Test 2 Flashcards
(121 cards)
1
Q
evolution
A
is responsible for the diversity of life on Earth
2
Q
what is evolution
A
evolution is a fact of nature
-USA is one of the few westernized countries where controversy still exists
3
Q
the process of evolution explains the connection between organisms and the environment
A
- unity of species
- adaptations to the environment
- diversity of species
4
Q
as the environment changes, organisms must adapt in order to survive and reproduce
A
- individuals with adaptations that increase their reproductive success have greater fitness
- while selection acts on the individual, only populations evolve
5
Q
Evolution is …..
A
Evolution is…Change in a population’s gene frequencies from one generation to the next
-Change is slow and gradual
6
Q
evolution is supported by….
A
supported by a tremendous amount of empirical evidence from many scientific disciplines
- Direct observation
- Fossil record
- Homology
- Biogeography
7
Q
evolutionary change:
Three predominant factors produce most evolutionary change
A
- natural Selection produces adaptive change
- Genetic Drift produces random change
- Gene Flow can homogenize populations
8
Q
two other factors less likely to produce evolutionary change
A
Mutation = required for variation
- Most are neutral, but may sometimes be harmful or beneficial
- nonrandom mating (i.e., sexual selection
9
Q
Genotypic and phenotypic changes in population
A
=microevolution
10
Q
over time, can lead to new species =
A
macroevolution
11
Q
Individuals are selected for, but……
A
it is the population that evolves
12
Q
natural selection in humans: Lactose Intolerance
A
lactose Intolerance:
- 75% of people (passed infancy) worldwide are lactose intolerant
- Recessive mutation common in Northern Europeans and their descendants
- Common ~10,000 ya…Why?
13
Q
adaptation
A
change in a pop to better align w/ specific environmental circumstances
14
Q
limitations of natural selection: scurvy condition
A
Scurvy Condition caused by vitamin C deficiency
- Can be lethal Most mammals do NOT need to take vitamin C, but humans and non-human primates do
- Pseudogene = gene carrying a mutation that halts expression, making gene nonfunctional
- If condition is lethal, why was the pseudogene mutation in primates not selected against?
15
Q
Pseudogene
A
gene carrying a mutation that halts expression, making gene nonfunctional
16
Q
coevolution and the “arms race”
A
common in predator-prey relationship
17
Q
modes of natural selection: directional
A
Directional = favors one extreme phenotype
-Common when environment changes or pop migrates to new (and different) habitat
18
Q
modes of natural selection: Disruptive
A
Disruptive = favors both extremes
19
Q
modes of natural selection: stabilizing
A
Stabilizing = favors intermediate
-Reduces variation and favors status quo
20
Q
Influence of Environment on Genes Epigenetics
A
Epigenetics = changes in gene expression w/o changing DNA sequence (i.e., gene potential)
-Some phenotypic variation results from environmental influences, not genetic variation
21
Q
convergent evolution
A
independent evolution of similar features in different lineages
-Sometimes similar adaptations arise due to similar environmental pressures oResemblance is analogous, not homologous
22
Q
adaptive evolution
A
when species suitability and environment match
-Continuous, dynamic process due to ever-changing environment
23
Q
natural selection
A
is the only evolutionary mechanism that consistently leads to adaptive evolution
24
Q
Genetic drift and gene flow do NOT consistently
A
lead to adaptive evolution
-Can either increase OR decrease species-environment match
25
genetic drift: random sampling
```
non predictable (or random) allele frequency changes from one generation to next
-smaller the sample/pop = greater the chance of random deviation from predicted result Reduces genetic variation due to allele loss
```
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two examples of genetic drift
Founder Effect
| Bottleneck Effect
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INBREEDING-
also an issue in newly formed small populations
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genetic drift: founder effect
Occurs when few individuals become isolated from larger population
- Smaller group establishes new population
- Gene pool differs from source population
- Less genetic diversity = more prone to risks
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accounts for many inherited disorders among isolated human pops
- amish 6th finger.... example of ....
genetic drift: founder effect
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genetic drift: bottleneck
drastic reduction in population size due to sudden environmental change
- By chance, certain alleles may be over or under represented, or completely absent in the pop
- Reduced genetic diversity even after pop size recovers Humans are notorious for causing species bottlenecks
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effects of genetic drift
- Significant in small pops
- Can cause allele frequencies to change at random
- Can lead to loss of genetic variation w/in pop
- Can cause harmful alleles to become fixed
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adaptive radiation follow:
- Mass extinctions
- Evolution of novel, adaptive characteristics
- Colonization of new regions
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adaptive radiations
rapid evolution of diversely adapted species from a common ancestor who fill different ecological niches
- Encouraged by reduced competition
- Occurred on a large-scale after mass extinctions
34
Worldwide Adaptive Radiations
Mammalian adaptive radiation
- Following dinosaur extinction (66 mya)
- Before, mammals small, nocturnal, and not yet morphologically diverse
- Expanded greatly in diversity and size
- Can lead to the co-evolution and diversification of mutualistic species
- Ex: flowering plants and bees (125 mya)
35
mass extinction
Mass Extinctions
- Large numbers of a species become extinct worldwide
- Majority of species that ever-lived are now extinct
- Slow, gradual extinctions are normal, but rapid anthropogenic-induced mass extinctions are not
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Five mass extinctions in fossil record over past 500 million years
- In each, 50% or more of marine species became extinct
| - More notable extinctions = Permian and Cretaceous
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background rate of extinction
average rate of extinction that occurs b/w mass extinction events
- Historically, background rate has been one species per one million per year
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mammalian species extinctions in last 400 years w/ 169 still listed as critically endangered Compared to 1
mammalian species every 200 years in fossil record
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Sixth Mass Extinction is Anthropogenic
due to habitat destruction, invasive species, overharvesting, and climate change
-All induced by human activity
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are we on track for a mass extinction ?
1,000 known species lost in last 400 years
- Rate is 1,000 to 10,000 times greater than the background extinction rate documented in the fossil record
- Past extinctions occurred in situ with a warming global climate
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unless there is dramatic change in human-activity, a
sixth mass extinction is likely imperative
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artifical selection
goal-directed selective breeding to produce desired traits -Observable in our lifetime
43
humans alter the ecosystem and affect evolution by:
introducing invasive species
- Causing biodiversity declines
- Altering ecological interactions
- Clear-cutting ecosystems for human us
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Humans Tend to View Biodiversity in terms of Ecosystem Services:
cultural benefits, human provisions, and ecosystem regulation and support
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Biodiversity is the...
Variety of life living on Earth,includes:
- Species diversity
- Genetic diversity
- Ecological diversity
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how many species are discovered to date?
1.9 million
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biodiversity is the common denominator that relates to:
- Health of an ecosystem
- Its ability to provide services
- Disruption human activity can cause
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maintaining biodiversity is one of our greatest
ecological challenge to date
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genetic diversity
variations in the genes among individuals of the same species
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species diversity
the variety of species present in an area; includes the number of different species that are present as well as their relative abundance
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ecological diversity
the variety of habitats, niches, trophic levels, and community interactions
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Species diversity is measured by
Species richness, Species abundance, Species evenness
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species richness
Species richness = number of species in a biological community
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species abundance
Species abundance = number of individuals of each species in a community
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species evenness
Species evenness = pattern of species abundance (rare or common?)
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species diversity index
mathematical formula accounting for richness, abundance, and evenness
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Measuring Biodiversity:
| Species diversity is highest when species
richness is high and species abundance is even
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Biodiversity Contributes to Ecosystem Health via:
productivity and stability
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productivity
indicator of how effectively plants photosynthesize
- More plants = higher productivity
- More plant diversity = more habitat coverage
- Some plants have mutualistic relationships to help each other grow
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stability
Ability of ecosystem to resist environmental disturbances -Biodiversity acts as a buffer Rivet hypothesis
-If too many species are lost, the ecosystem will crash
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Biodiversity Stabilizes the Food Web and the Ecosystem
predators keep prey densities in check and vice versa (population cycling)
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certain species may be more important to an ecosystems health, sustainability, and conservation than others
- indicator species
- Keystone species
- Umbrella species
- Flagship species
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invasive species can...
invasive species can damage an ecosystem and decrease biodiversity
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(Ecological) Indicator Species Species
(Ecological) Indicator Species Species -whose presence, absence, or abundance reflects a specific environmental condition
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(Ecological) Indicator Species Species
can signal a change in the biological condition of a particular ecosystem
-Serves as a proxy for health and stability
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(Ecological) Indicator Species Species
sensitive to slight fluctuations in abiotic and/or biotic environmental factors
-Serves as early warning signs or predictors
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Lichens can indicate ...
Lichens as an Air Quality Indicator Species
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bushy lichens
need really clean air
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leafy lichens
can survive a small amount of air pollution
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crusty lichens
can survive in more air pollution
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no lichens
air is heavily polluted with sulfur dioxide
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keystone species.....
have a disproportionate effect on biodiversity in an ecosystem
-Not necessarily abundant
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keystone species.....
Has an crucial ecological role or fills a critical ecological niche within the community
-Often predators, but NOT always apex predators
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loss of a keystone species will....
likely result in a dramatic shift in, or even complete collapse of (aka. trophic cascade), the ecosystem
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Yellowstone experienced a trophic cascade in
1920s when wolves were exterminated •Wolves reintroduced in 1995
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removal of keystone sea otter
sea urchins overgraze kelp and destroy the kelp forest community
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umbrella species.....
occupy large habitats (and home ranges) or have other important ecological requirements that overlap with many other species in the ecosystem
-Keystone species are often also umbrella species
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umbrella species.....
often selected for when making conservation-related decisions
-By protecting these species, all other species that fall under their ecological umbrella will also be protected
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Flagship Species
species selected to act as ambassador, icon, or symbol for a defined habitat, issue, campaign or environmental cause
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flagship species
Typically relatively large and highly charismatic species
- Are often iconic and hold cultural significance
- Typically are endangered
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Flagship species
provide an important focus for raising awareness and stimulating interest
-Helps drive conservation of other sympatric species or habitats
82
flagship species: most popular species for conservation
apes, elephants, big cats, black rhinoceros, giant pandas
83
Invasive Species
Species not native to an ecosystem which cause harm and sometimes localized extinctions
-Typically introduced by humans
84
invasive species
Often negatively impacts the biodiversity of the ecosystem -Typically are good competitors and often out compete endemic species, resulting in native species decline or localized extinction
-Ecosystem does NOT usually have time to adapt to the sudden pressure of the newly introduced invasive species
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Biodiversity hotspot
biogeographic region that is a significant reservoir of biodiversity AND is threatened w/ destruction
86
34 terrestrial regions worldwide are classified biodiversity hotspots, but cover only
2.3% of Earth’s land surface
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Biogeography and Biodiversity....contain many resident species, some of which are
endemic
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90% habitat loss in
hotspots
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high number of endangered endemic species covering a
small percentage of land
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all hotspots represent less than
12% of Earth’s total area, but contain at least 44% of all plant species and 35% of all vertebrate animal species on Earth
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Geographic Areas Producing Highest Biodiversity
- -Mountainous regions
- - Equatorial Regions ---------most diverse
- Particularly tropical rain forests
- -Marine Coral Reefs ------------most diverse
- -Large Islands
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Mountainous Regions
have more biodiversity than flatter areas
| -Provide diverse types of habitats and physical conditions
93
The Latitudinal Gradient
Species diversity highest near the equator
| -Decreases as you travel north or south
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Areas of Highest Biodiversity >
The Latitudinal Gradient
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Why does this gradient exist?
- stability hypothesis
- productivity hypothesis
- climate hypothesis
96
climate Hypothesis
Moving further away from the equator means the climate becomes colder and harsher
97
productivity hypothesis
rainfall and solar energy at equator allow for rich vegetation, which supports diverse food web
98
stability hypothesis
climate in tropics has been more stable allowing species to evolve over time
-Stable environmental conditions may also puts less selective pressures on species oPresent day species living in equatorials regions often more closely resemble their ancestor
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Allen’s and Bergmann’s Rules : Examples...
arctic fox, desert (kit) fox
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Coral bleaching due to
global warming
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Coral Reefs
- Most diverse environment rivaled only by tropical rain forests
- Called “rainforests of the sea”
- More than 6,000 species of coral
- ~25% of ocean’s fish depend on coral reefs
102
Large Islands
Large islands close to the mainland have more immigration and support more species
-Opposite true for small islands that are far away
103
Theory of Island Biogeography
Theory of island biogeography
-Islands are populated by immigrants
oMigration rate affected by distance to mainland
-Populations frequently go extinct on islands
oExtinction rate influenced by size of island
oLocalized extinctions allow for the adaptive radiation of new or less abundant species
104
Equilibrium Theory of Island Biogeography
Species diversity equilibrium occurs when two lines cross (indicated by black arrows).
105
Species – Area Relationship
Relationship b/w area of an island and number of species
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island Biogeography: Testing the Theory
Scientists counted insects on several islands, eradicated them, and allowed islands to recolonize
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Island Biogeography and Endemic Species
Many species on islands are endemic, putting them in grave danger of extinction Forest fragments are like islands
- Small patches cannot support the original species richness or population size
- Can cause extirpation
108
Blitzkrieg Hypothesis
Suggests that humans hunted large mammals to extinction when they colonized N. America Supported by similar evidence from other continents
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background extinction
- Extinction is a naturally occurring, ongoing process
- Allow for adaptive radiation of new or less abundant species Background extinction rate = number of species that go extinction during a “typical” time
- Approximately one extinction per million species per year
110
current extinction
- 100 to 1000x higher than background rate Endangered organisms (IUCN)
- 25% of mammals
- 40% of amphibians Ø28% of reptiles
- 27% of fish
- 71% of flowering plants If rates are accurate,60% of all species will be extinct w/i 100 years!
111
human Activity is Biggest Threat to
Biodiversity
112
habitat fragmentation
deforestation effects all three components of biodiversity
113
overharvesting (includes hunting)
leads to negative growth rate and can drive a population to extinction
114
Disease transmission
more common between closely related species
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pet trade
typically involves the commercial selling of young animals
116
climate change
climate change = global issue affecting all life
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habitat fragmentation
- human wildlife conflict
| - orangatans have lost 80% of there habitat
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Wildlife Corridors Can Provide
Practical Solutions to Fragmented Habitat
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disease transmission
- feeding apes by hand
- ebola killed 95% of gorillas in Congo in 2006
- humans can introduce new diseases to apes
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Ways to Preserve Biodiversity
Become educated about the long-term benefits of biodiversity
- Develop economic policies that take advantage of these benefits
- Develop a cooperative approach
- Design effective methods of conservation
- Curtail human population growth
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preserving biodiversity can prevent long-term
economic AND ecological catastrophes
