Flashcards in Ecology Deck (51):
what is ecology?
the study of the interactions of organisms with their environment
what kinds of ecosystems are there?
biotic and abiotic
at what levels can ecology be studied?
individual, population, communities, ecosystems
populations: groups of individual organisms that interbreed with each other
communities: populations of different species that interact with each other within a local
ecosystems: all living organisms as well as nonliving elements that interact in a particular area
what is predation?
when one organism feeds on another (community ecology)
this exerts a strong selective pressure on prey
what do animals do to avoid predation?
2) warning coloration (mimicry)
3) mechanical defense
4) chemical defense
5) behavioral defense
what is coevolution?
interactions between species are strong (community ecology)
selection and evolution across species boundaries
selection driven by interaction between species --> species are engaged in a "reciprocal adaptive response"
what is an example of coevolution?
what is symbiosis and what are some examples of it?
close interactions between species
what's an example of parasitism?
puts its eggs into other eggs nests so other birds will have to take care of their kids
what's an example of commensalism?
the birds eat the bugs off the cattle --> they get food and the cattle gets cleaned
what is the selective regime?
the selective regime is not set by the physical components of the environment but by the biological interactions occurring within the ecosystem
coevolution and fitness?
each participant in the coevolutionary relationship undergoes natural selection, with the highest fitness and associated with genotypes that address the partnership
other selective forces such as food availability, sexual reproduction, etc. still apply but are of lower importance and so don't determine the direction and mode of selection the way the partnership does
how does coevolution happen?
2) escalating "arms race" (predator/prey interaction)
3) cospeciation (host/parasite interactions)
what is an arms race?
what is cospecitation?
what are mutualistic relationships?
both partners derive some benefit from the interaction
typically fairly specific --> otherwise force of selective pressure may not be sufficient
how can you test differences in fitness in a mutualistic relationship?
fitness levels are higher when the organisms are together vs. when they're not
the predator-prey arms race
prey are under strong selection to avoid predator
predators are under strong selection to find sufficient food
if a predator specializes upon a single kind of prey or a prey item has only one significant predator, this interaction may be the strongest selective force facing the organism --> having multiple prey/predators diffuses the effect any one interaction has on overall fitness
how do you show that two organisms are actually in coevolution with each other?
all things that are eaten have a general defense against predators
to be co-evolution the predator-prey relationship must be the primary selective force and there must be **reciprocity** in the response
what is the Red Queen hypothesis of the evolutionary arms race?
it takes all the running you can do to keep in the same place, if you want to get somewhere else you must run at least twice as fast as that
organisms must constantly adapt, evolve, and proliferate not just to gain reproductive advantage, but also simply to survive while pitted against ever-evolving opposing organisms in an ever-changing environment, and intends to explain two different phenomena: the constant extinction rates as observed in the paleontological record caused by co-evolution between competing species, and the advantage of sexual reproduction (as opposed to asexual reproduction) at the level of individuals
does daphnia cyclomorphosis experience coevolution?
an abundance of predators induces metamophosis to pointier, more robust and less digestible morphology
however, this response can be induced by any one of 3/4 predators or by turbidity so there is no evidence that predators are reciprocally selected --> they may have other food sources
what are some expectations about arms races?
we expect predators to increase as prey increases initially
but then a boom in predators will decrease the number of prey
as prey becomes scarcer, predators die of starvation
as predators become scarcer prey populations rebound
**they will cycle through this until stable = equilibrium densities are reached
anti-herbivore defenses of plants
plants in the carrot family contain many noxious compounds that have been shown to deter herbivorous insects
Depressaria and parsnip
depressaria spends most of its life on a single plant and preferentially eats reproductive tissues (flowers and seeds)
in a controlled environment, more seeds are made and set compared to the wild but making furanocoumarins costs the plant in terms of energy and resource allocation
depressaria detoxifies the plants metabolically and the ability to detoxify furanocoumarins has a genetic basis --> the metabolic processes are expensive in terms of energy
there is a variation among depressor in terms of the ability to detoxify and a variation among parsnips in terms of the amount of furanocoumarins -->the most toxic genotypes co-occur with the most metabolically capable depressaria
cospeciation in pocket gophers and lice
pocket gophers live in burrow and play a critical role in soil ecology through tunneling
ectoparasitic chewing lice specific to gophers live on their body and eat debris and dead skin
in general, the more closely related the host, the more closely related the parasite
cospeciation: host a parasite lineages diverge in tantum = classic coevolution
how do communities change over time?
what is succession?
a gradual change in species composition over time
what is primary succession?
no soil exists
like after a volcano
what is secondary succession?
occurs when a community has been damaged but soil remains
what is a colonizing community?
the first arrivals to a lifeless and soil-less area (part of primary succession)
they are good dispersers but poor competitors so they gradually are replaced
ex. fungi, bacteria, lichens, and seeds
what are intermediate communities?
a variety of species is present, including both colonizers and competitors (secondary succession)
mosses begin to grow and trap moisture allowing the seeds of other plants to germinate
small herbs arrive and shrubs grow
small trees grown and outcompete the shrubs
what is a climax community?
longer living, larger species outcompete the initial colonizers and persist as a stable and self-sustaining community
disturbance and succession
disturbance is a fundamental part of most ecosystems and can repeatedly set a community back to an earlier stage of succession at which point secondary succession begins again
what are nutrient cycles?
nutrient cycles recycle the atoms that make up every object in an ecosystem
chemicals are cycled through the ecosystem
all ecosystems relay on a constant source of energy
ultimate source of energy is sunlight
energy flows in ONE direction only
what is a trophic level?
position in the food chain, relative to the energy source
what are the four trophic levels?
primary producers --> primary consumers --> secondary consumers --> tertiary consumers
what are primary producers?
plants convert light energy from the sun into food through photosynthesis
what are primary consumers?
herbivores are animals that eat plants
what are secondary consumers
carnivores are animals that eat herbivores
what are tertiary consumers?
top carnivores are animals that each other carnivores
ex. mountain lion
energy and the trophic levels
every trophic level wastes energy (10% rule)
eventually all stored energy is lost as heat
what is the 10% rule?
only about 10% of the biomass from each trophic level is converted into biomass in the next trophic level --> 90% is used in cell repression and lost as heat
this explains why there are so many more plants than animals and why top carnivores are relatively rare
what regulated population size?
births and deaths
how do you know if a population is growing or not?
growing population: the graph looks like a pyramid because the youngest age group is the largest
stable population: the graph looks like a square because every age group is about the same
declining population: looks like a diamond because the middle age group is the largest while the young and old age groups are small
what are ideal conditions for population growth?
exponential growth occurs under ideal conditions
growth rate = births - deaths
population grows at a rate proportional to its size
what is happening during exponential growth of a population?
when each individual produces more than the single offspring necessary to replace itself
what is Malthus' struggle for existence?
at the point where population size outstrips resource production, there are only two alternatives: find the means to expand the resource pool or die
AKA there is a carrying capacity
what are the limits of population growth?
exponential growth is met by environmental resistance such as limited resources, accumulation of wastes increased competition or predation
what is the carrying capacity?
maximum # of individuals the habitat can support indefinitely
growth slows then stops when approaching carrying capacity