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31 Cards in this Set
- Front
- Back
Define biological evolution: (2)
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- genetic change in populations of organisms across generations
- may be random or directed by natural selection |
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Define natural selection:
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- the process by which traits that enhance survival and reproduction are passed on more frequently to future generations than those that do not
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When did Darwin and Wallace propose natural selection as the mechanism of evolution?
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- 1858
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What are the four principles of natural selection?
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- organisms face a constant struggle to survive and reproduce
- organisms tend to produce more offspring than can survive - individuals of a species vary due to genes and the environment - some individuals are better suited to their environment and will pass on their genes |
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What is an adaptive trait?
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- a trait that promotes reproductive success
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What is a mutation?
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- accidental changes in DNA that may be passed on to the next generation
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What is:
a) directional selection b) stabilizing selection c) disruptive selection |
a) drives a feature in one direction
b) produces intermediate traits, preserving the status quo c) traits diverge in two or more directions |
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Define biological diversity:
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- an areas sum total of all organisms
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Define species:
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- a population or group of populations whose members share characteristics and can freely breed with one another and produce fertile offspring
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Define population:
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- a group of individuals of a species that live in the same area
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How many mass extinction events have occurred? (2)
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- five
- humans are causing the sixth |
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What are the different levels of ecology? (5)
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-biosphere
- ecosystems - communities - populations - organisms |
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Define the biosphere:
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- the total living things on earth and the areas they inhabit
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define an ecosystem:
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- communities and the nonliving material and forces they interact with
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Define population ecology:
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- investigates the quantitative dynamics of how individuals within a species interact
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Define community ecology:
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- focuses on interactions among species
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What is population distribution (dispersion) and what are the different kinds found in nature? (4)
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- spatial arrangement of organisms within an area.
- random - uniform - clumped (most common) |
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What is the growth rate formula?
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= (crude birth rate + immigration rate) - (crude mortality rate + emigration rate)
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What are limiting factors of population growth? (2)
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- physical, chemical, and biological characteristics that restrain population growth
- water, space, food, predators and disease |
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What is environmental resistance?
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- all limiting factors taken together
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What are the important features of carrying capacity?
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- max population size of a species in an environment
- s- shaped logistic growth curve |
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What are examples of density-dependent factors?
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- predation risk and competition for mates increases with density
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Examples of density independant limiting factors:
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- floods, fires, landslides
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What aspects are included in the study of ecosystems? (2)
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- all abiotic and biotic components
- energy flows, matter cycles |
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Define net primary production: (2)
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- energy remaining after respiration, and is used to generate biomass
- available for heterotrophs |
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What is a nutrient source?
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- reservoirs of nutrients that release more nutrients than they accept
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What is a nutrient sink?
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- reservoirs of nutrients that accept more nutrients than they release
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Define nitrification (2)
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-bacteria that convert ammonium ions first into nitrite ions then into nitrate ions
- plants can take up these ions |
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What are denitrifying bacteria?
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- bacteria that convert nitartes in soil or water to gaseous nitrogen, releasing it back into the atmosphere
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What is the haber-bosch process? (2)
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- synthetic production of fertilizers by combining nitrogen and hydrogen to synthesize ammonia
- humans fix as much nitrogen as nature does |
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What is eutrophication?
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- the process of nutrient over enrichment, blooms of algae, increased production of organic matter and ecosystems degradation
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