Week 27 Flashcards
Define the term sexual dimorphism, and explain why some animals exhibit sexual dimorphism, while others do not.
Sexual dimorphism: Differences between males and females in a species (e.g., size, color, ornaments).
Driven by sexual selection when one sex competes for mates.
Species with external fertilization or low competition show little/no dimorphism.
1.
Name each of the mating systems, and recognize examples of each.
Monogamy: One male, one female (e.g., Canada geese).
Polygyny: One male, multiple females (e.g., elephant seals).
Polyandry: One female, multiple males (e.g., some shorebirds).
Promiscuity: No stable pair bonds (e.g., common toads).
No functional mating system: Gametes released randomly (e.g., oysters).
Describe how mating system impacts the proportion of males and females that are reproducing in the population
In monogamy, nearly all males and females reproduce (~1:1).
In polygyny, few dominant males reproduce with many females, while many males fail to mate.
In polyandry, fewer females reproduce.
In promiscuous systems, reproductive success varies widely.
Explain how the concept of territories can be applied both to spatial resources, and to mates, and recognize examples of each scenario.
Spatial territories: Defended areas providing food, shelter, nesting sites (e.g., redwing blackbirds).
Mate territories: Males defend groups of females rather than physical space (e.g., lion prides).
Summarize the concept of sexual conflict.
Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction.
A trait or behaviour that is beneficial for the reproductive success of one sex can reduce the fitness of the other sex.
Explain monogamy, polygamy and promiscuity
Monogamy: Males and females form stable pair-bonds for a mating season, or in some cases, for their reproductive lives.
Polygamy:
◦ Polygyny: One male has active pair bonds with 2 or more females
◦ Polyandry: One female has active pair bonds with 2 or more males.
Promiscuity: Males and females have no pair bonds
beyond the time it takes to mate.
What happens when there is no functional mating system
Gametes are released into the environment at the same time, fertilization is entirely random. No mate choice or mate interaction.
Connect the concepts of outcrossing, ‘good genes’, sexual selection, and sexual conflict.
Outcrossing (mating with genetically different individuals) improves offspring survival.
Good genes hypothesis: Females choose mates with traits indicating health and genetic fitness.
Sexual conflict: Males and females evolve competing reproductive strategies.
Define sexual conflict, and compare it to the evolutionary arms race.
Sexual conflict: Traits that benefit one sex at the expense of the other.
Leads to an evolutionary arms race, where each sex evolves counter-adaptations to maximize their own fitness.
Differentiate between intrasexual competition, intersexual competition, and recognize cases where each – or both! – are occurring.
Intrasexual competition: animals of the same sex compete via display, song, or fighting for the
ability to mate.
Intersexual competition: one sex is “choosing” a preferred mate from the opposite sex.
◦ Visual cues, courtship dances, songs, and other displays may
be a part of the ritual.
Some species exhibit both (e.g., peacocks: males compete, and females choose based on display quality).
Which trait would NOT be found in a species modified by sexual selection?
Gametes dispersed into the environment by wind or water.
Male competition and female choice in terms of sexual selection
**◦ Male competition
**Males compete for access to females, the amount of time spent mating with females, and even whose sperm gets to fertilize her eggs.
*** Female choice
**Females choose which males to
mate with, how long to mate,
and even whose sperm will
fertilize her eggs. Some females
can eject sperm from an
undesirable mate.
: Can sexual selection produce traits that cause risks to the individual animals?
Yes – but that doen’t mean they are
maladaptive (detrimental to fitness)
What is an honest signal
An honest signal is a trait that indicates the quality (e.g.,
health, ability to obtain food) of the potential mate that
cannot be faked.
Is intersexual competition or intrasexual competition happening ?
Following mating, the female sits on the egg and cares for her offspring. The male mates with multiple females and does not participate in caring for the
offspring.
Intersexual
Male stalk-eyed flies have fights where they attempt to chase each other away using a ritualized battle. Females are also attracted to those individuals that have the longest stalks.
intersexual, intrasexual, or both ?
both
Which of the following terms accurately describes the tendency to see increasingly
exotic traits or large weapons in males?
A. Sexual conflict
B. Intersexual competition
C. Arms race
D. Outcrossing
E. Polyandry
C. Arms race
Define vicariance, and explain how a vicariance event can cause allopatric speciation.
. Vicariance: new physical barrier splits geographic range of a species
process of allopatric speciation by vicariance:
- Physical separation.
- Genetic drift and selection.
- Two populations are isolated.
Differentiate between vicariance and
speciation.
** Vicariance**: new physical
barrier splits geographic
range of a species
Speciation: the evolution of two or more distinct species
from one common ancestral species
Define allopatric vs sympatric speciation.
Allopatric speciation is initiated by a geographic barrier between individuals from two natural populations.
Sympatric speciation takes place in a single
geographic area.
What causes genetic isolation
Loss of gene flow
How does sexual selection work ?
Sexual selection usually works in two ways:
◦ Male competition
Males compete for access to females, the amount of time spent
mating with females, and even whose sperm gets to fertilize her
eggs.
- Female choice
Females choose which males to
mate with, how long to mate,
and even whose sperm will
fertilize her eggs. Some females
can eject sperm from an
undesirable mate.
Extravagant traits that might increase risk to the individual,
or require a lot of energy to produce, serve as an…
honest signal to the mate
What is an honest signal
An honest signal is a trait that indicates the quality (e.g., health, ability to obtain food) of the potential mate that cannot be faked.
Honest signals are a cost/benefit tradeoff between the likelihood of increasing fitness, vs. the increased risk of mortality.
Which of the following are “honest
signals” of resistance to parasites in male
turkeys? (choose all that apply)
A. Larger, wider tail fans
B. Demonstrated ability to care for young
C. Brighter, redder frontal caruncles
D. Longer snoods
E. High plumage reflectance in UV spectrum
D. Longer snoods
E. High plumage reflectance in UV spectrum
Which type of sexual selection is occurring in elephant seals?
B. Intrasexual competition
Which of the following terms accurately
describes the tendency to see increasingly
exotic traits or large weapons in males?
A. Sexual conflict
B. Intersexual competition
C. Arms race
D. Outcrossing
E. Polyandry
C. Arms race
Dispersal
Allopatric speciation
Physical separation/geographic isolation of popula
- Dispersal: population colonizes new habitat
Ex: Five large ground finches colonized Daphne Major in
Galapagos in 1982
- Over time, beak size diverged between populations.
- If isolation continued, divergence could lead to speciation
Which of the following mechanisms could cause
speciation in the finches of Daphne Major?
A. Founder event
B. Natural selection
C. Genetic Drift
D. Only A and B
E. A, B and C
E. A, B and C
Vicariance
allopatric speciation
Vicariance: new physical
barrier splits geographic range of a species
Examples of physical barriers:
- Mountain ranges
- Rivers
- Joining/separating
land masses
A group of scientists have been studying a species of frog
for several decades. Its habitat used to consist of two
mountain ranges connected by a valley. Over the last 10
years, climate change has caused the valley to become too
hot and dry for the frogs. This scenario represents what?
B. A vicariance event
speciation
the evolution of two or more distinct species from one common ancestral species
Allopatric speciation and sympatric speciation
Allopatric speciation is initiated by a geographic
barrier between individuals from two natural
populations.
Sympatric speciation takes place in a single
geographic area.
inbreeding depression
Decrease in health and fitness often observed in offspring resulting from inbreeding.
Male and female competition sexual selection.
Sexual selection usually works in two ways:
◦ Male competition
Males compete for access to females, the amount of time spent mating with females, and even whose sperm gets to fertilize her
eggs.
- Female choice
Females choose which males to
mate with, how long to mate,
and even whose sperm will
fertilize her eggs. Some females
can eject sperm from an
undesirable mate.
