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Transcript
Biological Communities and Species Interactions
1
Why is Earth "just right" for life?
• Distance from sun
• Size
• Rotation
• Orbit around sun
• Atmospheric evolution
© Brooks/Cole Publishing Company / ITP
2
Who lives where and why?
•
•
Interaction of several factors determines
biogeographical distribution.
 determine abundance and distribution
Species requirements and tolerances can also be
used as useful indicators.
3
Tolerance Limits
4
Adaptation
•
Adapt is used in two ways:
 Limited range of physiological modifications
 Inheritance of specific genetic traits allowing a
species to live in a particular environment.
 Evolution
 Microevolution
 Macroevolution
5
Evolution & Adaptation
• Microevolution- change in gene
frequency within a population
• Macroevolution- formation of new
species from ancestral species
© Brooks/Cole Publishing Company / ITP
Genes mutateindividuals selectedpopulations evolve
6
Microevolution
Four processes drive microevolution:
1. Genetic variability
2. Natural selection
© Brooks/Cole Publishing Company / ITP
7
Microevolution
Four processes drive microevolution, cont:
3. Gene flow
4. Genetic drift:
8
Natural Selection
Directional selection favors individuals with traits that
are at one end of a distribution
• giraffe example
• "It pays to be different.”
© Brooks/Cole Publishing Company / ITP
9
10
Natural Selection
Stabilizing selection eliminates individuals at both ends
in the spectrum of variation
• the average remains the same.
• "It pays to be average.”
•Ex. Plant height
© Brooks/Cole Publishing Company / ITP
11
12
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.“
© Brooks/Cole Publishing Company / ITP
13
14
Convergent Evolution
Species from different evolutionary branches may come to
resemble one another if they live in very similar environments
Example:
1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)
15
16
Coevolution
•
1.
2.
Evolutionary change

Competitive relationships lead to coevolution.
Example:
Cheetah and gazelle
Insects and flowers
17
Macroevolution
Speciation-Evolution of a new species-geographical
isolation or selective pressure can create an
entirely new species.
18
Speciation
Geographic
isolation can
lead to
reproductive
isolation,
divergence and
speciation.
© Brooks/Cole Publishing Company / ITP
19
Community Relationships
•
•
Habitat
Niche
 Includes:
 range of tolerance for various physical conditions
(temp and water)
 types and amounts of resources it uses
 interactions with abiotic and biotic components
 the role it plays
20
Niche
Fundamental niche: theoreticaly use
if there were no competition
Realized niche: actually uses
21
Resource Partitioning
•
Law of Competitive Exclusion
 One will either migrate, become extinct, or
partition the resource
22
Types of Species
•
Generalist
broad niches
 tolerate wide range of environmental variations

•
Specialist
narrow niches
 more likely to become endangered
 do better under consistent environmental conditions

23
r and k strategists
The r-strategists
1.
High biotic potential – reproduce very fast
2.
Are adapted to live in a variable climate
3.
Produce many small, quickly maturing offspring = early
reproductive maturity
4.
“Opportunistic” organisms
The K-strategists
1.
Adaptations allow them to maintain population values around
the carrying capacity
2.
They live long lives
3.
Reproduce late
4.
Produce few, large, offspring
24
What Different Roles Do Various Species Play in
Ecosystems?
•
•
•
•
Native
Nonnative
Indicator species
Keystone species
25
Non-native Species
•
Nonnative/Exotic/Alien Species
- Examples: Zebra Mussels in the Great Lakes,
Snakehead fish in MD, Mongoose in Hawaii,
Cane Toads in Australia
26
Keystone Species


Strong interactions with other species which affect the
health and survival of those species
If a keystone species is removed from a system
- the species it supported will also disappear
- other dependent species will also disappear
27
SPECIES INTERACTIONS
•
Predator
- Reduce competition, population overgrowth,
and stimulate natural selection.
o Coevolution
28
Predator Adaptations
29
Prey Adaptations
30
Competition
•
•
Interspecific -different species
 Results in: migration, population declines
Intraspecific - same species
 Intense due to direct competition for same
resources
- Territoriality
 Disadvantages?
31
Symbiosis
•
Symbiosis
 Mutualism - Both members benefit.
- Insects and flowers
 Ex. Yucca plant and moth
Yucca’s only pollinator is the
yucca moth. Hence entirely
dependent on it for dispersal.
Yucca moth caterpillar’s only
food is yucca seeds.
Yucca moth lives in yucca and
receives shelter from plant.
32
Mutualism
33
Symbiosis Cont…

Commensalism
- Sharks and remora
- Whales and barnacles
34
Symbiosis Cont…

Parasitism –
 Humans and Tapeworms
35
Ecological Processes
• Ecological Succession
•Primary Succession
•Secondary Succession
36
Primary Succession
• Gradual establishment of biotic
communities in an area where no life
existed before
• No preexisting seed bank
•newly formed islands (i.e. volcanic
origin)
•retreat of a glacier
37
38
Primary Succession
Glacier Retreat
39
Secondary Succession
• Gradual reestablishment of biotic
communities in an area where one was
previously present.
• Preexisting seed bank
•"old field succession"
•forest fire
40
41
42