Transcript Populations - Mrs. GM Biology 200

200
Unit 12—Ecology (& Populations)
Ch. 30 Populations & Communities
(sec. 1 & 4)
Populations, Communities, & Ecosystems
• What is a population?
– All organisms of same type (species) living in an area
• What is a community?
– All different organisms (populations) living in an area
• What is an ecosystem?
– A community interacting with the non-living (abiotic)
factors in an area
Population Changes
• What can cause
an increase in
the population
size of an area?
– births
– immigration
Population Changes
• What can cause a decrease in the population
size of an area?
– deaths
– emigration
Visualizing Population Structures &
Predicting Future Changes
• population pyramids (a.k.a. age structure diagrams)
– basic shape can help us predict what’s going to happen to
the population in the future…
– What do you think will happen to the population in each pyramid???
How Population
Pyramids Are
Made Video
Animated
Population
Pyramid
Rapid Growth
Guatemala
Nigeria
Saudi Arabia
Ages 0-14
Slow Growth
Zero Growth Negative Growth
U. S.
Spain
Germany
Australia
Austria
Bulgaria
Canada
Greece
Sweden
Ages 15-44
Ages 45+
Population
growth rate by
country
Population Pyramids
(Age Structure Diagrams)
Developing Countries
– wide base
– high #s of pre- &
reproductive age
• high birth rates
– fast growth
Census Bureau
International
Data-Pyramids
Developed Countries
– slightly wider base, width is same,
or inverted pyramid
– lower #s of pre- & reproductive age
– low birth rates
• slow growth, zero growth, negative
growth (pop. shrinks)
Population Clock
Population Growth
• Types of population
growth:
Exponential
Growth
– exponential growth
• represents species’
biotic potential
– ideal conditions
– logistic growth
• population reaches
“carrying capacity”
Logistic
Growth
point of maximum growth
Population Growth
• Why don’t populations
increase forever?
– limiting factors
• provide environmental
resistance
• prevent population from
growing indefinitely
– reach “carrying
capacity”
• can be:
– abiotic (non-living)
– biotic (living)
Examples of Abiotic Limiting Factors
Examples of Biotic Limiting Factors
• living factors in an ecosystem
Biotic
Limiting
Factors
• usually
described
in terms of
interactions
– especially
who eats
whom or
trophic
levels
Decomposers are heterotrophs
& must be part of every
ecosystem to break down dead
material & recycle nutrients!
Energy Flow: Food Chains
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e
t
e
r
o
t
r
o
p
h
s
Fourth trophic level
Tertiary consumers
Carnivores/omnivores
Third trophic level
Secondary consumers
carnivores
Second trophic level
Primary consumers
herbivores
First trophic level
Decomposers are Primary producers
autotrophs
heterotrophs & must
be part of every
ecosystem to break
down dead material
& recycle nutrients!
Energy Flow: Food Chains
Food Web
Interactive
• Does energy only flow through individual
organisms?
– No… through community
• in food chains & webs
***Arrow always points
toward organism taking in
energy & away from the
organism “giving up” energy.
Where do almost all
communities get their energy?
Energy Flow: Energy Pyramids
• Energy cannot be recycled, it can
only be transferred & transformed.
– ~90% is lost as heat &/or used by
previous organism for life functions
– ~10% passed to next level
• 10% Rule of Ecological Efficiency
Lost
Energy
Lost
Energy
20
J
80
Amount of energy
passed on to the
next level.
Energy Flow: Food Chains
• Another name for
autotrophs?
– producers
• How do they get nutrients?
– make their own food
(sugars)
• most by photosynthesis
– What is the equation for
photosynthesis?
Energy Flow: Food Chains
Another name for heterotrophs?
consumers
How do they get nutrients?
 absorption
 ingestion
Energy Flow: Food Chains
• Types of heterotrophs?
– herbivores (eat plants)
– carnivores (eat animals)
• scavengers (feed on dead animals)
– ex. vultures, buzzards, crabs
– omnivores (eat plants & animals)
– decomposers (break down dead
material & recycle nutrients)
• Must be part of EVERY ecosystem!
Nutrients in An Ecosystem
• Nutrients can be recycled!
– Biogeochemical or nutrient cycles
• Ex. carbon cycle & nitrogen cycle
• Decomposers play major role…
Carbon Cycle
Other Relationships in a Community
Predation
Competition
• one organism benefits• both organisms are
(predator), the other is harmed (not necessarily
harmed & usually
killed) (-, -)
killed (prey) (+, -)
Other Relationships in a Community
• symbiosis
– when 2 species
live closely
together in a
relationship
over (a long)
time
• commensalism
• mutualism
• parasitism
Other Relationships in a Community:
Commensalism
• one partner benefits from the relationship & the
other neither benefits, nor is harmed (+, 0)
Other Relationships in a Community:
Mutualism
• both partners benefit from the relationship (+, +)
Other Relationships in a Community:
Parasitism
• one partner benefits (parasite) & the other is
harmed, but not usually killed (host) (+, -)