Announcements
No section this week, but we will have lecture on
Friday
• Invasive species writing assignment due at
beginning of lecture this Wednesday
• Problem set will be handed out in lecture this
Wednesday
• Problem set is due Wednesday, November 24th
•
• we will not have lecture that day
• you can turn problem set into your TA’s box in the ES
Program office
• for on-time turn-in, put it in your TA’s box by 10am at
the latest on November 24th
Summary from Friday
•
Metapopulation Theory
•
•
•
•
•
subpopulations
maintenance of genetic diversity
source and sink populations
controls on immigration
Invasive Species
• definition of terms
• why invasive species are successful
• problems with invasive species
How can they be stopped?
•
Physical removal
• slow and costly
• leaves some to recolonize
•
Chemical eradication
• can harm natives
• expensive
•
Biocontrol
• may not work
• can create a bigger problem than you solve
Global Change
• What will the world be like in 100 years?
• Population growth
• Land use/cover change
• Climate change
With this kind of exponential
growth, when will we reach
carrying capacity?
Human Population Growth
• The maximum biological carrying capacity
for humans = 50,000,000,000
• this figure assumes that all primary production
is consumed by people…is this possible?
Human Population Growth
• The maximum biological carrying capacity
for humans = 50,000,000,000
• this figure assumes that all primary production
is consumed by people…is this possible?
So, what is a more meaningful estimate of
carrying capacity?
Human Population Growth
• The maximum biological carrying capacity
for humans = 50,000,000,000
• this figure assumes that all primary production
is consumed by people…is this possible?
So, what is a more meaningful estimate of
carrying capacity?
8 to 16 billion people
Slowing the growth
• What is the most effective way?
• provide access to birth control
• raise standard of living
• education
Why does population matter?
• More people will need space, food, and
other materials
• land clearing
• habitat destruction
• increased emissions of greenhouse gasses
• CO2 carbon dioxide
• CH4 methane
• N2O nitrous oxide
Land use and land cover change
•
Deforestation
•
Desertification
Greenhouse gases and global warming
• industrialization = higher emissions
CO2
• gases trap heat in the lower atmosphere
Secondary effects of warming
• Heat can alter hydrological cycles
• melting of ice caps
• rise in sea level
•
•
•
•
evaporation
cooling in certain areas
movement of air: wind
storms
Human Population
(size and resource use)
Industry
CO2 increase
Agriculture
Nitrogen cycle
Global climate
change
Land use and
cover change
Loss of biological
diversity
Studying climate change
•
•
Add CO2
Add heat
What happens?
Announcements
Invasive species writing assignment due now
• No section this week, but we will have lecture on
Friday
• Make sure to get the problem set today
• Problem set is due Wednesday, November 24th
•
• we will not have lecture that day
• you can turn problem set into your TA’s box in the ES
Program office
• for on-time turn-in, put it in your TA’s box by 10am at
the latest on November 24th
Summary from Monday
•
Global change
• Population growth
• why it matters
• carrying capacity for humans
• how to slow the growth
• Land use and land cover change
• deforestation
• desertification
• Climate change
• increased CO2 emissions by human activity
• studying climate change
Global change  community change
•
Different species have different responses
• elevated CO2 and C4 vs. C3 plants
Global change  community change
•
Different species have different responses
• elevated CO2 and C4 vs. C3 plants
• water use and drought-tolerant plants
• heat stress
Success
potential
survival, but
stressed
intolerant
potential
survival, but
stressed
optimum
Temperature
intolerant
Global change  community change
•
Different species have different responses
• elevated CO2 and C4 vs. C3 plants
• water use and drought-tolerant plants
• heat stress
Global change  community change
•
Different species have different responses
• elevated CO2 and C4 vs. C3 plants
• water use and drought-tolerant plants
• heat stress
•
With a change in community, biodiversity may…
• increase
• decrease
• stay the same
What is biodiversity?
Biodiversity = variation in living things
• Genetic diversity
• Species diversity
• Species richness: # of species
• Species evenness: how #’s are distributed
•
Growth-form diversity
Community diversity
•
How is biodiversity measured?
•
Measuring Biodiversity
•
•
•
Count the # of species present
Count the # of families represented
Look for different “functional groups”
Biodiversity Hotspots
Distribution of Biodiversity
•
general increase from poles to equator
Bird species in
North America
Diversity increases
from pole to
equator for many
species.
Why?
Diversity in the Tropics
•
50-80% of today’s species live in tropical rainforest
•
high temp. and rainfall in tropics
• many species rely on trees
•
however, tropical forests in Africa not as diverse as
those elsewhere  other drivers of biodiversity
aside from climate
Distribution of Biodiversity
•
general increase from poles to equator
Must also consider:
• history
• productivity of the system
• habitat structure
• specialization of species
• survival of specialists
History
•
•
Most of Earth’s land mass was once tropical
Evolution of flowering plants in tropics
increased diversity of:
plants
•
insects
mammals
When Earth’s climate cooled, some species
at high latitudes went extinct
Productivity
•
•
•
Tropics are near the equator
Sun’s rays are direct  high productivity
More energy at the bottom of the food
chain means more species can be
supported
With more
energy, 16
niches are
possible
With less energy,
only 8 niches exist
Habitat Structure
•
diverse structure  more biodiversity
• multi-aged stands of trees
• epiphytes
• gaps
•
physical structure provides
• feeding surfaces
• nesting sites
• microclimates
Specialization
•
•
•
constant presence of food in tropics
migration not necessary in tropics
certain specialized feeding strategies that
are not possible in temperate regions work
in the tropics
Survival of Specialists
•
temperate regions have been glaciated
several times in the past 2 million years
Survival of Specialists
•
•
•
temperate regions have been glaciated
several times in the past 2 million years
with every ice age, glaciers scour
temperate regions and primary succession
must take place
generalists are more successful than
specialists in temperate zones
Why is biodiversity important?
Genetic diversity
• Long term survival requires
responsiveness to small changes in the
environment
• Prevent genetic bottleneck
Population size
Genetic diversity
Time
Conserving a viable population
Goal of conservation: maintain a MVP
MVP: minimum viable population
• it is difficult to know what this number is
With too few mating pairs:
• inbreeding depression: lowered fitness of
offspring
• genetic drift: random loss of alleles from the
genetic pool
Why is biodiversity important?
Species Diversity
• Ethical Reasons
• some believe in a universal right to exist
• aesthetic, spiritual, or other intrinsic value
•
Practical Reasons
• medicines
• pest control
• ecosystem services
Announcements
•
•
•
Pick up the problem set from your TA if
you don’t have it already
Problem set is due Wednesday, November
24th by 10am in your TA’s box
No section this week
Summary from Wednesday
Global change drives community change
• Biodiversity
•
• increases from poles to equator
• higher temp. and rainfall in tropics
• other drivers:
•
•
•
•
•
•
history
productivity
structure
specialization
survival of specialists
Why is biodiversity important?
Ecosystem Services
•
Primary production for food, forage, fiber
Ecosystem Services
•
•
Primary production for food, forage, fiber
Control of water dynamics
• flood control
• water purification
Ecosystem Services
•
•
Primary production for food, forage, fiber
Control of water dynamics
• flood control
• water purification
•
Pollination
Ecosystem Services
•
•
Primary production for food, forage, fiber
Control of water dynamics
• flood control
• water purification
•
•
•
Pollination
Regulation of nutrient distribution
CO2 uptake and C sequestration
but how does biodiversity matter?
Control of ecosystem services
Redundancy
• more than one species has a similar “job”
• if one goes extinct, the others compensate
Atta sexdens
Atta cephalotes
Control of ecosystem services
Redundancy
• more than one species has a similar “job”
• if one goes extinct, the others compensate
Leaf-cutter ants are responsible for the
decomposition of 20% of the leaves in
South American rainforests!
Control of ecosystem services
•
Keystone species
• a single species with impacts on an ecosystem
that are disproportionate to its biomass
• if removed, the ecosystem changes a lot
Keystone Species
A healthy kelp forest
with sea otters present
When sea otters are
eliminated, urchins take
over
Island Biogeography
Islands are great for studying population
ecology because:
They are isolated
• You can potentially quantify all occurring species
•
Patterns of Biodiversity on Islands
•
Large islands have more species than
small islands
Larger islands have more species
Patterns of Biodiversity on Islands
•
Large islands have more species than
small islands
Why is this true?
A larger area will support more
species, and larger populations
of a single species
Patterns of Biodiversity on Islands
•
•
Large islands have more species than
small islands
Islands close to the mainland have more
species than islands further away
Controls on immigration
mainland
Distance to source population
Lots of immigration
Little immigration
Patterns of Biodiversity on Islands
•
•
•
Large islands have more species than
small islands
Islands close to the mainland have more
species than islands further away
With more physical diversity, and island
will have more species
• more habitats provide more niches
Patterns of Biodiversity on Islands
•
•
•
Large islands have more species than
small islands
Islands close to the mainland have more
species than islands further away
With more physical diversity, and island
will have more species
• more habitats provide more niches
•
Small islands are unlikely to have top
predators
• not enough prey available as food
Do islands have high diversity?
•
if biodiversity increases with area, how
can islands be diverse?
Patterns of Biodiversity on Islands
Required for high biodiversity on islands:
• evolution of new species requires isolation
• long geologic time period
• high temperature and rainfall
• topographic complexity
Designating a “biodiversity hotspot”:
• many endemic plant species
• impacted by humans