Download ES 10ecologyF122.pptx

11/8/12
What we’ve learned so far…
• 
• 
• 
• 
• 
Biotic/abiotic
Tolerance limits
Habitat fragmentation
Genetic bottlenecks
Adaptation
Today’s agenda
• 
• 
• 
• 
• 
• 
• 
Natural selection
Speciation – allopatric and sympatric
Taxonomy
Adaptation – more
Species diversity
Species interactions
Keystone species
–  Convergent
–  Co-evolution
Function and design
•  Co-evolution
•  Convergent evolution
Natural Selection
Adaptation
Evolution
http://www.youtube.com/watch?v=OMVN1EWxfAU
Natural Selection
Charles Darwin
Alfred Russel Wallace
1
11/8/12
Natural selection: Facts and inferences
The Galapagos mockingbirds differ only slightly in size, shape, and coloration.
Fact 1. Natural populations have large excess reproductive capacities.
Nesomimus melanotis
Nesomimus macdonaldi
Fact 2. Population sizes generally remain stable.
Fact 3. Resources are limiting.
Inference 1. A severe struggle for existence must occur.
Nesomimus parvulus
Nesomimus trifasciatus
Fact 4. An abundance of variation exists among individuals of a species.
Fact 5. Some of this variation is heritable.
ul
u
s
fa
sc
ia
tu
s
tri
pa
rv
N.
Inference 2. Genetically superior individuals outsurvive and outreproduce
others.
N.
i
al
d
el
an
o
ac
do
n
m
m
N.
N.
Geographic proximity
of similar but distinct
species
tis
Darwin reasoned that they are similar because they share a common ancestor.
Inference 3. Over many generations, evolutionary change must occur in
the population.
In tundra habitats above timberline, the alpine skypilot is pollinated primarily by bumblebees.
28
24
20
16
12
8
4
0
10 12 14 16 18 20 22
Tundra flower:
Flower size (mm)
big and sweet-smelling
In forested habitats below timberline, the alpine skypilot is pollinated primarily by flies.
Number of individuals
•  Case Study of Natural Selection by Pollinators of
Alpine Skypilot Plants
Number of individuals
Experimental Evidence of Evolution by
Natural Selection
10
8
6
4
2
0
Below-timberline flower:
small and skunky-smelling
10 12 14 16 18 20 22
Flower size (mm)
For example, very small and very large babies are most
likely to die, leaving a narrower distribution of birthweights.
The sickle cell allele
100
20
Genotypes: Relative fitness
HbA HbA: susceptible to malaria
Percentage of Population
Alleles:
HbA = normal hemoglobin allele
HbS = sickle cell allele
70
50
Mortality
15
30
20
10
Heavy
mortality
on
extremes
10
7
5
5
3
2
HbA HbS: resistant to malaria, experiences mild anemia
HbS HbS: susceptible to severe anemia
Percentage of mortality
- overdominance occurs when fitness of the heterozygote
exceeds either homozygote.
0
1
2
3
4
5
6
7
8
9
10
11
Birthweight (pounds)
2
11/8/12
Adaptation by the process
of Natural Selection
Speciation: new species evolve, others go extinct
Sexual selection is a (one)
strong force maintaining
separate species
• Survival and differential reproductive
success over a period of time
• Traits that increase ‘fitness’ are ‘selected
for’, and are passed on through generations
Taxonomy
Allopatric speciation: speciation occurs as a result of a
physical separation - barriers
Sympatric speciation: speciation occurs as a result of
hybridization – within a population, a new species arises
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Taxonomy of two common species
Five Kingdoms
3-3
3
11/8/12
Three Domains
Evolutionary Trees
Evolution/adaptation can also lead to
design ‘innovations’ – increase fitness
The Flower and fruit
allowed the
angiosperms
(flowering plants) to
diversify to over
350,000 species Monarch Butterfly
Viceroy Butterfly
Batesian mimicry
Blue Jay
Pitfalls
-  Giraffes
- Polar Bears
4
11/8/12
The neck of the Giraffe
The neck of the Giraffe
Most feeding is done below neck height.
7
7
Feeding height (meters)
6
6
5
Males
4
4
3
3
2
2
1
1
0
0
Gerenuks
(Giraffe necks)
“Sterling 1974”
1 “sneak and pounce”
20
40
Females
5
0
0
20
Percentage of feeding bites
40
Polar Bears
Polar Bears
UV Hypothesis
Polar Bears
54 “jump and crush”
233 “sit and wait”
5
11/8/12
Species Diversity
•  What is species diversity: both
–  Species richness
–  Relative abundance
•  What leads to high diversity?
–  Habitat heterogeneity
–  High levels of competition
–  Other…interspecific interactions, functional
group diversity, abiotic factors?
Species Interactions (Biotic):
Interspecific and Intraspecific
Factors affecting organisms
•  Abiotic: non-living (temperature, water,
sedimentation etc.) physical and chemical
•  Biotic: living interactions (between living
organisms)
–  Symbiosis
–  Predation
–  Herbivory
–  Competition
Adaptation, speciation, and
the concept of the niche
•  Symbiosis
•  Competition** - we’ll start here
•  Predation/herbivory
•  Symbiosis
Niche
The ‘role’ an organism plays in its environment or
ecosystem
Competitive exclusion principle (CEP) = if
there are two species, one will outcompete
1 niche = 1 species
the other and ‘win’, OR, a process of niche
partitioning will begin. They will divide up
and ‘share’ the parts of the niche
Niche partitioning
Competition can also lead to niche partitioning – ‘dividing’ up a niche
6
11/8/12
Effects of competition
•  Competitive exclusion: One species dominates
•  Resource partitioning – a niche can be
‘partitioned’: owls/hawks •  Competition can lead to speciation
•  Competition is an important factor in
maintaining ecosystem function. When one
species is removed, the structure of competition
is changed too.
•  Introduced species?
Types of Symbiosis
Zooxanthellae: the key to coral reef productivity
Symbiosis means ‘living together’
+/+ = mutualism. Both benefit. Often obligatory
+/0 = commensalism. One benefits, the other – no effect
+/- = parasitism. One benefits, the other is ‘harmed’ or compromised
Cleaning symbiosis:
mutualism
mutualism
7
11/8/12
Commensalism…
Predation: powerful effects on populations
and on evolution
Ecosystem structure
Herbivory has large effects on ecosystems
Ecosystem change: an example
•  Keystone species - is there such a thing? –  A species whose ‘role’ or niche has a major
impact on the structure of an ecosystem
–  Some case studies?
Killer whales and
their appetite for
sea otters
8
11/8/12
Sea Otters and Sea Urchins:
a kelp forest paradigm
Sea Urchins eat kelp, especially new recruits
If kept in check, they eat drift kelp
If populations expand, they will eat established kelp
Sea Otters eat urchins, especially exposed ones
They will keep sea urchin populations in check
The Aleutian Island studies
Sea Otters as a keystone predator
9