Transcript Biodiversity

Biodiversity
Balance
Between
Speciation and extinction
What is biodiversity?
• Type 1: Total number of species in world
• Type 2: Genetic variation within and
between species.
• Type 3: Ecosystem biodiversity: huge
variety of ecosystems and habitats
Total number of species
• What patterns do you see?
• How do you think scientists estimate the ``unnamed species’’?
Genetic biodiversity
•
European sheep
breeders protecting
genetic diversity of
their breeds.
These are all one
species
• These are all
different
species
•
Genetic biodiversity
• For example, humans are one species, but
we have a great variety of variation in many
genes, such as blood type
• Each species has thousands of genes
Ecosystem biodiversity
What is an ecosystem??
• A community of organisms, its abiotic
environment, and their interactions
Levels of ecological organization
• Biosphere: all life on Earth and the life-supporting
region of Earth
• Ecosystem
• Community?
– Populations of different species in the same area or
habitat
• Population?
– Group of individuals of same species in same area or
habitat
Origin of biodiversity
• EVOLUTION
• Simple definition:
Descent with modification
– Includes microevolution: changes in gene
frequency from one generation to the next
• Includes macroevolution: descent of different
species from a common ancestor
Natural Selection
• Darwin’s big contribution
• Inherently logical:
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Organisms produce more offspring than survive
Individuals vary in important characteristics
Many characteristics are inherited
SO:
• some individuals will be better suited to the environment
• Those individuals will be more likely to survive and reproduce
• Their offspring likely to be more suited to the environment
Definition of evolution
• Descent with modification
– KEY: Evolution proceeds by changes in genes
• NOT JUST: ``Change over time’’
– Lots of things change over time:
• Trees change color
• Mountains erode
• Continents move
– These are NOT evolution
Evolution is NOT
• Just a process of getting better
• Something that organisms TRY to do
Geneology: sharing a
common ancestor
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Evolution: sharing a
common ancestor
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Natural Selection
• Darwin’s big idea
• HOW evolution can happen
• Follows logically from some simple ideas:
Logic of natural selection
• Organisms produce more offspring than can
survive.
– Even elephants—if all survived . . .
• Often, these differences are due to
differences in the genes and therefore can
be inherited
Logic of natural selection
• Individuals vary in their characteristics
Logic of natural selection
• Often, these differences are due to
differences in the genes and therefore can
be inherited
Logic of natural selection -2
• As a result of individuals inheriting
characteristics from parents:
– Some individuals will be better suited to their
environment than others
– These better-suited individuals produce more
offspring that survive
• They may survive longer to reproduce
• They may produce more offspring
• They may produce offspring of higher quality
Logic of natural selection - 3
• As a result of some individuals producing
more fit offspring:
– Future generations will contain more genes, and
more characteristics, of the better-suited
individuals.
– Better suited are called ``more fit’’
Natural selection doesn’t mean:
• Only the strong survive NO
– Sometimes, other ways of being fit (e.g., hiding)
• Only the best-suited individuals survive NO
– Many types may survive. Over long periods, the
more fit will leave more offspring.
Natural Selection
• Often MIScharacterized as ``evolution by
random chance’’
• What IS random about natural selection?
– The production of variation by mutation and
genetic recombination
Adaptations
• Traits that are successful in their
environment
• An adaptation to one environment may be
NEUTRAL or UNFAVORABLE in another
environment
• May be simple—heavier coat in colder
climate—or complex—the mammalian eye
Again:
• Adaptations are specific to the
environment.
– A zebra’s coat pattern is camouflage in the
African savannah. It would not be
advantageous in a North American grassland.
– Running speed is advantageous for a cheetah on
the savannah. But cats in the rainforest (e.g.,
jaguar) are not fast. Strength and stealth are
more important than speed there.
•
Adaptation examples: mimicry
• Some orchids
have evolved to
mimic wasps,
fooling other
wasps to ``mate’’
with them and
thus transfer their
pollen
Adaptation examples: more
mimicry
•
• Katydids have evolved
a body form that looks
like a leaf.
• Why? What is the
advantage to the
katydid?
Adaptation examples: still more
mimicry
• Non-poisonous king
snakes mimic
poisonous coral snakes
• Many examples of
mimicry in nature
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Speciation
• One species evolves into another OR splits
into two.
• How can this happen?
– Geographic isolationallopatric speciation
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History of life
• As previous picture shows:
– Complex creatures and structures have evolved
– But simple life forms still common and
dominate in many habitats ``Earth still belongs
to the bacteria’’
– Speciation generates diversity; extinction
reduces it
Extinction
• The disappearance of a species from Earth
• Local disappearance is called extirpation
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