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Transcript of Chapter 9 Population Ecology - effinghamschools.com · Population Distribution aka Dispersion: ......
Population Ecology
Dynamics of Ecosystems
Chapter 9
Thursday October 8th
Reminders: Enjoy your fall break! Be safe.
Released FRQs http://www.kwanga.net/apesnotes/frq-topics.pdf
http://apcentral.collegeboard.com/apc/public/exam/exam_information/2003.
html
Read chapters 8-9
Agenda: Notes Population Ecology
Individual
Population
Community
Ecosystem
Biome
Biosphere
I. Ecological Hierarchy
Uniform – helps reduce intraspecific competition
Population Distribution aka Dispersion:
Clumped– helps w/ protection, often occurs b/c of resource availability
Random – seen in some plants
Check for understanding…
• Raise 1 finger
for random
• 2 fingers for
uniform
• 3 fingers for
clumped.
Which dispersion pattern is this?
Uniform – everyone has space to nest
Clumped – safer from predators
Which dispersion pattern is this?
Random
Clumped
Population Births Immigration Deaths Emigration Change
A 200 0 100 0
B 10 0 10 100
C 10 10 100 100
D 10 100 10 0
E 10 100 10 100
Growth rate= rate of increase – rate of decrease (births + immigration) – (deaths + emigration)
Calculate the change below
Intrinsic rate of increase (r)
= rate of pop growth w/ unlimited resources
A pop with few limitations will grow exponentially (J-shaped curve)
Most pops grow < intrinsic rate of increase (r)
b/c of environmental resistance
factors that act to limit pop growth
Can be Abiotic or Biotic
Can be Density-independent
or Density-dependent
Density-independent factors: Any factor in the
environment that does not depend on the number
of members in a population per unit area
Weather events, Fire, Human alterations of the landscape
(Air, land, and water pollution)
Density-Dependent Factors: Any factor in the
environment that depends on the number of
members in a population per unit area Predation, Disease, Competition, Parasites
Limiting Factor Density Independent Density Dependent
Climate Change
Competition for Food
Parasitism
Frost
Infectious Disease
• Biotic Potential
vs.
Environmental
Resistance o Generally come to
some equilibrium:
Carrying Capacity (K): max number of individuals of a given
species that can be sustained indefinitely in a given space
• Populations w/ a carrying capacity
show logistic growth (S-shaped curve): o Start off with rapid exponential growth
o Followed by a steady decrease at K
Some organisms overshoot carrying
capacity results in a pop crash (dieback)
Due to reproductive time lag (period
needed for birth rate to fall & death
rate to rise in response to resource
overconsumption)
Population Fluctuations
1. Stable: stay generally around K
2. Irruptive: stay stable except for occasional peaks & crashes
often due to density independent limiting factors (nutrients,
weather), Seen in insects & algae (in temperate climates)
3. Cyclic: regular fluctuations
Seen in predator – prey relationships; lynx & hare
4. Irregular: no pattern
http://www.arkive.org/eurasian-lynx/lynx-lynx/video-08a.html
Sexual Strategies & Patterns:
• Asexual reproduction: does not require sex cells (gametes).
Aka Mitosis – cloning.
o Bacteria reproduce this way. Only 3% of all species use this form
• Sexual reproduction: requires gametes results in genetic
recombination
Disadvantages
½ pop doesn’t give birth
Increased chance of genetic defect/error
Courtship and mating rituals can be
complex
Advantages
Genetic variety/diversity!!
Parents can divide responsibilities
Reproductive Patterns: 2 types
K-selected species
r-selected species
https://www.youtube.com/watch?v=Bu6ouKt9zhs
Bozeman Science
Survivorship Curves
3 Types of Survivorship Curves:
• Type I: Late Loss
o Low infant mortality &
long life spans (k-selected)
o Examples: humans (in
developed countries); large
mammals (elephants, big
cats, etc.)
• Type II: Constant Loss
o Death rate even among all
ages
o Examples: some birds,
some invertebrates, rodents
• Type III: Early Loss
o High infant mortality and
then constant mortality for
few remaining (r-selected)
o Examples: annual plants,
small fish, insects
I
II
III
Community Ecology How do organisms interact?
Chapter 8
• Species Equilibrium Model (E.O. Wilson)
• aka Theory of Island Biogeography
oBalance b/w 2 variables determines
the number of different species found on an “island”:
• rate at which new species immigrate to the island
• rate at which existing species become extinct on the island
• 3 factors must be taken into account:
1.Immigration and extinction rates
2.Island size
3.Distance from “mainland”
Useful when protecting wildlife on “habitat Islands”
a.k.a areas surrounded by development
• Species Equilibrium
Model
o “Islands” closer to a
mainland will have
higher immigration
higher equilibrium
species richness
• Remember the Major Roles
that Species Can Play
within Ecosystems cont.:
1. Native
2. Nonnative
3. Indicator
4. Keystone
5. Foundation species
SE Asia Durian Fruit & Bats (a.k.a Flying Foxes)
Endangered due to
1. hunting for their meat
2. Deforestation
3. Targeted to keep them from eating
commercially grown fruit
Keystone
1. sustains tropical community
2. pollinates many plant species
3. disperses seeds in droppings &
therefore maintains forest biodiversity
Mutualism (+, +)
https://www.youtube.com/watch?v=69IGcIp-AZg
Invasive Species
• 1957 Brazil imported
African Bees for honey
production, instead
they displaced
domestic bees and
reduced honey supply
• They have since
moved north &
reached the United States
• They are aggressive &
unpredictable, kill
1000’s of
domesticated livestock
and about 1000
people due to allergies
https://www.youtube.com/watch?v=y7C--Cv4gPw
Indicator Species
Species What do they Indicate?
Trout Water Quality; require clean water w/high D.O.
Birds & Butterflies Chemicals & habitat loss; found everywhere
Amphibians (frogs, salamanders, & toads
Pollutants in air, water, & soil, UV light, habitat loss (filling in wetlands), drought, overharvesting; Live in water as herbivores & as adults on land as carnivores, thin permeable skin, eggs have no protection,
https://www.youtube.com/watch?v=BvidpapF1bg
Sci Show
https://www.youtube.com/watch?v=1q5oe33M15Q
Scary Bat Die off
http://www.smithsonianmag.com/videos/category/wildlife/saving-amphibians-from-deadly-
fungus/
Amphibian Chytrid Fungus
Keystone & Foundation Species:
American Alligator
hunted for meat, skin, and/or for
sport
1967 put on endangered
species list
1977-1987 upgraded to
threatened list in 8 states
Keeps areas free of vegetation,
digs deep depressions that fill
with water & serve as refuge for
aquatic life, feed on predatory
gar
https://www.youtube.com/watch?v=_IWw8Ruz8Uo
Keystone Species and their Role 3:59
https://www.youtube.com/watch?v=0-PE3ve3w2w
Bozeman Science 7:35
Species Interactions:
Gause’s principle states that
no 2 species can occupy same
niche at same time 1
species must relocate, die out
or change niche
Resource Partitioning
minimizes competition
Different
species of
warbler
Forage for
food in
different parts
of the same
tree to
minimize
competition
Species minimize competition by
filling specific niches within an
ecosystem (traits allow them to utilize
resources at different times, locations or ways)
Ex: North American warblers hunt for insects
in same spruce trees, but at different parts &
times
Symbiotic Relationships An interactive
association between two or more species living
together
Predation (+, -) Interaction b/w organisms in which one
organism (predator) captures and feeds
upon another (prey)
Preys’ Defense Mechanisms:
Physical adaptations: highly developed sight & smell; shells; spines;
thorns; Camouflage & mimicry
Chemicals: poisons, irritants, odors, ink clouds
Behaviors: puffing up, mimicking a predator, playing dead
Hognose snake
Praying mantis
Cuttlefish
Parasitism: when one organism (parasite) feeds on or otherwise
harms another organism (host) in close association (+,-)
Different from predation in that parasite is generally smaller than host and
doesn’t kill host, but harms over time
Brood parasitism Mistletoe Tick (Ectoparasites)
Video: https://www.youtube.com/watch?v=XuKjBIBBAL8
David Attenborough Parasites
Commensalism: benefits one species but has little or no
effect on other species (+, 0)
Epiphytes (Bromeliads &
some Orchids)& Trees Whales & Barnacles
Mutualism: interaction benefitting
both species (+, +)
Pollination Mutualism Nutritional Mutualism:
Lichen (fungi & algae)
Gut Inhabitant Mutualism
All communities change their structure & composition over time in
response to each other & changing environmental conditions
Disturbances: change in environmental conditions that disrupts a
community or ecosystem. These disturbances can range from mild to
catastrophic and can be caused by natural occurrences or human
activities:
Ecological Succession = gradual change in species composition
Two Types:
• Primary Succession
• Secondary Succession
• Primary Succession: the gradual establishment of
biotic communities on lifeless ground (rock)
Pioneer
Species
(Lichens,
Algae,
Bacteria,
Moss)
Pioneer
Species start
soil formation
process: trap
soil particles &
detritus in
wind, secrete
acids to break
down rock
Late
successional
species
Mid
successional
species
End in Mature
Community
(long-lived
hardwoods)
• Secondary Succession: when biotic communities are
established in an area where some type of biotic
community is already present
• Occurs after disturbance (burned forest, polluted stream,
abandoned farmland)
• Intermediate Disturbance Hypothesis: communities
that experience fairly frequent but moderate
disturbances have the greatest species diversity
https://www.youtube.com/watch?v=jZKIHe2LDP8
Crash Course
Succession Model Online • http://www.mrphome.net/mrp/succession.swf