Download Intro to Ecology

Intro to Ecology
TURK
CHAPTERS 18-20
Levels of organization
 biosphere
 ecosystem
 community
 population
 organism
Ecosystem components
Biotic and Abiotic Factors
Both biotic, or living, factors and
abiotic, or nonliving, factors influence
organisms. Examples of abiotic factors
are climate, sunlight, and pH.
 A niche is a way of life, or a role in an
ecosystem.
Producers and consumers
 Most
producers are photosynthetic and make
carbohydrates by using energy from the sun.
 Consumers
obtain energy by eating other
organisms and include herbivores, omnivores,
carnivores, detritivores, and decomposers.
Consumers
obtain energy by eating other
organisms and include herbivores, omnivores,
carnivores, detritivores, and decomposers.
Energy Flow
Food Chains and Food Webs
A
single pathway of energy transfer is a
food chain.
A
network showing all paths of energy
transfer is a food web.
Energy flow cont…
 Energy Transfer
 Ecosystems
contain only a few trophic levels because
there is a low rate of energy transfer between each
level.
Water cycle
 Key
processes in
the water cycle are
evaporation,
transpiration, and
precipitation.
Carbon cycle
 Photosynthesis
and cellular
respiration are
the two main
steps in the
carbon cycle.
Nitrogen Cycle
 Nitrogen-fixing
bacteria are
important in the
nitrogen cycle
because they
change nitrogen
gas into a usable
form of nitrogen for
plants.
Phosphorus cycle
 In
the phosphorus
cycle, phosphorus
moves from phosphate
deposited in rock, to
the soil, to living
organisms, and finally
to the ocean.

Phosphorus is needed to
make DNA, RNA, and
proteins.
Populations

A population is a group of organisms that belong
to the same species and live in a particular
place at the same time.

Populations can be measured in terms of size,
density, dispersion, growth rate, age structure,
and survivorship.
Populations cont…
Population Size
A population’s size is the number of individuals that
the population contains.
Population Density
Density is a measure of how crowded the
population is.
Dispersion
 Dispersion describes the distribution of individuals
within the population and may be random,
uniform, or clumped.
Three Population Dispersion Patterns
Population Dynamics

Age Structure
A
population’s age structure indicates the
percentage of individuals at each age.
 Patterns of Mortality
 Populations
show three patterns of mortality or
survivorship curves:
 Type
I (low mortality until late in life)
 Type
II (constant mortality throughout life)
 Type
III (high mortality early in life followed by
low mortality for the remaining life span).
Population Growth Rate
the growth rate of a population is the amount by
which a population’s size changes in a given time.
 Population Size



Birth rate - death rate = growth rate
The exponential model describes perpetual growth
at a steady rate in a population.
The model assumes constant birth and death rates
and no immigration or emigration.
Population Growth Rate cont…

In the logistic model, birth rates fall and death
rates climb as the population grows.

When the carrying capacity is reached, the
number of individuals the environment can
support is reached and population growth
becomes stable.
Population limiting factors

Population-limiting factors, such as competition,
are density-dependent because the effect on
each individual depends on the number of other
individuals present in the same area.

Population-limiting factors, such as bad weather
and fires, are density-independent because the
effect on each individual does not depend on
the number of other individuals present in the
same area.
Small populations
 Small
populations have low genetic
diversity and are subject to inbreeding, so
they are less likely to adapt to
environmental changes.
Human Population Growth
 Around
1650, improvements in hygiene, diet, and
economic conditions further accelerated population
growth.
 After
World War II, the human population grew at the
fastest rate in history, largely because of better
sanitation and medical care in poorer countries.
Human Population Growth
Demographic Transition

Today, developing countries have faster human
population growth and lower standards of living
than developed countries do.

Human populations have undergone rapid
growth, yet in some developed countries,
populations have stopped growing.

The demographic transition model shows how
these population changes happen.
Demographic Transition
Predation
Predation is an interaction in which one organism (the
predator) captures and eats all or part of another individual
organism (the prey).
 Predator Adaptations

 Predators
have adaptations to efficiently capture prey,
whereas prey species have adaptations to avoid capture.
 Adaptations in Animal Prey
Mimicry is an adaptation in which a species gains an
advantage by resembling another species or object.
 Adaptations in Plant Prey
Many plants produce secondary compounds as a chemical
defense.
Competition
 Competitive Exclusion
 Competition
may cause competitive exclusion, the
elimination of one species in a community.
Competition
Character Displacement
Competition may drive the
evolution of niche differences
among competitors. This
evolution of differences in a
characteristic due to
competition is called character
displacement.
Resource Partitioning
Differential resource use to
avoid competition is called
resource partitioning.
Symbiosis
Parasitism
In parasitism, one species (the parasite) feeds
on, but does not always kill, another species
(the host).
Mutualism
 In
mutualism, both interacting species benefit.
Commensalism
In commensalism, one species benefits, and
the other is not affected.
Species richness

Species richness is the number of species in a
community.
Species evenness is the relative abundance of
each species.
Latitude and Species Richness
In general, species richness is greatest near
the equator, and larger areas support more
species.

Species richness
 Species Interactions and Species Richness
Species interactions such as predation can promote
species richness.
 Community Stability and Species Richness
Disturbances can alter a community by eliminating or
removing organisms or altering resource availability.
 Species
 Areas
richness may improve a community’s stability.
of low species richness may be less stable in the
event of an ecological disturbance.
Succession
Ecological succession is a change in the species
composition of a community over time.
Primary Succession
Primary succession is the assembly of a community
on newly created habitat.

 Primary
succession occurs in areas that have been
recently exposed to the elements and lack soil.
 Primary
succession typically proceeds from lichens
and mosses to a climax community.
Succession
Secondary Succession
Secondary succession is the change in an existing
community following a disturbance.
 Secondary
succession occurs in areas where the original
ecosystem has been cleared by a disturbance.
The community proceeds through a predictable series of stages
until it reaches a stable end point, called the climax community.
 Secondary succession typically proceeds from weeds to a climax
community.

Succession