Download Extinction

October 02, 2013
Topic outline:
Review: evolution and natural selection
Evolution
1. Geologic processes
2. Climate change
3. Catastrophes
Niche
Speciation
Extinction
Biodiversity
Genetic engineering
October 02, 2013
http://www.cengage.com/cgi-wadsworth/course_products_wp.pl?fid=M20b&product_isbn_issn=9780495015987&discipline_number=22
How do we know what organisms lived in the past?
• Fossils-record of evolutionary change in life forms over time.
• Ice-core drilling-examine kinds of life found at different layers
• Chemical/DNA analysis
October 02, 2013
Evolution (recap)
Evolution = change in a population's genetic makeup
over time.
Mechanisms for evolution:
• Natural Selection (including coevolution)
• Mutation (some are neutral, negative, others
beneficial)
• Migration
• Genetic drift (bottleneck and founder effect)
• Horizontal gene transfer *microorganisms
October 02, 2013
Sexual Reproduction is adaptive--maintains genetic
diversity in a population
• Genetic diversity is important to be able to adapt to
constantly changing and challenging environment.
• Remember traits are passed from parent to offspring
(vertical gene transfer)
Some microorganisms can
exchange genes without
sexual reproduction by
horizontal gene transfer
• Adaptations can occur
quickly--doesn't require
generations.
• Confounds phylogenetic
trees
http://www.nature.com/nrmicro/journal/v4/n1/fig_tab/nrmicro1325_F2.html
October 02, 2013
Changes in the environment necessitates adaptation by
natural selection.
• Geologic processes
• Climate change
• Catastrophes
October 02, 2013
Geologic Processes
Tectonic plates
Alfred Wegener
The Earth's lithosphere is broken up into a series of giant
solid plates.
These plates sit on the asthenosphere (a layer of molten
rock) and drift across the Earth's surface.
http://www.rsc.org/Education/Teachers/Resources/jesei/platerid/plates.htm
October 02, 2013
Geologic Processes
Tectonic plates
Effect on evolution:
http://www.rsc.org/Education/Teachers/Resources/jesei/platerid/plates.htm
1) Locations of continents and oceans influences earth's
climate -->distribution of animals and plants.
2) Separation and joining of continents have allowed
species to move, adapt to new environments, and form
new species by natural selection.
3) Volcanic eruptions (at plate boundaries) destroys
habitats and reduce or wipe out populations. Opens up
habitat to be repopulated. Lava can yield fertile soil (rich
in nutrients like phosphorous and other minerals)
4) Earthquakes can separate and isolate populations
(leads to speciation)
October 02, 2013
Climate Change
Repeated changes in earth's climate throughout history.
Alternating periods of cooling and heating
-Ice age and interglacial periods
http://geology.utah.gov/surveynotes/gladasked/gladice_ages.htm
October 02, 2013
Climate Change
Effects on evolution:
1) Determines where plants/animals can live
(distribution)
2) Changes distribution of ecosystems--deserts,
grasslands, forests, etc.
3) Some species become extinct when climate change
occurs rapidly.
October 02, 2013
Catastrophes
Asteroids and meteorites
Asteroids and meteorites collide with earth.
Impact causes destruction of ecosystems and extinction
of species
Effects on evolution:
1) Long period of environmental stress--wipe out species
and habitat
2) Mass extinctions open up opportunities for new
species
October 02, 2013
Ecological Niche
Every species has a ecological niche, or a specific
role in the ecosystem.
> Where it lives/grows (habitat)
> Where it reproduces and how
> What it eats, how it eats.
> How it interacts with other species and
environment.
> "How an organism makes a living"
October 02, 2013
Ecological Niche
Fundamental niche - the full potential range of
physical, chemical, and biological conditions and
resources a species could theoretically use if it could
avoid competition from other species.
Realized niche - the actual niche a species occupies. Is
only a part of the fundamental niche.
Experiment by Joseph Connell
\\
Figure 53.13, page 1117, Campbell's Biology, 5th Edition
http://www.hammiverse.com/lectures/53/1.html
October 02, 2013
Ecological Niche
Generalist species have
broad niches.
• Can live in different places,
eat many types of foods,
tolerate wide range of
environmental conditions.
• Better able to survive
changing environment.
Specialist species occupy
narrow niches.
• Use only one/few types of
food, tolerate narrow range
of environmental conditions.
• More prone to extinction
• Low competition.
• Ex:
alm
alm
Co
wit
hig
phy
sur
yea
• Ex:
bam
hab
rat
October 02, 2013
Specialist species can allow for resource
partitioning. Resource partitioning reduces
competition and allows sharing of limited resources.
October 02, 2013
When different species compete for
scarce resources, what is likely to
happen due to natural selection?
Increase in specialized species. Reduces
competition and sharing of limited resources.
October 02, 2013
How do new species evolve?
We just saw an example of
how competition can lead to
specialization of ecological
niche.
How does this lead to
evolution of new species?
What are the mechanisms of
speciation?
October 02, 2013
Speciation = formation of new species. Two species
arises from one.
For sexually reproducing species--when some members
of a population can no longer breed with other members
to produce fertile offspring.
http://evolution.berkeley.edu/
evolibrary/article/0_0_0/evo_42
October 02, 2013
Mechanism of Speciation
Reproductive isolation is the key to speciation-barriers to gene flow allow genetic differences to
accumulate and result in different species.
Reproductive isolation may occur due to
• Different mating location, time, or rituals.
• Lack of "fit" between sexual organs.
• Offsprings not viable or fertile.
These damselfly penises illustrate just how complex insect genitalia may be
http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_44
October 02, 2013
Mechanism of Speciation
Why does reproductive isolation occur?
Reduced gene flow!
1) Allopatric speciation: Geographic Isolationmembers of the same population become physically
isolated. Adapt to different environmental conditions
> physical barriers (mountain range, stream, lake,
road)
> volcanic eruptions
> earthquake
> individuals taken away by wind or water
http://evolution.berkeley.edu/evosite/evo101/VC1bAllopatric.shtml
October 02, 2013
Mechanism of Speciation
Why does reproductive isolation occur?
Reduced gene flow!
2) Peripatric speciation
A small number of individuals move into a new niche,
and by chance (think genetic drift), have genes that are
rare in the original population.
October 02, 2013
Mechanism of Speciation
Why does reproductive isolation occur?
Reduced gene flow!
3) Parapatric speciation
No extrinsic barrier to random mating, but population
mates non-randomly over a large geographic area.
More likely to mate with others in same geographic
location within population.
Although continuously distributed, different
flowering times have begun to reduce gene flow
between metal-tolerant plants and metal-intolerant
plants.
http://evolution.berkeley.edu/evosite/evo101/VC1dParapatric.shtml
October 02, 2013
Mechanism of Speciation
Why does reproductive isolation occur?
Reduced gene flow!
4) Sympatric speciation
Does not require large-scale geographic distance
(physical isolation).
Disruptive selection.
http://evolution.berkeley.edu/evosite/evo101/VC1eSympatric.shtml
October 02, 2013
Mechanism of Speciation
These mechanisms of speciation occur very slowly-over many years.
There are other mechanisms of evolution that can
happen quickly (in one generaiton)
1) Hybridization
Two individuals of different species are able to mate and
produce viable offspring. (often happens in plants by
polyploidy).
2) Horizontal gene transfer
October 02, 2013
Extinction
Also affects number of species on earth.
Extinction = entire species ceases to exist.
Why might a species become extinct?
Populations cannot adapt to changing environmental
conditions.
What kinds of species are more likely or more vulnerable
to extinction?
Endemic species = species that are only found in one
area. (Islands, small unique areas, highly specialized)
October 02, 2013
All species eventually become extinct.
background extinction = ongoing extinction of
species dues to changes in environmental conditions.
Estimated to be about 1-5 species for each million
species on earth.
mass extinction = widespread event of high extinction
rate. Large groups of existing species (25-70%) are
wiped out.
Estimated there have been 5 mass extinctions during
past 500 million years.
mass depletion = extinction rates higher than normal
but not high enough to be considered mass extinction.
October 02, 2013
When a mass extinction or mass depletion occurs, what
generally occurs afterwards?
Gives other species opportunity to fill previously
occupied niches or newly created ones!
October 02, 2013
Biodiversity = speciation - extinction
Why is biodiversity important for the ecosystem?
October 02, 2013
Human Effects on Earth's Biodiversity
Human activities are decreasing earth's biodiversity.
Why?
As h
incre
Hum
prim
Degr
October 02, 2013
Predictions by Stuart Primm and Edward O. Wilson (2005
Millenium Ecosystem Assessment)
• Extinction rates have increased 100-1,000 times natural
background extinction rates.
• by 2030: premature extinction of 1/5 earth's species.
Can we recover from these major losses?
Species formed over millions of years.
Humans are depleting and destroying habitats with in
years.
October 02, 2013
Artificial Selection and Genetic
Engineering
Artificial selection = selective breeding. Humans
breed certain animals or plants for certain traits.
http://en.wikipedia.org/wiki/Selective_breeding
http://en.wikipedia.org/wiki/File:Cornselection.jpg
October 02, 2013
Artificial Selection and Genetic
Engineering
Genetic engineering = alteration of an organism's
genetic material through adding, deleting, or changing
segments of its DNA to produce desirable traits or
eliminate negative ones.
October 02, 2013
Artificial Selection and Genetic
Engineering
recombinant DNA = DNA that has been altered or
contain gees or portions of genes from organisms of
different species.
GMOs or transgenic organisms = organisms that
have been genetically engineered using recombinant
DNA
Synthetic biology = use fundamental components of
other organisms to build new organisms.
October 02, 2013
For Homework:
Please look up 3 examples or uses of genetic engineering
that is relevant to environmental science.
Then identify
1) What is the genetically modified organism?
2) What is the goal or purpose of developing the GMO?
3) What is the origin of the recombinant DNA?
4) What are some opinions or evidence that supports or
refutes the use of these GMO's?
5) What are your opinions about the GMO?
6) Cite your sources.
October 02, 2013
Some ideas to get you started:
• Various crops (tomatoes, corn, strawberries, wheat,
rice, potatoes, plums...)
• Mosquitoes
• Bacteria (many many different products)
• Algae
• Salmon
• Livestock (pigs, cows, goats).