Transcript Evolution and Ecology

It is not the strongest of the species that survives, nor the most intelligent that survives.
It is the one that is the most adaptable to change.
Charles Darwin
 Background extinction rate
 Typical low rate of extinction (natural)
 Mass extinction
 Significant rise above background level
Fig. 4-13, p. 90
 Starting in 1958, Mao Zedong, leader of the Communist
Party of China, initiated a series of policies to transform
the country into a modern, industrialized, communist
society.
 One of the first actions taken was known as the Four
Pests Campaign.
 This campaign sought to eliminate rats, flies, mosquitoes,
and sparrows.
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 Masses of people were mobilized
to eradicate the Eurasian Tree
Sparrow.
 Tactics included:
 Banging pots and pans,
preventing the birds from
landing, until they were
exhausted.
 Tearing down nests.
 Shooting them from the sky
using guns and sling shots.
“Everyone come and fight
sparrows.”
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 The sparrows were hunted because they ate grain
seeds; reducing crop yields.
 By April of 1960, Chinese leaders came to realize that
the sparrows also ate a large number of pest insects,
including locusts.
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 The government made a series of other poor
agricultural decisions at this time, including:
 Ordering farmers to increase the density of their
planting by 6 times, believing that the same species of
plant would compete with itself.
 Deeper plowing of the soil, which brought up sand and
rocks instead of more topsoil.
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 The locust plague, overplanting, and overplowing
combined with a severe drought.
 The number of victims is unknown, but estimated
between 20-43 million.
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 Another significant cause of the great famine was
planting too densely. This caused the rice plants to
compete with each other directly for water and soil
nutrients.
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 Today, textbooks in China omit discussion of the true
causes of the famine, instead citing “three years of
difficulty” caused by “bad weather.”
 Mao Zedong’s portrait still hangs at the center of
Tiananmen Square.
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 Evolution is the process by which all of the living
organisms on the Earth changed over time from their
early ancestor species.
 Ecology is the study of the relationships/interactions
between organisms and the biotic (living) and abiotic
(nonliving) parts of the environment.
 Evolution is heavily influenced by these interactions.
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 The smallest unit of life
that can still respond to
its environment, selfreplicate, and perform all
other biological
functions, is the cell.
 Groups of cells that have
similar shape and
function are called
tissues.
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 Collections of tissues that
work together to perform
a task in the body are
organs.
 Organ systems include
multiple organs that
work together to perform
one or more functions.
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 Ecosystems have similar levels of
organization.
 An organism is an individual living
thing.
 A single species of organism is one
that is similar enough to breed and
produce healthy, fertile offspring.
 A population includes all members
of a species that live in the same
area at the same time.
 The biological community is made
of all populations living and
interacting in one area.
 An ecosystem
includes the
biological community
and its surrounding
physical environment.
 Nonliving factors
like soil,
precipitation, etc.
 The biosphere is the
part of Earth that
supports life -- all
ecosystems are found
here.
 Each species plays a specific ecological role called its
niche
 Any given species may play one or more of five
important roles—native, nonnative (exotic), indicator,
keystone, or foundation species—in a particular
ecosystem
 Ecological niche
Pattern of living, way of life or role a species plays in its ecosystem
 Generalist species
Broad niche - can live in many different places and eat a variety of
foods, and tolerate a broad range of environmental conditions
Ex. Cockroaches, rats, mice, humans
 Specialist species
 Narrow niche – consumes just one or only a few types of food,
and can live in only a narrow range of conditions
Ex. Some shorebirds, Pandas
Number of individuals
Specialist Species and
Generalist Species Niches
Specialist species
with a narrow niche
Niche
separation
Generalist species
with a broad niche
Niche
breadth
Region of
niche overlap
Resource use
Fig. 4-15, p. 92
 Cockroaches
 Generalists galore
 High reproductive rates
 Can live in pretty much any
conditions…your house,
your bed, hot, cold
can survive nuclear fallout,
can hold
breath for 10 minutes, and
can live without their head
for about a week.
 1) Native species
 Normally live in an ecosystem
 2) Nonnative species
 Not native to the ecosystem (introduced, alien or exotic
species) – not all are villainous!
 3) Indicator species
 Are usually found almost everywhere and are affected
quickly by environmental changes
 Provide early warning of damage to a community
 Can monitor environmental quality
 Examples: Lichens (sensitive to pollutants, like factory
smoke), Macroinvertebrates (some are sensitive to water
pollutants/low quality water), Amphibians (sensitive to
pesticides, habitat fragmentation), Birds
(pesticides/habitat fragmentation)
 4) Keystone species
 Have a large effect on the types and abundances of other
species
 Can play critical roles in helping sustain ecosystems
 Ex. Bees and pollination (essential for plant
reproduction, and therefore essential for LIFE)
 Top predators (keep populations of other species in
check)
 Remember the Coyote removal activity?
 Biologists describe foundation species as “engineers of
ecosystems.”
 The activities of foundation species physically modify
the environment and produce and maintain habitats
that benefit other organisms that use those habitats.
 Examples:
 Corals build coral reefs that many other species use.
 Beavers harvest trees and create dams, thus creating
wetlands that other species utilize.
 American Alligators dig gator holes that become
microcosm ecosystems
 Each organism has a particular type
of environment where it can survive
called its habitat. Habitats are made
of two kinds of factors:
 Abiotic factors, which include all
non-living factors like soil
composition, surrounding
landforms, climate, etc.
 Biotic factors, which include all the
living organisms.
 These factors can LIMIT the
growth, abundance, or distribution
of an organism(s) in an ecosystem,
and are therefore called limiting
factors
 These limiting factors establish a
geographic range for each organism.
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 Some organisms have a single critical factor that plays
the greatest role in determining its range.
 Critical factors have a “Goldilocks Effect”, meaning there
can be too much or too little of it.
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 Tolerance ranges are based on the right level of an
environmental factor being present.
 At the optimal range, population levels will be growing
or at their peak. This is the optimal range for that
factor.
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 At the zone of physiologic stress, levels of the factor
are too high or too low. The population barely
survives.
 At the zone of intolerance, the population dies out.
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 Coniferous trees
have a much wider
geographic range
(zones 3,5,6,7,8)
than broadleaf
deciduous trees
(zone 8 only).
 What biotic and
abiotic factors
create this range?
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 The range of tolerance for a species is largely defined by
the presence of physical, behavioral, or physiologic
adaptations.
 Physical adaptations are structural differences in
coloration, body shape, musculature, etc.
 Behavioral adaptations include migration, or marking a
territory.
 Physiologic adaptations, such as skin tanning, occur at the
cell or tissue level in an organism.
The gorilla is
adapted for living
and feeding on the
ground, while
chimpanzees
gather food from
trees.
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 All of the unique adaptations found in different
organisms are the result of evolution -- small,
advantageous mutations that have accumulated over
countless generations.
 Natural Selection describes the process where
individuals with better genes survive and reproduce
more successfully, while those with weaker genes do not.
 The primary source of this genetic variety is random
mutations. These are small DNA changes.
 Usually these changes produce no effects or bad effects,
but occasionally, they can be quite beneficial.
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 Evolutionists will cite three categories
of evidence in support of the theory.
 Physical Similarities
 Most animals have similar bones in
their limbs (fins, arms, wings).
 These similarities can also be found
between living species and fossils.
 Comparing DNA
 Chimpanzees, bonobos, and humans
share about 99% of the same DNA.
 Vestigial Structures
 Still exist in the body but are no longer
needed
 Ex: Appendix, wisdom teeth, brains
(that’s a joke)
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 An example of natural selection in the human race can
be seen in sickle-cell anemia.
 Normal red blood cells have a biconcave –disc shape.
 Sickle-shaped red blood cells are the result of a single
mutated gene.
 Sickle cells can get stuck in small blood vessels, causing
tissues to become oxygen-deprived.
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 Individuals with sickle-cell anemia or carriers are also
highly resistant to malaria.
 The mutation is a disadvantage in climates where
malaria is absent due to the long-term health issues.
 The mutation is an advantage in climates where malaria
is present due to the resistance it provides.
Sickle cell
gene
frequency in
Africa.
Source:
University of
Oxford study.
Distribution
of malaria
transmission
in Africa.
Source:
American
Journal of
Tropic
Medicine and
Hygiene
Study.
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 Evolution is an
very slow process.
 Current life on
Earth represents
billions of years of
small mutations
and natural
selection (due to
selective
pressures).
 Four ecological factors (called “selective pressures”) will
“encourage” natural selection to favor certain individuals
in a population.
 Speciation is more likely to occur in these situations.
 Physiological stress, inappropriate levels of a critical
environmental factor.
 Moisture, Light, pH, temperature
 Predation, when one organism is hunted and killed by
another.
 Competition, the result of other organisms attempting to
use same resources.
 Sexual Selection occurs when the female (usually)
responds to specific behaviors or physical traits.
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 Over a long enough period of time, enough mutations
occur that a new species emerges.
 When a population splits and become two different
species, it is called divergent speciation.
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Geographic Isolation Can Lead to Reproductive Isolation – results
in Speciation
Adapted to cold through
heavier fur, short ears,
short legs, and short
nose. White fur matches
snow for camouflage.
Arctic Fox
Northern
population
Early fox
population
Different environmental
conditions lead to different
selective pressures and
evolution into two different
species.
Spreads
northward and
southward and
separates
Gray Fox
Southern
population
Adapted to heat through
lightweight fur and long
ears, legs, and nose,
which give off more heat.
Fig. 4-12, p. 88
 Chimpanzees and bonobos are very closely related
primates, with only a few differences between the
species.
 They likely diverged during a severe drought millions of
years ago.
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PBS Evolution – Chimps vs. Bonobos
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PBS Evolution – Peacock Experiment
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 Convergent speciation can occur when natural
selection favors unrelated organisms to evolve to
look similar. This is also called Convergent
Evolution.
Mantis Fly
Preying Mantis
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 Artificial selection
works on the same
principal as natural
selection, but with
humans driving the
selection process
(selecting traits
desirable to them).
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 Evolution has produced a tremendous amount of
biodiversity on Earth.
 Biodiversity is defined as the number of different species
within an ecosystem or area.
 The number of species is unknown.
 About 1.5 million have been identified.
 A recent study estimates 8.7 million exist currently.
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 The majority of known species are insects, followed by fungi and
bacteria.
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 The biodiversity found in genes, species, ecosystems,
and ecosystem processes is vital to sustaining life on
the earth
Functional Diversity The biological and
chemical processes such as energy flow and
matter recycling needed for the survival of
species, communities, and ecosystems.
Genetic Diversity The variety
of genetic material within a
species or a population.
Ecological Diversity The variety of
terrestrial and aquatic ecosystems
found in an area or on the earth.
Species Diversity The number and
abundance of species present in
different communities.
Fig. 4-2, p. 79
 The Number and variety of species in a given area is
called species diversity (combo of species richness and
evenness)
 The number of different species in a given area is called
species richness
 The comparative (abundance) number of individuals of
each species present is called species evenness
 For example, if a scientist found 20 different plant
species in a 1 m2 area, but only ONE of each species,
it could be said that there is a high species
evenness, and a high species richness.
 Habitat fragmentation is the process by which habitat loss results in the
division of large, continuous habitats into smaller, more isolated remnants.
 The more habitat is fragmented, the more biodiversity suffers
 There is a theory that larger
habitat “islands” are more
holistically healthy than smaller
islands. This theory is called
island biogeography.
In bigger habitat areas, all aspects
of biodiversity remain more intact
for that reason, scientists have tried to
build corridors between habitat
fragments, connecting them with more
habitat
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 With the tremendous diversity of living organisms,
systems have been devised to organize and classify
them based on physical traits, DNA, and other
characteristics.
 The three-domain system classifies organisms based
on differences in cellular structure.
 Prokaryotes, which have no nucleus or membrane-
bound organelles, are classified as archaea and bacteria.
 Eukaryotes, which have a nucleus and organelles, have
their own domain called Eukarya.
 The five-kingdom classification system starts with these groups:
 Monerans, include all prokaryotic organisms.
 Protists are a diverse group that includes producers, consumers,
single-celled, and multicellular organisms.
 Fungi directly absorb nutrients from the external environment.
 Plantae includes organisms that are multicellular and can perform
photosynthesis.
 Animalia are mostly motile, consumers, and eat by ingestion.
 Each kingdom has a series of smaller classifications that narrow
organisms down into more closely-related groups.
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Phylum
Class
Order
Family
Genus
Species
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 The final two levels of classification, genusand species, are used to
devise the scientific name.
Taxon
Reason
Domain
Eukarya
Cells have nuclei and organelles (eukaryote).
Kingdom
Animalia
Multicellular. Unable to produce own food
(heterotrophic).
Phylum
Chordata
Have a nerve cord along the back.
Class
Mammalia
Warm-blooded, gives birth to live young, has hair.
Order
Primates
Forward-facing eyes, enlarged brains, vertical
posture.
Family
Hominidae Capacity for language, culture, empathy.
 The final two taxa, genus and species, are used to define the species’
scientific name.
 Homo sapiens
 Italicized or underlined
 Genus capitalized, species lower-case.
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 The scientific naming
system is important, as
many species have
multiple common names.
 The cougar holds the
Guinness world record for
number of common
names, with 40 in English
alone!
 Cougar, catamount,
painter, panther, ghost
cat, puma, shadow cat,
mountain lion, deer tiger,
devil cat, sneak cat, plain
lion, fire cat, mountain
screamer, Florida
panther, silver lion……
Puma concolor
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 Two animals with many classification levels in
common are considered very closely related – they
diverged recently.
 Wolves and dogs share the same domain, kingdom,
phylum, class, order, family, and genus.
Canis lupus
Gray Wolf
Canis familiaris
Domesticated dog
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 As their ecosystem and communities change,
populations of organisms undergo different growth
patterns.
 The most common
growth pattern is
called logistic growth,
which takes the shape
of an “S”.
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 Logistic growth starts off fast, but gradually slows down as
the population encounters environmental resistance
(factors that act to limit the growth of a population) .
Included in env resistance are limiting factors, chemical
and physical factors that determine the number of
organisms in a population.
 Environmental
resistance can come in
two forms:
 Density-dependent
factors, such as disease,
which affect dense
populations more.
 Density-independent
factors, such as natural
disasters or climate
change, which similarly
affects all populations.
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 The density-dependent growth-limiting factors will
cause the population’s growth to slow and eventually
stabilize.
 The point at which it stabilizes is the carrying capacity,
or the maximum
population size that can
be sustained by the
ecosystem.
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 China’s great famine in 1958 was partially due to the
removal of a density-dependent growth limiting factor
for locusts – the predatory Eurasian tree sparrow.
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 Locusts were able to grow exponentially, creating
swarms with millions of individuals.
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 Exponential growth, which takes the shape of a “J”,
does not experience growth-limiting factors.
 The population will continue to grow, with the growth
rate increasing over time, eventually exceeding the
carrying capacity.
 This is called an overshoot.
 When a population
overshoots the
carrying capacity,
it experiences a dieback,
often in the form of
mass-starvation.
 Exponential growth is
unusual, and does not
typically occur under
normal conditions.
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r-Selected species, opportunists
K-selected species, competitors
 R strategists usually create an abundance of offspring in the hopes that a few
will make it.
 These species usually have a very short maturation time, often breed at a very
young age,
have a short lifespan, produce many offspring very quickly, have young with
high mortality
rates and invest relatively little in parental care.
 The parents do not focus on passing down memes, units of cultural
information, to their young.
 Instead the behavior of the young is determined by their genes.
 The young are precocial, meaning that they often can make it on their own
without any instruction from their parents.
 Examples of r-selected species include bacteria, insects, and fish.

K strategists are very different in that they attempt to ensure the survival of their offspring by
investing time in them, instead of investing in lots of them.

It is a reproductive strategy that focuses on quality over quantity. K strategist have relatively few
offspring and make an effort at being good parents. Their young are altricial meaning that they
cannot survive on their own until they reach adulthood.

This extended period of maturation is used for memetic transference- the parents teach the young so
that they can go on to reproduce themselves.

K strategists are known to have a relatively long life span, produce relatively
few offspring, the offspring have low mortality rates and the parents provide extensive
parental care.

The offspring are also relatively intelligent so that they can internalize the
lessons from their parents.

K-selected species include elephants, apes and whales.

Humans are perhaps the most K-selected because their young are truly helpless- they
necessitate a full two decades of parental care and tutelage and the parents usually only
produce one offspring at a time.
 Five types of species interactions—competition,
predation, parasitism, mutualism, and
commensalism—affect the resource use and
population sizes of the species in an ecosystem
 How quickly populations grow
and the maximum size they
attain are often the result of
interactions with other
populations of organisms.
 One of the most basic
interactions is predator-prey
(predation), where one
organism consumes the other.
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 Competition, where organisms and populations
compete for resources, is another common interaction.
 Water, food, territory, mates.
 When the competition occurs within members of the
same species, it is called intraspecific.
 When the competition occurs between different
species, it is called interspecific.
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 Some organisms have
developed adaptations to
avoid directly competing
with their own species.
 Plants will send their seeds
far away to avoid sharing
the same soil.
 Wolves mark and occupy a
territory so they have
enough hunting area.
 Adult monarch butterflies
and their caterpillars each
utilize a different part of
plants (this is called
resource partitioning).
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 The closest relationships of all are symbiosis. These
involve a lot of close contact between two species.
 When the relationship benefits both organisms, it is
called mutualism.
 When one organism benefits while the other is
unaffected, it is called commensalism.
 When one organism benefits at the expense of the other,
it is called parasitism.
 When one organism benefits at the expense of another
but ultimately ends up killing or consuming the host, it
is called parasitoidism.
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 Barnacles create homes by attaching themselves to
whales. The whales are unaffected.
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 Clownfish have a mucus coating that allows them to live in sea
anemones. Their presence attracts other fish for the anemone to eat.
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 As bison walk through grass, insects are disturbed and fly
away. They are eaten by cowbirds.
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 Ostriches and gazelles feed next to each other. Ostriches have excellent
eyesight, while gazelles have stronger senses of hearing and smell.
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 Mistletoe extracts water and nutrients from the spruce
tree directly.
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 Primary succession occurs when a new ecosystem
develops where there was none before.
 A combination of wind, water, and pioneer species such
as lichens break down rock into soil.
 Once the soil has enough organic matter, small plants
and shrubs can be supported. Over time, trees spout
and become dominant.
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 Secondary succession occurs following the disruption
of an existing ecosystem.
 Fire, flood, volcanic eruption, clear-cutting, etc.
 This form of ecological succession does not take as
long. Soil is already in place, and pioneer species
appear within days or weeks.
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 Biomes are dynamic – they change as the Earth
changes. This process is called succession.
 Organisms that thrive during the early stages of
succession are called pioneer species. Those only found
in later stages are called climax species.
 Ecosystem succession takes two forms, depending on
the starting point.
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 The diversity of organisms, genetic traits,
relationships, and population growth patterns all
combine to create the complex system that is an
ecosystem.
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