Download Chapter 5 Lecture 09

Chapter 5
Ecosystems and the
Living Environment
Your Responsibility
BY NEXT CLASS
HINT…HINT…
• Pages 81-88
– Evolution basics
– Kingdoms of Life
– Biological Communities/Succession
• Pages 92-94
– Predation
– Competition
• Don’t ignore the Envirobriefs!!!
Evolution:
How
Populations
Change
Over Time
R&B Pages 82-84
Miller Chapter 5
Where’d we all come from?
The Science
Perspective….
Evolution
Genetic change in a
population of
organisms that
occurs over time.
– Dates back to
Aristotle…
– Charles Darwin
proposed the
mechanism that is
accepted today.
Main Idea: inherited traits favorable to survival
in a given environment tend to be preserved,
and unfavorable ones are eliminated.
“Survival of the Fittest”
Results in ADAPTATION
evolutionary modification
that improves chances of
survival & reproductive
success of the population
in a given environment.
Accumulation of
modifications may result
in a new species.
EVOLUTION BY NATURAL SELECTION
• Darwin proposed his theory in The Origin of
Species by Means of Natural Selection (1859)
Main idea:
More favorable genes
increase in frequency in
successive generations, and
fewer unfavorable genes
survive.
•Well accepted in science
•Mechanisms of evolution are still
debated.
Darwin’s Voyage
Evolution by Natural Selection
4 observations about nature:
1. Overproduction
• More offspring produced
than will survive to
maturity.
2. Variation
• Individuals have unique
combinations of traits
that make them
more/less “fit”
for their environment.
3. Limits on population growth, or struggle for survival
• Environment can’t support everyone…
– competition for resources,
predation, or disease!!
4. Differential reproductive success
• Those individuals with the most “fit”
traits for their environment are more
likely to survive, reproduce, and pass
their traits on to the next generation!
VIDEO:
How Evolution Works
http://www.pbs.org/wgbh/evolution/library/11/
2/e_s_4.html
Types of
NATURAL SELECTION
DIRECTIONAL
SELECTION
• One extreme of a
specific trait is more
advantageous than both
the other extreme and
the average trait.
• It pays to be different!!
• Examples:
– Peppered Moth
– Bacteria that are
genetically resistant to
some antibiotics.
Video
http://www.pbs.o
rg/wgbh/evolutio
n/library/10/4/l_
104_03.html
STABILIZING
SELECTION
• Tends to eliminate
individuals on both
ends of the genetic
spectrum.
• It pays to be average!!
• Occurs when the
environment changes
little and most species
are well-adapted.
• Often mistaken for no
selection
Example:
Birth Weight
DIVERSIFYING
(DISRUPTIVE)
SELECTION
• It pays to be extreme!!
• Examples:
– Green vs.
Brown Anole
– Darwin’s Finches
Environmental conditions
favor individuals at both
extremes of the genetic
spectrum and eliminate or
sharply reduce individuals
with intermediate genes.
Darwin’s Finches
Each finch species is specialized
for a particular lifestyle
(structure of their beaks)
An adaptation to their specific
diets seed eaters, cactus eaters,
insect eaters, fruit eaters) and
different from finches on the
South American mainland.
14 species of Galapagos finches
decended from a single ancestorone or a small population of
finches that originally colonized
the Galapagos.
ADAPTIVE RADIATION
NATURAL SELECTION
REVIEW..
Types of
SPECIES EVOLUTION
A. CONVERGENT EVOLUTION
• Two different species who live in the same
type of habitat evolve to have similar traits.
• Example: Sharks and dolphins
– Dolphins are mammals, Sharks are fish.
– So how did they convergently evolve?
• They look the same and act in similar manners
because they both live in the ocean, so they’ll need
similar traits!
CONVERGENT
EVOLUTION
CONVERGENT
EVOLUTION
B. DIVERGENT EVOLUTION
• Two populations of the same species who
live in different places evolve to become
different…
• Example: Birds
– Now we have penguins & puffins!!
– So how do they divergently evolve?
• Penguins live where it’s cold and where there’s lots of
water. There’s more food for them in the water, so
they evolved to “fly” underwater.
• Puffins live where it’s slightly warmer. There’s lots of
food sources outside of the water, so they continued
to fly normally.
Adaptive Radiation
Process by which ancestral species
evolve into a number of diff species.
Divergent Evolution
DIVERGENT EVOLUTION
C. COEVOLUTION
• Two species that interact closely
may become adapted to one another
He is
getting too
fast! I have
to run faster
to eat!!
Yummy….
Rabbit!
Why does
he want to
eat me? I
am sooo
cute!
If I want to
live, I have to
run faster!
Ex: a wolf and a rabbit
– How are they related in an ecosystem?
– So how do they co-evolve?
• If the rabbit evolves to be faster, the wolf will have to
keep up, so it must also evolve to be faster.
Animal/Plant
Coevolution
The gracefully
curved bill of the
‘I’iwi enables it to
sip nectar from
flowers of the
lobelia. The ‘I’iwi
bill fits perfectly
into the long tubular
lobelia flowers.
ACACIA TREE & ANTS
Tree has large hollow thorns
that provide a protected
nesting site for stinging
ants. Ants attack any animal
and clear away vegetation
surrounding the tree which
helps the tree get the
sunlight it needs.
CATIPILLARS & PLANTS
•Plants may have poisonous
chemicals that prevent
insects from eating them.
•Some caterpillars have the
ability to resist these poisons.
•They can feed on plants that
other insects can’t
•As the plant adapted by
producing poisonous
chemicals, the caterpillar
adapted by resisting them.
COEVOLUTION
Types of
Species Evolution
Let’s Play JEOPARDY!!!
NATURAL
SELECTION
&
SPECIES EVOLUTION
THERE IS A BIG DIFFERENCE!!!
What is it???
Biological Communities
• Species compete with one another for
food, water, living space and other
resources.
• Vary greatly in size, lack precise
boundaries and are rarely completely
isolated- they interact and influence one
another.
• There are communities nestled within
one another like a set of Chinese boxes.
Rotting Log Community
SUCCESSION
The gradual change in species that occupy a given area.
– As the environment changes, the community living in that
environment changes as well
– Two types:
• Primary: Originates from a lifeless habitat (bare rock, lava flow etc).
–
–
Takes thousands of years to complete.
Lichens & moss are primary species (first organisms in barren env.)
Rock  Lichens  Soil  Grass Non-woody Plants  Pine Trees  Hardwood Trees
• Secondary: Occurs where a disturbance eliminates most organisms
but does not destroy the soil
–
–
Crabgrass is the primary species
Fire, storms, human activity
Grass Non-woody Plants  Pine Trees  Hardwood Trees
What
Succession is
this?
Succession and Energy Flow….
ORDER UP ACTIVITY
(PG 89-92)
•Get into a group of 2-3 people
•Grab a packet of order up slips
•Start with the SLIP #1
“What is a keystone species”
•Find the answer to that question
on another slip.
•Write the answer on your sheet.
•Flip up the fold and start the
next question.
•Continue the process until
done.
Keystone Species
Species that are more crucial to the
maintenance of their ecosystem.
Species that are vital in determining the
nature and structure of the entire
ecosystem.
Not the most abundant organisms but
exert a profound influence on the entire
ecosystem b/c they often affect the
available amount of food, water or other
resources.
1. Wolves in Yellowstone
-Wolves taken out by hunting.
- Population of elk goes up
- Grass is overgrazed
- Beavers leave (do not have saplings
to dam streams and create water holes)
- Birds do not have nesting/resting sites (water)
2. Sea Otters in Kelp Beds
- Otters hunted for pelts so population decreases
- Urchin population increases
- feed off the kelp roots destroying the kelp forest
- loss of habitat causes a decrease in fish populations,
seal hide out and makes animals more vulnerable to shark attack.
Loss of one organism (keystone species) has a
ripple effect throughout the entire community!
Symbiotic Relationships
Mutualism (+/+) Both organisms benefit
:
Nitrogen Fixing bacteria & Legumes
Protozoa in termite stomach
E.coli bacteria & Humans
Commensalism (+/0):1 benefits one is not
affected
Remora Fish & Shark
Barnicle & Whale
Parasitism (+/-): 1 benefits, 1 harmed
Tapeworm & Dog/Cat/Human
Lamprey Eel & Fish
PREDATION
Consumption of one species (prey) by another (predator)
Strategies:
1. Pursuit- actively pursue prey
ex) cat & mouse
2. Ambush- wait in hiding to catch prey item moving by
ex) angler fish & other fish
-Adaptations that protect plants from being eaten include
spines, thorns, tough leaves and protective chemicals
- Strategies that help animals avoid being killed and eaten include
flight, association in groups, camouflage, & mechanical/chemical defenses
Evolution of Camouflage: http://www.pbs.org/wgbh/evolution/library/01/1/quicktime/l_011_03.html
Warning Coloration: Warning to other animals that they
possess chemical defenses
What is MIMICRY?
Poisonous 
(coral snake)
Non-Poisonous
(King Snake)
Predation Adaptations continued…
Rattle snakes can sense heat
through pits in their heads.
Scorpions can kill prey with
their stinger & venom.
Big teeth & claws assist
catching prey. Horns help
defend prey attack.
Do I need to explain?
Insect killed by plant
poison.
There is a spider in
there…. Do you see it?
Change color
throughout the year to
help blend in.
What is a Niche?
• Niche: role of an organism in the ecosystem
•
•
•
•
Same as Habitat?? NO!
Does it relate to Habitat?? YES!
What the organism does- its “job”
Includes abiotic and biotic factors
No two species can share exactly
the same niche!
If they do…..
they compete for the same resource!
Species CAN have similar niches
ex: Lizards
Same except for the size
of insects they eat
FUNDAMENTAL V.S. REALIZED NICHE
• Fundamental: Theoretical niche
• Realized: Organism actually uses the area
Ex) Barnacles in Scotland
Live on rock surf zone
Species A: Live higher on rocks- exposed to air
Species B: Survives in lower zones
Scientists took out species B and found that once it
was gone, species A began to grow lower on rocks
…therefore the presence of one species could
limit the niche of another.
A FUNDAMENTAL NICHE
is the resources an
organism or population
is theoretically capable
of using under ideal
circumstances.
However biological
constraints
(competition) restrict
organisms to their
REALIZED NICHE: the
resources an organism
or population actually
uses.
Species cannot coexist in a
community if their niches
are identical.
FUNDAMENTAL & REALIZED NICHE
Theoretical
Actual
FUNDAMENTAL
REALIZED
LIMITING FACTORS
• Limiting Factor:
– forces that slow the growth of a population
– 2 kinds
• Density DEPENDENT Limiting Factor
– Dependent on population size
– Related to competition and other interactions
– EX) Food supply, predation, living space, water availability
• Density INDEPENDENT Limiting Factor
– Affects the same % of a population regardless of its size
– Climate, human disturbance, natural disaster (fire)
» Ex) Hurricane Andrew & Katrina
- destroyed trees and other organisms
but considered density independent
because it destroyed organism
regardless of population
WRITE THIS IF YOU WANT TO…
LIMITING FACTOR PRINCIPLE
Limiting Factor Principle: too much or too little of
any abiotic factor can limit or prevent the
growth of a population.
– Limiting Factors in Terrestrial Biomes:
• Temp, water, light, soil
• Too little precipitation (Desert)
– Limiting Factors in Aquatic Biomes:
• Temp, sunlight, dissolved oxygen, nutrients, salinity
• Deeper water had colder temp, more oxygen, less sun
LIMITING FACTORS
COMPETITION
• INTER-SPECIFIC
– Competition between two DIFFERENT species.
– Cardinals & Finches both compete for the same bird
seed
• INTRA-SPECIFIC
– Competition between two individuals of the
SAME species
– A big cardinal & a little cardinal fight for the same
bird seed
INTERSPECIFIC COMPETITION
Interspecific
Competition:
The competition that
occurs between two
species. Competition
regulates the size of
each population and
changes the relative
population density over
time due to competition
for resources.
COMPETITIVE EXCLUSION
The extinction of a local population due
to direct competition with another
species for resources.
P. caudatum is excluded by P. aurella over time
due to competitive exclusion.
SPECIES RICHNESS
Pages 98-100
SPECIES RICHNESS
•
The number of species present in a
community
•
Ex: Tropical Rainforest & Coral Reefs VS
Geographically isolated islands &
Mountaintops
Factors that affect species richness:
•
1.
2.
3.
4.
5.
6.
Abundance of potential ecological niches
Closeness to margins of adjacent communities
Geographical isolation
Dominance of one species over others
Habitat stress
Geological history
Which ecosystem has higher
richness? Evenness?
The species richness map shows historic and current
species richness for 17 species that experienced range
contractions over more than 20% of their historic range. The
change map was created by subtracting the current from the
historic species richness map. The legend shows the
number of species present and the number of species lost in
the change map
.
1. Abundance of
Potential Ecological Niches
• A more structurally
complex community
will have more varied
food & habitat
sources, allowing a
greater # of species.
– Ex: forest vs.
grassland
2. Near the Margins of
Adjacent Communities
• Here, species richness is usually greater as
compared to the center.
– ECOTONE = transitional zone where 2 or more
communities meet
– Why would species richness be greater here??
• Contains many niches from the ecotone as well as
many niches from the adjacent communities!
– Change in species composition at the ecotones
= EDGE EFFECT
Edge effect & Ecotone
3. Geographical Isolation
• Species Richness is inversely related to this.
• Isolated communities tend to be less
diverse… why???
– Difficult to reach & successfully colonize the
area.
– Species may become locally extinct, and it is
difficult to replace them.
– Isolated areas tend to be small, thus there are
fewer potential ecological niches.
– Leads to reproductive isolation….evolution of
characteristics.
Notice that isolated populations on small islands (upper left) differ
quite substantially in color, pattern, and tail feather structure and
length, and bill size, whereas kingfishers on the large island (right)
have similar characteristics. This pattern is typical for species of many
kinds of organisms that are isolated on islands, mountain tops, etc.
Isolation over periods of time provides opportunity for mutations to
spread through small populations, thus leading to physical and
physiological diversity
Geographic Isolation leads to speciation
??? HOW ???
Grand Canyon
World
Isolation
4. One species is dominant over others
• This reduces species richness! Why???
– The dominant species out-competes the others,
crowding them out.
• Evidence: James H. Brown, Univ. of NM
– Removed 3 species of dominant kangaroo rats
from a section of the Chihuahuan desert.
– In all cases, species richness increased (more of
the submissive, smaller rat species)
5. Habitat Stress
Habitat Stress (increases / decreases)
species richness?
DECREASES!
WHY??????
6. Geological History
• A region that has gone through many climate
changes will have lower species richness…
why??
– Extinction often occurs with climate change, so
fewer species will have been able to re-establish
themselves.
• So, in terms of geological
history, name some places...
– With High species richness?
– With Low species richness?
Species Richness Summary…
• Species Richness is great when…
– There are ______
MORE potential ecological niches
– You’re ________
CLOSE TO adjacent communities
– The community is/is not isolated
– The community is/is not severely stressed
– There is _____
LOW species dominance over others
STABLE geologic history
– Communities have _______
Effects of Species Richness on
Ecosystem Services & Community Stability
• The greater the ecosystem’s species richness…
– the greater the ecosystem’s ability to supply
ECOSYSTEM SERVICES
• purifying air and water, absorbing CO2, providing wildlife
habitats, etc.
– the greater the COMMUNITY STABILITY (the
ability of a community to withstand environmental
disturbances).
• This is a consequence of community complexity…
• There’s more species variety, so the overall ecosystem will
be better able to cope with changes (if one species is
diminished, another species will flourish in its place)
The End!
Old Slides to follow…