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

Copyright © 2010 Pearson Education, Inc.

Chapter 14

Conserving BiodiversityCommunity 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

goneFigure 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 FragmentationPLAY



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



Competition: How a Deliberately Infected Chicken Could Save a Life

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 - Competition: How a Deliberately Infected Chicken Could Save a Life

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 takenin by deer is available tomountain lion.

About 10% of energytaken in by grass isavailable to deer.

Biomass in grass population

Biomassin mountain lions

Biomassin 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 organicmatter

Plantprotein

Nitrogen(N2)

Nitrate(NO3

–)

Nitrite (NO2

–) Ammonia(NH3)

Decomposers(bacteria and fungi)

Nitrogen-fixingbacteria in plantroot nodules

Free-living,nitrogen-fixingbacteria



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’sCerrado

Brazil’sAtlanticCoast

TropicalAndes

Cape FloristicProvince

W. AfricanForests

MediterraneanBasin

Caucasus

SouthwestAustralia

New Zealand

Philippines

India-Burma

South CentralChina

NewCaledonia

Polynesia/Micronesia

SucculentKaroo

WesternGhats andSri Lanka

Wallacea

Madagascar

Tanzaniaand

KenyaSundaland

CaliforniaFloristicProvince

Mesoamerica

Diversity hot spots

CentralChile

Choco/Darien

WesternEcuador


Caribbean


MediterraneanBasin

Tanzaniaand

Kenya



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



Population Size & Environmental Disasters 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



Population Size & Environmental Disasters 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: Conservation Genetics

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.

Homozygote 2: Relatively low fitness(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.

Homozygote 2: Relatively low fitness(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

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