chapter 9: evolution and behavior communication, cooperation, and conflict in the animal world...

Chapter 9: Evolution and Behavior

Communication, cooperation, and conflict in the animal world

Lectures by Mark Manteuffel, St. Louis Community College

Learning Objectives

Be able to explain the following:

Behaviors are traits that can evolve Selfishness, cooperation, and altruism Communication and the design of

signals Reproductive investment and sexual

conflict Parental care and mating systems

Animals should maximize energy consumed and minimize energy used.

1) Behavior has adaptive value just like other traits.

Humans like to eat foods high in fat and sugar.

Why do species have taste preferences?

Feeding choices directly influence fitness.

Living and reproducing require energy.

Maximal extraction of energy and acquisition of essential nutrients

Natural selection can shape feeding behavior.

Behaviors can be influenced by natural selection.

Feeding behavior• Humans; starlings; shore crabs examples

Maternal care• Mice example

Singing behavior• Songbirds example

Effects of evolution by natural selection are all around.

Peacock feathers Cryptic coloration observed in many

species

BEHAVIOR is part of an organism’s phenotype.• also under the influence of natural

selection

Take-home message 9.1

Behavior is any and all actions performed by an organism.

Behavior is as much a part of an organism’s phenotype as is an anatomical structure.

Behavior is produced and shaped by natural selection.

9.2 Some behaviors are innate.

Genes and the Environment

The production of a trait is not completely genetically determined.

Certain environmental conditions are also required.

The degree to which a behavior depends upon the environment varies a great deal.

Instincts or innate behaviors

Fixed action pattern

Role of the Environment

Triggered under certain conditions

Requires no learning

Does not vary

Once started, runs to completion

Fixed Action Pattern


The degree to which a behavior depends on the environment varies a great deal.

Instincts and innate behaviors are present in all individuals in a population and do not vary much from one individual to another.

Innate behaviors don’t require environmental input to develop.

9.3 Some behaviors must be learned (and some are learned more easily than others).

Learning

Involves behaviors that are altered and modified over time in response to past experiences

Tremendous variation among behaviors that require learning• Some are easy to learn• Others are not

Production of Behaviors and the Role of the

Environment Primates—fear of snakes

Appears not innate, but learned

Prepared Learning

Behaviors that are learned easily and by all (or nearly all) individuals

Snake-fearing behavior of monkeys Acquisition of language in humans

Why is it so much easier for an infant to learn a complex language than for a college student to learn biology?

Examine the evolutionary basis for the acquisition of certain

behaviors.

Prepared Learning

However, organisms don’t learn everything with equal ease.


In contrast to innate behaviors are behaviors that are influenced more by the environment.

These behaviors require some learning and are often altered and modified over time in response to past experiences.

Organisms are well-prepared to learn behaviors that have been important to the reproductive success of their ancestors.

Organisms are less prepared to learn behaviors irrelevant to their evolutionary success.


9.4 Complex-appearing behaviors don’t require complex thought in order to evolve.

“I must maximize my reproductive success!”

Why do animals have sex?

Why do people have sex?

Animals don’t consciously try to maximize their reproductive success, yet they behave as if they do?

How do they do it?

Rules of Thumb

Relatively easy-to-follow responses to cues that reliably lead to a desired outcome

Rules of Thumb

Pleasures, incentives, and reproductive success

Not necessary for the animal to be consciously seeking that outcome

How do we know?

Tricking animals

Unrelated people who grow up together from infancy on the same kibbutz never marry each other?

Why?


If an animal’s behavior in natural situations usually increases its relative reproductive success, the behavior will be favored by natural selection.

The natural selection of behaviors does not require an organism to consciously try to maximize its reproductive success.

9.5 A general theory of “kindness” helps explain the evolution of apparent acts of altruism.

Does unconditional love exist in the animal kingdom?

Altruistic behaviors—behaviors that come at a cost to the individual doing the behavior while benefiting the recipient.

Darwin

Natural selection generally works to produce selfish behavior.

Altruistic-appearing behavior is common.

Fatal to his theory?

Apparent Acts of Altruism

Kindness toward close relatives: kin selection

Kindness toward unrelated individuals: reciprocal altruism

Take-home message 9.5 Many behaviors in the animal world

appear altruistic.

In almost all cases, these are not really acts of altruism and have evolved as a consequence of either kin selection or reciprocal altruism.

These behaviors are beneficial to the individual engaging in the behavior.

9.6 Apparent altruism toward relatives can evolve through kin selection.

Hamilton’s Rule

Altruistic-appearing behavior will occur when the benefits to close relatives are greater than the cost to the individual performing the behavior.

They are really acting in their own genes’ best interests.

Who are people most likely to bequeath money to upon their death?

Redefining an Individual’s Fitness

Direct fitness• An individual’s total reproductive output

Indirect fitness• The reproductive output brought about

by altruistic behaviors toward close kin Inclusive fitness

• The sum of an individual’s indirect and direct fitness

Conflicts

Because different individuals do not share all of the same alleles, we should always expect some conflict.

Example: gestational diabetes


Kin selection describes behavior in which an individual assists its genetic relative.

Although the individual’s direct fitness decreases, the relative’s fitness increases.

Thus, the individual’s inclusive fitness increases.

9.7 Apparent altruism toward unrelated individuals can evolve through reciprocal altruism.

Vampire Bats

In many cases, individuals give blood to unrelated individuals.

How might this behavior have arisen?

Are they repaid the favor?

Reciprocal Altruism

Storing goodwill

We’re all born with a spare kidney, yet virtually no one donates theirs to non-relatives in need.

Why?

Certain Conditions Must Be Met

1) Repeated interactions among individuals

2) The benefits to the recipient must be significantly greater than the costs to the donor.

3) The ability to recognize and punish cheaters

Why are humans among the only species to have friendships?

Why is it easier to remember gossip than physics equations?


In reciprocal altruism, an individual engages in an altruistic-appearing act toward another individual.

The actor only gives up something of value when likely to get something of value later.


Reciprocal altruism occurs only if:• individuals have repeated interactions• individuals can recognize and punish

cheaters

These conditions are satisfied in humans but in few other species.

9.8 In an “alien” environment, behaviors produced by natural selection may no longer be adaptive.

Behaviors favored by natural selection over evolutionary time can cause individuals to behave in a way that reduces their fitness. Belding’s ground squirrels Craving high-fat foods Donations to refugees


When organisms are in environments that differ from the environment to which they are adapted, the behaviors they exhibit are not necessarily evolutionarily adaptive.

9.9 Selfish genes win out over group selection.

Does evolution ever lead to behaviors that are for the good of the species or population, while being detrimental to

the individual?


Behaviors that are good for the species or population but detrimental to the individual are not generally produced in a population under natural conditions.

9.10 There are big differences in how much males and females invest in reproduction.

Definition of “Male” and “Female”

A female produces the larger gamete. A male produces the smaller gamete.

The mother’s material contribution to the offspring exceeds the father’s.

Evolution of Differences in Male/Female Behaviors

1) Extent of energetic differences in the reproductive investment.

Why do males usually compete for females rather than the opposite?

Differences in Reproductive Investments

Fertilization within the female

Lactation in female mammals

Offsets and Reversals in Reproductive Investment

Examples: Birds

• Gestation external

• No lactation

Examples: Fish and amphibians

• External fertilization

Offsets and Reversals in Reproductive Investment

Evolution of Differences in Male/Female Behaviors

1) Extent of energetic differences in the reproductive investment

2) Paternity uncertainty• also has profound influence on reproductive

behavior


In mammals and many other types of animals, there are important differences between males and females relating to reproduction.


Fertilization usually takes place in the female.

Lactation occurs only in the female.

In species where fertilization occurs inside the female, males cannot be certain that offspring are their progeny.


These physical differences have led to the evolution of differences in male and female reproductive behavior.

9.11 Males and females are vulnerable at different stages of the reproductive exchange.

Predictions About Sex-Related Behavior

1) The sex that invests more will be more discriminating.

2) The sex that invests less will compete amongst themselves for access to the higher-investing sex.

Potential Exploitation at Different Stages of the Reproductive

Process

At the point of mating

At the point of parental care to offspring


Differing patterns of investment in reproduction make males and females vulnerable to exploitation at different stages.

This has contributed to the evolution of differences in sexual behavior.


The sex with the greater investment is more discriminating about mates.

The sex with less investment competes for access to the higher-investing sex.

9.12 Tactics for getting a mate: competition and courtship

Take-home message 9.12 Males tend to increase their

reproductive success by mating with many females and have evolved to compete for the opportunity to mate.

Females tend to increase their reproductive success by caring for their offspring and being choosy about selecting a mate.

9.13 Tactics for keeping a mate: mate guarding can protect a male’s reproductive investment When offspring survival can be

enhanced with greater parental investment…

Tactics for Keeping a Mate: Mate Guarding

When offspring survival can be enhanced with greater parental investment…

there is an incentive for males to provide some parental care…•even though such behavior makes

him vulnerable to paternity uncertainty.

Tactics for Keeping a Mate: Mate Guarding

When offspring survival can be enhanced with greater parental investment…

there is an incentive for males to provide some parental care…

even though such behavior makes him vulnerable to paternity uncertainty.

Why do so few females guard their mates as aggressively as

males do?

Mate guarding in order to reduce vulnerability

Attempt to reduce paternity uncertainty

“Danger zone” for males

Mate Guarding:From Simple to Macabre

Copulatory Plugs

Reptiles, insects, and many mammalian species

Males block the passage of sperm into the female

Coagulated sperm and mucus


Because paternity certainty is low in animals with internal fertilization, males that provide parental care are vulnerable to loss of their investment.

Mate guarding and other tactics have evolved to increase paternity certainty.

9.14 Monogamy versus polygamy: mating patterns can vary across human and animal cultures.

Mating Systems

Polygamy• when some individuals attract multiple

mates while other individuals attract none

Monogamy • most individuals mate and remain with

just one other individual

Mating Systems

Polygamy subdivided into:

Polygyny • individual males mate with multiple

females

Polyandry• individual females mate with multiple

males

Mating Systems Are Not Easy to Define

Three issues complicate the task:

1) differences between animals’ mating behavior and bonding behavior

Pair bond—appears monogamous



2) mating system variation within the species



3) males and females vary in their mating behavior

Examination of Birds and Mammals Reveals One Sharp Split

Are humans monogamous or polygamous?


Mating systems—monogamy, polygyny, polyandry—describe the variance in mate number of males and females.

They are influenced by the relative amounts of parental investment by males and females.

9.15 Sexual dimorphism is an indicator of population mating behavior.

Body Size Is an Important Clue to Behavior

Level of competition among the individuals of each sex

Selection for larger and larger body size when competition is high

It’s almost impossible to distinguish males from females among most bird species.

Why does that mean they are monogamous?

Men are bigger than women.

What does that tell us about our evolutionary history of monogamy

versus polygamy?


Differences in the level of competition among individuals for mating opportunities can lead to male-female differences in body size and other aspects of appearance.


In polygynous species, this results in larger males that are easily distinguished from females visually.

In monogamous species, there are few such differences between males and females.

Chemical Communication in Animals

Communication

An action or signal on the part of one organism that alters the behavior of another organism.

What types of animal behavior require communication?

What types of communication do animals use?

Types of Animal Communication

Chemical Acoustical Visual

Complex Forms of Communication

Honeybee waggle dance

What is language?

How is language identified?

Vervet monkeys

American Sign Language taught to chimpanzees and gorillas

Human language


Methods of communication have evolved among animal species, enabling them to convey information.

These abilities influence fitness and the evolution of virtually all other behaviors.

9.17 Honest signals reduce deception.

Conveying accurate information

Honest Signal

Cannot be faked

Given when both the individual making the signal and the individual responding to it have the same interests

Carries the most accurate information about an individual or situation

Deception Evolves!

“Begging” allele

Evolutionary “arms race”• Unambiguous signals• Sophisticated patterns of deception

An organism’s phenotype includes its behaviors


Animals have evolved to rely primarily on signals that cannot easily be faked in order to gain the maximum amount of information from them.

chapter 9: evolution and behavior communication, cooperation, and conflict in the animal world...

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