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54 Cards in this Set
- Front
- Back
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R & K selection
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different life-history categories based on habitat use & competition
-r selected species specialize in disturbed environments w/ out much competition. -k is better w/ more intense competition |
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Dispersion (distribution)
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spacing of individuals within local populations
3 Types (1) Clumped - social groups - clumped resources - poor dispersal (2) Random (3) Even - territorial - spaced resources |
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Population
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group of individuals of the same species living together in time & space
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Local Population
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individuals that live together within a habitat patch -> limited area with suitable habitats
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Source population
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- good habitats
- produce more offspring than a population can hold - offspring disperse, extra offspring leave original habitat (K is exceeded) |
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Sink population
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- bad habitats produce fewer offspring than population can hold
- population maintained by immigrants from source population |
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Age-specific mortality rates
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proportion of deaths occurring per unit time as a function of age class
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Age-specific schedule of births
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average # of offspring produced per individual per unit time as a function of age class
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Life Tables
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- track births & deaths of individuals at different ages
- tool for determining age-specific mortality |
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Demography
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- study of life tables
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Types of life tables
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(1) Cohort - follow a group from birth to death
(2) static - compare different age groups @ one point in time |
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Survivorship curves (3)
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- Survival, Lx (x-axis) vs Age (y-axis)
3 Types: (1) Mortality increases w/ age (2) Mortality is constant w/ age (3) Mortality decreases w/ age |
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Categories of population regulation (2)
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(1) Density Independent - occur regardless of population size
Examples: - climate - natural disasters - growing season (2) Density Dependent - increases as population size grows Examples: - food - sunlight (plants) - water - space |
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K
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carrying capacity, the population size at which r=0
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Reasons populations fluctuate
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(1) Population tracks changes in environment
- altered carrying capacity (K) - altered weather may affect density independent growth rate - altered death rate due to increase in predators/ pathogens (2) Due to certain intrinsic characteristics of the organism - *slow r -> populations can't keep up w/ changes in environment - *high r -> allows rapid adjustments |
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time lags
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rate at which populations respond to density effects
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Types of extinction (4)
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(1) True extinction/ global extinction - no member of a species remains anywhere in the world
(2) Extinct in the wild - exist only in captivity (3) Locally extinct (4) Ecologically extinct - numbers too low to affect the biological community |
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3 General Patterns of Extinction
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(1) Background - regular, slow pace of extinction & replacement in natural ecosystems
(2) Mass extinction - Massive, global die-offs at a few, rare times in history (3) Anthropogenic Extinction - recent, greatly accelerated pace caused by man |
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Characteristics that increase risk of extinction
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(1) Specialization
(2) Small population - low genetic diversity (3) Asexual - low genetic variation (4) Low reproductive rate (small r) (5) Top predators - need a lot of resource space (6) Small geographic range (Ex: live on an island) (7) Dispersal ability |
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Mass Extinction
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- global in extent
- involve a broad range of organisms - very rapid - ~50% of species go extinct |
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The Big Five (Oldest to Youngest)
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(1) Ordovician - 500 mya
(2) Devonian - 408 mya (3) Permian - 290 mya (4) Triassic - 250 mya (5) Cretaceous - 65 mya Hint: Only Dumb People Try Crack |
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Anthropogenic Extinction
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- large mammals (mega fauna) underwent massive extinction rates when humans colonized
- for every colonization event, there is extinction |
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Reasons for high extinction rate of island species
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- narrow distribution
- low dispersal - susceptibility to disease and invasive species - small population sizes (not enough room for big populations) |
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Ways humans are causing extinctions (5)
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(1) Habitat degradation/ loss (85%)
(2) Invasive species (49%) (3) Pollution (24%) (4) Exploitation (17%) (5) Disease (6%) |
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Interactions between populations
Mutualism, Parasitism/Predation/Herbivory, Commensalism, Amensalism, Competition |
Mutualism + +
Parasitism, + - Predation, Herbivory Commensalism + o Ammensalism o - Competition - - |
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competition
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any use or defense of a resource by one individual that reduces the availabilty of that resource to other individuals
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resources
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- required by organism (growth, survival, reproduction)
- using it reduces amount available |
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limiting resource
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one resource that ultimately restricts growth
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exploitative competition
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consuming a resource before your competitor (no direct contact necessary)
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interference competition
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actively displace competitors for the resource (often by physical force)
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intraspecific
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between members of same species
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interspecific competition & outcomes (2)
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between different species.
Major Outcomes: (1) may cause one species to be eliminated (2) may limit (reduce) sizes of both species |
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Principle of Competitive Exclusion
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two species cannot coexist if they share the same limiting resource
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Lotka (1925) & Voltera (1926)
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modified logistic equation to incorporate interspecific competition
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a
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coefficient of competition
when a=1, inter = intra a>1, inter > intra a<1, inter < intra |
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Conclusions about competition
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1. 2 competing species cannot coexist if they share the same limiting resource
2. heavy overlap of resource use increases interspecific competition 3. coexistence is made possible by reducing the interspecific competition relative to intraspecific competition **this occurs by ecological segregation |
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ecological segregation & how it occurs (2)
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reduces value of "a" (effect of one species on another)
(1) Natural selection - causes organisms to evolve to reduce overlap (2) Competitive exclusion - too much overlap, no evolution required |
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How can coexistence happen?
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- coexistence of interspecific competitors may occur if an external factor holds the population below carrying capacity
Examples: Density independent regulation - harsh climate - short growing season - predation - parasitism - disease - disaster - keystone species |
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predation
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an individual kills and consumes an individual (not plants)
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parasitism
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consumption of a living host, w/o immediate death, but may cause death in the long run
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antipredator adaptations
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- camouflage
- distastefulness (chemicals, venom) - masting - mimicry (deceive by resembling another organism/ object) - defensive weaponry - speed/agility - building a defensive home - phenologically separated - good senses - confusion - aposematic coloration - intimidation (frilled neck lizard) |
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phenologically separated
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not active at the same time
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predator adaptations
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- speed/agility
- weaponry - stealth - sensory system (smell, eyesight, hearing) - gorging - group hunting - camouflage - aggressive mimicry (resembles a harmless species) - traps |
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masting
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- producing huge amounts of seeds
- through this large amount of potential offspring release, it will be too much for others to eat them all, so higher amount of offspring will survive Examples: -trees -cicada |
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endoparasite
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inside host
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ectoparasite
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outside host
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monophagus
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feed on 1 species
Example: cats have a specific species of flea that can live & reproduce, same for dogs, humans... |
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polyphagus
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feed on multiple species
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microparasites
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multiple within hosts, often within cells
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macroparasites
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larger bodied than mirco-, may be internal or external
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parasitoids
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develop within host but inevitably kill host
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Rp (growth rate of parasite) = ?
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Rp = N x L x B
where N= # available hosts L= period of infection B= transmission rate between host when Rp >1, disease spreads, when Rp <1, disease dies out |
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mutualism
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both species benefit from the interaction
- results from mutually beneficial coevolution - may originate from ancestral parasitic relationships |
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How does mutualism evolve from parasitic relationships?
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(1) Parasite reproductive success becomes (completely) dependent on host reproductive success
- reproductive interests of host & parasite become (completely) convergent (2) Host evolves to exploit byproducts of parasitism - natural selection on host will increase resistance to parasite & increase exploitation of incidental benefits of parasitism |
