chapter 7-8 powerpoint
TRANSCRIPT
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Chapter 7 - Biological Diversity and Biogeography
Case StudyPurple Loosestrife
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What is biological evolution?• It’s the change in inherited characteristics
of a population from generation to generation.
• What are some process that lead to biological evolution?
• 1.• 2.• 3.• 4.• 5.
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Mutations may:
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• Natural SelectionRelies on variation of individuals within a species. Genetic diversity is key!
Those orgs with traits that make them better fit or adapted survive well, reproduce more and pass these helpful traits on to their offspring.
Peppered moth = classic example.
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Photos by Ken Miller
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• Speciation (evolution of a new species)1. Geographic isolation of two populations of the same species
2. They each evolve separately
3. Eventually differences accumulate
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Reproductive isolation can occur due to mutations too.
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MigrationDuring migration different selective pressures may be encountered.
Populations may become separated Genetic DriftChanges in gene frequency of a population due to chance - not due to being better adapted
May greatly impact small populations Dangerous for rare and endangered species
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Extreme hunting left only 20 Few individuals left – why?
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Basic Concepts of Biodiversity
• 3 major concepts:1. Genetic diversity
2. Habitat diversity:
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3. Species diversity: a. Species richness –
b. Species evenness –
c. Species dominance -
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Hwk• Shannon-Weiner Biodiversity Index• Read and do sample problems.• Show all work and solve for H’• Also: Calculate Evenness for each problem:– Evenness:– Formula = H’ / ln S– S = number of different species – (Absolute evenness = 1)
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Hwk
• Pre-lab work for Wed.• Answer pre-lab questions.• #1 in INB.• #2 and 3 become your hypothesis, under
purpose on title pg.• Calculate S-W biodiversity index for both
pictures (fig. 7.4) on page 123.• Solve for H’ and Evenness.• Show all work.
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• Species habitat terms: exotic = introduced
endemic = native
cosmopolitan - very broad distribution but need similar habitat
ubiquitous = found almost everywhere even very different habitats
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How many species on Earth?
• Uncertain• Prior to fogging study:
Range = 1 - 3 million
• After study: 10 -100 million!
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Interactions Between Species
• 3 kinds:1. Competition: negative for both
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2. Symbiosis: both benefit• It is very common; exists amongst most
plants and animals
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• 3. Predation - parasitism: positive for one and negative for the other
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• Exclusion Dominance and Diversity: The
Competitive Principle• Competitive exclusion = 2 species with exact
same requirements cannot coexist in the same habitat. They will compete and the more fit one will win out and persist
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© 2003 John Wiley and Sons Publishers
Fig 7.6 A classical experiment with flour beetles.
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• Niche: how species co-exist.• A habitat is where an org lives as compared to
what it does to survive, which is its’ ecological niche
• Species that require the same resources can coexist only if they can utilize them under different env. conditions (different ecological niches).
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• Species that require the same resources can coexist only if they can utilize them under different env. conditions (different ecological niches).
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• Niches can be measured:• The range of niche a species will occupy with no
competitor is called its’ fundamental niche
• The range in which it actually lives, if it is having to compete, is called its’ realized niche
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© 2003 John Wiley and Sons Publishers
Fig 7.7 The occurrence of freshwater flatworms in cold mountain streams in Great Britain.
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Environmental Factors That Influence Diversity!!
• Diversity varies from place to place• Generally, greater in lower latitudes
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• Ecological gradient: the change in relative abundance of a species over an area (ie: change in elevation in the mtns.)
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© 2003 John Wiley and Sons Publishers
Fig 7.10 Change in the relative abundance of a species over an area or a distance is referred to as an ecological gradient.
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• Factors that increase or decrease diversity:• Increase diversity:
1. Physically diverse habitat
2. Moderate disturbance
3. Small variation in env. conditions
4. High diversity at one trophic level increases diversity of another level
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• Decrease diversity1. Environmental stress
2. Extreme environmental conditions
3. Severe limitation of an essential resource
4. Extreme disturbance
5. Recent exotic species
6. Geographic isolation (island effect)
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• Humans greatly affect diversity :
– Development and industry
– Favoring one species over another
– Manipulating environments
• Species diversity in an area may change over time, seasons, decades, centuries...
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The Geography of Life• The kinds and numbers of species varies
greatly from place to place. These large-scale global patterns are called biogeography
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• Biotic Provinces• Six “realms” were identified in 1876 based
on the types of animals found there:• (Remember: classification of orgs are based
on evolutionary relationships or similar characteristics)
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© 2003 John Wiley and Sons Publishers
Fig 8.3 The major vegetation realms are also based on genetic factors.
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• Continental drift explains the origin of these provinces as land masses periodically unified (genetic mix and spread of species) and then separated (isolation and speciation)
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• Biomes:• Each continent has diverse climates and habitats
so diversity of species is high
• Biome = a kind of ecosystem
• Similar environmental conditions (selective pressures) lead to evolution of orgs similar in form and function but not genetic heritage or internal make-up.
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© 2003 John Wiley and Sons Publishers
Fig 8.13 Global distribution of the major land biomes.
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• Divergent evolution occurs when a pop. is separated and evolves in isolation from main groups, often under different selective pressures. They have common ancestry and retain some common characteristics of their ancestors. (ex: marine mammals)
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© 2003 John Wiley and Sons Publishers
Fig 8.10 Evolutionary divergence among honeycreepers in Hawaii.
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• Island Biogeography– Generally observe adaptive radiation: species
evolve by divergent evolution as they separate into smaller groups, often on different islands, each adapting to a more specialized role (niche)
– Species diversity and islands:
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© 2003 John Wiley and Sons Publishers
Fig 8.11 Idealized relation of an island’s size, distance from the mainland, and number of species. Pg 138