Exam 2 Flashcards
- describes how environmental conditions change over time
- some is predictable, such as the changing conditions that occur during the day versus during the night or the changes in seasonal conditions that are typical for a given climate
temporal environmental variation
occurs from place to place due to large-scale variation in climate, topography, and soil type
spatial environmental variation
- the position of each individual is independent of the position of other individuals in the population
- not common in nature
random dispersion
why are random dispersions not common in nature
abiotic conditions, resources, and interactions with other species are not randomly distributed
- a type of dispersion in which each individual maintains a uniform distance between itself and its neighbors
- arises from direct interactions between neighbors
evenly spaced dispersion
- individuals are aggregate in discrete groups
- a result of social groups, clustered resources, or offspring that remain close to their parents
clustered dispersion
describes the spacing of individuals with respect to one another within the geographic range of a population; can be clustered, evenly spaced, or random
dispersion
true or false:
A population can exhibit one pattern of dispersion at a large scale but a different pattern of dispersion at a smaller scale
true
the total number of individuals that exist within a defined area
abundance
why is the total abundance of a population important
it provides a measure of whether a population is thriving or on the brink of extinction
- the number of individuals in a unit of area or volume
- a valuable measure because it tells ecologists how many individuals are packed into a particular area
density
what happens if a habitat can support a higher density than currently exists
the population can continue to grow in the area
what happens if the population density is greater than what the habitat can support
either some individuals will have to leave the area or the population will experience lower growth and survival
where is the highest concentration of individuals located across a large geographic area
the center of a population’s geographic range
what happens as one moves closer to the periphery of the geographic range
biotic and abiotic conditions become less ideal and support fewer individuals
- a measure of the total area covered by a population
- includes all the areas its members occupy during their life
- an important measure because it tells us the size of the area a population occupies
geographic range
why don’t individuals of a species or population often don’t occupy every location within their geographic range
climate, topography, soils, vegetation structure, and other factors influence the abundance of individuals
which type of temperatures are more hospitable to a greater variety of species
warmer
the more suitable the habitat,
the larger a population can grow within that habitat
The process of determining the suitable habitat conditions for a species
ecological niche modeling
The range of ecological conditions that are predicted to be suitable for a species
the ecological envelope of the species
The habitat in which an organism lives is determined by the organism’s
niche
includes the range of abiotic and biotic conditions it can tolerate
niche
- elaborate male secondary sexual characteristics act as handicaps
- argues that the greater the handicap and individual carries in terms of a more extreme trait, the greater its ability to offset that handicap with the other superior qualities
handicap principle
- a situation in which selection for preference of a sexual trait and and selection for that trait continue to reinforce eah other
- continues until males run out of genetic variation for the trait or until the fitness costs of possessing extreme traits begin to outweigh the reproductive benefits
runaway sexual selection
- individuals choose the healthiest mates
- could be the outcome of either superior genetics or a superior upbringing with abundant resources
good health hypothesis
- an individual chooses a mate that possesses a superior genotype
good genes hypothesis
hypotheses that would cause a female to choose a male based on his traits
good genes hypothesis
physical items that a male can provide a female, including a site for raising offspring, a high-quality territory, or abundant food
material benefits
types of female preferences for male traits
material and nonmaterial benefits
- a difference in the phenotype between males and females of the same species
- includes differences in body size, ornaments, color, and courtship behavior
sexual dimorphism
Traits related to fertilization–such as gonads
primary sexual characteristics
traits related to differences in body size, ornaments, color, and courtship
secondary sexual characteristics
how does sexual dimorphism evolve
- differences in life history between the sexes, contests between males, or mate choice by females
- humans (hunting)
a behavior in which one partner prevents the other partner form participating in extra-pair copulations or makes breeding physically impossible
mate guarding
mating systems are shaped by
- natural selection
- ecological conditions under which each species lives
when is monogamy favored
when males can make important contributions to raising the offspring
While a given female hsa a social bond by spending most of her time with only one male, she is actually breeding with other males
extra pair copulation
a mating system in which a social bond between one male and one female persists through the period that is required for them to rear their offspring
monogamy
a mating system in which a single individual of one sex forms long-term social bonds and mates with more than one individual of the opposite sex
polygamy
a male mates with more than one female
polygyny
a mating system in which a single female breeds with multliple males
polyandry
when does polygyny evolve
- when males compete for females and the females all prefer only the best few best males
- when a male is able to defend a group of females from other males or when a male can control access to a resource that is attractive to multiple females
when does polyandry evolve
when the female is in search of genetically superior sperm or has received material benefits from each male with whom she mates
- a mating system in which individuals mate with multiple partners and do not create a lasting social bond
- most common mating system
promiscuity
which takes more energy to produce sperm or egg
egg
what does a females reproductive success depend on
- number of eggs she can produce
- quality of mates she finds
occurs when competition for mates takes place in a limited area and only a few males are required to fertilize multiple females
local mate competititon
what does a male’s reproductive success depend on
how many females he can fertilize
- describe the number of mates each individual has and the permanence of the relationship among mates
- subject to natural selection
- promiscuity, polyandry, polygyny, and monogamy
mating systems of species
when mating options are restricted such that the only mates available for daughters are their brothers, mothers that produce a higher proportion of daughters than sons will have
more grand offspring and therefore greater evolutionary fitness
why do individuals of the less abundant sex enjoy greater reproductive success
because they compete with fewer individuals of the same sex for breeding
whenever the population has an abundance of one sex, natural selection will favor any parents that produce offspring of the less abundant sex
the best sex ratio strategy depends on
the frequencies of males and females in a population
occurs when natural selection favors the rarer phenotype in a population
frequency-dependent selection
a process of sex selection in which sex is determined largely by the environment
environmental sex selection
Because the genotype has the ability to produce multiple phenotypes, temperature-dependent sex determination is a type of
phenotypic plasticity
environmental sex determination that depends on temperature
temperature-dependent sex determination
mechanisms of sex determination
- gametic
- environmental
benefits of asexual reproduction
- 100% of genes passed
- no investment on sexual organs or behaviors
costs of asexual reproduction
- accumulation of mutations over generations
- no new allele combinations
- higher chances of extinction
benefits of sexual reproduction
- mutations can be purged
- new allele combinations (meiosis and fertilization)
- lower chances of extinction
costs of sexual reproduction
- 50% of genes passed
- sexual organs and behaviors are costly (resources, time, exposure to predator and parasites)
when a mate can be found, the individual prefers to breed by outcrossing to avoid the costs of inbreeding
mixed mating strategies
- occurs when an individual uses its male gametes to fertilize its own female gametes
- poses a fitness cost due to inbreeding depression
self-fertilization
should selection favor individuals that use selfing when they have an opportunity to breed w/ other individuals
NO
when hermaphroditic species do not use selfing when they have an opportunity to breed with other individuals
outcrossing
how do some hermaphroditic species avoid the problems of selfing
by being sequential hermaphrodites
If a male individual can invest in female function and gain a great deal of female fitness while only giving up a small amount of male fitness, then selection will favor
the evolution of hermaphrodites
true or false
the total fitness achieved from being a hermaphrodite (i.e. fitness through male function plus female function) exceeds the fitness of being only a male or only a female
true
When male and female structures function at the same time
simultaneous hermaphrodite
Plants that have separate male and female flowers on the same individual plant
monoecious
When an individual plant contains only male flowers or only female flowers
dioecious
When an individual possesses one sexual function and then switches to the other
sequential hermaphrodite
The hypothesis that sexual reproduction allows hosts to evolve at a rate sufficient to counter the rapid evolution of parasites
the red queen hypothesis
when progeny inherit DNA from two parents through the union of two gametes
sexual reproduction
- produced through meiosis within sex organs called gonads
- contains a single full set of chromosomes
gametes
- inherit DNA from a single parent
- occurs via vegetative reproduction or parthenogenesis
asexual reproduction
occurs when an individual is produced from the nonsexual tissues of a parent
vegetative reproduction
- Individuals that descend asexually from the same parent and bear the same type
- produced when germ cells develop directly into egg cells without going through meiosis
clones
a process in which bacteria and some species of protists reproduce by duplicating their genes and then dividing the cell into two identical cells
binary fission
- reproduce asexually by producing an embryo without fertilization
- arise from diploid eggs
- composed entirely of females
parthenogenesis
- germ cells pass through the first meiotic division, but suppression of the second meiotic division results in diploid egg cells
- differences arise from recombination and independent assortment of chromosomes
partial meiosis
gamete-forming cells of the female are haploid then fuse to form a diploid embryo
complete meiosis
- a 50% reduction in the number of a parent’s genes passed on to the next generation via sexual reproduction vs asexual reproduction
- ounterbalanced in hermaphrodites
- can be offset when an individual is either male or female and the male helps the female take care of the offspring
cost of meiosis
individuals that possess both male and female function
hermaphrodites
- The schedule of an organism’s growth, development, reproduction, and longevity
- Represent the combined effects of many morphological, behavioral, and physiological adaptations of organisms, all of which interact with environmental conditions to affect survival, growth, and reproduction
life history
which is the number of offspring produced per reproductive episode
fecundity
the number of episodes of reproduction
parity
the amount of time and energy given to offspring
parental investment
the life span of an organism
longevity or life expectancy
how do life history traits vary
- consistently with respect to life form, habitat, or conditions in the environment
- variation in one life history trait is often correlated with variation in other life history traits
- long life spans, low numbers of offspring, and a high investment in the energy the parent gives to the offspring, such as parental care, the amount of yolk in an egg, or the amount of energy stored in a seed
- slow
K-selected
- short times to sexual maturity, higher numbers of offspring, little parental investment, and short life spans
- fast
R-selected
conceptualized the relationship between life history traits and environmental conditions as a triangle, with each of the three points representing an extreme environmental condition: abiotic stress, competition, and the frequency of disturbances
Grime
can survive and reproduce under extreme environmental conditions, such as very low water availability, very cold temperatures, or high salt concentrations
stress tolerators
- compete for nutrients
- can grow relatively quickly, because they often spread by vegetative reproduction
- tend to grow to larger sizes and exhibit long life spans
competitors
- low stress and high frequency fo disturbance
- colonize disturbed patches of habitat, exhibit fast growth and earl maturation, and use a high proportion of their energy to make seeds
- typically have seeds that are easily dispersed and that can persist in the environment for many years as they wait for favorable environmental conditions to germinate
ruderals
- reflects the genetic makeup of the organism
- the result of how an organism allocates a finite amount of time, energy, or nutrients
trade-offs
when resources are devoted to one body structure, physiological function, or behavior, they cannot be allocated to another
principle of allocation
selection favors what type of offspring size
a uniform, perhaps even optimal, offspring size and that an individual able to acquired additional energy can use it to make greater numbers of offspring
As the number of offspring increases, the efforts of the parents to provide food and protection will be
increasingly spread thin
neither phenotype does well in both environments
phenotypic trade-off
the ability of a single genotype to produce multiple phenotypes
phenotypic plasticity
when does the fitness advantage of phenotypic plasticity occur
whenever environmental variation in space or time occurs frequently
an environmentally induced change in an individual’s physiology
physiological plasticity / acclimation
induced changes in what are more difficult to reverse
morphology and life history
When environments fluctuate rapidly relative to the length of an individual’s lifetime, selection should favor
plastic behavioral and physiological traits because these traits can often respond rapidly and reverse rapidly
the seasonal movement of animals from one region to another
migration
Where environmental variation shifts the food supply from feast to famine and migration is not a possibility, what can be an adaptive strategy
storing resources
a condition in which animals dramatically reduce their metabolic processes
dormancy
types of dormancy
diapause
hibernation
torpor
aestivation
a type of dormancy that is common in insects and other animals in response to unfavorable environmental conditions
diapause
a less extreme type of dormancy that occurs in endotherms, in which animals reduce the energetic costs of being active by lowering their heart rate and decreasing their body temperature
hibernation
a brief period of dormancy during which the animal reduces its activity and its body temperature decreases to help conserve energy
torpor
the shutting down of metabolic processes during the summer in response to hot or dry conditions
aestivation
The idea that animals should strive for the best balance between the costs and benefits of different foraging strategies
optimal foraging theory
responses to food variation in space and time
central place foraging, risk-sensitive foraging, optimal diet composition, and diet mixing
acquired food is brought to a central place, such as a nest with young
central foraging theory
The total time it takes to obtain the food depends on the time needed to fly round-trip to the food site
traveling time
time spent obtaining food once the animal arrives at the site
searching time
Animals that incorporate the risk of predation into their foraging decisions
risk-sensitive foraging
why does natural selection occur
because of differences in survival or reproduction among individuals endowed with different phenotypes in a particular environment
favors any combination of traits that collectively provide improved survival or reproduction to an individual
natural selection
a type of seleciton in which humans decide which individuals will breed and the breeding is done with a preconceived goal for the traits desired in the population
artificial selection
- the evolution of populations
- pervasive
- affected by both random processes and selection
- can be divided into artificial and natural selection
microevolution
what types of populations tend to experience more genetic drift
small populations
- individuals with extreme phenotypes at either end of the distribution can have higher fitness than individuals with intermediate phenotypes
- increases genetic and phenotypic variation within a population
disruptive selection
occurs when an extreme phenotype experiences higher fitness than the average phenotype of the population
directional selection
- individuals with intermediate phenotypes have higher survival and reproductive success than those with extreme phenotypes
- sweeps away harmful genetic variation
stabilizing selection
the nonrandom process by which certain phenotypes survive and reproduce better within a given environment than other phenotypes
selection
how can selection influence the distribution of traits in a population in three ways
- stabilizing selection
- directional selection
- disruptive selection
occurs when genetic variation is lost due to random variation in mating, mortality, fecundity, or inheritance
genetic drift
why is genetic drift more common in small populations
because random events can have a disproportionately large effect on the frequencies of genes in the population
ways genetic drift occurs
- bottleneck effects
- founder effects
- when a population experiences a severe reduction in population size
- the survivors carry only a fraction of the genetic diversity that was present in the original, larger population
- smaller population will possess different gene frequencies than the earlier, larger population
bottleneck effect
A substantial barrier that prevents dispersal between suitable habitats
dispersal limitation
what is a common dispersal limitation
the presence of large expanses of inhospitable habitat that an organism cannot cross
strips of favorable habitat located between large patches of favorable habitat
habitat corridors
- When all individuals have perfect knowledge of habitat variation and they distribute themselves in a way that allows them to have the same per capita benefit
- tells us how individuals should distribute themselves among habitats of differing quality
ideal free distribution
resources available to each individual
per capita benefit
Lack’s hypothesis
- life history traits not only contribute to reproductive success, but also influence ecolutionary fitness
- life histories vary consistently w/ respect to factors in the environment
- number of offspring parents can successfully rear is limited by food supply
which types of birds contradicted Lack’s hypotheses
tropical birds
more food per nestling
what diminishes benefits to the parents in terms of the number of offspring that survive
increasing the number of offspring
how do we determine the optimal food decision
balance the energy obtained from the prey and the handling time
energy benefit / handling time
the time required to subdue and consume the prey
handling time
- occurs when a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation
- genetic variation remains low until enough time has passed to accumulate new mutations
founder effect
if several genes influence body size
an individual’s size will depend on the mix of alleles for all of these genes
the tendency for individuals to be concentrated toward the center of the distribution reflects
the relative improbability of an individual inheriting mostly alleles that code for large body size or mostly alleles that code for small body size
a phenomenon when females do not grow anymore after initiating reproduction
determinate growth
continued growth after initiating reproduction
indeterminate growth
what is the key feature of shaping the trade-off between growth and reproduction is that
larger females commonly produce more offspring
increased fecundity during one year occurs at the cost of
further growth that year
an organism with a long life expectancy should favor what during the early years of its life
growth over fecundity
the number of new individuals that are produced in a given amount of time minus the number of individuals that die
growth rate of a population
when individuals reach maximum reproductive rates and minimum death rates under ideal conditions
intrinsic growth rate (r)
- growth is exponential under ideal conditions
- when conditions are ideal, the size of the population in the future (Nt) depends on the current size of the population (N0)
- the population’s intrinsic growth rate (r), and the amount of time over which the population grows (t)
- e = base of natural log (2.72)
exponential growth rate
populations with higher intrinsic growth rates or a larger number of reproductive individuals will
experience a greater rate of increase in population size
applies to humans
the exponential growth model produces what shaped curve
J
how do we determine the rate of growth at any point in time using the exponential mdoel
dN/dt = rN
- this equation tells us that the rate of change in population size at any particular point in time depends on the population’s intrinsic growth rate and the population’s size at that point in time
- The derivative form of the equation tells us the slope of the line relating population size to time at any given point
the time required for a population to double in abundance
doubling time
which animals grow more rapidly: endotherms or ectotherms
endotherms
for species that breed once…
physiological decline and death follow rapidly
for species that breed many times…
the decline in physiology comes more gradually
- the phenomenon of an organism reproducing only once
- relatively rare in vertebrate animals, more common in insects and many species of plants
- live under more extreme ecological conditions
semelparity
- the phenomenon of an organism reproducing multiple times throughout their life
- a common life history that occurs in most species of birds, mammals, fish, reptiles, and amphibians
iteroparity
variable environment + variable phenotype =
better survival
true or false:
plastic individuals are usually fitter than a non-plastic individual in their own environment
false
Plastic individuals aren’t usually fitter than a non-plastic individual in their own environment, it’s the ability to react that increases fitness
- micro + speciation
- descent with modification, speciation
macroevolution
requirements for evolution to occur
- phenotypic varaiton
- traits are heritable
- differential reproductive success
- success determined by heritable traits
have similar gamets in both parents
isogamy species
have different gametes in each parent
smaller ones - male, larger ones - female
anisogamy species
how individuals try to maximize their own reproductive fitness
- mate guarding
- copulatory plugs
- infanticides
- traumatic insemination
sex ratio in a population is controlled by
frequency-dependent selection
- a sexual trait and selection for that trait reinforce each other
- might impose a handicap on the bearer
runaway selection
the result of diverse sex determination systems
sexual dimorphisms
save up resources to “finance” reproduction
capital breeders
reproduction depends on available resources in current environment
income breeders
higher latitude =
better clutch size
the decrease in fertility and increase in probability of death over the course of a lifespan
senescence
live only in one specific are
endemic species
live in a wide range of geographic areas
cosmopolitan species
density varies by
body size, resource availability, location within range
higher population density has negative effects on population growth (disease)
negative density dependence
higher population has positive effects on population growth (mating and allee effects)
positive density dependence
a phenomenon characterized by a correlation between population size or density and the mean individual fitness of a population or species
allee effect
methods to measure abundance
- subsampling (line transect and area/volume search)
- indices (indirect counts of evidence)
- mark-recapture
M/N = R/C
M = # caught in first sampling
N = total # in population
R = # recaptured (in second sample)
C = # captured in second sample
mark-recapture method
how do we measure indices
indirect counts of evidence
the rate of deterioration can be modified by
- a variety of physiological mechanisms that either prevent or repair damage (take time, energy, nutrients, and tissues
- depends on the expected life span of the individual
when a population has a low survival rate, selection should favor
improvements in reproductive success at young ages and selection to delay senescence should be weak
in a population with a high survival rate, selection for … should be strong
delayed senescence
- compares population sizes at regular time intervals
- expressed as a ratio of a population’s size in 1 year to its size in the preceding year (or some other time interval)
N1=N0λ
geometric growth model
λ > 1 means
the population size has increased from 1 year to the next because there have been more births than deaths
when λ > 1,
the population size has decreased from 1 year to the next because there have been fewer births than deaths
why is the value of λ always positive
there cannot be a negative number of individuals
Nt=N0λt where t equals time.
geometric growth model
how are geometric and exponential growth related
by λ=er which can be rearranged to logeλ=r
λ and r are directly related to each other
when a population is decreasing,
λ<1 and r<0
when a population is constant,
λ<1 and r<0
When a population is increasing
λ>1 and r>0
equation for doubling time (the exponential model)
e^(rt) = Nt/N0
doubling time equation (geometric model)
loge2/logeλ
