Earth.
Some types of organisms rely
on the energy stored in
inorganic chemical
compounds.
Autotrophs – plants, some
algae and certain bacteria can
capture energy from sunlight or
chemicals and use that energy
to produce food.
Producers – organisms that
make their own food
(autotrophs).
Energy Flow –
With NO Light!
Thermal vent
Chemosynthesis – when organisms use
chemical energy to produce
carbohydrates. Such as sulfur bacteria
converting sulfur compounds into
carbohydrates around thermal vents in
the ocean. Ex: Chemosynthetic Bacteria
Energy Flow – From the Sun
Photosynthesis – the conversion of light energy into
chemical energy which is stored
within organic compounds.
Energy Flow – Consumers
Heterotrophs – organisms that rely on other organisms
for their energy and food supply; also
known as consumers.
Consumers include animals, bacteria & fungi
Energy Flow – Consumer Types
Herbivores – animals that obtain energy by eating only
plants. Ex: cows & caterpillars
Carnivores – organisms that obtain energy by eating
animals. Ex: snakes, dogs & owls
Omnivores – organisms that obtain energy by eating
both plants and animals.
Ex: humans, bears & crows
Detritivores – organisms that feed on plants and animal
remains and dead matter (detritus).
Ex: mites, earthworms & snails
Decomposers – break down organic matter.
Ex: bacteria & fungi
Feeding Relationships
Energy flows through an ecosystem in
one direction, from the sun or
inorganic compounds to autotrophs
(producers) and then to various
heterotrophs (consumers).
Food chain – a series of steps in
which organisms transfer energy by
eating and being eaten.
TROPHIC LEVEL
Trophic Levels
Quaternary
consumers
•Each step in a food chain
or food web is called a
trophic level.
•Producers make up the
first trophic level.
Carnivore
Carnivore
Tertiary
consumers
Carnivore
Carnivore
Secondary
consumers
•Consumers make up the
second, third, or higher
trophic levels.
Carnivore
•Consumers depend on
the trophic level below it
for energy.
Herbivore
Carnivore
Primary
consumers
Zooplankton
Producers
Plant
Phytoplankton
A TERRESTRIAL FOOD CHAIN
AN AQUATIC FOOD CHAIN
Food Web – the
feeding relationships
among the various
organisms in an
ecosystem form a
network of complex
interactions; the
interactions of all the
food chains in an
ecosystem.
Wastes and
dead organisms
Tertiary
and
secondary
consumers
Secondary
and
primary
consumers
Primary
consumers
Producers
(Plants, algae,
phytoplankton)
Detritivores
(Prokaryotes, fungi,
certain animals)
Ecological Pyramids
An ecological pyramid is a diagram that shows the
relative amounts of energy or matter contained within
each trophic level in a food chain or food web.
Energy Pyramid – shows the relative amount of energy
available at each trophic level.
Only about 10 % of the energy available within one
trophic level is transferred to organisms at the next
trophic level.
Ecological Pyramids
Biomass – the total amount of living tissue within a
given trophic level. Biomass is usually
expressed in terms of grams of organic
matter per unit area.
Cycles of Matter
Unlike the one-way flow of energy, matter is recycled
within and between ecosystems.
Biogeochemical cycle – process in which elements,
chemical compounds, and other forms of matter are
passed from one organism to another and from one part
of the biosphere to another.
Water Cycle
Solar
heat
Water vapor
over the sea
Precipitation
over the sea
(283)
Net movement
of water vapor
by wind (36)
Evaporation
from the sea
(319)
Water vapor
over the land
Evaporation
and
transpiration
(59)
Precipitation
over the land
(95)
Oceans
Flow of water
from land to sea
(36)
Surface water
and groundwater
Water Cycle
Evaporation – the process by which water changes from
liquid form to an atmosphere gas.
Transpiration – when water enters the atmosphere by
evaporating from leaves of plants.
Nutrient Cycles
Nutrients – all the chemical substances that an organism
needs to sustain life.
Every living organism needs nutrients to build tissues
and carry out essential life functions. Like water,
nutrients are passed between organisms and the
environment through biochemical cycles.
Carbon Cycle
CO2 in atmosphere
Burning
Cellular respiration
Plants,
algae,
cyanobacteria
Photosynthesis
Higher-level
consumers
Primary
consumers
Wood and
fossil fuels
Decomposition
Detritivores
(soil microbes
and others)
Detritus
Nitrogen Cycle
• Nitrogen is plentiful in the atmosphere as N2
– But plants cannot use N2
Nitrogen Fixation
• Various bacteria in soil (and legume root nodules)
convert N2 to nitrogen compounds that plants can use
– Ammonium (NH4+) and nitrate (NO3–)
• Some bacteria break down organic matter and recycle
nitrogen as ammonium or nitrate to plants
Denitrification
• Other bacteria return N2 to the atmosphere by
converting nitrates into N2
Nitrogen Cycle
Nitrogen (N2) in atmosphere
Assimilation
by plants
Denitrifying
bacteria
Amino acids
and proteins in
plants and animals
Nitrogen
fixation
Detritus
Nitrogen-fixing
bacteria in root
nodules of legumes
Nitrates
(NO3–)
Detritivores
Nitrifying
bacteria
Decomposition
Nitrogen
fixation
Ammonium (NH4+)
Nitrogen-fixing
bacteria in soil
Phosphorus Cycle
Phosphates (compounds containing PO43-) and other
minerals are added to the soil by the gradual weathering
of rock.
Consumers obtain phosphorus in organic form from
plants.
Phosphates are returned to the soil through excretion by
animals and the actions of decomposers.
Phosphorus is essential to living organisms because it
forms part of important life-sustaining molecules such as
DNA & RNA.
Phosphorus Cycle
Uplifting
of rock
Phosphates
in organic
compounds
Weathering
of rock
Phosphates
in rock
Animals
Plants
Runoff
Detritus
Phosphates
in solution
Phosphates
in soil
(inorganic)
Decomposition
Rock
Precipitated
(solid) phosphates
Detritivores
in soil
Nutrient Limitation
Primary productivity – the rate at which matter is created
by producers.
Limiting nutrients – single nutrient that either is scarce
or cycles very slowly, limiting the
growth of organisms in an
ecosystem.
Algal bloom – the result of runoff
from heavily fertilized fields – the
result is often immediate increase
in the amount of algae and other
producers.