Download Matter and Energy Flow in Ecosystems

SAM GIRLS COLLEGE,
BHOPAL
DEPARTMENT OF LIFE SCIENCES
FOOD CHAIN
Presented by
Ms. Razda
Asst. Proff.
Life Science Department
Energy Flow and Energy Loss in
Ecosystems: Food Chains
• Scientists use different
methods to represent
energy moving through
ecosystems.
– Food chains
– Food webs
– Food pyramids
FOOD CHAIN
• The foods are synthesized by producers are
utilized by primary consumers.
• The primary consumers are eaten by
secondary consumers & in turn they are
consumed by tertiary consumers which are
utilized by decomposers.
• In this way a chain is formed by consuming
food of different trophic levels, sequentially
which is called FOOD CHAIN.
The transfer of energy from sun to
producer to primary consumer to
secondary consumer to tertiary
consumer can be shown in a FOOD
CHAIN.
TYPES OF FOOD CHAIN
• GRAZING FOOD CHAIN – Begins from
green plants & proceeds towards
herbivores & then towards carnivores.
DETRITUS FOOD CHAIN- starts from rotten
organic substances & proceeds towards
carnivores through detrivores.
FOOD CHAINS
CONSUMER
(CARNIVORE)

Food chain that includes
the following organisms:
grasshopper
 mouse
 grass
 owl

CONSUMER
(CARNIVORE)
CONSUMER
(HERBIVORE)
PRODUCER
FOOD CHAINS
Examples of terrestrial and aquatic food chains
FOOD CHAINS
• A food chain shows the path of
energy from one organism to the
next
– energy flows from producers to
consumers
– arrows point to who is eating
(plant is eaten by herbivore)
– Usually decomposers are left
out
FOOD WEBS


In an ecosystem, numerous food chain are
interrelated to each other & form a food web.
A food web shows all feeding relationships in an
ecosystem (made of many food chains)
Food Webs:
• Are interconnected
food chains
• They show the feeding
relationships in an
ecosystem
Red-tailed hawk
Producer
to primary
consumer
Gambel's
quail
Primary
to secondary
consumer
Yucca
Jack
rabbit
Agave
Collared
lizard
Prickly
pear
cactus
Secondary to
higher-level
consumer
All producers and
consumers to
decomposers
Roadrunner
Diamondback rattlesnake
Darkling
beetle
Bacteria
Fungi
Kangaroo rat
Food Webs
• Food chains don’t exist in real
ecosystems
• Almost all organisms are eaten by
more than one predator
• Food webs reflect these multiple and
shifting interactions
TROPHIC LEVELS
• The various steps of food chain where food or energy are
transferred are called TROPHIC LEVEL.
• Energy is lost with each trophic
– ~90% is released to the environment as heat
– ~10% of the energy is used
Only about 10%
of the energy
from one level
is passed on to
the next level
TROPHIC LEVELS
• In an ecosystem following trophic level are present– Producers = 1st trophic level
– Primary consumers that eat producers(herbivores) = 2nd
trophic level
– Secondary consumers that eat primary consumers
(carnivores)= 3rd trophic level
– Tertiary consumers that eat secondary consumers(top
carnivores /omnivores) = 4th trophic level
– Saprophytes that obtain
their food from all the trophic level
th
by decomposition = 5 trophic level.
ENERGY PATHS
3 ways to
illustrate
energy flow
2. Food Web: many paths
1. Food Chain: Single path
3. Food Pyramid
FOOD CHAINS
• A food chain shows the path of
energy from one organism to the
next
– energy flows from producers to
consumers
– arrows point to who is eating
(plant is eaten by herbivore)
– Usually decomposers are left
out
Another way of showing the transfer of
energy in an ecosystem is the
ENERGY PYRAMID.
Energy Pyramids
• The graphical representation
of number, biomass & stored
energy of various trophic levels
of food chain in an ecosystem
is called ecological pyramids.
Energy pyramids show
• That the amount of
available energy decreases
down the food chain
• It takes a large number of
producers to support a
small number of primary
consumers
• It takes a large number of
primary consumers to
support a small number of
secondary consumers
Ecological Pyramids
 Pyramid of
numbers
 Pyramid of
biomass
 Pyramid of
energy flow
Fig. 4-20 p. 79
Pyramid of numbers
• A pyramid of numbers indicates the number of
individuals in each trophic level.
# of carnivores
# of herbivores
# of producers
Pyramid of biomass
• A pyramid of biomass indicates how much
biomass is present in each trophic level at any
one time.
biomass of carnivores
biomass of herbivores
biomass of producers
Pyramid of energy
• A pyramid of energy depicts the
energy flow, or productivity, of each
trophic level.
carnivores
herbivores
producers
Ecological pyramids
• The standing crop, productivity, number of
organisms, etc. of an ecosystem can be
conveniently depicted using “pyramids”,
where the size of each compartment
represents the amount of the item in each
trophic level of a food chain.
•
carnivores
herbivores
producers
Note that the complexities of the interactions in a food web are not
shown in a pyramid; but, pyramids are often useful conceptual devices-they give one a sense of the overall form of the trophic structure of an
ecosystem.
Pyramid of energy
• A pyramid of energy depicts the
energy flow, or productivity, of each
trophic level.
• Due to the Laws of Thermodynamics,
each higher level must be smaller
than lower levels, due to loss of some
Energy flow in :
energy as heat (via respiration) within
each level.
carnivores
herbivores
producers
FOOD CHAINS/WEBS & ENERGY PYRAMIDS
• Food chains/webs can be
written as a pyramid:
– Producers form the base of
the pyramid

Consumers form the upper
layers
ENERGY PYRAMIDS
The energy pyramid shows energy
flow in an ecosystem:
Top
• A level of the energy
pyramid is called a
TROPHIC LEVEL
• Each trophic level
represents the
energy for those
organisms
Consumer
Energy stored by
Secondary Consumers
Energy stored by
Primary Consumers
ENERGY STORED
BY PRODUCERS
QUICK REVIEW
• Practice!
If 100% of the energy is available at the first trophic level,
what percentages of the energy are available at the second
and third trophic levels?
1%
10%
100%
QUICK REVIEW!
All organisms in an ecosystem need _______
from
energy
food to live. An energy ________
shows how much
pyramid
food energy is passed from one ________ to
another
organismthrough food chains. __________ have the
largest
spot at the base of the pyramid. Altogether,
Producers
only about _____ of the food energy at each
level
10%
gets passed up to the next level.
Energy Flow and Energy Loss in
Ecosystems: Food Chains
Consumers in a food chain can be classified as:
1. Detrivores – consumers that obtain energy and nutrients
from dead organisms and waste matter
 Examples include earthworms, bacteria and fungi.
 Detrivores feed at every trophic level.
 Detrivores have their own, separate food chains
and are very numerous.
2. Herbivores – primary consumers
 Herbivores eat plants (producers) only.
3. Carnivores – secondary or tertiary consumers
 Secondary consumers eat non-producers, such
as herbivores.
 Tertiary consumers eat secondary consumers.
 Also called top consumers or top carnivores.
4. Omnivores – consumers that eat both plants and
animals
 Examples include humans and bears.
Energy Flow and Energy Loss in
Ecosystems:Food Webs
• Most organisms are part of many food chains.
– Food webs represent interconnected food chains.
– Food webs are models of the feeding relationships in an ecosystem.
– Arrows in a food web represent the flow of energy and nutrients.
– Following the arrows leads to the top carnivore(s).
This food web
represents a
terrestrial
ecosystem
that could be
found in
British
Columbia.
Energy Flow and Energy Loss in
Ecosystems: Food Pyramids
• Food pyramids show the changes in available energy
from one trophic level to another in a food chain.
– Energy enters at the first trophic level (producers),
where there is a large amount of biomass and
therefore much energy.
– It takes large quantities of organisms in one
trophic level to meet the energy needs of the next
trophic level.
• Each level loses large amounts of the energy it
gathers through basic processes of living.
• 80 – 90 percent of energy taken in by
consumers is used in chemical reactions in the
body and is lost as thermal energy.
• There is very little energy left over for growth
or increase in biomass.
Ninety percent of this mouse’s food energy is used to maintain its life functions.
• Lower trophic levels
have much larger
populations than
upper levels.
• This shows the
importance of
maintaining large,
biodiverse
populations at the
lowest levels of the
food pyramid.
Food pyramids are also known as
ecological pyramids
– Ecological pyramids may show biomass, population, or
energy numbers.
– The amount of life an ecosystem can contain is based
on the bottom level of the ecological pyramid, where
producers capture energy from the Sun.
– Each level in the energy pyramid = a loss of 90 percent
of total energy available.
Energy Flow & Nutrient Cycle
Food Chains
• Artificial devices to
illustrate energy flow
from one trophic level
to another
• Trophic Levels:
groups of organisms
that obtain their
energy in a similar
manner
Food Chains
• Total number of levels in a food chain
depends upon locality and number of
species
• Highest trophic levels occupied by adult
animals with no predators of their own
• Secondary Production: total amount of
biomass produced in all higher trophic levels
Nutrients
• Inorganic nutrients incorporated into
cells during photosynthesis
- e.g. N, P, C, S
• Cyclic flow in food chains
• Decomposers release inorganic forms
that become available to autotrophs
again
Energy
• Non-cyclic, unidirectional flow
• Losses at each transfer from one trophic
level to another
- Losses as heat from respiration
- Inefficiencies in processing
• Total energy declines from one transfer to
another
- Limits number of trophic levels
Energy Flow
Energy Flow through an Ecosystem
sun
Food Chain
Primary
Producer
phytoplankton
Primary
Consumer
Secondary
Consumer
zooplankton
Tertiary
Consumer
larval fish
fish
heat
heat
heat
water
Nutrients
Fungi & bacteria
Decomposer
Transfer Efficiencies
• Efficiency of energy transfer called
transfer efficiency
• Units are energy or biomass
Et = Pt
Pt-1
Pt = annual production at
level t
Pt-1 = annual production at
t-1
Transfer Efficiency Example
• Net primary production = 150 g C/m2/yr
• Herbivorous copepod production = 25 g C/m2/yr
Et = Pt
Pt-1
= Pcopepods
Pphytoplankton
= 25 = 0.17
150
• Typical transfer efficiency ranges
*Level 1-2 ~20%
*Levels 2-3, …: ~10%
Energy and Biomass Pyramids
Kaneohe Bay
Tertiary
consumers
10 J
Secondary
consumers
100 J
Primary
consumers
Primary
producers
1000 J
10,000 J Limu
1,000,000 J of sunlight
Algae eaten by
Uhu
Cellular
Respiration
Feces
Growth
Food Webs
• Food chains don’t exist in real
ecosystems
• Almost all organisms are eaten by
more than one predator
• Food webs reflect these multiple and
shifting interactions
Antarctic Food Web
Some Feeding Types
Many species don’t fit into convenient categories
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Algal Grazers and Browsers
Suspension Feeding
Filter Feeding
Deposit Feeding
Benthic Animal Predators
Plankton Pickers
Corallivores
Piscivores
Omnivores
Detritivores
Scavengers
Parasites
Cannibals
Ontogenetic dietary shifts
Food Webs…
Competitive relationships in food webs can reduce productivity at top levels
Phytoplankton
(100 units)
Herbivorous
Zooplankton
(20 units)
Carnivorous
Zooplankton A
(2 units)
Fish (0.2 units)
Phytoplankton
(100 units)
Herbivorous
Zooplankton
(20 units)
Carnivorous
Zooplankton A
(1 units)
Fish (0.1 units)
Carnivorous
Zooplankton B
(1 units)
Recycling: The Microbial Loop
• All organisms leak and excrete dissolved
organic carbon (DOC)
• Bacteria can utilize DOC
• Bacteria abundant in the euphotic zone
(~5 million/ml)
• Numbers controlled by grazing due to
nanoplankton
• Increases food web efficiency
Microbial Loop
Solar
Energy
Phytoplankton
Herbivores
CO2
nutrients
Planktivores
DOC
Piscivores
Bacteria
Nanoplankton
(protozoans)
An Ecological Mystery
Keystone Species
Kelp Forests
An Ecological Mystery
• Long-term study of sea otter populations
along the Aleutians and Western Alaska
• 1970s: sea otter populations healthy and
expanding
• 1990s: some populations of sea otters were
declining
• Possibly due to migration rather than
mortality
• 1993: 800km area in Aleutians surveyed
- Sea otter population reduced by 50%
Vanishing Sea Otters
• 1997: surveys repeated
• Sea otter populations had declines by 90%
- 1970: ~53,000 sea otters in survey area
- 1997: ~6,000 sea otters
• Why?
- Reproductive failure?
- Starvation, pollution disease?
Cause of the Decline
• 1991: one researcher observed an orca
eating a sea otter
• Sea lions and seals are normal prey for
orcas
• Clam Lagoon inaccessible to orcas- no
decline
• Decline in usual prey led to a switch to sea
otters
• As few as 4 orcas feeding on otters could
account on the impact
- Single orca could consume 1,825
otters/year
Energy Flow Through an
Ecosystem
Food Chains, Food Webs, Energy
Pyramids
•Begins with the SUN
•Photosynthesis
6CO2 + 6H2O + sunlight & chlorophyll C6H12O6
+ 6O2
• The chemical reaction by which green plants use
water and carbon dioxide and light from the sun to
make glucose.
• ENERGY is stored in glucose; glucose is stored as
starch.
Organisms that can make
glucose during photosynthesis
are called PRODUCERS.
Producers use most of the energy
they make for themselves.
Producers use cellular respiration to
supply the energy they need to live.
6O2 + C6H12O6 --> 6H2O + 6CO2 + energy
CELLULAR RESPIRATION is the
chemical reaction that releases the
energy in glucose.
The energy that is not used by
producers can be passed on to
organisms that cannot make their
own energy.
Organisms that cannot make their
own energy are called CONSUMERS.
Consumers that eat producers to get
energy:
• Are first order or
primary consumers
• Are herbivores
(plant-eaters)
Most of the energy the primary
consumer gets from the producer is
used by the consumer.
Some of the energy moves into
the atmosphere as heat.
Some energy in the primary
consumer is not lost to the
atmosphere or used by the
consumer itself.
This energy is available for
another consumer.
A consumer that eats another consumer
for energy:
• Is called a secondary or
second order consumer
• May be a carnivore or a
herbivore
• May be a predator
• May be a scavenger
Most of the energy the secondary
consumer gets from the primary
consumer is used by the secondary
consumer.
Some of the energy is lost as
heat, but some energy is
stored and can passed on to
another consumer.
A consumer that eats a consumer that
already ate a consumer:
• Is called a third order or
tertiary consumer
• May be a carnivore or a
herbivore
• May be a predator
• May be a scavenger
Consumers that eat producers & other
consumers
• Are called omnivores
• Omnivores eat plants
and animals
Consumers that hunt & kill other
consumers are called predators.
They animals that are hunted & killed
are called prey.
Consumers that eat other
consumers that have already died
are called scavengers.
Another way of showing the transfer of
energy in an ecosystem is the
ENERGY PYRAMID.
Energy pyramids show
• That the amount of
available energy decreases
down the food chain
• It takes a large number of
producers to support a
small number of primary
consumers
• It takes a large number of
primary consumers to
support a small number of
secondary consumers