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Ecology
What is ecology?
Ecology is the scientific study of
the interactions of organisms
with their environments
Ecologists describe where
organisms live and how many
live there
Ecologists look at variables that
affect organisms. These
variables are biotic and abiotic
The biosphere contains the combined
portions of the planet in which all of life
exists, including:
• land
• water
• air, or atmosphere
The biosphere extends from about 8
kilometers above Earth's surface to as far as
11 kilometers below the surface of the ocean.
What is ecology?
Biotic factors: living things in an environment
examples include…
Abiotic factors: nonliving things in an environment
examples include…
An organism’s habitat, includes both factors
Habitat: where an organism lives
Factors affecting life in a biosphere
1. Energy source – sunlight, chemicals (inorganic),
food (organic)
2. Temperature – affects metabolism
3. Water – how much is needed depends on
organism
4. Nutrients – nitrogen, phosphorus (in soil), pH
5. Other aquatic factors – dissolved oxygen, tides,
salinity, current
6. Other terrestrial factors – wind, fire
Ecologists study environmental interactions at these different levels
Levels of organization (lowest to highest)
Species/ Organism - individual living thing
Population – group of organisms of same species in same area
Community – many populations or organisms living close enough for interaction
Ecosystem – include biotic & abiotic components in an environment
Biome – group of ecosystems with same climate
Biosphere – all of Earth
What could an ecologist study at each level?
Biosphere
Biome
Ecosystem
Community
Individual
Population
What levels of organization include nonliving
things?
Energy, Producers, and
Consumers
Where does the energy for life
processes come from?
Producers
Without a constant input of energy, living
systems cannot function.
Sunlight is the main energy source for life on
Earth.
In a few ecosystems, some organisms obtain
energy from a source other than sunlight.
Some types of organisms rely on the energy
stored in inorganic chemical compounds.
Only plants, some algae, and certain bacteria
can capture energy from sunlight or chemicals
and use that energy to produce food.
These organisms are called autotrophs.
Because they make
their own food,
autotrophs are
primary producers.
The best-known
autotrophs harness
solar energy through a
process known as
photosynthesis.
During photosynthesis,
these autotrophs use
light energy to convert
carbon dioxide and
water into oxygen and
energy-rich
carbohydrates.
Photosynthesis
is responsible
for adding
oxygen to—
and removing
carbon dioxide
from—Earth's
atmosphere.
Life without Light
Some autotrophs can produce food in the
absence of light.
When organisms use
chemical energy to produce carbohydrates,
the process is called chemosynthesis.
Consumers
Many organisms cannot harness energy
directly from the physical environment.
Organisms that rely on other
organisms for their energy
and food supply are called
heterotrophs.
Heterotrophs are also called consumers.
There are many different types
consumers.
• Herbivores eat plant
Leaves, roots, seeds, or
fruits
• Carnivores kill and
Eat other animals
• Omnivores eat both plants and animals.
• Detritivores feed on detritus, small pieces
of dead and decaying plant/animal
remains
Decomposers, like bacteria and fungi, break
down organic matter. (produce detritus)
Scavengers consume the carcasses of other
animals that have been killed gy predators or
have died of other causes
How does energy flow through
living systems?
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 food chain is a series of steps in which
organisms transfer energy by eating and
being eaten.
Food Web
Ecologists describe a feeding relationship in an
ecosystem that forms a network of complex
interactions as a food web.
A food web links all the food chains in an
ecosystem together.
Trophic Levels
Each step in a food chain or food web is called
a trophic level.
Producers make up the first trophic level.
Consumers make up the second, third, or
higher trophic levels.
Each consumer depends on the trophic level
below it for energy.
Ecological Pyramids
A diagram that shows the relative amounts of
energy or matter contained within each trophic
level in a food chain or food web.
The amount of energy/matter in an ecosystem can
be represented by an ecological pyramid.
Three types includes:
Energy pyramid
Biomass pyramid
Pyramids of numbers
Ecological Pyramids
Energy Pyramid:
Shows the relative
amount of energy
available at each
trophic level.
Only part of the
energy that is
stored in one
trophic level is
passed on to the
next level.
Copyright Pearson Prentice Hall
Biomass = total
amount of living
tissue in a
trophic level
WHAT DO YOU
NOTICE AT EACH
TROPHIC
LEVEL?
Copyright Pearson Prentice Hall
Ecological Pyramids
WHAT DO YOU
NOTICE AT EACH
TROPHIC LEVEL?
Copyright Pearson Prentice Hall
Cycles of Matter
How does matter move among
the living and nonliving parts of
an ecosystem?
Recycling in the Biosphere
Energy and matter move through the
biosphere very differently.
Unlike the one-way flow of energy,
matter is recycled within and between
ecosystems.
Biogeochemical Cycles
The Water Cycle
Water continuously moves between the oceans,
the atmosphere, and land – sometimes out of living
organisms and sometimes inside them
The Carbon Cycle
The Nitrogen Cycle
The Phosphorus Cycle
Nutrient Limitation
Limiting nutrient –
nutrient whose supply limits productivity
How Populations Grow
Describing Populations
4 important characteristics of a population are:
1. population density – number of individuals
per unit area
2. geographic distribution/range – area
inhabited by a population
3. growth rate – determines if the population
is icreasing, decreasing, or staying the same
4. age structure – the number of
males/females of each age a population
contains
Population Growth
Three factors can affect population
Growth:
1. the number of births
2. the number of deaths
3. the number of individuals that enter
or leave the population
A population can grow when its birthrate is
greater than its death rate.
Population Growth
- Immigration, the movement of individuals
into an area
- Emigration, the movement of individuals out
of an area
Exponential Growth
Under ideal conditions with unlimited resources, a
population will grow exponentially.
Exponential growth occurs when the individuals in a
population reproduce at a
constant rate.
The population becomes
larger and larger until it
approaches an infinitely
large size.
Logistic Growth
As resources become less available, the growth of a
population slows or stops.
Logistic growth occurs when a population's growth
slows or stops following a period of exponential growth.
Carrying capacity =
largest # of individuals
in a population that an
environment can
support
Human Population
Growth
Answer the following based upon the graph:
1.What type of growth is the human population in?
2. It is believed that the carrying capacity of humans is between 8 and
10 billion. When could these numbers be reached according to the
graph?
3.What factors have contributed to the world’s
overall population growth in the last 150 years?
4.Hypothesize what will happen when the human population exceeds
Earth’s carrying capacity.
Limits to Growth
The primary productivity of an ecosystem
can be reduced when there is a small t
supply of a particular nutrient – called
limiting nutrients
A limiting nutrient is an example of a more
general ecological concept: a limiting factor.
In the context of populations, a limiting
factor is a factor that causes population growth
to decrease and reach carrying capacity.
Density Dependent Factors
A limiting factor that depends on population
size is called a density-dependent limiting
factor.
Density-dependent limiting factors include:
• competition
• predation
• parasitism
• disease
Density Dependent Factors
Density-dependent factors operate only
when the population density reaches a
certain level. These factors operate most
strongly when a population is large and
dense.
They do not affect small, scattered
populations as greatly.
Density Dependent Factors
Competition occurs…
• When populations become crowded, organisms
compete for food, water space, sunlight and
other essentials.
• among members of the same species
• between members of different species.
–This type of competition can lead to
evolutionary change.
Density Dependent Factors
- Populations in nature are often controlled by
predation.
- The regulation of a population by predation takes
place within a predator-prey relationship, a
known mechanisms of population control.
Wolf and Moose Populations
Moose
Wolves
Density Dependent Factors
Parasitism Parasitism and Disease
- Parasites and disease causing agents
(bacteria/virus) feed at the expense of their
hosts.
- Weakens, causes disease, and sometimes
death in host
Density Dependent Factors
Stress from Overcrowding
- Some species fight among themselves if
overcrowded.
- Too much fighting = high stress levels → weakens
body’s ability to resist disease
Density Independent Factors
Density-independent limiting factors affect all
populations regardless of the population size.
Examples of density-independent limiting factors
include:
• unusual weather
• natural disasters
• seasonal cycles
• certain human activities—such as damming
rivers , clear-cutting forests, introducing species
Cane Toads
1. What are some benefits for species
that are introduced into a new
ecosystem?
2. What are some things that can go
wrong when an organism is
introduced into a new ecosystem?
3. How are organisms introduced into
a new ecosystem?
Questions
1. Population size is based upon density
dependent and independent factors.
Briefly explain the difference between
the two.
2. What are examples of density
dependent factors?
3. What are examples of density
independent factors?
What shapes an ecosystem?
Biotic factors – biological influences on organisms in
an ecosystem
examples include…
Abiotic factors – physical, nonliving,
factors that shape ecosystems
examples include…
Climate includes precipitation,
temperature, and humidity
In any ecosystem, removing biotic elements can
dramatically affect the ecosystem’s abiotic
conditions.
for example: if you remove trees from the forest → no
more shade for soil, can’t contribute organic matter
to soil, can’t return water to the atmosphere
through evaporation or transpiration
Think of other examples of how removing biotic
elements from an ecosystem could affect the
abiotic elements.
What shapes an ecosystem?
Together, biotic and abiotic factors determine
the survival and growth of an organism and
the productivity of the ecosystem in which the
organism lives.
The area where an organism lives is called its
HABITAT. This is like an organisms address.
The Niche
A niche is the full range of physical and biological
conditions in which an organism lives and the
way in which the organism uses those conditions.
If a habitat is like an organisms address, a niche is
like its occupation.
It includes the type of food an organism eats, how
it obtains the food, and which other species use
the organism as food
Cape May Warbler
Community Interactions
Community interactions can affect an
ecosystem.
Types of interactions include…
Competition
Predation
Symbiosis
Competition
Organisms attempt to use an ecological
resource in the same place at the same time
and competition occurs
resources include… food, shelter, water
Competitive exclusion
principle states that no
two species can occupy
the same niche in the
same habitat at the
same time.
Predation
An interaction in which one organism captures
and feeds on another organism
Predators can be
passive or active
What does it mean to be a passive predator?
Active predator?
Symbiosis
Any relation in which two species live
closely together
3 types include:
Mutualism
Commensalism
Parasitism
Symbiosis
Mutualism – both species
benefit from the relationship
ex: flowers and insects
rhinos and cleaning birds
Symbiosis
Commensalism – one
member of the association
benefits and the other is
neither helped nor harmed
ex: barnacles and whales
orchids on a tree
Symbiosis
Parasitism – one organism lives on or inside another
organism and harms it
ex: caterpillar and parasitic wasp, tapeworms and
mammals, fleas/ticks/lice
Type of
Species
relationship
harmed
Commensalism
Species
benefits
Species
neutral
Parasitism
Mutualism
= 1 species
Can you think of any other symbiotic
relationships? Give 5 examples and tell what
type of symbiotic relationship is occurring.
Symbiotic Videos
Clip 1: Shark/Turtle
Clip 2: Shark/Jack,
Shark/Mackerel,
Shark/Shark Suckerfish,
Hammerhead Shark/Barberfish
Clip 3: Shark/Fishermen
Symbiotic Relationships
Symbiotic Relationships
Ecological Succession
A series of predictable changes that occur in
a community over time
What types of human activities can disturb
an ecosystem and cause succession?
There are two types:
Primary
Secondary
Primary Succession
- Occurs in an area with no remnants of an older community (ex:
after volcanic eruption)
1. First species are pioneer species (lichens)
2. Lichens break the rock down adding organic material to form
soil
3. When the soil is rich grasses colonize the area. Then bushes
and trees.
4. As most plants colonize the area more animals do also.
Secondary Succession
-occurs faster than primary succession
-Soil has survived after a disturbance (wildfire,
hurricane)
-Surviving vegetation regrows rapidly