The multiple levels of
biological systems
Ecology
- The study of the
interactions of organisms
with one another and their
physical environment
The multiple levels of
biological systems
organism – an individual living thing
ex) a black bat
population – all of the individuals of a
species that live in the same area
ex) the black bats
The multiple levels of
biological systems
Community – a group of different species that
live together in one area
ex) the black bats, worms, moss,
mushrooms, bacteria, and beetles living in
the cave
Habitat – place where an organism usually lives
ex) a cave is a habitat for a black bat
The multiple levels of
biological systems
ecosystem – the different species (community)
plus the environment (soil, water, weather);
biotic factors + abiotic factors
ex) soil in the bottom of the cave, light
entering the cave, temperature in the cave,
humidity in the cave, plus the community
biome – major regional or global community of
organisms characterized by the climate
conditions and the plant communities that thrive
there
Vocabulary Quiz
match the phrase to the correct word
1. fish, snails, & plants
that live in a stream
2. a large group of zebras
3. tropical rainforest
4. rocks, water, mice,
deer, oak trees
5. one mockingbird
•
•
•
•
•
•
community
ecosystem
population
organism
biome
habitat
Biotic & Abiotic Factors
biotic factors – are
organisms in a habitat
ex) animals, plants,
fungi, protists, bacteria
abiotic factors – are the
physical aspects of a
habitat” ex) wind,
water, rocks, sunlight,
shade, etc.
What abiotic factors do you see here?
What biotic factors do you see?
Ecosystems are complex. Changes
to the biotic OR abiotic factors in an
ecosystem affect all species.
 biodiversity – the assortment or
variety of living things in an ecosystem
 biodiversity is threatened by human
activity
– pollution
– global warming
– habitat destruction
Biotic and Abiotic Factors
 keystone species – a species that
has an unusually large effect on its
ecosystem
 ex) sea otter – has a tremendous
effect on the ecosystem it is a part of
 sea otters eat sea urchins, which
keeps the sea urchin
 population under
 control
Biotic and Abiotic Factors
keystone species continued
 when the sea otter population
is over-hunted, there are not
enough otters to eat the sea
urchins
 the sea urchins, in turn, eat
too much kelp (an aquatic
plant, like seaweed) from kelp
beds and the kelp population
declines
 without kelp beds, fish have
no place to lay their eggs, so
the fish population declines;
when hunters stop hunting
the sea otter population, the
urchin populations decrease
and the kelp beds and fish
populations go back to normal
Food Chains and Food Webs
 Producers provide energy for other organisms
in an ecosystem
 producer – organism that obtains energy from
nonliving resources; organism that makes its own
food
 basis for ecosystem’s energy
 most rely on sunlight
almost all producers obtain energy from sunlight
 most producers use sunlight as their energy source
 photosynthesis – 2-stage process that green plants and
algae use to produce energy
6CO2 + 6H2O
C6H12O6 + 6O2
(SUNLIGHT)
Food Chains and Food Webs
 autotroph – another word for producer; word
parts: self feeder
 consumer – organism that gets its energy by
eating other living or once-living resources,
such as plants and animals; connected to
producers through energy, which ultimately
comes from the sun
 heterotroph – another word for consumer;
word parts: different feeder
Food Chains and Food Webs
Label the organisms below as
producer, autotroph, consumer, heterotroph
(use all words that apply)
producer,
autotroph
consumer,
heterotroph
consumer,
heterotroph
producer,
autotroph
Types of Consumers
 herbivores – organisms that eat only plants; ex) rabbit
 carnivores – organisms that eat only animals;
ex) snake
 omnivores – organisms that eat both plants and
animals; ex) chicken (eats seeds and insects)
 detritivores – organisms that eat dead, organic matter;
ex) millipede
 decomposers – organisms that break down organic
matter into simpler compounds; ex) fungi and bacteria
 responsible for the last step in every food chain,
returning nutrients to the environment
 receive energy from every other level
A food chain is a model that shows a
sequence of feeding relationships
***Energy FLOWS through ecosystems***
• food chain – sequence that links species by
their feeding relationships
• note that the arrows that
link one organism to
another show the
direction that energy
is flowing; energy flows
from the organism being
eaten to the organism
doing the eating
Draw the arrows to complete
the food chain below:
Hawk
Trophic Levels
• trophic levels – levels of nourishment in a food
chain; ex) producer  herbivore  carnivore
represents a food chain with 3 trophic levels
• energy flows up the food chain from the lowest
trophic level to the highest
– producer – autotrophs – level 1
– primary consumer (1̊ ) –
herbivores &
omnivores – level 2
– secondary consumer ( 2̊ ) –
carnivores & omnivore – level 3
– tertiary consumer (3̊ ) – carnivores
that eat carnivores, and some
omnivores – level 4
Trophic Levels
tertiary
consumers
secondary
consumers
primary
consumers
producers
A food web shows a complex
network of feeding relationships
• food web – model that shows the complex
network of feeding relationships and the
flow of energy within and sometimes beyond
an ecosystem
─ at each link, some energy
is stored in the organism
and some energy is
dissipated (lost) to
the environment
─ stability depends on
the base – the
producers (plants, algae,
phytoplankton, some
bacteria)
marine food webs
show multiple
trophic levels and
food chains
Don’t forget about the online textbook
resources like “Build a Food Web”
Pyramid Models
• An energy pyramid shows
the distribution of energy
among trophic levels
– energy in ecosystems
comes from sunlight
– energy flows UP the food
chain from producer to
consumer
– some energy is lost from the ecosystem,
mostly as heat
– each level of a food chain contains less
useful energy than the level below it
Pyramid Models
10%
10%
10%
Loss of Available Energy
• biomass – measure of the total dry mass of
organisms in a given area
– incorporated into the body of a consumer
– up to 90% of the energy stored in the
eaten organism may be lost as heat
(energy)
Energy Pyramids
– the longer a food chain, the more energy lost
• energy pyramid – diagram that compares energy
used by producers, primary consumers, and other
trophic levels
– illustrates how available energy is distributed
among trophic levels in an ecosystem
– energy is measured in kilocalories (kcal)
Label the correct amount of
energy at each trophic level:
?
?
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End of Part 1