Download Population Ecology

Ecology
Chapters 2-5
Define ecology
• Study of interactions among organisms
and between organisms and their
environment
• Biosphere – all the parts of the planet in
which life exists including land, ocean, and
atmosphere
– Interactions within biosphere create a web of
interdependence between the organisms and
their environment
Principles of Ecology
The Biosphere
Principles of Ecology
Biotic Factors
 Living factors in an organism’s environment
Ex: predation
Abiotic Factors
 Nonliving factors in an organism’s
environment
Ex: sunlight, temperature
Principles of Ecology
Levels of Organization
 Levels increase in complexity as the
numbers and interactions between
organisms increase.
 organism
 population
 biological community
 ecosystem
 biome
 biosphere
Principles of Ecology
Organisms and Their Relationships
 The lowest level of organization is the
individual organism itself.
 Organisms of a single species that share
the same geographic location at the same
time make up a population.
 A biological community is a group of
interacting populations that occupy the same
geographic area at the same time.
Principles of Ecology
 An ecosystem is a biological community
and all of the abiotic factors that affect it.
 A biome is a large group of ecosystems that
share the same climate and have similar
types of communities.
Principles of Ecology
Ecosystem Interactions
 A habitat is an area where an organism lives.
 A niche is the role or position that an
organism has in its environment.
Principles of Ecology
Community Interactions
 Competition
 Occurs when more than one organism
uses a resource at the same time
 Predation
 Many species get their food by eating
other organisms.
Principles of Ecology
Symbiotic Relationships
 The close relationship that exists when
two or more species live together
 Mutualism
 Both species benefit
 Commensalism
 One organism benefits, the
other is not helped or harmed
 Parasitism
 One organism is helped, the
other is harmed
Principles of Ecology
Energy in an Ecosystem
 Autotrophs
 Organism that collects energy from sunlight
or inorganic substances to produce food
 Heterotrophs
A lynx is a heterotroph.
 Organism that
gets it energy
requirements by
consuming other
organisms AKA:
consumers
Types:
Herbivores: plant eaters
Carnivores: meat eaters
Omnivores: plant and meat eaters
Detritivores: eat plant and animal remains
Principles of Ecology
 Detritivores eat fragments of dead matter in
an
ecosystem, and
return nutrients
to the soil, air,
and water
where the
nutrients can
be reused by
organisms.
Fungus
Principles of Ecology
Models of Energy Flow
 Food chains and food webs model the
energy flow through an ecosystem.
 Each step in a food chain or food web is
called a trophic level.
How does energy flow through an
ecosystem?
• In one direction- from sun to
producers then to consumers
Principles of Ecology
Food Chains
 A food chain is a
simple model that
shows how energy
flows through an
ecosystem.
Principles of Ecology
Food Webs
 A food web is a
model representing
the many
interconnected food
chains and pathways
in which energy flows
through a group of
organisms.
Principles of Ecology
Ecological Pyramids
 A diagram that can show the relative
amounts of energy, biomass, or numbers of
organisms at each trophic level in an
organism
What are trophic levels?
• Trophic levels represent each step in a food
chain
– 1st level = producers
– 2nd level = herbivores
– 3rd level and up = carnivores and omnivores
How can we show all of the energy in
an ecosystem?
• Ecological pyramids – shows
amounts of energy or matter
within each trophic level
• Energy pyramids – shows
amounts of energy transferred
to the next trophic level is only
about 10% of the previous
level
• Biomass pyramid – shows
total amount of living tissue
• Numbers pyramid – shows #s
of individuals in each trophic
level
Principles of Ecology
Cycling of Matter
Cycles in the Biosphere
 Energy is transformed into usable forms to
support the functions of an ecosystem.
 The cycling of nutrients in the biosphere
involves both matter in living organisms
and physical processes found in the
environment such as weathering.
How does water move around an ecosystem?
• The water cycle – water
continually moves from the ocean
to the atmosphere to the land and
back to atmosphere
– Evaporation – change from
liquid to gas – from oceans or
any standing water or lakes,
etc.
– Transpiration – evaporation
from plant leaves
– Condensation – gas to liquid
in atmosphere forming clouds
– Precipitation – liquid falls back
to the earth where it drains
into oceans, rivers, and lakes
or soaks into the ground for
storage
– Run-Off- liquid runs back into
water source
– Percolation- liquid seeps into
the soil.
Principles of Ecology
The Water Cycle
Principles of Ecology
Principles of Ecology
 Approximately 90 percent of water vapor
evaporates from oceans, lakes, and rivers; 10
percent evaporates from the surface of plants
 Freshwater constitutes only about 3 percent of
all water on Earth.
 About 69 percent of all freshwater is found in
ice caps and glaciers.
Principles of Ecology
The Carbon and Oxygen Cycles
Principles of Ecology
Principles of Ecology
 Carbon and oxygen often make up
molecules essential for life.
 Carbon and oxygen recycle relatively quickly
through living organisms.
Principles of Ecology
The Nitrogen Cycle
 The capture and
conversion of
nitrogen into a form
that is useable by
plants is called
nitrogen fixation.
Principles of Ecology
Principles of Ecology
 Nitrogen enters the food web when plants
absorb nitrogen compounds from soil.
 Consumers get nitrogen by eating plants or
animals that contain nitrogen.
Principles of Ecology
 Nitrogen is returned to the soil in several
ways:
 Animals urinate.
 Organisms die.
 Organisms convert ammonia into nitrogen
compounds.
 Denitrification
Principles of Ecology
The Phosphorus Cycle
Principles of Ecology
Communities, Biomes, and Ecosystems
Limiting Factors
 Any abiotic factor or biotic factor that restricts
the numbers, reproduction, or distribution of
organisms is called a limiting factor.
 Includes sunlight, climate, temperature,
water, nutrients, fire, soil chemistry, and
space, and other living things
Communities, Biomes, and Ecosystems
Range of Tolerance
 An upper limit and lower limit that define the
conditions in which an organism can survive
 The ability of any organism to survive when
subjected to abiotic factors or biotic factors is called
tolerance.
How do ecosystems change over time?
• Always changing in response to natural and
human disturbances
– Older inhabitants die out, new organisms move in
• Ecological succession – predictable
changes in a community over time; the change
in an ecosystem that happens when one
community replaces another as a result of
changing abiotic and biotic factors
– Caused by slow changes in physical environment
– Caused by sudden natural disturbance
Communities, Biomes, and Ecosystems
Ecological Succession
 There are two types of ecological
succession—primary succession and
secondary succession.
What is primary succession?
• Succession on land
where no soil previously
existed
– Hardened volcanic lava
or ash
– Rocks exposed from
glacier melt
• Pioneer species – 1st to
populate an area
– i.e. Lichens
– Creates soil
Communities, Biomes, and Ecosystems
What is secondary succession?
• Follows a community changing
disturbance
– Wild fires, humans clearing land
• Climax Communities – ending point of
succession – mature stable community
– Still goes through change over time
Communities, Biomes, and Ecosystems
Secondary Succession after a fire
Secondary
Succession
of a
Lake
Communities, Biomes, and Ecosystems
What role does climate play?
• Weather – day to day
atmospheric conditions at a
certain place
• Climate – average year-round
conditions of temperature and
precipitation
• Causes of climate
– Trapping of heat by atmosphere
– Latitude
– Transport of heat by winds and
currents
What is the greenhouse effect?
• Gases in the
atmosphere trap heat
energy and maintain
Earth’s temperature
range
• Carbon dioxide,
methane, water vapor
• Traps heat being
released from the earth
• Naturally occurring
• Magnified by the
burning of fossil fuels
What effect does latitude have on
climate?
• Earth is tilted on it’s
axis and receives
varying angles of solar
radiation at different
latitudes.
• Creates 3 climate
zones:
– Tropical: at the equator,
hot
– Temperate: middle
latitudes, hot and cold
depending on season
– Polar: high latitudes,
cold
Communities, Biomes, and Ecosystems
 Biomes are classified
by their plants,
temperature, and
precipitation.
Tropical forests
Deserts
Temperate deciduous forest
Where we Live!
Tundra
• Permafrost
Chaparral: Shrubland
Coniferous forests
Savanna
Describe some aquatic ecosystems.
• Determined by depth,
flow, temperature, and
chemistry of overlying
water
• Inhabitants specially
adapted to each
ecosystem
• Freshwater
ecosystems
– Flowing water – rivers,
streams, creeks
– Standing water – lakes,
ponds
More aquatic ecosystems
• Estuaries –
wetlands where
rivers meet the
sea, fresh and
salt water – made
of mostly
detritivores
– Salt marshes
– Mangrove
swamps
Marine Ecosystems
• Light zones
– Photic – well lit upper layer
where organisms are able to
carry out photosynthesis
– Aphotic – permanently dark
zone bottom of ocean.
Population Ecology
Population Density
 The number of organisms per unit area
Spatial Distribution
 Dispersion is the pattern of spacing of a
population.
Population Ecology
Exponential Growth Model
 Exponential growth occurs
when the growth rate is
proportional to the size of the
population.
 if it has the perfect
environment. Limited to short
periods and small areas.
 Population multiplies quickly.
 All populations grow
exponentially until
some limiting factor slows the population’s
growth.
J-Curve
This is mostly unrealistic.
Population Ecology
Logistic Growth Model
 The population’s
growth slows or
stops following
exponential growth,
at the population’s
carrying capacity.
 S-Curve
Population Ecology
Population Ecology
Population-Limiting Factors
 There are two categories of limiting
factors—density-independent factors and
density-dependent factors.
Population Ecology
Density-Independent Factors
 Any factor in the environment that
does not depend on the number of
members in a population per unit area
is a density-independent factor.
•Shows a “boom & bust” curve
 Weather events
 Fire
 Human alterations of the landscape
 Air, land, and water pollution
Population Ecology
Density-Dependent Factors
 Any factor in the environment that depends
on the number of members in a population
per unit area is a density-dependent factor.
 Biotic factors
 Disease
 Competition
 Parasites
•Produces s-shaped curve
Population Ecology
 The maximum number of individuals in a
species that an environment can support
for the long term is the carrying capacity.
 Carrying capacity is limited by the energy,
water, oxygen, and nutrients available.
Population Ecology
Reproductive Patterns
 Species of organisms vary in the number of
births per reproduction cycle, in the age
that reproduction begins, and in the life
span of the organism.
Population Ecology
 The rate strategy, or r-strategy, is an
adaptation for living in an environment
where fluctuation in biotic or abiotic factors
occur.
 An r-strategist is generally a small organism.
 Short life span
 Produces many offspring
 Ex: Mice
Population Ecology
 The carrying-capacity strategy, or kstrategy, is an adaptation for living in stable
environments.
 A k-strategist is generally a larger organism.
 Long life span
 Produces few offspring
 Ex: Elephant, Humans
Population Ecology
Population Growth Rate
 The population growth rate (PGR)
explains how fast a given population
grows.
 The natality of a population is the birthrate
in a given time period.
Population Ecology
 A population stops increasing when the
number of births is less than the number
of deaths or when emigration exceeds
immigration.
Population Ecology
Human Population Growth
 The study of human population size, density,
distribution, movement, and birth and death rates is
demography.
HUMAN POPULATION GROWTH
• Currently our growth
is exponential.
• Exponential growth
due to:
– Advances in
technology
– Energy development
– Advances in agriculture
– Transportation
– Medicine
• We do not know our
carrying capacity.
Population Ecology
Human Population
Growth Rate
 Although the
human population
is still growing, the
rate of its growth
has slowed.
Population Ecology
Trends in Human Population Growth
 Population
trends can
be altered
by events
such as
disease and
war.
 Human
population
growth is not the same in all countries.
Population Ecology
Zero Population Growth
 Zero population growth (ZPG) occurs
when the birthrate equals the death rate.
Population Ecology
Age Structure
 A population’s
age structure
is the number
of males and
females in
each of three
age groups:
pre-reproductive stage, reproductive stage, and
post-reproductive stage.
Population Ecology
Human Carrying
Capacity
 Scientists are
concerned about the
human population
reaching or exceeding
the carrying capacity.
 An important factor is
the amount of resources
from the biosphere that
are used by each
person.
Biodiversity and Conservation
Threats to Biodiversity
Pollution
 Pollution and atmospheric
changes threaten
biodiversity and global
stability.
 Biological magnification is
the increasing concentration
of toxic substances in
organisms as trophic levels
increase in a food chain or
food web.
Biodiversity and Conservation
Threats to Biodiversity
Eutrophication
 occurs when substances rich in nitrogen
and phosphorus flow into waterways,
causing extensive algae growth.
 The algae use up the oxygen supply during
their rapid growth and after their deaths
during the decaying process.
 Other organisms in the water suffocate.
Biodiversity and Conservation
Conserving Biodiversity
 Resources that are replaced by natural
processes faster than they are consumed
are called renewable resources.
 Resources that are found on Earth in limited
amounts or those that are replaced by
natural processes over extremely long
periods of time are called nonrenewable
resources.