Shared Flashcard Set


Final review: Natural Selection
Natural Selection
Undergraduate 1

Additional Anthropology Flashcards





1/3 Modes of Natural Selection:    Stablizing Selection

give an example of stablizing selection:


-a type/mode of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value.


-due to selection against variants deviating from these means.



Example: Japanese Pheasants- most individuals have very similar size, coloration, & tail length.


(1/3 Modes of Natural Selection)

_________ selection:  in which both extreme variations of a trait are selected for is known as:

a) sexual selection


b) directional selection


c) stabilizing selection


d) disruptive Selection



d) Disruptive Selection


-selects against the average (very few individuals in the middle) in a population, & where both extreme variations of a trait are selected for


Example: Japanese Pheasants-- males look very different tahn females due to sexual selection that disfavored intermediate forms that were useful for both fighting & caring for young.


1/3 Modes of Natural Selection:    Directional  Selection





Among the ground finches in the Galapagos, there is some genetic variation in beak depth. After dry  years, when small seeds are scarce & larger seeds are more common, average beak depth increases in the population.


This is most likely due to __________   __________.


-a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.

-due to selection favoring these extremes.




Example: Japanese Pheasants-- males that have longer tails & specially mobile sharp spurs on their feet, compared to other species, will end being the reproductive victor


What are the 3 neccessary & sufficient conditions in order for Natural Selection to occur?



1) Variation in a trait


2) Inheritance of the trait


3) Differential Reproductive Success



The tail feathers of the male ping-pong bird are long & colorful. This is a costly adaptation, because the long tail allows predators to catch them more easily  & is energetically expensive (they need more food sources to grow & sustain their tails.)


You hypothesize that these brightly colored tail feathers attract female ping-pong birds for mating opportunities (& preservation of these characteristics in the species).


This is an example of  ________   _______


a) genetic drift

b) sexual selection

c) gene flow

d) speciation

b)  Sexual Selection

(component of sexual selection)


__________ hypothesis:


under certain conditions, it may be advantageous for the female to choose, as the father of her offspring, the male with a exagerated traits/handicap.


if he has survived to reproductive age, it is almost certain that this must be an abnormally fit individual.


Handicap Hypothesis

(a component of sexual selection)


the _________ _________ hypothesis describes:


• Male “exaggerated traits” are indicators of male condition.


• The features that are used to indicate condition cannot be “lied” about … the indicator must be honest


 • “Dishonest” indicators cannot evolve because females will be selected to ignore them (being effectively lied to is costly)

Honest Advertising Hypothesis

An __________ is a trait shaped by natural selection 


 An _________ can be a physical or behavioral trait

How do we know its an Adaptation?


we know its an adaptation if they there are these conditions:


• its complexity

 • A feature tracks change in function or niche over space and time

• A feature has a cost

• A feature measurable enhances fitnes


a strategy is an adaptation manifest in a particular context.


if a new & "improved" strategy comes along, it will "invade" the population & become the common strategy.


A strategy that cannot be "invaded is a _________ ______ _________.

Evolutionary Stable Strategy

What are a few of the Evolutionary Stable Strategies?


What are some of the limits?


______   ______   ________   are strategies that maximize access to resources will be selected for.


Primary strategy: turning energy into offspring.


-Limiting Factors: females are limited to access to resources since they are in most cases, physically committed to producing offspring.


-males are limited to access to females.


In mammals, female reproductive success (RS):


a) usually exhibits a higher variance than male RS

b) usually exhibits a lower variance than male RS

c) is most limited by access to males

d) increases with the decrease in resource availability

e) is the same as male RS

b)  usually exhibits a lower variance than male RS.
What are the 5 Male (evolutionary) Strategies?

5 Male Reproductive Strategies:  (components of sexual selection)


• Honest Advertisement


• Resource Defense Polygyny


• Female Defense Polygyny


 • Philandry


• Handicap Hypothesis


_______  ________ Polygyny described by:


  • Male(s) defends a group of females that are already social for other ecological reasons
  • Female 'puts up' with another female because of male's resources
  • Females form the stable core of the group, independent of any attributes the group's males might have.
  • Males migrate, females remain in the groups in which they were born.


ex. Bighorn rams go where potential mates are and then fight with other males to monopolize females there

Female Defense Polygyny

the model of evolution characterized by rapid bursts of change, followed by long periods of stasis.


Punctuated Equilibrium

__________  _________ polygyny:    which may occur when a male defends territory with sufficient resources for more than one female to breed and thrive.


Resource Defense Polygyny

The Honest Advertising Hypothesis of sexual selection suggests that the female chooses the male based upon the coloration of his tail feathers because:


a)  males with the fanciest tails take better care of offspring

b)  females want their sons to have fancy tails too

c)  his bright & fancy tail is an indicator of his health status & fitness

d)  females have an innate aesthetic sense



c)  his brigth & fancy tail is an indicator of his health, status, & fitness.
What are the 3 female (sexual) strategies in evolutionary biology?

female reproductive  strategies: (component of sexual selection)


• Sexy Son

• Internal Gestation

 • Cuckoldry


__________  ___________:  


a female strategy in which she can internally determine which male's sperm will be selected to fertilize her eggs.

Internal Gestation


this female strategy is where females choose males with a trait that will be preferred by females, so they can have "____  sons"

Sexy Son

a female strategy




In evolutionary biology, the term is also applied to males who are unwittingly investing parental effort in offspring that are not genetically their own.


Parental Investment:





________   investment:


• Investment is the energy an individual gives to its offspring through:

Genetic contribution:  DNA (relatively cheap)

 – Ecological contribution:  milk or food for offspring (expensive)

Parental Investment

____________   behaviors will spread if they favor altruism within the family – Among siblings, 50% chance there will be your alleles present.


What's true about Altruism & Natural Selection --- selfish strategies will defeat _______  strategies


According to the Trivers-Willard hypothesis, it makes sense to invest resources/energy in a female offspring when enviornmental conditions are bad, & to invest in a male offspring when the enviornment is good.


Explain this idea. Why does this make sense?



It makes sense to invest resources/energy in female offspring when enviornmental conditions are bad because females require fewer resources & if female offspring survive to adulthood, they will be more likely to reproduce offspring.


-Males require MORE resources & in bad conditions, are less likely to survive.


"____ at the ____"


term used to describe a social structure in which juveniles and sexually mature adolescents, remain with their parents and help them raise subsequent broods or litters, instead of dispersing and beginning to reproduce themselves

"helper at the nest"

Direct  fitness & Indirect fitness make up Inclusive Fitness.


What is the difference between the two?


Direct Fitness & Indirect Fitness= Inclusive Fitness.


Direct Fitness: the individual's survival & ability to reproduce offspring


Indirect Fitness: any impact that an individual has on the survival and reproduction of relatives


Suppose you (as a human) spend energy helping to improve your mother's reproductive success at the expense of your own. What concept best describes why this behavior may be consistent with natural selection?


a) direct fitness

b)  eusociality

c)  recipricol altruism

d)  sexual selection

e) inclusive fitness


The Formula for ______ ______ :



Where C is the cost to the actor, B is the benefit to the recipient of the act, and “r” is the degree of relatedness.

e)  Inclusive Fitness

A Colobus Monkey spots an eagle overhead & issues an alarm call, warning the other monkeys of danger. This action increases the chances that the monkey's relatives will be able to hide, but it calls attention to her, placing her in greater risk of attack by the eagle.


This example demonstrates which of the following evolutionary principles?


a)  survival of the fittest

b)  sexual selection

c)  kin selection

d)  genetic drift


Kin Selection

__________ selection:


-an evolutionary theory that proposes that people are more likely to help those who are blood relatives because it will increase the odds of gene transmission to future generations.


The theory suggests that altruism towards close relatives occurs in order to ensure the continuation of shared genes. The more closely the individuals are related, the more likely people are to help

Kin Selection

__________  - ___________  Hypothesis: predicts greater investment in males by parents in good conditions




greater investment in females by parents in poor conditions (relative to parents in good condition).


Under good resource conditions:
Females will opt to have male (during high variance)

Under bad resource conditions:
Females will opt to have a female (during low variance)

Trivers-Willard Hypothesis


have these 3 Social characteristics:

  1. overlapping generations - Different generations are represented at any given time with the colony. Eggs, immatures, and adults live together.

      2.   cooperative brood care - Members of the colony share responsibility for caring for the young.



3. sterile worker caste - The colony is organized by a caste system, and workers are not reproductive.



Example: Found in bee hive colonies, & naked mole rat "society"


How is Sickle Cell Anemia relevant to evolution?

List 3



-Some times adaptations suck


-Evolution works with what it has – there is no plan 


- Adaptations are the result of tinkering


Sickle Cell Anemia:

What is it? What is the likelyhood of someone inheriting it?


What is the relevance of Sick Cell Anemia? How does it pertain to Natural Selection?



-genetic disease that causes lack of oxygen in cells because red blood cells cannot carry oxygen – lesions, reduced growth

Sickle-cell disease occurs when a person inherits two abnormal copies of the haemoglobin gene, one from each parent (homozygous- dominant alleles).  A person with a single abnormal copy does not experience symptoms and is said to have sickle-cell trait (heterozygous).

Relevance to Natural Selection & Natural Selection: fitness of heterozygote is enhanced (since only homozygous carriers will have disease).


_________  ____________:  is a situation in which two different versions of a gene are maintained in a population of organisms because individuals carrying both versions are better able to survive than those who have two copies of either version alone.


example: the peppered moths that are dark grey (Bb genotype) & all black (BB genotype) peppered moths are more likely to survive & have fitness of trait over peppered moths that are much lighter in color (bb-genotype).

Balanced Polymorphism

True or False:


Lactose intolerance is the normal mammalian condition. Certain human populations have since overcome this & are able to drink milk past the point of weaning.




Asians & Africans remain lactose intolerant, but many others have become tolerant over time.


In the film "Voyage to the Galapogos," you saw that masked boobies allow one chick to kill the other in the nest. This seems cruel & maladaptive, but is actually the result of natural selection.


Imagine a similar species, in which some mothers lay 2 eggs & raise 2 healthy babies to adulthood, while other mothers lay 3/4 eggs, but whose babies do not get enough food & so none survive to a healthy adulthood.


briefly explain the relationship between fitness & reproductive success. How are these concepts related?


Fitness: the measure of reproductive success of an organism in its ability to pass on genes to the next generation.


Reproductive success: the absolute number of offspring that an individual can maintain to survive.


The 2 concepts are related because in this scenario, the fewer # of babies will survive because it costs less energy from the parents to try to find food resources for all offsprint & themselves


-those traits & adaptations that have kept the babies alive into adulthood are considered fit enough to be able to be passed on.


Inclusive Fitness



Provide an example of Inclusive Fitness:


_________   __________ of an organism is judged by the number of offspring it has, how they support them, and how their offspring could support others.


- close relatives of an organism share some identical genes, a gene can also increase its evolutionary success by promoting the reproduction and survival of these related or otherwise similar individuals.


Example: Ground Squirrels

-make an alarm call to warn its family of predators (ensuring the success of their offspring surviving)

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