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Biodiversity
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the species’ occupation and its
Niche is the species’ occupation and its Habitat location of species (its address)
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Niche A species’ functional role in its ecosystem; includes anything affecting species survival and reproduction Range of tolerance for various physical and chemical conditions Types of resources used Interactions with living and nonliving components of ecosystems Role played in flow of energy and matter cycling
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Niche Fundamental niche: set of conditions under which a species might exist in the absence of interactions with other species Realized niche: more restricted set of conditions under which the species actually exists due to interactions with other species
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Species Diversity Def: the variety of species in an area
Two subcomponents: species richness species evenness
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Species Richness vs. Evenness
Species Richness: measurement of the number of species in a given area Species Evenness: measurement of how evenly distributed organisms are among species Community A Community B species species species species species
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Determining Species Diversity
Scientists may want to: * get an estimate of # of species in an area * compare species diversity of two communities To be accurate, need to: * take both species evenness and species richness into account
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Comparison of Two Communities
Richness (number of species) Relative abundance How do we describe these differences?
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Biodiversity Biodiversity
increases with speciation decreases with extinction Give-and-take between speciation and extinction changes in biodiversity Extinction creates evolutionary opportunities for adaptive radiation of surviving species
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Interpretations of Speciation
Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change
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Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments Example: Hawaiian Honeycreepers
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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)
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Coevolution Evolutionary change Example: Wolf and Moose
One species acts as a selective force on a second species Inducing adaptations that act as selective force on the first species Example: Wolf and Moose Acacia ants and Acacia trees Yucca Plants and Yucca moths Lichen
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Extinction Extinction of a species occurs when it ceases to exist; may follow environmental change - if the species does not evolve Evolution and extinction are affected by: large scale movements of continents gradual climate changes due to continental drift or orbit changes rapid climate changes due to catastrophic events
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Extinction Background extinction - species disappear at a low rate as local conditions change Mass extinction - catastrophic, wide-spread events --> abrupt increase in extinction rate Five mass extinctions in past 500 million years Adaptive radiation - new species evolve during recovery period following mass extinction
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Date of the Extinction Event Marine vertebrates and invertebrates
Mass Extinctions Date of the Extinction Event Percent Species Lost Species Affected 65 mya (million years ago) 85 Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected. 213 mya 44 Marine vertebrates and invertebrates 248 mya 75-95 380 mya 70 Marine invertebrates 450 mya 50
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Species Richness on Islands
Depends on: Rate of immigration to island Rate of extinction on island These in turn depend on: Island size Distance from mainland Because of their size and isolation, islands provide great opportunities for studying some of the biogeographic factors that affect the species diversity of communities. Imagine a newly formed island some distance from the mainland. Robert MacArthur and E. O. Wilson developed a hypothesis of island biogeography to identify the determinants of species diversity on an island.
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How do species move? Humans (accidental and intended)
Animals (sticky seeds and scat) Wind and ocean currents (+ or -) Land bridges Stepping stone islands affected by climactic changes (glaciation) ocean levels short-term weather patterns Aerial dispersal cause by wind, birds, flying insects. Dependent on long-term viableility of seeds, spores, etc. Decreasing ocean levels may allow flow of organisms between land masses normally isolated. This allows for genetic mixing. Coconuts are a good example of well adapted marine dispersed organism. Long-lasting climactic changes such as glaciation may allow for the expansion and subsequent reduction of range, but during that expansion, gene-flow will occur.
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What allowed colonization?
Niche opening No competition Endemics not utilizing resources Accessibility to colonists Colonization of young islands is especially rapid compared to older islands and especially the mainland 4 - Of course, if there is no access to colonists, there will be no colonization.
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Theory of Island Biogeography
Immigration rate decreases as island diversity increases Extinction increases as island diversity increases Species equilibrium on islands is a balance of immigration and local extinction
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Theory of Island Biogeography
Smaller islands have lower total populations Probability of extinction increases with lower population Smaller islands have lower species diversity
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Theory of Island Biogeography
Islands further from mainland have lower immigration rates More distant islands have lower species diversity
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Biogeographical Changes
Richness declines from equator to pole Due to: Evolutionary history Climate Generally tropical communities are older than temperate than polar communities Organisms have a richer evolutionary history in an area where they are adapted to the climate. Energy input (solar) and water availability factor into this phenomenon. Fig Bird species numbers
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Geographic (Sample) Size
Species-area curve The larger the geographic area, the greater the number of species Note that both scales are logarithmic Fig North American Birds
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Community Relationships
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Types of Species Generalist Specialist large niches
tolerate wide range of environmental variations do better during changing environmental conditions Specialist narrow niches more likely to become endangered do better under consistent environmental conditions
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r and k strategists Depending upon the characteristics of the organism, organisms will follow a biotic potential or carrying capacity type reproductive strategy The r-strategists High biotic potential – reproduce very fast Are adapted to live in a variable climate Produce many small, quickly maturing offspring = early reproductive maturity “Opportunistic” organisms The K-strategists Adaptations allow them to maintain population values around the carrying capacity They live long lives Reproduce late Produce few, large, offspring
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Types of Species Native species normally live and thrive in a particular ecosystem Nonnative species are introduced - can be called exotic or alien Indicator species serve as early warnings of danger to ecosystem- birds & amphibians Keystone species are considered of most importance in maintaining their ecosystem
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Nonnative Species Nonnative plant species are invading the nation's parks at an alarming rate, displacing native vegetation and threatening the wildlife that depend on them At some, such as Sleeping Bear Dunes National Lakeshore in Michigan, as much as 23 percent of the ground is covered with alien species, and the rate of expansion is increasing dramatically.
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Indicator Species a species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem reflect the quality and changes in environmental conditions as well as aspects of community composition
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Keystone Species A keystone is the stone at the top of an arch that supports the other stones and keeps the whole arch from falling a species on which the persistence of a large number of other species in the ecosystem depends. If a keystone species is removed from a system the species it supported will also disappear other dependent species will also disappear Examples top carnivores that keep prey in check large herbivores that shape the habitat in which other species live important plants that support particular insect species that are prey for birds bats that disperse the seeds of plants
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Species Interaction
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Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition
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Competition
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Resource Competition
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Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition Preemptive competition
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Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition Preemptive competition Competitive exclusion
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Competitive Exclusion
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Competition Any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species Resource competition Preemptive competition Competition exploitation Interference competition
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Competition
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PREDATION
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Predator Adaptations Prey detection and recognition
sensory adaptations distinguish prey from non-prey
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Predator Adaptations Prey detection and recognition Prey capture
sensory adaptations distinguish prey from non-prey Prey capture passive vs. active individuals vs. cooperative
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Predator Adaptations Prey detection and recognition Prey capture
sensory adaptations distinguish prey from non-prey Prey capture passive vs. active individuals vs. cooperative Eating prey teeth, claws etc.
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Prey Adaptations Avoid detection camouflage, mimics, diurnal/nocturnal
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Prey Adaptations Avoid detection Avoid capture camouflage, mimics,
diurnal/nocturnal Avoid capture flee resist escape
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Prey Adaptations Avoid detection Avoid capture
camouflage, mimics, diurnal/nocturnal Avoid capture flee resist escape Disrupt handling (prevent being eaten) struggle? protection, toxins
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Herbivory Herbivore needs to find most nutritious
circumvent plant defenses
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Herbivory Herbivore needs to find most nutritious
circumvent plant defenses Herbivory strong selective pressure on plants structural adaptations for defense chemical adaptations for defense
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Herbivory
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Herbivory
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Herbivory
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Symbiosis: Mutualists, Commensalists and Parasites
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Symbiosis and symbiotic relationship are two commonly misused terms
Translation of symbiosis from the Greek literally means “living together” Both positive and negative interactions
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Mutualism DEFINITION:
An interaction between two individuals of different species that benefits both partners in this interaction
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Yucca and Yucca 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.
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Lichen (Fungi-Algae) Symbiotic relationship of algae and fungae…results in very different growth formas with and without symbiont. What are the benefits to the fungus?
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Commensalists Benefit from the host at almost no cost to the host
Eyelash mite and humans Us and starlings or house sparrows Sharks and remora
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Parasites and Parasitoids
Parasites: draw resources from host without killing the host (at least in the short term). Parasitoids: draw resources from the host and kill them swiftly (though not necessarily consuming them).
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Parasitic wasps Important parasites of larvae.
In terms of biological control, how would this differ from predation? ovipositor
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Ecological Processes
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Ecological Succession
Primary and Secondary Succession gradual & fairly predictable change in species composition with time some species colonize & become more abundant; other species decline or even disappear.
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Ecological Succession
Gradual changing environment in favor of new / different species / communities
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Primary Succession Glacier Retreat
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Bibliography Miller 11th Edition
rob.ossifrage.net/images/ Biology, 2003, Prentice Hall
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