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Ecology
WHAT IS ECOLOGY?
Ecology- the scientific study of
interactions between organisms
and their environments, focusing
on energy transfer
Ecology is a science of relationships
The environment is made up of
two factors:
• Biotic factors- all living
organisms inhabiting the
Earth
– plants, animals,
bacteria, etc.
• Abiotic factors- nonliving
parts of the environment
– temperature, soil, light,
moisture, air currents
Nutrient Cycles
• Abiotic factors are often nutrients
needed by plants and animals and
they must be cycled within the
biomes and ecosystems.
• Cycling maintains homeostasis
(balance) in the environment.
• 3 cycles:
1. Water cycle
2. Carbon cycle
3. Nitrogen cycle
Water Cycle
• Evaporation – liquid to gas
• Transpiration – loss of water from
plant leaves
• Condensation – gas to liquid in the
clouds
• Precipitation – rain, sleet, snow
Water Cycle
Carbon Cycle
• Photosynthesis and respiration
cycle carbon and oxygen through
the environment.
•
Carbon dioxide (CO2) is removed from
the atmosphere by the ocean and
plants during photosynthesis
•
Carbon dioxide (CO2) is returned to
the atmosphere by volcanic activity,
burning of fossil fuels and cellular
respiration by plants and animals.
Carbon cycle
Nitrogen Cycle
Atmospheric nitrogen (N2) makes up nearly
78%-80% of air.
Organisms can not use it in that form.
Lightning and bacteria convert nitrogen into
usable forms.
Nitrogen Cycle
Nitrogen-fixing bacteria
• Some live in a
symbiotic relationship
with plants of the
legume family (e.g.,
soybeans, clover,
peanuts).
• Some nitrogen-fixing
bacteria live free in
the soil.
Nitrogen Cycle
Nitrogen fixation – convert
atmospheric nitrogen (N2) into
ammonia (NH3) and nitrates (NO3)
N2
NH4+
Denitrification – other bacteria
change ammonia and nitrates back
into nitrogen gas (N2)
Biosphere
Levels of Organization
Biome
Ecosystem
Community
Population
Organism
Organism - any unicellular or
multicellular form exhibiting all of the
characteristics of life, an individual.
•The lowest level of organization
POPULATION - a group of
organisms of one species
living in the same place at
the same time that
interbreed
• Produce fertile offspring
• Compete with each other
for resources (food,
mates, shelter, etc.)
Community - several interacting
populations that inhabit a common
environment and are interdependent.
Ecosystem - populations in a
community and the abiotic factors
with which they interact (ex.
marine, terrestrial)
Biome – a group of ecosystems that
have the same climate and similar
dominant communities
•
Each biome
contains distinctive
plant and animal
groups, which are
adapted to that
particular
environment
Biosphere - life supporting portions
of Earth composed of air, land,
fresh water, and salt water.
•The highest level of organization
Major Land Biomes
• Biome- complex of terrestrial communities
that cover a large area; characterized by
soil, climate, plants, and animals
• Plants and animals vary by tolerance to
temperature and precipitation
• 8 Major Biomes
Tropical Rain Forest
• Hot and Wet
Boa constrictor
– close to equator so
warm temperatures
year round
– Over 250 cm rain per
year
Toucan
Black Jaguar
Sloth
Jaguar
Orchids
Tapir
Tropical Rain Forest
• Most species of
plants & animals
(species diversity)
• Soil lacks nutrients
• Plants: broad leaved
evergreen trees, large
woody vines, climbing
plants, orchids,
bromeliads
• Animals (photos)
Tapir
Boa constrictor
Toucan
Black Jaguar
Sloth
Jaguar
Tropical Rain Forest
• Adaptations of Plants and Animals
– Toucans and parrots have large, strong beaks to crack
open nuts.
– Animals have camouflage to blend in to the surroundings
of the rain forest.
• Example: Insects may be shaped like leaves or twigs
– Some animals have very bright colors to warn predators
that they are poisonous.
• Example: Poison arrow frogs
Tropical Savanna
• Seasonal rainfall: 100-150 cm
per year
• Warm year round
• Frequent fires
Giraffe
Storks
Aardvark
Hyena
Lion
Tropical Savanna
• Plants: Tall perennial
grasses, small trees and
shrubs that are often
drought-tolerant and fireresistant
• Animals: (photos)
Giraffe
Storks
Aardvark
Hyena
Lion
Tropical Savanna
• Adaptations of Plants and Animals
– Drought tolerant and fire resistant plants can retain
water or survive the frequent fires of this biome
Kangaroo rat
Desert
• Dry, less than 25 cm
of rain a year
• Extreme changes in
temperature
throughout the day
Roadrunner
– Extremely hot during
the day and cold at
night
Desert big horned sheep
Golden eagle
Mule deer
Mountain
lion
Creosote bush
Desert
Kangaroo rat
• Plants with short
growth cycles that
Roadrunner
can retain water:
cacti, succulents,
creosote bush
• Animals with high
tolerance to
temperature changes
Desert big horned sheep
Golden eagle
Mule deer
Mountain
lion
Creosote bush
Desert
• Adaptations of Plants and Animals
– Reptiles have thick, waterproof skin to hold in water
– Cacti and other succulents have thick fleshy leaves
that can hold large amounts of water for a long time
– Many animals are nocturnal. They sleep in shade
or underground during the day and are active at
night when it is cool.
Pronghorn antelope
Temperate Grassland
• Moderate precipitation: Polecat
25-75 cm per year
• Hot summers & Cold
Bison
winters
• Periodic fires
Black-tailed
prairie dog
Blazing stars
sunflowers
Coyotes
Badgers
Pronghorn antelope
Temperate Grassland
Polecat
• Plants: lush grasses
and herbs, drought and
fire-resistant plants
Bison
• Animals: many
herbivores and
carnivorous
predators (photos)
Black-tailed
prairie dog
Blazing stars
sunflowers
Coyotes
Badgers
Temperate Grassland
• Adaptations of Plants and Animals
– Drought and fire-resistant plants
– Rich soil allows many lush grasses to grow and
makes this biome excellent for farming.
Temperate Woodland
and Shrubland
• Also called the CHAPPARAL
• Hot, dry summer with cool,
moist winter
• Rainfall: 25-45 cm per year,
mostly during winter
Squirrel
Fox
Warbler
California quail
Black-tailed deer
Temperate Woodland
and Shrubland
• Plants: Woody, evergreen
shrubs with small leathery
leaves, oily herbs
• Animals (photos)
Squirrel
Fox
Coyotes
Warbler
California quail
Black-tailed deer
Raccoon
Temperate Forest
• Warm summer with cold,
moderate winters
• Year around rain:
200-350 cm per year
Skunk
Bobcat
Turkey
Black bear
Raccoon
Temperate Forest
• Plants: Deciduous and coniferous
trees, mosses, and ferns
• Animals (photos)
Squirrel
Skunk
Deer
Bobcat
Turkey
Black bear
Temperate Forest
• Adaptations of Plants and Animals
– Deciduous trees lose their leaves when winter
approaches to keep them from freezing.
– Some animals migrate during cold seasons to a
warmer climate.
Boreal Forest
• Also known as TAIGA
• Northern hemisphere
• Long, cold winter, short
summers
• Moderate precipitation:
20-200 cm per year, mostly
snow
Spruce
Snowshoe hare
Boreal Forest
• Plants: Needle leaf
coniferous trees, broad leaf
deciduous trees, small berry
bearing shrubs
• Animals: migratory animals
and large herbivores
(photos)
Timber wolves
Lynx
Moose
Boreal Forest
• Adaptations of Plants and Animals
– Waxy coating on conifers to retain water.
– Animals such as bears hibernate during the coldest
months.
Tundra
• Northern hemisphere
• Characterized by
permafrost, permanently
frozen snow
• Cold & windy
• Little precipitation: 15-25 cm
per year (almost as little as
desert)
Bearberry
Artic fox
Artic willow
Caribou
Polar bear
Caribou
Tundra
• Plants: small with short roots
because of permafrost, no
trees
• Animals: Migratory animals
or animals with high
tolerances for harsh
conditions (photos)
Polar bear
Snowy owl
Artic fox
Tundra
• Adaptations of Plants and Animals
– Animals such as the arctic fox have
white fur to camouflage themselves in
the snow.
– Plants have adapted to grow with short
roots because they cannot grow deep
roots in the permafrost.
Habitat vs. Niche
Habitat- the place in which an
organism lives out its life
Niche - the functional role a
species plays in a community; how
it fits in to its particular
community and ecosystem
Habitat vs. Niche
A niche is determined by the
tolerance limitations of an
organism, or a limiting factor.
Limiting factor- any biotic or
abiotic factor that restricts the
existence of organisms in a
specific environment.
Limiting Factors
Examples of limiting factors •Amount of water
•Amount of food
•Temperature
•Amount of space
•Availability of mates
Limiting Factors
Density dependent factors – depend
on the number of organisms in a
population
•Ex: Available food & water
Density independent factors – do not
depend on the number of organisms
in a population
•Ex: Weather, natural disasters & human
activities
Interrelationships of
Organisms
• There are 3 main types of
feeding relationships
1. Producer – Consumer
2. Predator – Prey
3. Parasite - Host
Feeding Relationships
Producers (Autotrophs)
• Make their own food
through
photosynthesis or
chemosynthesis
– Ex: plants, algae
• Bottom of the food
chain
Feeding Relationships
Consumers (Heterotrophs)
• Must eat other organisms to obtain
energy
Herbivores
Carnivores
Omnivores
Decomposers
Feeding Relationships
• Herbivores
• Primary consumers
• Eat plants
• Carnivores
• Secondary & Tertiary
consumers
• Eat animals
Feeding Relationships
Carnivores
• Meat eaters
• Predators
– Hunt prey
animals for food.
Feeding Relationships
• Omnivores
– Eat both plants and animals
– Ex: humans
Feeding Relationships
• Detritivores
• Scavengers
• Feed on
carrion, dead
animals
Feeding Relationships
• Decomposers
– Breakdown the
complex
compounds of
dead and decaying
plants and animals
into simpler
molecules that
can be absorbed
Symbiotic Relationships
Symbiosis- two organisms living
closely together
3 Types of
symbiosis:
1. Commensalism
2. Parasitism
3. Mutualism
Symbiotic Relationships
• Commensalism
– one species
benefits and
the other is
neither harmed
nor helped
– Ex. orchids on a tree
Symbiotic Relationships
• Parasitism
– one species benefits (parasite)
and the other is harmed (host)
– Ex. lampreys,
leeches, fleas,
ticks, tapeworm
Symbiotic Relationships
• Mutualism
– beneficial to both species
– Ex. cleaning birds and cleaner
shrimp
Energy Flow in Ecosystems
• All living organisms require energy
to function.
• Energy is used up and lost as heat
as it moves through ecosystems
• Each step in the energy transfer
from one organism to another is
called a trophic level
Energy Flow in Ecosystems
• Trophic levels represent a feeding
step in the transfer of energy
and matter in an ecosystem.
• Producers (Autotrophs)
are at the lowest level
• Consumers
(Heterotrophs)
are at the
higher levels
Energy Flow in Ecosystems
• 10% Law
– Approx. only 10% of the
energy from one trophic level
is transferred to the next
Heat
Heat
Heat
Producers
Consumers
Decomposers
100 Units
of Energy
10 Units
of Energy
1 Unit
of Energy
Energy Flow in Ecosystems
Food chain- simple model that
shows how matter and energy
move through an ecosystem
The arrows
show the
direction of
energy flow
Energy Flow in Ecosystems
• Food web- shows
all possible feeding
relationships in a
community at each
trophic level
• Represents a more
complex network of
interconnected food
chains
Energy Flow in Ecosystems
• An ecological pyramid shows the
relative amounts of energy or
matter contained within each trophic
level in a food chain or food web.
• Three types of ecological pyramids:
• energy pyramids
• biomass pyramids
• pyramids of numbers
Energy Pyramid:
Shows the
relative amount
of energy
available at each
trophic level.
0.1% Third-level
consumers
1% Second-level
consumers
10% First-level
consumers
100% Producers
Only 10% of the energy that is
stored in one trophic level is passed
on to the next level.
Biomass - The
total amount of
living tissue within a
given trophic level
50 grams of
human tissue
500 grams of
chicken
5000 grams
of grain
Biomass Pyramid:
Represents the amount of living organic
matter at each trophic level. Typically, the
greatest biomass is at the base of the
pyramid.
Pyramid of Numbers:
Shows the relative
number of individual
organisms at each
trophic level.
Biological Magnification
While energy decreases as it moves
up the food chain, toxins increase in
potency (concentration).
•This is called biological magnification
Example:
DDT used in pesticides in the mid
50’s and 60’s contributed to the
near extinction of bald eagles
before it was banned
Biological Magnification
Ecological Succession
Succession – the series of
predictable changes that occurs in
a community over time
Primary Succession – occurs on
surfaces where no soil exists
– Ex: On rock surfaces formed after
volcanoes erupt
Ecological Succession
Pioneer species – the first species
to populate the area
Ecological Succession
Secondary Succession – occurs when
a community experiences a
disturbance such as a fire,
plowing a field for farming, or
clearing a field for construction
– Occurs on pre-existing soil
Ecological Succession
Climax community– the final community
of organisms in a ecosystem once it
becomes stable
Human Impact on Ecosystems
Biodiversity – the variety of life in
an area
Biodiversity my be decreased by
human activities such as:
– Using pesticides and chemical
fertilizers
– Clearing land for construction
– Introducing non-native species