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