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145 Cards in this Set

  • Front
  • Back
Population
group of organisms of the same species living in the same place
Poulation Genetics
sudy of properties of genes in populations
Allelic Frequencey
Sum of allele( 36 B)/ 100
p=
individuals homozygous for first allele
2pq
individuals heterozygous for alleles
q=
individuals homozygous for the second allele
Hardy-Weinberg Principle
Original proportions of genotypes in a population will remain constant from generation to generation
-sexual reproduction (meiosis and fertilization) alone will not change allelic (genotypic) proportions
Hardy Weinberg Principle based on 5 assumptions:
* the population size is large
* random mating is occuring
*No mutations take place
*No genes are input from other sources (no immigration)
* No selection occurs
Polymorphism
a locus with more variation than can be explained by mutation
Five Agents of Population Change
1. Mutation
2. Gene Flow
3. Nonrandom Mating
4. Genetic Drift
5. Selection
Mutation
rates re generally so low that they have little effect on Hardy-Weinberg proportions of common alleles
* ultimate source of genetic variation
Gene Flow
movement of alleles from one population to another
- tend to homogenize allele frequencies
Nonrandom Mating
assortative mating: phenotypically similar individuals mate
Genetic Drift
frequencies of particular alleles may change by chance alone
founder effect
few individuals found new populations (small allelic pool)
bottleneck effect
drastic reduction in populationand gene pool size
Artificial Selection
breeders exert selection
Natural Selection
nature exerts selection
- variation must exist among individuals
- variation must result in differences in number of viable offspring produced
variation must be genetically inherited
Selection Pressures
avoiding predators
matching climatic condition
pesticide resistance
Fitness
the number of surviving offspring left in the next generation
- relation measure
-selection favors phenotypes with the greatest fitness
Natural Selection:
Frequency
dependen selection
- phenotype fitness depends on its frequency within the population
Negative Frequency
dependent selection favors rare phenotypes
Positive Frequency
dependent selection eliminateds variation
Oscillating Selection
selection favors different phenotypes at different times
Disruptive Selection
selection eliminates intermediate types
Directional Selection
Selection eliminates one extreme froma phenotypic array
Stabilizing Selection
Selection acts to eliminate both extremes from an array of phenotypes
Pleiotropy
Genes have multiple effects
Evolution requires genetic variation
Intense selection may remove variation from a population at a rate greater than mutation can replenish
Gene Interactions
affect allelic fitness
Epistatic interations
an allele for one gene may have different effects, depending on the allele present at other genes
Key elements of an organism's enviroment
temperature
water
sunlight
soil
Enviromental elements determine Population Habitats
Many organisms actively employ mechanisms to maintain homeostasis, while others conform to their enviroment
Individual Response to Enviromental Change
phisology
morphology
behavior
Population size
# of individuals making up its gene pool
Population Density
the number of individuals per unit of area or volume
Range
Size and type of area; boundaries determined by habitat
Population dispersion or distribution
the general pattern n which the population memebers are dispersed through its habitat
Randomly spaced Dispersion
Individuals are randomly spaced within a population
Uniformly Spaced Dispersion
Uniform spacing within a population often results from resource competition
Clumped Spacing Dispersion
Individuals clump into groups or clusters in response to uneven distribution of resources in their imediate enviroment (social interactions play key role)
Human Effect on Dispersion
by altering the enviroment humans have allowed some species to expand their ranges, although the overall effect has most often been detrimental
Dispersal mechanisms
light seeds(wind)
hooks and hair (animal fur)
fruits (animal digestive systems)
Metapopulations
a network of distinct populations interacting with each other by exchanging individuals
- degree of interaction depends on dispersal
- rate of extinction in habitats is balanced by the rate of colonization of empty habitats
- prevent long term extinction
Source-sink
metapopulations occur in areas where some habitats are suitable for long term maintenance, while others are not
Demography
measurement and statistical study of population
Factors of population growth
sex ratio
generation time
fecundity
moratlity
age structure
sex ratio
# of births usually directly related to the # of females
generation time
short generation time>> usually short life span >> more unstable
Fecundity
number of offspring produced per time unit; birth rate
cohort
group of individuals of the same age
mortality
death rate
age structure
relative number of individuals in each cohort
Survivorship
percentage of an original population that survives to a given age
Type I survivorship
full life span
Type II survivorship
mortality unrelated to age
Type III survivorship
early susceptibility and low mortality in adults
Negative Density-dependent factors of population regulation
more competition for resources
higher mortality, decreased birth rates
infectious diseases
accumulation of toxic wastes
behavioral problems
Positive Density-dependent factors of population regulation
easier mating
hormonal stimulation influences behavior
Density-independant factors of population regulation
natural disaster
weather
Community
refers to the species that occur together at any particular locality
- interaction among comunity members govern many ecological processes
Individualistic Concept
Cleason
-Community is simply an aggregation of species
-predics different communities through space or time
Holistic Concept
Clements
-Community is an integrated unit viewed as a superorganism
- Each constituent species coevolves and functions together
- predicts same communities through space or time
- changes when enviromental differences are sufficiently great
Ecotone
enviroment changes abrubtly here
niche
the total of all ways it utilizes the resources of its enviroment
fundamental niche
entire niche potentially available to an organism
realized niche
actual nice utilized by an organism
Habitat
the place where an organism lives
Neutral Interaction
no observed relationship
Competition Interaction
utilizing same resources
intraspecific or interspecific
Interference Interspecific
individuals fighting over the same resource
Exploitative Interspecific
individuals utilizing shared resources
competative exclusion
no two species utilizing the same niche can coexist indefinitely, one will eventually eliminate the other
Resource Partitioning
when species living in the same area partition available resources to avoid direct competition
Sympatric Species
similar species that live in the same geographical area
Character Displacement
when two animals of similar phenotype change phenotypes to live together, they end up changing their niche
Prey Adaptions
Chemical (poisons and stings)
Morphological (thorns, spines)
Defensive Coloration ( warning or blending)
Mimicry
Symbiosis Relationships
two or more kinds of organisms live together in permanent relationship
Commensalism
benefits one species and neither hurts nor helps the other
Mutualism
both species benefit
Parasitism
beneficial to one organism, harmful to the other
Keystone Species
species that have a particularly strong effect on community composition
Ecosystem
all the organisms living in a particular place, and the abiotic enviroment in which they interact
Two Main Ecosystem Processes
energy entering ecosystem
(usually from the sun)
biogeochemical cycles
Same Ecosystem Pathways
Photosynthesis> feeding > decompostion
Different Ecosystem Fates
Energy cannot be recycled and is eventually converted to heat

matters continuously recirculate
Water Evaporation from Ocean
into the atmosphere
Water Evaporation fom land
90% of water reaching the atmosphere transpires from plants
Amount of Water Captured in any form
2%, the rest is free water circulating between the atmosphere and the oceans
Ground Water in Aquifiers
amounts to more than 96% of all fresh water in the US
Water Table
upper unconfined portion of water
* is partially accessible to plants, while lower layers are generally out of reach
-recharged via percolation from rainfall
Ground Water provides
25% of all water used in the US
50% of the US population with drinking water
Underground Aquifers
have much higher withdraw rates than recharge rates
- water mining
- increasing chemical pollution
Breaking the Water Cycle
In dense forest ecosystems, more than 90% of moisture is taken up by plants and transpired back into the atmosphere
-Deforestation breaks this cycle
The Carbon Cycle
based on carbon dioxide which makes up only about .03% of the atmosphere
- all terestrial heterotrophic organisms obtain carbon indirectly from photosynthetic organisms
-most organic cmpds formed as a result of CO2 fixcation are ultimately broken down and released back into the atmosphere
Carbon Dioxide
-700 billion metric tons of CO2 in the atmosphere
-1 trillion metric tons dissolved in the oceans
- 5 trillion in fossil fuels (fuel consumptions liberating Carbon at increasing rate, green house effect)
- 600 million to 1 trillion metric tons locked up in living organisms
Nitrogen Cycle
Relatively few types of organisms can fix nitrogen into forms that can be used for biological processes
Nitrogen Fixation
N2 + 3H2 >> 2NH3

only symbiotic bacteria fix enough nitrogen enough to be of major significance in nitrogen production
Ammonification
releasing of ammonium ions
Denitrificaiton
Conversion of nitrate to N2 and N2O
The Phosphorous Cycle
Phosphates weather from soils into water, enter plants and animals and are redeposited in the soil when plants and animals decompose
-relatively insoluble
Guano
Rich isn Phosphorous
Seas
the only inexhaustible source of phosphorous
Increase in crop production due to
millions of tons of phosphorous added to agricultural land annually
Autotrophs
capture light energy and manufacture own chemical energy
-primary producers
Heterotrophs
must obtain organic molecules that have been synthesized by autotrophs
Primary Consumers
herbivores
Secondary Consumers
organisms that feed on herbivores
Decomposers
break down complex organic material into simpler compounds
Detritivores
live on refuse of an ecosystem
Tropic Level
refers to the feeding level of an organism.
organisms from each level constitute a food chain
food web
interconnected food chains
__ % of organic matter transfers from one _____ _____ to the next
10% transfers from one trophic level to the next
Primary productivity
refers to the amount of organic matter produced from solar energy in a given area during a given period of tiem by photosynthetic organisms
Gross Primary Productivity
the total organic matter produced
Net Primary Productivity
the amount of organic matter produced that is available to heterotrophs
Secondary productivity
biomass generated by heterotrophs
____ ____ as _____ during transfers
energy loss as heat
Second Law of Thermodynamics
food chains are generally limited to three or four trophic levels
A Community's Productivity determined by
the amont of sunlight it recieves
northern climates
net productivity often increases as the growing season lengthens
Tropic Level Cascade
refers to the idea that the effect of one trophic level flows down or up to other levels
Top-down effect
a higher tropic level flows down
Bottom-up Effect
When productivity of an ecosystem is low, herbivor populations will be too small to support an predators
Bottom-Up
Increase in productivity
will increase herbivore population
Bottom-Up
Further Increase in productivity
will not increase herbivore propulation but will increase predator population
Factors Promoting Species Richness
ecosystem productivity
spatial heterogeneity
climate
Ecosystem Productivity
ecosystems with intermediate levels of productivity tend to have the most species
Spatial Heterogeneity
Heterogeneous ecosystems provide a greater variety of microhabitats and microclimates
Climates
difficult to asses. in western N. America, species richness is inversely correlated with mean temperature range
Biodiversity Crisis
Since 1600, 2.1% of known mammal species and 1.3% of known birds have become extinct
-most extinctions occur on islands
Endemic
a species found naturally in only one geographic area
Isolated Geographical areas
such as oceanic islands, often have many endemic species
Notable Hotspots for Endemism
Madagascar, eastern Himalayas, and Australia
Factors responsible for extinction
habitat loss
overexploitation
introduced species
Factors of Habitat Loss
Destruction
Pollution
disruption
habitat fragmentation
Destruction
clear-cut tree harvesting
1% or more per year in tropical forests
Pollution
habitat degradation
acid rain and pesticides
Disruption
park visitors
Habitat Fragmentation
fragmenting of populations into unconnected patches
Edge Effects
significantlly alter mircroclimates near the edge and may reduce appropriate habitat for many species
Overexploitation
Case Study: Whales
commercial whaling began in the 16th century and reached its apex in early 20th century
Colonization and extinction as natural processes
-colonization may bring together species with no previous hsitory of interaction
-successful establishment of a new population is rare
-increase biodiversity or lead to extinction of natives
Human Effect on Extinction
Out compete native species
impact on human health
ecosystem transformation
Preservation approaches
habitat restoration
pristine restoration
removal of introduced species
cleanup and rehabilitation
captive breeding