Part 4 Flashcards
what is a fundamental unit of evolution?
populations (not individuals) that evolve, it is also a fundamental unit of ecology
population
all the individuals of a given species that live and reproduce in a particular place; one of several interbreeding groups of organisms of the same species living in the same geographical area
natural selection enables populations to adapt to:
the abiotic and biotic components of their environment
what determines whether a population will grow or shrink under a given set of physical and biological conditions?
the traits evolved under natural selection
what are three key features of a population?
size, range, and density
population size
the number of individuals of all ages alive at a particular time in a particular place
range
the extent of the geographic area over which populations of a species are distributed
the range of any species reflects the range of ….
climates a population a tolerate and determines how many other species the population encounters
population density
the size of a population divided by its range
when is population distribution clumped?
if resources are clustered or if close proximity to other individuals enhances fitness
when is population distribution uniform?
when resources are limited or if it’s better to be spread out, ex. in case of predators
how do ecologists estimate population size?
by taking repeated samples of a population and estimating the total number of individuals from the sample to determine population density
mark-and-recapture
a method in which individuals are captured, marked in a way that doesn’t affect their function or behaviour, and then released. The percentage of marked individuals in a later exercise of capture enables ecologists to estimate population size
what is an assumption that needs to be made for the mark-and-recapture method?
that the population has not changed in size between the first and second samples
community
the set of all populations found in a given place
biodiversity
biological diversity; the aggregate number of species, or, more broadly, also the diversity of genetic sequences, cell types, metabolism, life history, phylogenetic groups, communities, and ecosystems
how is biodiversity usually measured
by counting the number of species present in a particular area
keystone species
pivotal populations that affect other members of the community in ways that are disproportionate to their abundance or biomass
how might keystone species be identified?
species that influences the transfer of a large proportion of biomass and energy from one trophic level to another or when the species can modify its physical environment
disturbance
a severe physical impact on a habitat that has density-independent effects on populations of interacting species
species diversity tends to be highest when…
disturbance is frequent or intense enough to inhibit competition, but not so strong as to limit the number of species that can tolerate the environment
succession
the replacement of species by other species over time
climax community
a mature assembly, a final stage in succession, in which there is little further change in species composition
ecosystem
a community of organisms and the physical environment it occupies
what do food webs trace?
the cycling of carbon through communities and ecosystems
community
the set of all populations found in a given place
primary producer
an organism that takes up inorganic carbon nitrogen, phosphorus, and other compounds from the environment and converts them into organic compounds that will provide food for other organisms in the local environment
what is the first biological reservoir of carbon once it has been taken out of the physical environment
primary producers
consumer
an organism that obtains the carbon it needs for growth and reproduction from the foods it eats and gains energy by respiring food molecules; heterotrophic organisms of all kinds that directly consume primary producers or consume those that do
primary consumers
herbivores, which consume primary (plant or algae) producers. sometimes called grazers
secondary consumers
predators or scavengers that feed on primary consumers
carnivores
a monophyletic group of animals, including cats, dogs, seals and their relatives, that consumer other animals
decomposer
an organism that breaks down dead tissues, feeding on the dead cells or bodies of other organisms
what happens to the carbon as it is passed from one carbon to another?
it eventually returns to the atmosphere by the respiration of decomposers
food web
a map of interactions that connect consumer and producer organisms within the carbon cycle; the movement of carbon through an ecosystem
biodiversity
AKA biological diversity; the aggregate number of species, or, more broadly, also the diversity of genetic sequences, cell types, metabolism, life history, phylogenetic groups, communities, and ecosystems
food chain
the linear transfer of carbon from one organism to another
trophic level
an organism’s typical place in a food web as a producer or consumer
when sunlight is absent (ex. depths of ocean), how does primary production occur?
through the chemical reactions of bacteria and archaeons
how is energy in an ecosystem different than carbon?
it does not cycle, new energy must be continually harvested by primary producers
what generally decreases from one trophic level to the next?
biomass and energy
energy transfer is….
unidirectional
trophic pyramid
a diagram that traces the flow of energy through communities, showing the amount of energy available at each level to feed the next. The pyramid shape results because biomass and the energy it represents generally decrease from one trophic level to the next
why is only 10% of energy passed to the next trophic level?
because energy is used in defecation, work, and lost as heat dissipation
what is the shape of the biomass diagram for marine ecosystem?
it is inverted (smaller on the bottom), because plankton are tiny and reproduce very fast
Liebig’s Law of the Minimum
the principle that primary production is limited by the nutrient that is least available relative to its use by primary producers
the biodiversity of a given region reflects:
its level of primary productivity
