Lect_ch14-Palmer-post.ppt

Copyright © 2010 Pearson Education, Inc.
Chapter 14
Conserving Biodiversity
Community and Ecosystem Ecology

Chapter 14 Section 1
The Sixth Mass Extinction

14.1 The Sixth Extinction
Terms
 Biodiversity – the entire diversity of living
organisms in an area
 Extinction – the complete loss of a
species
Endangered Species Act (ESA)
 law passed in 1973 to protect and
encourage population growth of
threatened and endangered species

Measuring Extinction Rates
 History of life on earth has been
punctuated with five mass extinctions
Figure 14.2

Causes of Previous Mass Extinctions
 Climate changes
 Changes in sea level
 Continental drift that changed ocean to
land
 Asteroid impact
Figure 14.2

Measuring Extinction Rates
 Is the sixth mass extinction event
occurring now?
 Need to know the background extinction rate
 Fossils indicate that average species
exists for ~1,000,000 years
 Estimate of background extinction rate is
0.0001% per year

Current rate of extinction
 more bird and mammal species have
disappeared in the last 150 years
 Current Extinction Rate = 0.01%
Figure 14.4

Definition of Extinction of modern species
 no individuals of a species must have been
seen in the wild for 50 years
However:
 44 of 68 shallow-water mussel species missing in
Tennessee River
 144 of 266 fresh-water fish in Malaysia are
missing
 200 of 300 fish from Africa’s Lake Victoria are
gone
Figure 14.4

International Union for the Conservation of
Nature (IUCN)
 Highly respected organization of scientists,
governments and organizations
 Predicts that the following are endanger of
extinction:
 11% of all plants
 12% of all birds
 24% of all mammals
Figure 14.4

Four Major Causes of Extinction
1. Loss or degradation of habitat
 Most important cause
2. Introduction of non-native species
3. Overexploitation
4. Pollution
 Most of these are due to human activities

1. Habitat Destruction
 As human population increases, pressure on
natural areas increases
 Species area curve – the number of species
that a natural area of a given size can support

Tropical Rainforest Destruction
 ~7722 square miles of So. American rainforest
are cut each year.
 This rate will reduce rainforest to 10% of original
size within 35 years
 Will mean extinction of about 50,000 species

Habitat destruction not limited to rainforests
 Freshwater lakes and streams, grasslands, and
temperate forests are also threatened
 If worldwide habitat destruction continues at
present rate, as many as 25% of all world’s
species could become extinct in 50 years
 But other threats, such as habitat fragmentation,
could push extinction rates even higher

14.1 The Sixth Extinction - Habitat
Destruction
Animation—Tropical deforestation and the species
area curve
PLAY

Habitat Fragmentation
= large natural areas
subdivided into
smaller areas
 Large predators are
threatened because
they require large
home ranges
 Human activity
usually results in
habitat fragmentation
Figure 14.5b

14.1 The Sixth Extinction - Habitat
Fragmentation
Animation—Habitat Destruction and Fragmentation
PLAY

2. Introduced Species
= non-native species introduced to a new area either
purposely or accidentally by human activity
Figure 14.5c
 Often destructive because they have
not evolved with local species
 Brown tree snake, introduced to
Guam, caused many local bird species
to go extinct
 Domestic cats in Wisconsin kill 39
million birds/year
 Zebra mussels, accidentally released
in the Great Lakes from Europe, are
outcompeting native species.
 Kudzu, a vine brought from Japan, is
now called “the vine that ate the south”

3. Overexploitation
= When human use of a natural resource
exceeds its reproductive rate.
 Can occur if species is highly prized by humans,
which can spur illegal hunting.
 3 of 8 species of tigers are extinct, other
extremely endangered
 Partly due to ‘Traditional Chinese Medicine’
 Can also occur if species competes with humans
 Gray wolves almost exterminated by ranchers

4. Pollution
= The release of poisons, toxins, excess
nutrients, and other waste products.
 Excess fertilizer runoff leads to eutrophication
of waterways
 Eutrophication is the excess growth of
bacteria that depletes oxygen from the water
 Herbicide atrazine is killing amphibians
 Carbon dioxide is another atmospheric pollutant,
associated with climate change

END Chapter 14 Section 1
The Sixth Mass Extinction

The Consequences of Extinction

14.2 Consequences of Extinction
So Why Should We Care If Species Become Extinct?
 Extinction is forever
 It is unethical to kill entire species
 Selfish Reasons
 Causing extinction has negative impacts on
us too!
 Loss of Resources
 Environmental instability
 Disrupted Energy & Chemical Flows
Figure 14.11

14.2 Consequences of Extinction
Loss of Resources
 Loss of species can lead to economic impacts for
humans
 Some biological resources harvested directly include
wood (lumber and fuel), shellfish (protein), and algae
(gelatin)
 Wild species provide biological chemicals (medicines)
 Wild species have alleles that are not present in
domestic species, which can increase vigor of
domesticated species
 Wild species can
contribute other
means of combating
pests (biological
control)
Figure 14.11

14.2 The Consequences of Extinction –
Environmental Instability
 Species interact with one another and their
environment in complex ways, not just a
simple food chain
Figure 14.12
 Communities = all
organisms living in a
habitat
 Niche = the role each
species plays in the
community
Food Web

Environmental Instability: Terminology
 Mutualism = organism that interact with
each other in a mutually beneficial way
Figure 14.12

Mutualism: How Bees Feed the World
 Mutualism – relationship in which both species
benefit from their interaction
 Many examples:
 Cleaner fish
 Fungal mycorrhizae
 Ants and acacia trees
 Bees are primary pollinators of many wild plants
 Wild bees pollinate 80% of agricultural crops in U.S.
 Bee populations are falling due to “colony collapse
disorder”
 Humans benefit from mutualism, and will lose if
bees go extinct

 Predation = survival of one species by
feeding upon another
Figure 14.12

Predation: How Songbirds May Save Forests
 Predator – species that survives by eating
other species
 Songbirds consume many insects
 Most insects eaten by songbirds consume
plants
 Songbirds help to sustain
forests
 As songbird numbers
decline, damage to
forests increase

 Competition = when two species both need
the same resources (food, shelter, etc), they
will be in competition if those resources are
limited
Figure 14.12

14.2 The Consequences of Extinction
Competition: How a Deliberately Infected
Chicken Could Save a Life
 A leading cause of food illness in the U.S. is
caused by Salmonella enteritidis.
 About 2 million Americans infected each year
 About 400 die each year as a result of infection
 Most common source of infection is eggs
 S. enteritidis contaminates egg when it forms in
the hen

 Competitive exclusion is the use of food
and space resources by one species, making
it impossible for another species to establish
 On this principle, chickens are deliberately
infected with harmless bacteria
 Harmless bacteria establish and prevent S.
enteritidis from living in chicken’s gut

14.2 The Consequences of Extinction -
Figure 14.16

Competition & Humans
 Competition between species can have
consequences for humans as well
 Mosquitos, snails and tadpoles compete for
same resources in ponds
 When populations of snails and tadpoles
decrease, mosquitoes increase
 Potentially serious because mosquitoes can
spread malaria, West Nile virus, and yellow
fever

 Keystone Species = the activities of a
single species can play a dramatic role in
the composition of a community
Figure 14.12

Keystone Species: Wolves in Yellowstone
 Keystone species are key figures in
determining the food web of an ecosystem
 Wolves were eradicated from Yellowstone
Park in 1920s
 With wolves gone, aspen, cottonwood, and
willow trees declined
 Trees declined due to predation by elk
 Trees are crucial for beavers, songbirds, and
fish
 With reintroduction of wolves, trees and other
species rebounded

Ecosystem Energy and Chemical Flows
 Ecosystem – includes:
 All living organisms in an area
 Plus nonbiological environment
 Loss of some species can dramatically
affect both of these ecosystem
properties
Figure 14.8

Disrupted Energy Flows
 Energy flow - only a small portion ( ~10%) of the
energy in one level of a trophic pyramid can be
converted to biomass at the next level
 Diversity also affects energy flow, such as in
more diverse grasslands, more biomass is
produced
Figure 14.8
About 10% of energy taken
in by deer is available to
mountain lion.
About 10% of energy
taken in by grass is
available to deer.
Biomass in grass population
Biomass
in mountain lions
Biomass
in deer
population

Disrupted Chemical Flows
 Nutrient cycling – nutrients that pass
through a food web rarely leave the system
Figure 14.18
Animal protein
Animal protein
Dead organic
matter
Plant
protein
Nitrogen
(N2)
Nitrate
(NO3
–)
Nitrite
(NO2
–) Ammonia
(NH3)
Decomposers
(bacteria and fungi)
Nitrogen-fixing
bacteria in plant
root nodules
Free-living,
nitrogen-fixing
bacteria

Disrupted Chemical Flows
 The soil community has an important role in
nutrient cycling
 Introduction of non-native earthworms in NE
U.S. had dramatic impact on forest plants
 Non-native worms changed the soil community
Figure 14.19

Psychological Effects
 Our experience with nature has strong
psychological effects
 Instinctive desire to commune with nature is
called biophilia
 Pets can improve mental well-being
 Dental patients viewing landscapes showed a
decrease in blood pressure
 Hospital patients who could view trees recovered
from surgery more quickly
 Loss of biodiversity could make human
experience less pleasant

Replacing Extinction
 5-10 million years to recover species lost from
a mass extinction
 Species that replace those lost are different
 After mass extinction of dinosaurs, mammals
replaced them as dominant large animals
 We can not predict what biodiversity will look
like after another mass extinction
 The mass extinction we are witnessing today
will have consequences for thousands of
human generations (if humans survive)

The Consequences of Extinction

Saving Species

14.3
Saving Species - Protecting Habitat
 Biodiversity hotspots = less than 2% of
the earth’s surface contain up to 50% of
the earth’s mammal, bird, reptile, and plant
species. These areas are.
Figure 14.21
Brazil’s
Cerrado
Brazil’s
Atlantic
Coast
Tropical
Andes
Cape Floristic
Province
W. African
Forests
Mediterranean
Basin
Caucasus
Southwest
Australia
New Zealand
Philippines
India-
Burma
South Central
China
New
Caledonia
Polynesia/
Micronesia
Succulent
Karoo
Western
Ghats and
Sri Lanka
Wallacea
Madagascar
Tanzania
and
Kenya
Sundaland
California
Floristic
Province
Mesoamerica
Diversity hot spots
Central
Chile
Choco/
Darien
Western
Ecuador
Polynesia/
Micronesia
Caribbean
Polynesia/
Micronesia
Mediterranean
Basin
Tanzania
and
Kenya
Polynesia/
Micronesia

14.3 Saving Species
Protecting Habitat
 Converting wild areas to agricultural production
is a major cause of habitat destruction.
 Altering our consumption patterns can help
decrease habitat destruction.
 Eating low on the food chain (less meat
and dairy) makes a difference.
 Reduce consumption of wood and paper
 Support conservation organizations
 Ultimately, slowing human population growth
rate must occur

14.3 Saving Species –
Population Size & Environmental Disasters
 A large population provides group protection
from environmental disaster.
 A species with a slow growth rate is at
greater risk if its numbers diminish.
 The longer a population remains small, the
greater its risk.
Figure 14.22

 The Heath Hen
 Lived in New England & numbered in 100,000s
 Declined due to habitat loss to 50 hens
 Reserve created on Martha’s Vineyard in 1908
 Rebounded to 2000 hens by 1915
 1916, fire destroyed much of reserve
 1917 cold winter brought hungry
Goshawks
 Then disease from domestic turkeys
 1927, only 14 remained, mostly males
 1932 last survivor seen
Figure 14.22

 Lessons from the Heath Hen
 Large populations can survive better
 EXP: population of 100,000 can loss 90%,
but pop. of 1,000 can not.
 Don’t put all members of species in same
reserve
 Whooping crane preserves are
in Maryland, Wisconsin, Calgary
Canada, and Louisiana
Figure 14.22

14.3 Saving Species
Conservation Genetics
 Loss of genetic variability is a two-fold
problem.
1. On individual level, low genetic variability
leads to low fitness, and is more likely to
express harmful mutant alleles.
2. On population level, loss of genetic variability
can lead to extinction due to the low fitness of
individuals.

14.3 Saving Species - A Closer Look:
The Importance of Genetic Variability
 When individuals are heterozygotic for many
genes, the overall effect is greater fitness.
Figure 14.23
Homozygote 1: Relatively low fitness
(only one type of jacket in wardrobe)
Heterozygote: Relatively high fitness
(two types of jackets in wardrobe)
Being heterozygous may confer higher fitness for responding to a changing environment.
(only one type of jacket in wardrobe)

 Heterozygotes can avoid deleterious
effects of recessive alleles.
Figure 14.24
Homozygote 1: Relatively high fitness
(two functional jackets in wardrobe)
Heterozygote: Relatively high fitness
(one functional jacket in wardrobe)
Being heterozygous may confer higher fitness by masking deleterious recessive alleles.
(two nonfunctional jackets in wardrobe)

 In a small population, individuals are more likely
to be related to their mates (inbreeding)
 Result can be inbreeding depression,
a decline in heterzygotes
 Because of this, cheetahs have poor
quality sperm and low rate of cub
survival
 In humans, children of first cousins
have lower rates of heterozygosity and
higher rates of infant mortality

The Extinction Vortex
 The Consequences of
Low Genetic Variability
in a Population
 A small population can
become stuck in a
cycle that leads to
extinction.
Figure 14.26

Irish potato famine
 a human example of the potentially
disastrous effects of low genetic diversity
 In 1840s, Irish potato crop had very low
genetic diversity
 Fungus that causes potato blight arrived in
Ireland; plants rotted in fields
 Because of crop failure, nearly 1 million Irish
died of starvation and disease

14.4 Protecting Biodiversity
Table 14.3

Conservation Organizations
Table 14.3
NATIONAL WILDLIFE FEDERATION http://www.nwf.org/
WORLD WILDLIFE FUND http://www.wwf.org/
NATURE CONSERVANCY http://www.nature.org/
SIERRA CLUB http://www.sierraclub.org
NATIONAL AUDUBON SOCIETY http://www.audubon.org/
GREENPEACE http://www.greenpeace.org/
NATIONAL RESOURCES DEFENSE COUNCIL http://www.nrdc.org/
ENVIRONMENTAL DEFENSE FUND http://www.edf.org/
DEFENDERS OF WILDLIFE http://www.defenders.org/
OCEAN CONSERVANCY http://www.oceanconservancy.org/

Saving Species

END Chapter 14

Lect_ch14-Palmer-post.ppt

Recommandé

Recommandé

Contenu connexe

Similaire à Lect_ch14-Palmer-post.ppt

Similaire à Lect_ch14-Palmer-post.ppt (14)

Dernier

Dernier (20)

Lect_ch14-Palmer-post.ppt