Transcript 4.2.2-.4 Causes of Extinction

The amount of biological diversity
per unit area.
It includes: genetic, habitat and
species diversity
Is the total number of genetic characteristics of a
specific species.
Variety of forests, deserts, grasslands, lakes, oceans, coral
reefs, wetlands, and other biological communities,
(niches per unit area).
Is the number of species
or organisms per unit
area found in different
habitats of the planet.
State of US species.
Projected Status of Biodiversity
1998–2018
Arctic Circle
60°
EUROPE
NORTH
AMERICA
30°N
Tropic of Cancer
Pacific
Ocean
0°
150°
120°
90°
Tropic of Capricorn
ASIA
Atlantic
Ocean
AFRICA
30°W
SOUTH
AMERICA
0°
Pacific
Ocean
60°E
90°
150°
Indian
AUSTRALIA
Ocean
30°S
Antarctic Circle
60°
ANTARCTICA
Critical and endangered
Threatened
Stable or intact
What are the relationships
among ecosystem stability,
diversity, succession and
habitat ?
• How does diversity change during succession?
• How does habitat diversity influence species diversity and
genetic diversity?
• How does ecosystem complexity, with its variety of nutrient
and energy pathways, provide stability?
• How do human activities (agriculture, mining, logging, etc.)
modify succession?
• What are the potential positive and negative results of human
activities that simplify ecosystems? (monocrop agriculture)
Why Should We Care About
Biodiversity?
Instrumental value:
usefulness to us.
Intrinsic value:
because they exist,
Regardless of whether
they are useful to us or
not.
Goods
 Food, fuel, ecosystems, species, fiber, lumber, paper, …
 90% of today’s food crops
 40% of all medicines (85% of antibiotics)
Foxglove
Digitalis purpurea,
Europe
Digitalis for heart failure
Pacific yew
Taxus brevifolia,
Pacific Northwest
Ovarian cancer
Ecological
 Flow of materials, energy, Services:
and information in the biosphere
 Photosynthesis
 Pollination
 Soil formation and maintenance
 Nutrient recycling
 Moderation of weather extremes
 Purification of air and water
Information:
 Genetic information: adaptation and evolution
 Genetic information for genetic engineering
 Educational and scientific information
Option:
• People would be willing to pay in advance to preserve the
option of directly using a resource such as a tree, an elephant,
a forest or a clean lake.
Recreation:
• Hunting, fishing, swimming, scuba diving, water skiing, . . . .
• Eco-tourism
Nonutilitarian:
 Existence
 Aesthetic
 Protect natural capital for future generations
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Darwin and Evolution
Evolution are the changes in the gene pool of a
population over time.
Natural selection process by which individuals that are
better suited to their environment survive and
reproduce most successfully.
Adaptation is an inherited characteristic that increases
an organism’s chance of survival.
Darwin
Wolf
Pinta
Marchena
Genovesa
Santiago
Bartolomé
Fernandia
Råbida
Pin zon
Seymour
Baltra
Santa Cruz
EQUATOR
Santa Fe
Tortuga
Isabela
San Cristobal
Española
Floreana
Galåpagos
Islands
Marine Iguana
Land Iguana
KONA
FINCH
extinct
KAUAI AKIALAOA
AMAKIHI
LAYSAN
FINCH
IIWI
AKIAPOLAAU
APAPANE
MAUI
PARROTBILL
fruit and seed eaters
insect and nectar eaters
FOUNDER SPECIES
Based on his observations, Darwin
proposed that EVOLUTION
occurs by NATURAL SELECTION.
Darwin’s Postulates
 Variation within populations.
 Overproduction of offspring.
 Struggle for existence.
 Unequal survival and reproduction rates.
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Population of organisms
Overproduction of
offspring
Mutations & Sexual
reproduction produces
variations among
offspring.
Limited resources leads to a
struggle for survival between
offspring.
Survivors reproduce more
successfully.
Population changes over
time.
Evolution of Mammals
DISPERSAL
OF HIGHLY
EVOLVED
PLACENTAL
MAMMALS
South
America
Extinctions of many marsupials and
early placental mammals
About 5 million years ago, during the Pliocene
Fig. 27.19d, p. 471
Nonvertebrate chordates
Jawless fishes
Cartilaginous fishes
Bony fishes
Amphibians
Reptiles
Birds
Mammals
Eurasia
North
America
MONOTREMES,
MARSUPIALS
EVOLVE AND
MIGRATE
THROUGH
PANGEA
South
America
Africa
India
Australia
Antarctica
About 150 million years ago, during the Jurassic
Fig. 27.19a, p. 471
MONOTREMES
Platypus
Spiny anteater
MARSUPIALS
Koala
Tasmanian Devil
PLACENTAL
MAMMALS
EVOLVE;
ADAPTIVE
RADIATIONS
BEGIN
Isolation of the
early
monotremes,
marsupials on
this land mass
Between 100 and 85 million years ago, during the Cretaceous
Fig. 27.19b, p. 471
PLACENTAL MAMMALS
Bat
Arctic Fox
Walruses
Manatee
Beaver
Beaver
Muskrat
NORTH AMERICA
Muskrat
Beaver and
Muskrat
Coypu
Capybara
Coypu and
Capybara
Capybara
SOUTH AMERICA
Coypu
North
America
ADAPTIVE
RADIATIONS
OF MORE
EVOLVED
PLACENTAL
MAMMALS
South
America
Eurasia
Continued isolation of
early monotremes and
marsupials
Africa
Extinctions of mammals
Antarctica
About 20 million years ago, during the Miocene
Fig. 27.19c, p. 471
RACCOON RED PANDA
DIVERGENCE
approximately
40 million years ago
GIANT PANDA
SPECTACLED
BEAR
SLOTH SUN
BEAR BEAR
BLACK
BEAR
POLAR
BEAR
BROWN
BEAR
DIVERGENCE
15-20 million years ago
Fig. 20.10, p. 319
A group of potentially or actually interbreeding
populations, with a common gene pool, which are
reproductively isolated from other groups
The problem with the species definition
The species concept is a human construct used to
make sense of the natural world. While
extraordinarily helpful in understanding life, it
fails to capture the full complex reality of
continually evolving populations of organisms.
Sibling Species
Species that can’t
interbreed, but have no
significant differences in
appearance.
Very different appearance that can interbreed?!
Two tigons (male to the left, female to
the right)

A Liger-Lion/Tiger
A "boblynx" -- a hybrid of bobcat and
lynx;
A "zonkey" -- a hybrid of zebra and
donkey;
 The "Toast of Botswana", -- a hybrid of a female goat to a male sheep;
A "cama" -- a hybrid of camel and llama;
A "yakalo" - a hybrid of buffalo or bison and yak;
A "cattalo" (or "beefalo") -- a cross of a bison with a domestic cattle;
A "coywolf" -- a hybrid of coyote and wolf;
A "wholphin" -- a hybrid of a bottlenose dolphin mother and a false
killer whale father. Same situation like with the "pumapard" (parents
belong to different genera).
Some intraspecies hybrids (both genders fertile):
A "wig" -- a cross of a wild and a domestic pig;
An unnamed cross of a Siberian and a Manchurian tiger.
tulips
EXTINCT is FOREVER!!
Non-human causes of extinction:
 Volcanic events
 Ocean temperature change
 Sea level changes
 Meteorites
 Glaciations
 Global climate change
 Competition/predation
Human causes of extinction/loss of biodiversity HIPPO
Habitat destruction and fragmentation
Introduced species
Pollution
Population
Over consumption
Rates of Extinction:
= number of species becoming extinct per unit time.
 Rates of extinction are very difficult to estimate,
because we don't even know within an order of
magnitude how many species there are.
 Fossil records can reveal the average "lifetimes" of
species, or how long different classes of plants and
animals generally exist on the earth before going
extinct.
 From this information, scientists can determine a
"background" rate of extinction, or the natural rate of
extinction without human intervention.
 Because of human intervention the Earth's species are
dying out at an alarming rate, up to 1,000 times faster
than their natural rate of extinction.
 By carefully examining fossil records and ecosystem
destruction, some scientists estimate that as many
as 137 species disappear from the Earth EACH DAY,
which adds up to an astounding 50,000 species
disappearing every year.
The Earth has experienced 5 MASS EXTINCTIONS
 Mammals average species lifespan 1 million years.
 With ~ 5,000 mammalian species the background extinction rate = 1 every 200
years.
 In the past 400 years, though, 89 extinctions have been recorded, almost 45
times the natural rate.
 Over 50 of those
extinctions have
occurred in the past
century,
 Rate = 100 times the
background rate!!
Extinction Rates over geological time
Middle Cambrian age (about 540 million years ago)
•The locality is special because
of the soft-bodied preservation
of a wide diversity of fossil
invertebrate animals.
•Period of great speciation.
Characteristics of vulnerable species
 Small population size - island species.
 Small population size - species with limited habitats.
 Extremely specialized species.
 Species with low reproductive potential.
 Species that require large territories.
 Species with limited dispersal ability.
Vulnerable species - continued
 Migratory species.
 Species that are economically valuable or hunted for
sport
 Predators.
 Species that are vulnerable to pollution.
 Species that are incompatible with civilization.
Rainforest
 Tropical rainforests contain at least half of the Earth's species.
 Most species have evolved to inhabit very specialized niches in their
environment.
 When humans disrupt that environment, many species cannot survive.
 Because species depend on each other in a complicated web of relationships,
changing just one part of that web harms the entire ecosystem.
 This breakdown of rainforest ecosystems will likely lead to the disappearance of
up to 10% of the world's species within the next 25 years.
Rainforest continued
 The human species depends on the rainforest's millions of life forms for its
own existence  The genetic diversity found within the rainforests provides invaluable
additions to the gene pool which help maintain and improve domestic crops.
 Without a diversity of strains, crops become overly homogenous and
vulnerable to mass blight.
 Many medicines that we regularly use come from rainforest species.