BIO 331 EXAM 1 MODULES 1-4 ASU
What are the types of mating systems? - Answer- monogamy, polygyny, polyandry, promiscuity, Polygynandry
Monogamy - Answer- One single mate
Polygyny - Answer- Male mates with multiple females
Polyandry - Answer- Female mates with multiple males
Polygynandry - Answer- Social bond between male and female and they have multiple mates
Promiscuity - Answer- No social bond between male and female and mates with multiple partners
Spatial mating variation - Answer- Affiliative (who you socially bond and hang out with) vs. genetic (who you share
gametes with)
Temporal mating variation - Answer- Sequential (switching partners within a season) vs. serial (switching partners among
seasons) vs. lifetime (never changing)
What type and category of mating system do modern humans exhibit and why? - Answer- Today we exhibit serial
monogamy. We bond with one partner, but don't do it for a lifetime typically and we don't really have mating seasons (so we
are not sequential monogamists).
Environmental Potential for Polygamy - Answer- Proposed by Stephen Emlen and Lewis Oring.
The probability that an individual is likely to mate with more than one other individual is governed by "their ability of control
the mating access of others". In other words, how monopolizeable and/or defensible are potential mates, such that they can
be sequestered in time or space and restricted to mate only with you and not others
Identify the three critical proximate environmental factors that shape the environmental potential for polygamy (EPP). -
Answer- (1) spatial distribution of mates - Are potential mates dispersed or clumped in the habitat?
(2) temporal distribution of mates - Is breeding synchronous or asynchronous in the population?
(3) operational sex ratio - What is the ratio of sexually receptive males to females in the population?
If potential mates are spatially clumped in the habitat, then there is a high environmental potential for polygamy. - Answer-
In other words, they can be more easily monopolized by one individual and there is a positive relationship between mate
density and the EPP. A good example of this is the mating system of most primates, like gelada baboons (Theropithecus
gelada; see figure below), which form small, stable social groups of females that travel with one male and with whom they all
mate.
If potential mates breed all around the same time, then there is a high environmental potential for polygamy. - Answer- In
other words, their fertilizations can be more easily monopolized by one individual, and there is a positive relationship
between mating synchrony and the EPP. An example of this is red-winged blackbirds
If the operational sex ratio is skewed, then there is a high environmental potential for polygamy. - Answer- In other words,
there are more members of the opposite sex than there are your sex, so there is more than one potential partner to go
around, and thus there is a positive relationship between sex ratio skew and the EPP. An example of this are the now-
endangered southwestern populations of the Willow Flycatcher (Empidonax traillii extimus; see figure below), which vary in
the degree to which there is a dominance of females in the population. The more female-dominated a population is, the
more likely males are to mate with more than one female.
Explain why mating with only one partner for life is typically maladaptive in animals. - Answer- Because this is a risky and
limiting fitness strategy. If your mate dies or leaves you, and other animals in the population take on a new mate under a
similar circumstance, they then have more opportunities than you to pass on more genes. This ultimately means that your
"stubborn faithfulness" (and associated genotype) is likely to be outpaced by the other strategy of continuing to mate/breed
later in life.
four hypotheses to explain why males are polygynous. - Answer- When resources are evenly distributed in space but
females form groups to better access those resources or to help dilute the risk of predation, males can simply follow and
guard a group of females, more easily gaining access to reproductively ready females at the appropriate time (female
defense polygyny hypothesis).
, In contrast, when resources are clumped, attract multiple females, and are easily defended by males, males will simply
guard the resources—and by extension the females—by setting up a territory (resource defense polygyny hypothesis).
However, when resources are distributed heterogeneously and females are widespread and do not form groups, the only
chance a male may have to find more than one female is to wait for females to come in search of him and his competitors
(lek polygyny hypothesis) or simply to seek them out (scramble competition polygyny hypothesis
explosive breeding assemblage - Answer- occurs in species with a highly compressed breeding season in which females
may be receptive only during a short window of time. One such species is the horseshoe crab Limulus polyphemus, in which
females lay their eggs on just a few nights each spring and summer. Males are under the gun to be near the egg-laying
beaches at the right times and to accompany females to the shore, where egg laying and fertilization occur (Brockmann and
Penn 1999). Explosive breeding assemblages are also common in amphibians that typically breed on only one or a few
nights each year, such as the wood frog (Rana sylvaticus)
What makes lek and scramble competition polygyny distinct from the two forms of defense polygyny? - Answer- 1) Males
aren't defending females in lek and scramble competition polygyny.
2) Males don't provide any material benefits, other than sperm/genes, to females in lek and scramble competition polygyny
several potential benefits to females of being choosy (Polyandry) - Answer- both indirect benefits in the form of genetic
advantages to a female's offspring, as well as direct benefits (such as parental care, access to resources, safety from
predators, or reduced harassment by other males) that can increase a female's fitness
Polyandry and Indirect Genetic Benefits - Answer- good genes hypothesis Females mate polyandrously to produce
offspring of higher genetic quality or viability.
genetic compatibility hypothesis Females mate polyandrously to increase the odds of receiving genetically complementary
sperm.
genetic diversity hypothesis Females mate polyandrously to increase the heterozygosity (genetic diversity) of either
individual offspring or of the group of offspring produced in a single bout.
inbreeding avoidance hypothesis In the context of mating, females mate polyandrously to avoid inbreeding with their social
partner.
good genes hypothesis - Answer- females can receive a genetic benefit in terms of increased offspring quality or viability
by mating multiply. The same factor may be at work in a wild guinea pig, the yellow-toothed cavy (Galea musteloides), in
which females will copulate with more than one male when given the opportunity. The payoff for polyandry in this species
appears to be a reduction in stillbirths and losses of babies before weaning
genetic compatibility hypothesis - Answer- When gametes with especially compatible genotypes unite, they can result in
highly viable progeny.
genetic diversity hypothesis - Answer- One reason that females might choose more genetically compatible males is to
produce offspring that are more heterozygous (Westneat et al. 1990). According to this genetic diversity hypothesis, females
benefit by increasing the heterozygosity (genetic diversity) of either individual offspring or of the group of offspring produced
in a single bout. At the individual level, those offspring with two different forms of a given gene often enjoy an advantage
over homozygotes, which are more likely to carry two recessive alleles that might cause defects (see Fossøy et al. 2008). At
the group level, a greater diversity of individuals might allow at least some members of a colony to withstand a disease
outbreak or some offspring produced in a single breeding bout survive in a range of environmental conditions. If genetically
similar pairs are in danger of producing inbred offspring with genetic defects, then we can predict that females that are
socially bonded with genetically similar individuals will be prime candidates to mate with other males that are either
genetically dissimilar or highly heterozygous themselves (which means these males are likely to carry rare alleles that, when
donated to offspring, will increase the odds that the offspring will also be heterozygous) (Tregenza and Wedell 2000).
Polyandry and Direct Benefits - Answer- Non-mutually exclusive hypotheses to explain the potential direct benefits that
females receive from being polyandrous
additional resources hypothesis Females mate polyandrously to gain access to additional resources from their partner.
additional care hypothesis Females mate polyandrously to gain more caregivers to help rear young.
infanticide reduction hypothesis Females mate polyandrously to create greater uncertainty about the paternity of offspring in
order to reduce the risk of infanticide.
additional resources hypothesis - Answer- Females often mate multiply to gain access to resources that are necessary for
successful reproduction
additional care hypothesis - Answer- In some animals, polyandry enables females to indirectly access resources through
greater parental assistance from their several mates (additional care hypothesis). For example, in the dunnock (Prunella
modularis), a small European songbird, a female that often lives in a territory controlled by one (alpha) male may actively
