ecology 1 to 4 Flashcards
what is a population?
a group of organisms of the same species occupying a particular space at a particular time
what is the difference between unitary and modular organisms?
- unitary: one thing
- modular: offspring grow from parent (like some plants and corals)
what is density?
a measure of population size
which sized animals tend to be more and less abundant?
small animals tend to be more abundant
what are ways to assess population density?
- quadrant
- capture-recapture method
- sampling
what is the quadrant method to determine population density? when is this used?
- take a sampling area of any shape (of a determined size)
- take many replicates, randomly positioned
- average for the total area
- used for plants, and marine invertebrates
what is the capture and recapture method to determine population density? when is this used?
marked 1st sample/total population =
# marked 2nd sample/total caught 2nd sample
- used for mobile animals
what is the sampling method to determine population density?
- take a large sample (of water for example) and look for relative changes
Quantitative methods to assess the change in population size due to what?
- Mortality (death)
- Natality (birth)
- Immigration and emigration (important, but harder to study) often assume imm.= em.
what is a life table?
a table that records survivorship (or mortality) in a population
what is a cohort table?
follows all the individuals born at the same time from birth to death
what is lx?
the proportion surviving since the beginning (=nx/no)
what is dx?
the number dying each step (=nx-nx-1)
what is qx?
the proportion dying in each step (=dx/nx)
what is a survivorship curve and what is it used for?
- A plot of number of survivors (Y-axis) vs. age (X-axis). (usually a log scale)
- used to understand how mortality changes with
age in a population.
why is a log scale used in a survivorship curve?
because it shows a multiplicative process (per capita effects) more clearly
what are the three patterns/categories of survivorship?
- Type I: High juvenile survivorship (low juvenile mortality)
- Type II: Constant rates of survival
- Type III: Low juvenile survivorship (high juvenile mortality)
what are the assumptions made with static survivorship life tables?
- Proportion of skulls (or any other remnants) in each age class represented typical proportion of individuals dying at that age.
- Population size was constant, and birth and death rates in each age group remain constant.
what is bx?
number of female offspring per female aged x per 5-year period
what can intrinsic rate of natural increase be used for?
can be used to compare growth rates of populations of a species that have different generation times
r increases as…
- As the age at first reproduction decreases
- As the # of progeny per reproductive event increases
- As the # of reproductive events increases
when do populations grow exponentially?
- at initial stages of colonization,
- when conditions are favorable or,
- sometimes, when recovering from negative environmental perturbation.
what are the two types of growth?
geometric (exponential growth) and logistic (limitations)
what is logistic growth? what is the observed pattern?
- As population size increases, growth eventually slows and ceases.
- The observed pattern is sigmoidal or S-shaped.
what is K?
the carrying capacity; the number of individuals of a particular population that the environment can support.
when does competition occur?
when organisms use or seek out a common resource that is in limited supply.
what is intraspecific competition?
competition between members of the same species
what is interspecific competition?
competition between members of different species
what is a fundamental niche?
The ecological space (conditions, niche resources, time) occupied by a species in the absence of competition and predation by other species.
lab results how competitive exclusion, but field results show many species living together? why?
- No competitive exclusion – because the species occupied separate niches? (Competition rare in nature)
- Among closely related species – did competition occur in the past? Selection pressure caused adaptation to specialize which minimized competition? (Competition has been very common)
what is a realized niche?
the actual environment where a species live in
what is the time-lag effect?
allow populations to ʺovershoot“ (Leads to negative growth, and to oscillations)
what is predation?
when members of one species eat members of another species
what is the effect of species 1 on species 2 when it comes to predation and competition?
- predation: increasing species 1 has negative effect on 2; increasing species 2 has negative effect on 1 (-/- effect)
- competition: increasing species 1 has positive effect on 2; increasing species 2 has negative effect on 1 (+/- effect)
what is the effect of predation?
- Affects distribution and reduces abundance of prey
- Alters community organization
- Acts as a selective force, leading to adaptations among prey (and adaptations to those adaptations in the predator)
what are the different dynamics of predator-prey populations?
1) Stable oscillation between predator and prey
2) Stable equilibrium with no oscillations
3) Convergent oscillation
4) Divergent oscillation (Leads to extinction of either predator or prey)
what are reasons why the predator-prey model might be wrong?
- Multiple prey species and multiple predator species (Generalist predators vs. specialists)
- Refugia
- Environmental heterogeneity for both predator and prey
- Evolutionary change in both
is predation random?
there are examples of both:
- random predation
- non-random predation of poor condition individuals
how do predators respond to prey numbers?
- functional response
- numerical response
- aggregative response
- developmental response
what is the functional response?
predators consume more prey per capita when more prey are abundant (eventually plateau based on how fast they can eat/digest the prey)
what is the numerical response?
predators become more abundant when prey are abundant (assume food is their limiting factor)
what is the aggregative response?
predator distribution shifts in response to prey distributions
what is the developmental response?
predator consume more of less depending on life stage
how do preys persist?
often involve refugia or predator switching prey
what are different types of refugia?
- spatial
- temporal: don’ be where predator are when they are there (can be due to seasonal changes)
- population size: safety in numbers
- masting (predator satiation): for plants, make so many seeds that even if predators eat a lot, there will still many left
- body size: large animals
- coevolution: evolution of defenses (like have bright coloration that tell predators that they are toxic, or mimic color of other species that have toxin even if that species doesn’t have any)
what is a community?
- Group of species linked together by their feeding relationships
- Effect flow of energy, cycling of elements, evolution of species within the community
what are some applications of community ecology?
- manage and conserve a species in isolation
- area-based protection
- understanding umbrella species that can help other species at well
what is succession?
the process of change in ecological communities over time
what are the two types of succession?
primary and secondary
what is primary succession?
Occurs on a new sterile area, such as that uncovered by a retreating glacier or created by an erupting volcano
what did lupinus plant due after the mt. st. helens eruption?
- was an early colonizer that created shelter for other plants
- fixes nitrogen, creates better soil
what does succession lead to?
a more final stable state
what factors affect the rate of primary succession?
- the availability of colonizers
- The abiotic and biotic environment (e.g: nutrient availability, soil formation, presence of herbivores)
- Processes among the successional species (Early species can help, hinder, or not affect the establishment of later species. - Facilitation and Inhibition)
what is secondary succession?
the recovery of disturbed sites, where a biological legacy (propagules, living organisms) exists
what is a climax community?
the end-state of succession, which may or may not cycle
how does a community differ from a population?
- population: look at single species dynamics and 2 species interactions
- community: who is present? who is dominant? how does energy flow? who does what?
