Transcript Evolution & Biodiversity: Origins, Niches, Adaptation

Evolution & Biodiversity:
Origins, Niches and
Adaptation
© Brooks/Cole Publishing Company / ITP
1. Life on Earth
Biodiversity- (=biological diversity) variety of different species, genes,
or ecosystems.
Two main types of life:
• Prokaryotes- (means "before nucleus") organisms (bacteria) whose
cells do not have a distinct nucleus or other internal parts enclosed in
membranes.
• Eukaryotes- (means "true nucleus") organisms whose cells have a
distinct nucleus and various internal parts enclosed in membranes.
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Six Kingdoms
Living organisms are classified into six
kingdoms:
• Eubacteria
• Archaebacteria
• Protista (protists)
• Fungi
• Plantae (plants)
• Animalia (animals)
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Six Kingdoms
• Eubacteria and archaebacteria- single–celled, microscopic
prokaryotic organisms, in particular bacteria and cyanobacteria.
• Protista (protists)- mostly single–celled eukaryotic organisms,
such as diatoms, dinoflagellates, amoebas, golden–brown &
yellow–green algae and protozoans.
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Six Kingdoms
• Fungi- mostly many–celled (some single–celled) eukaryotic
organisms, such as mushrooms, molds, mildews and yeasts.
• Plantae (plants)- mostly many–celled eukaryotic organisms,
such as red, brown and green algae, mosses, ferns, conifers and
flowering plants.
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Six Kingdoms
• Animalia (animals)- many–celled eukaryotic organisms,
including invertebrates (e.g., sponges, jellyfish, sponges,
mollusks, worms, arthropods) and vertebrates (e.g., fish,
amphibians, reptiles, birds and mammals).
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What is a Species?
Species- a distinct kind of organism; groups of organisms
that resemble each other and, in cases of sexually
reproducing organisms, can potentially interbreed.
• Each known species is assigned a scientific name
(derived from Latin) consisting of two parts (genus +
species) which is always written in italics or underlined.
examples: Ursus horribilis is the grizzly bear
Taraxacum officinale is the dandelion
• Each species is classified in a hierarchical taxonomic
classification:
kingdom, phylum, class, order, family, genus, species
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Classification of Organisms
Example of
the
classification
of human
beings.
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Classification of Organisms
Example of the
classification of
human beings
(continued).
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All Living Things Have Genetic Material
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The universal genetic code, A,
G, C, and T tie all living things
together and show their
relatedness.
Every population of a species
has a gene pool
Members of a population
generally have the same
number and kinds of genes.
A particular gene may have
two or more different
molecular forms, called alleles
– I.e. eye color B for brown
and b for blue
2. Origins of Life
Summary of
the evolution of
the earth and
its life over the
past 4.7 to 4.8
billion years.
© Brooks/Cole Publishing Company / ITP
Why is Earth "just right" for life?
• Distance from sun: leads to a temperature favorable to life
(for liquid water); energy flow from sun sufficient to drive
weather and supply energy for life
• Size: enough gravitational mass to hold atmosphere of light
molecules (N2, O2, CO2, and H2O) and to keep core molten
• Rotation: leads to daily patterns (night & day)
• Orbit around sun: leads to seasonal patterns
• Atmospheric evolution: accumulation of O2 in lower
atmosphere; formation of ozone shield to screen harmful
ultraviolet (UV) radiation.
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What Evolution Is Not:
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It is NOT a fact…..it is a theory: a highly
probable explanation affecting all biological
phenomena, with much supporting evidence,
and NO evidence against it
It is NOT something one should believe
in….it is based on science NOT faith
It is NOT just concerned with the origin of
humans….no more or no less than any other
species.
It was NOT first explained by Darwin….many
people proposed the idea long before Darwin
It is NOT something which happened only in
the past….it is still going on.
What Evolution Is Not:
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It is NOT something that happens to individuals…ONLY
populations
It is NOT accidental or random (mutations are)…it is
influenced by environment and other factors
It was NOT developed to undermine religion…it was
developed to explain observations of life in a testable way.
It does NOT deny the existence of God….it is neutral; God is
neither required nor eliminated.
What Evolution Is:
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Idea that populations of species
change over time.
New species develop from earlier
species by accumulated genetic
mutations—descent with
modification
– Life comes from life
– Speciation proceeds with time,
increasing numbers of species
that become increasingly
different.
– All species we see today are
the growing tips of a branching
tree: close clusters of tips have
most recently branched
(evolved)
Found to be supported in all cases
Holds the high status of near
certainty…it is Scientific Theory
3. Evolution & Adaptation
Evolution- the change in a population's genetic makeup
through successive generations.
• Microevolution- change in gene
frequency within a population
(short–term evolutionary changes)
due to beneficial changes (mutations)
in DNA being passed on to offspring
• Macroevolution- formation of new
species from ancestral species
(long–term evolutionary changes).
Other species are lost through
extinction.
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Publishing Company / ITP
Genes mutateindividuals selectedpopulations
Microevolution
Four processes drive microevolution:
1. Genetic variability: Random mutations
serve as the ultimate source of genetic
variation that results in changes in a
population’s gene pool over time.
-Exposure of DNA to external agent
-Random mistakes in DNA replication
-Only mutations that occur in
reproductive cells can be passed on to
future generations
2. Natural selection: the process by which
some individuals of a population have
genetically based characteristics that cause
them to survive and produce more offspring
than other individuals.
© Brooks/Cole Publishing Company / ITP
Microevolution
Four processes drive microevolution, cont:
3. Gene flow: the movement of genes between
populations;
4. Genetic drift: change in genetic composition
that results by chance, especially in small
populations
Natural Selection
Three conditions required for natural
selection:
• Variability: there must be natural variability
for a trait within a population
• Heritability: the trait must be
heritable, such that it can be passed
from generation to generation
• Differential reproduction: the trait
must enable individuals with the trait to
leave more offspring than other
members of the population.
Adaptation- a heritable trait that enables
organisms to better survive and reproduce within
a given set of environmental conditions.
Will they survive
and reproduce?
Natural Selection
Example: peppered moth (Biston betularia)
• Variability: two color forms, one dark and
one light; light form originally more
common because it blended in with lichens
on
• Heritability: color form was genetically
based
• Differential reproduction: In industrial
revolution mid–1800s in England soot
coated trees dark form became more
common because they survive to
reproduce
Classic example of microevolution – change
in gene frequency in a population.
© Brooks/Cole Publishing Company / ITP
Natural Selection
Directional selection favors individuals with traits
that are at one end of a distribution (such as the
peppered moth example).
"It pays to be different.”
Video-click through
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Natural Selection
Stabilizing selection eliminates individuals at both
ends in the spectrum of variation; the average
remains the same.
"It pays to be average.“
Video--click through
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Natural Selection
Disruptive (diversifying) selection eliminates
average individuals, but favors individuals at
either extreme of the spectrum of variation.
"It doesn't pay to be normal.“
Video--click through
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Coevolution
Coevolution- interactions between two species that
result in ongoing evolutionary changes in each of the
species. Changes in the gene pool of one species can
lead to changes in the gene pool of the other.
**Competitive relationships lead to coevolution.
Examples:
• Moths with sensitivity to sound frequencies of bats
will be selected for. Bats then with different
frequencies moths can’t hear will be selected for,
etc.
Bats vs. Moths--7min
• Plants with defenses against herbivores (thorns,
camouflage, toxins) and their herbivores (ability to
deal with defenses).
• Camouflage
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Ecological Niche vs. Habitat
Niche- the functional role of a species in
an ecosystem—it’s occupation.
Includes:
• Range of tolerance for conditions (physical
and chemical)
• Resources the species uses (nutrients or
food)
• Interactions with living (biotic) and
nonliving (abiotic) components of
ecosystem;
• Role in flow of energy cycling of matter.
Habitat- the actual location where an
organism lives—it’s address.
© Brooks/Cole Publishing Company / ITP
Ecological Niche
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Fundamental niche- full potential range of physical,
chemical and biological conditions and resources a
species could theoretically use if there were no
competition
Realized niche- actual niche a species occupies that
represents only part of its fundamental niche. This
partial occupation of its fundamental niche is due to
competition
Generalist vs. Specialist Species
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Scientists use the niches of species
to broadly classify them as
generalists or specialists
– Generalists- broad niches, eat a wide
variety of food, tolerate a wide range of
environmental conditions, more secure
under rapidly changing conditions,
 Cockroaches, mice, white-tailed deer,
humans etc.
– Specialists- narrow niches, able to live in
only one type of habitat, tolerate only a
narrow range of environmental
conditions, more secure when conditions
constant b/c fewer competitors due to
their specialization
 Tiger salamanders can only breed in
fishless ponds
Number of individuals
Niche
separation
Specialist species
with a narrow niche
Niche
breadth
Region of
niche overlap
Resource use
Generalist species
with a broad niche
Ecological Niche and Convergence
Relation between ecological niche and convergence:
• Species with similar niches tend to evolve similar sets of traits
• Convergence- the resemblance of different species with similar
niches
• Examples of convergence:
- Desert shrubs of different parts of world have deep roots, small
leaves, and high tolerance to hot, dry conditions.
- Herbivores of different parts of world have traits to forage and
digest plant material, escape predators, and migrate or become
dormant when food is scarce.
© Brooks/Cole Publishing Company / ITP
4. Speciation, Extinction, &
Biodiversity
Macroevolution-changes in evolutionary
lineage over much longer periods.
Involves three processes:
• Evolutionary change of lineage through
time
• Speciation- formation of new species
• Extinction- loss of species
New species typically evolve by two steps:
• Geographic isolation – separation into
distinct populations with different
evolutionary pressures
• Reproductive isolation – evolutionary
changes in each population that prevent
interbreeding when populations come into contact.
© Brooks/Cole Publishing Company / ITP
Speciation
Geographic
isolation can
lead to
reproductive
isolation,
divergence
and
speciation.
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Extinction
Fossil record shows evidence of extinction
as a natural process:
Biologists estimate that 99.9% of all the
species that ever existed are now extinct.
• Background extinction- loss of species at a
relatively low rate, often due to changes in
local conditions
• Mass extinction- abrupt increases in
extinction rates above the background
level
• Believed to result from global climate
changes
• Recent extinctions caused by humans at
exceptionally high rates.
Continental Drift
Continental drift, the slow movement of
continents, has played a major role in both
speciation and extinction.
© Brooks/Cole Publishing Company / ITP
LAURASIA
120° 80°
40°
80°
120°
120° 80°
80°
120°
GONDWANALAND
135 million years ago
225 million years ago
EURASIA
AFRICA
120° 80°
120°
120°
0°
MADAGASCAR
65 million years ago
Present
40°
120°
Adaptive Radiation
Adaptive radiationinvolves splitting of
a lineage to form
many species with
different ecological
niches The
adaptive radiation
of mammals began
about 65 million
years ago.
© Brooks/Cole Publishing Company / ITP
Adaptive Radiation
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Earth’s mass extinctions and depletions have been followed by
periods of recovery -adaptive radiation
Numerous new species evolved to fill new or vacated niches.
Speciation – extinction = biodiversity
The existence of millions of species today means that
speciation on average has kept ahead of extinction for the past
250 million years, but this increase has leveled off.
5. Sustainability & Evolution
What is the appropriate time
frame for thinking about
environmental problems?
• Humans have barely existed
in geological or evolutionary
time scales
• Earth's biodiversity has taken
millions of years to evolve
• Extinction is natural process,
but human–induced
extinction is occurring at
unprecedented rates 1001,000 X’s the natural
background extinction rate
• EXTINCTION IS FOREVER!
© Brooks/Cole Publishing Company / ITP
The Future of Evolution: Genetic
Engineering
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Artificial selection- has been
used to by farmers for millennia
to change genetic
characteristics of populations
by selecting one or more
desirable genetic traits and
selectively breeding them.
Genetic engineering- used to
create genetically modified
organisms (GMO’s) by
transplanting genes from one
species to the DNA of another.
– Has great promise
– Unpredictable—trial and
error
– Future problems with results
can’t always be anticipated
GMO’s and GMF’s
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Advantages:
– Increased nutritional value
– Greater crop yield
– Medicinal benefits such as
addition of vaccines or
removal of allergens
from food
– Resistance of plants to
pests so decreased
use of pesticides
– Resistance of plants to
herbicides so weed
tilling can be decreased
resulting in less soil erosion
GMO’s and GMF’s
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Disadvantages:
– Possible production of new
allergens or toxins by GMF’s due to
mutation
– Decrease in genetic diversity
by planting only a few
“superfoods.”
– Cost of raising/growing
food will increase due to
high costs of creating and
patenting GMF’s. Drive out some
independent farmers
– Pest populations may become
resistant to some pesticides.
– Grocery Store Wars
Organic Certification
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Fruits, veggies, livestock and eggs
can all be certified organic.
How?
– Avoidance of most synthetic
chemicals:
 Antibiotics
 Pesticides
 Fertilizer
 Food additives
– No GMO’s or irradiation
– No use of sewage sludge for
fertilization
– Use of farmland that has been
free from chemicals for a # of
years