Download D. Adaptive Radiation

D. Adaptive
Radiation
One species
new
new
new
new
species:
species:
species:
species:
A
B
C
D
• Typically occurs when populations of a single species
...
• invade a variety of new habitats,
• evolve under different environmental pressures
(selective forces)
• Examples: Darwin’s Galapagos Finches, Hawaiian
Silverswords
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IV. Pace of
Evolution
• Gradualism
phenotypic change
• Evolutionary change is slow and imperceptible from generation to
generation
• Over the course of thousands and millions of years, major changes could
occur
• Punctuated equilibrium
• Evolution normally proceeds in spurts, with long periods of little
evolutionary change in between.
• The proposed stasis would be expected in large populations experiencing
stabilizing selection over long periods of time.
V. Extinction
•
Extinction = death of all the members of a
species
• How and why does it happen?
(1) Localized distributions & overspecialization
• Increase an organism’s likelihood of extinction
Devil’s Hole pupfish:
Lives in isolated water
pools in Mojave
Desert
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What Causes Extinction?
• (2) Interactions with other organisms
• - competition, parasitism, predation
• EX. the Panama land bridge: connected 2 continents, formed during
the Pleiocene (~3 mya)
• N. American species & South American species mixed
– ! For the first time in history
• Many S. American species were out-competed
•
! went extinct
What Causes Extinction?
• Habitat change / destruction
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Speciation and Extinction Through Time
•
There have been 5 major mass extinctions interspersed
within relatively consistent extinction patterns.
– most famous ! end of Cretaceous period (65 mya); dinosaurs went
extinct
• Mammals quickly experienced evolutionary radiation.
– Biological diversity tends to rebound after mass extinctions
What Causes Extinction?
• (3) habitat change / destruction
• What can we do?
BOZEMAN PASS WILDLIFE LINKAGE
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Ecology
I. Definitions
II. Population Ecology
III. Community Ecology
IV. Ecosystem Ecology
Ecological Hierarchy
• An ecosystem
consists of all the
organisms living in a
community as well
as all the abiotic
factors with which
they interact
– Microcosm to lakes
to forests, etc.
– Biosphere as global
ecosystem made up
of all the local
ecosystems on Earth
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Chemicals cycle within ecosystems
Two major processes occur w/i ecosystems:
I. Energy enters (sun) and is fixed within the system.
This energy can be transferred b/n organisms or
converted to heat.
II. Chemical elements move through ecosystems in
biogeochemical cycles.
Water Cycle
! All life depends on water
! Only ~2% of the Earth’s water
is captured in any form
!All of the rest is free water
! 96% of all fresh water in the
US is groundwater
Carbon cycle
! CO2 makes up ~0.03% of our atmosphere, much more
in our oceans
! Photosynthetic bacteria, protists, & plants fix CO2
! Essentially all heterotrophic organisms obtain their
carbon either directly or indirectly from photosynthetic
organisms
! Increasing amounts
of carbon dioxide in our
atmosphere appear to
be a major player in
Global Climate Change
(aka Global Warming)
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Nitrogen cycle
! Nitrogen is an essential component of organic
compounds such as proteins and amino acids
! The atmosphere is ~78% N2 (N
N)
! Certain prokaryotes can “fix” nitrogen from the
atomosphere
Root nodules
Energy flows through ecosystems
! An ecosystem includes both autotrophs and heterotrophs
! Autotrophs are the primary producers
Much of the energy that passes
through ecosystems is converted to heat
Trophic levels within a food chain
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Food chains
!B/C considerable energy is converted to heat at each
stage, the length of food chains is limited
! Food chains generally consist of 3 or 4 steps
Smelt
Biogeographic patterns of species diversity
! The tropics contain the greatest amount of biodiversity
! The reasons for this include higher productivity,
climatic predictability, increased predation, and spatial
heterogeneity
Bird diversity
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Ecosystem change over time
Mature ecosystems are complex networks.
Emerge in very slow stages.
Begins with disturbance
e.g. fire, landslide
Succession:
Structural change in ecosystem over time.
Two main types
1. Primary succession
2. Secondary succession
1) Primary succession: “from scratch”
1) Bare Rock! Weathering
2) Pioneer species: lichens,
mosses
3) start the soil creation process, in
conjunction w/ prokaryotes
4) Then herbs…shrubs…animals
5) Eventually: Mature ecosystem
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2) Secondary succession
Occurs after an established ecosystem
is disturbed
! Fire
! Abandoned farm fields
! Already soil, seed bank
! In the case of fire, it is very patchy
! Faster than primary succession
(…200 yrs)
Will eventually recover to a mature
ecosystem.
Secondary succession & disturbance
Some ecosystems undergo
regular disturbance:
In this case, all organisms
have evolved to live under
these conditions (e.g. fire
adapted ecosystems)
! Can promote diversity
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Secondary succession
1980. Pristine lowland
rainforest in Eastern Borneo
dominated by trees of the
dipterocarp family.ﾊ
Secondary succession
1982. Initial surface fire in the
same forest, which has been
selectively cut since 1980.
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Secondary succession
1985. Three years after the initial
fire. Most trees are killed by the
surface fire, some by drought
stress, but some trees are still
standing.
Secondary succession
1995. Thirteen years after
the initial fire. More
standing trees have died
and collapsed. The
undergrowth is dominated
by pioneer tree species
(predominantly
Macaranga spp.). This
secondary succession
becomes highly
flammable in extremely
dry years.
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Secondary succession
1998. A second fire. The tree
layer, including the postfire
secondary succession, is
almost completely killed by a
high-intensity fire.
Secondary succession
1998. Final stage of fireinduced savannization of
the rainforest in a nearby
site. The area is
dominated by an
aggressive invading
grass species (Imperata
cylindrica)
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Secondary succession
Biomes
Major ecosystems that cover
broad geographical regions
What determines the type of biome?
Broadscale climatic conditions interacting
with other abiotic factors:
Climate: Rainfall, elevation, temperature
Abiotic factors: Soils, nutrient availability
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Major terrestrial biomes
30ºN
Tropic of
Cancer
Equator
Tropic of
Capricorn
30ºS
Tropical forest
Savanna
Desert
Chaparral
Temperate grassland
Temperate broadleaf forest
Coniferous forest
Tundra
High mountains
Polar ice
The
Onion
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