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UA / Biology / BSC 385 / How does behavior evolve?

How does behavior evolve?

How does behavior evolve?

Description

School: University of Alabama - Tuscaloosa
Department: Biology
Course: Ecology and Evolution
Professor: Benstead
Term: Fall 2016
Tags: Ecology, Biology: Ecology and Evolution, and ecology&evolution
Cost: 50
Name: BSC 385 Exam 2 Study Guide
Description: This study guide contains my textbook notes from chapters 6-8 and study guides from Dr. Benstead's notes from the end of chapter 5 notes through October 6's lecture notes (end of chapter 8)
Uploaded: 10/07/2017
29 Pages 45 Views 3 Unlocks
Reviews


Chapter 6 textbook notes Tuesday,  September  26, 2017 7:09 PM


How does behavior evolve?



I.

How Does Behavior Evolve?

a.

Fundamental Mechanisms of behavior interaction

i.

Stimulus-response = specific behaviors elicited  by a specific stimulus

1)

Behavioral response is invariant

a) Courtship displays exemplify this

b)

If each individual does not perform the prescribed  behavior, courtship breaks own and mating does not  occur

ii.

Communication = any action by one individual that alters the  probability of behavior in another

1)

Some stimulus-response systems like alarm calling are forms  of communication  

2)

Commonly used

a) Visual, auditory, olfactory, or tactile signals


What are the ecological factors that influence the mating system?



3)

Optimal choice of the signal is determined by the nature of  the communication and the physical properties of the  environment  

4) May convey discrete or graded information b.

How does selection differ for Males and females?  

i.

Sexual dimorphism = differences in size, coloration, or morphology  between males and females

1)

Suggests different selective forces operate on males and  females  

ii.

Females bear direct anatomical, physiological, and energetic  costs  of reproduction  

1) Lay and incubate eggs or carry them to term internally

2)

There is a point at which female fitness cannot increase by  producing more young  


What role does the ecosystem play in the evolution of behavior?



3)

Her fitness increases as a function of the quality of young she  produces

iii.

Male contribution, sperm, can be produced in great numbers so  male fitness increases with the number of females he inseminates iv. If you want to learn more check out What is the difference between isaac newton's and descartes's way of thinking and ideas?

Bateman's principle = the idea that males experience greater  variance in reproductive success than females

1)

Opportunity for selection to affect one sex increases the  degree of sexual dimorphism

iii.

Male contribution, sperm, can be produced in great numbers so  male fitness increases with the number of females he inseminates iv.

Bateman's principle = the idea that males experience greater  variance in reproductive success than females

1)

Opportunity for selection to affect one sex increases the  degree of sexual dimorphism

2)

Results in sexual selection = a form of natural selection in  which traits that enhance the ability of one sex (usually  males) to compete for or attract mates are favored  

v.

Sexual selection

1)

Female choice = a mechanism of sexual selection in which  females choose mates on the basis of their physical or  behavioral characteristics  If you want to learn more check out What is the doctrine of preparationism?

a)

Male phenotypic traits that improve their chances of  being chosen may be greatly exaggerated  by this  process Don't forget about the age old question of In business strategies, what is vertical integration?

2)

Male-male competition a form of sexual selection in which  males compete with one another directly or indirectly for  access to females  

3)

Balance hypothesis  

a)

Male traits are exaggerated by female choice until their  overall fitness cost is too high We also discuss several other topics like What is the annexation of crimea?

i)

Natural and sexual selection gradually come to a  balance  

ii) Exemplifies the concept of evolutionary trade-offs

iii)

Natural selection optimizes the costs and benefits  of male traits

4)

"truth in advertising"  

a)

Elaborate physical traits of males are an indicator of  overall fitness

b)

Explains the elaboration of the traits important to  females that otherwise seem irrelevant  to fitness

c.

Ecological factors that influence the mating system

i.

Mating system = the length of relationships between males and  females, the relative contributions of males and females to parental  care, and the number of mate san individual copulates with  

1)

Number of mates an individual copulates with during the  breeding season

2)

The relative  contribution of males and females to parental  care

3) How long the relationship between males and females lasts  ii.

Monogamy = a mating system in which each male mates with a  single female

1)

Social monogamy = monogamy that lasts for one breeding  We also discuss several other topics like What does the cost of goods sold mean?

            

care

3) How long the relationship between males and females lasts  ii.

Monogamy = a mating system in which each male mates with a  single female

1)

Social monogamy = monogamy that lasts for one breeding  season

2)

Pure monogamy is rare

a)

Advantages of female promiscuity  We also discuss several other topics like What is the classic stallings fiber-tempered pottery?

i) Increase genetic diversity of offspring

ii)

Ensure the female has opportunity to mate with a  number of males with high fitness or to increase  the probability that at least one mate is fertile

iii.

Polygyny = a mating system in which males mate with more than  one female

1) Most common relationship between males and females

2)

Female defense polygyny = a form of polygyny that occurs  when groups of females are guarded by males

3)

Resource defense polygyny

a)

If critical  resources are distributed such that males can  defend them, the males may obtain a territory that  attracts multiple females

4)

Lek-mating species = a species that uses a form of polygyny  and female choice in which males gather to display to females  on traditional places

a) Few males obtain the majority of copulations

iv.

Polyandry = a mating system in which each female mates with more  than one male

1) Rarest of mating systems

2)

Direct benefits to females

a)

Nuptial gifts provided by male insects to their mates  

i)

Energy or nutrient rich resources that increase  the female's reproductive success

3)

Indirect benefits

a) Superior male genes

4)

Guards against the fitness costs of choosing an infertile,  closely related, or genetically inferior mate

v.

Plant mating systems

1)

2)

3)

Outcrossing = a plant mating system in which mating occurs  between different individuals

Autogamy = a plant mating system in which individuals self fertilize  

Apomixis = a plant mating system in which individuals  reproduce asexually  

-=

between different individuals

2)

Autogamy = a plant mating system in which individuals self fertilize  

3)

Apomixis = a plant mating system in which individuals  reproduce asexually  

4)

Degree of self-incompatibility = a phenomenon in plants in  which individuals cannot self-fertilize

a)

Protogynous = describes a pattern of development in  which female function develops first  

b)

Protandry = a developmental phenomenon in plants in  which the male parts of the flower mature before the  female parts  

II.

What role does the ecosystem play in the evolution of behavior?  

a.

What behaviors are important in obtaining resources

i.

Habitat = the abiotic and biotic characteristics of the place where an  organism lives

1)

For mobile animals, habitat selection is a behavior that is  often genetically encoded  

ii.

Microhabitat = the subset of the habitat that differs in important  abiotic and biotic characteristics

1)

Ex: caribou choose different microhabitats within the tundra  during different seasons

2)

Microhabitat selection is important for many species as a  means of maintaining homeostasis  

iii.

Home range = the portion of the habitat used by an individual on a  daily or seasonal basis

iv.

Territoriality = exclusive  use of a portion of the home range

1)

Resources of importance and their spatial distribution  determine the size of the territory

2) Balance between energy cost and resources gained

3)

Size of food-resource territories increases as a function of  body mass

a)

Large animals have larger territories but they have to  share them with smaller animals  

4)

Territory size also related to the process of sexual selection  and the mating system

b.

How does the environment affect movement?

i.

Migration

1) Daily vertical migration/seasonal migration  

2)

Both genetic and environmental control

a)

Selection for individuals with greater unrest and  mobility during a certain season results in lines with  higher migratory tendency  

b)

Some species modify their migration patterns to take  

1 Daiy vertica migrationseasona migration  

2)

Both genetic and environmental control

a)

Selection for individuals with greater unrest and  mobility during a certain season results in lines with  higher migratory tendency  

b)

Some species modify their migration patterns to take  advantage of new conditions and resources

ii.

Dispersal = the one-way movement of an individual from the natal  area

1) Philopatric = describes individuals that do not disperse 2) Natal area = place where individual was born

3) Mortality costs of dispersal

4)

Saturation dispersal = dispersal of individuals that occurs  when the habitat is filled or resources are limiting

5)

Pre-saturation dispersal = individuals that disperse before the  habitat is filled or resources are limiting

a)

Dispersal is sex-biased in a number of vertebrate  species

b)

Inbreeding depression = a decrease in fitness due to  mating among related individuals

III.

How does the social system evolve?

a.

What are the components of the social system?

i.

Group size and composition

1)

Over time we expect selection to optimize the group size  relative to the ecological  situation and prey base  

ii.

Degree of cooperation among individuals 1) Cooperative hunting. Ex: lions and wolves

2)

Altruistic behavior = any behavior that increases fitness of  others at the expense of the altruist's fitness

a) Ex: alarm calling behavior of Belding's ground squirrels

b)

How did this behavior evolve?

i)

Inclusive fitness = a concept of fitness based on  the relative ability of an individual to transmit its  genes or copies of them to the next generation  

c)

Coefficient of relationship (r ) = the proportion of genes  shared by 2 individuals

i)

rB-C > 0

One. Where r is the coefficient of the altruist  Two. B is the fitness benefit to the recipient

Three. C is the fitness cost to the altruist

d)

How does the altruist recognize if its behavior benefits  kin?

i)

Direct kin recognition may not be necessary  

One.

If it is, olfaction in mammals  

.        

Three. C is the fitness cost to the altruist

d)

How does the altruist recognize if its behavior benefits  kin?

i)

Direct kin recognition may not be necessary  

One.

If it is, olfaction in mammals  

iii.

First.

Mating system

Kin discrimination is greater in  species where the average  relatedness in the group is lower

1)

Ecological factors that underlie the mating system interact  with group size and structure and the frequency of altruism  a) Ex: honeybees

b.

How are the organism's ecology and social systems related?  i. Mating systems shaped by pattern of resource distribution

ii.

Group size and composition as well as dispersal are products of  spatial distribution of resources

iii. Predation pressure selects for behaviors like alarm calling

iv.

Eusocial = describes a complex social system in which there is  division of labor or castes, a high level of cooperation, and  sometimes altruism  

1) Termites Example of eusocial species that is not haploid 2) Strict monogamy predisposes species to cooperative breeding  

Ch 5/6 Study Guide

Saturday, October  7, 2017 2:57 PM

Leftovers from chapter 5 

- Water moves in the global hydrolytic cycle via fluxes between major pools

Abiotic forces such as temperature, salinity, light and pressure are important in  

-

shaping aquatic communities

Lotic ecosystems (streams and rivers) are organized along environmental  

-

gradients controlled by channel size (stream order)

Lakes are subject to stratification, caused by density differences with  

-

temperature, that result in physical and chemical gradients with depth The open ocean is subdivided according to physical-chemical properties that  

-

vary with distance from shore, depth, and latitude  

- Ocean acidification is affecting biological carbon pump

The most variable marine communities occur near shore. Each is associated  

-

with a particular substrate, salinity gradient, and tidal regime

Chapter 6: Definitions:

Broad sense heritability = the proportion of the total variation in a phenotypic  

-

trait that is due to the genetic differences among individuals

○ Ranges from 0 to 1

Narrow-sense heritability = the proportion of the total phenotypic variance that  

-

is due to additive genetic variance, �" 

○ Ranges from 0 to 1

Stimulus-response = a specific behavior elicited  by a specific stimulus. Ex:  

-

courtship displays

Communication = any action by 1 individual that alters the probability of a  

-

behavior of another

Natural selection: fitness refers to both an organism's ability to survive and  

-

reproduce

Sexual selection: some traits may improve reproductive success while reducing  

-

survival

- Female = whichever produces larger gamete

Monogamy = males mate with a single female -

Natural selection: fitness refers to both an organism's ability to survive and  

-

reproduce

Sexual selection: some traits may improve reproductive success while reducing  

-

survival

- Female = whichever produces larger gamete

Monogamy = males mate with a single female -

Serial monogamy = monogamous relationship that lasts for a single  

breeding season

- Polygyny = males mate with more than one female during a breeding season - Polyandry = females mate with more than one male during a breeding season

Inclusive fitness = the relative ability to transfer one's genes, or copies of them,  

-

into the next generation

Equations:

Broad sense heritability  

-

�$ = �'�( 

○ ⎯⎯

�( = �' + �+ 

▪ Where �' = genetic variation among individuals ▪ �+ = environmental variation

▪ �( = total phenotypic variation

Narrow sense heritability -

ℎ$ = �" 

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

�" + �- + �. 

Where �" = variation due to additive genetic differences between  

individuals

�- = the effect of dominance (the masking of recessive genes by  

dominant ones)  

▪ �.  = environmental variation

"the breeder's equation"

-

Concepts:

� = ℎ$�

▪ Where s = selection coefficient ▪ R is the change in the trait over time ℎ$ ▪ = heritability

Behaviors are a result of genetic makeup as well as environment and experience  

-

as an individual

ℎ$ can be measured as the correlation between the average offspring  

-

phenotype and the average of the parental phenotypes

○ Closer dots = higher correlation

Twin studies in humans

-

Behaviors are a result of genetic makeup as well as environment and experience  

-

as an individual

ℎ$ can be measured as the correlation between the average offspring  

-

phenotype and the average of the parental phenotypes

○ Closer dots = higher correlation

Twin studies in humans

-

One way ℎ$ can be obtained in humans is by comparison of monozygotic  

and dizygotic twins, which differ in relatedness by 50%

▪ Each pair of twins have shared environment

▪ Any difference in correlation is due to genetics

Traits with high heritability respond to natural selection more rapidly than traits  

-

with low heritability

If heritability is lower, selection must be more intense to initiate same  

response  

If ℎ$ ○ is high, the rate of evolution is greater Sexual selection acts on the sexes differently

-

○ Mothers make a larger investment than fathers

Females limited by number of eggs they can make (and other  

investments), not mates

Female fitness increases as a function of the quality of the progeny,  

making mate choice more important

Males limited by number of mates, not sperm

▪ Male fitness increases with number of females he inseminates

○ When there is competition for mates, sexual selection will be stronger

Asymmetries in reproductive success lead to behavioral/morphological  

differences in the sexes

▪ One sex is competitive (usually males)

▪ One sex is choosy (usually females)

▪ Helps explain sexual dimorphism in many species  

Bateman's Principle -

Because males compete, they experience greater variation in  

reproductive success than females

○ Leads to strong selection on males

○ Sexual selection and asexual dimorphism are tightly related Males compete in 3 ways:

-

○ Combat - direct male-male competition, females may be oblivious  

Post-copulatory competition ○

Where females mate with more than one male

□ Make lots of sperm

□ Males guard their mates

□ Add pheromones to make females less attractive □ Prolonged copulation

□ Block next guy's sperm

□ Remove previous sperm

□ Make lots of sperm

□ Males guard their mates

□ Add pheromones to make females less attractive

□ Prolonged copulation

□ Block next guy's sperm

□ Remove previous sperm

Infanticide - killing other male's offspring can make female receptive to  

mating sooner and avoids investment in non-related offspring ▪ Mostly in mammals

Balance hypothesis - male traits are exaggerated  by female choice until their  

-

overall fitness cost is too high

"truth in advertising" hypothesis - elaborate phenotypic traits of males are an  

-

indicator of overall fitness

Help females choose a superior male, thereby increasing the quality of her  

progeny  

The mating system

-

○ Number of mates an individual copulates with during mating season ○ Relative contribution of males and females to parental care ○ How long the relationship between males and females lasts Types of mating systems

-

Monogamy  

Social monogamy

□ Female bonds with 1 male

□ Male and female share in parental care Genetic monogamy  

All progeny of a socially monogamous pair is produced by the  male and the female of that pair

□ Rare

Ecological determinants of monogamy ▪

If successful rearing of the young requires both parents,  monogamy is advantageous for both sexes

□ If reproduction is highly synchronous

□ Most common type of mating system in passerine birds Polygyny

Ecological determinants of polygyny ▪

Spatial distribution of females

The potential for males to control and ensure access to  

more than one female is dependent on the spatial  distribution of females

□ Spatial distribution of other critical resources Behavioral determinants of polygyny

Lek-mating species

Males display together on traditional sites known as  

leks

   

□ Spatial distribution of other critical resources Behavioral determinants of polygyny

Lek-mating species

Males display together on traditional sites known as  

leks

◆ Females choose their mate based on these displays ◆ A few males obtain the majority of copulations

Polyandry

Ecological determinants ▪

Fitness benefit to females

◆ Nuptial gifts from male to female

Reduces the probability of mating with a poor-quality  

male  

- A male with a larger territory size may attract more females

Social systems -

Fundamental components ○

Group size and composition ▪

Depends on the abundance, distribution, and types of  resources  

Degree of cooperation among individuals

□ Cooperative hunting in wolves □ Shared care of the young

Altruistic behaviors ◆ Inclusive fitness

Hamilton's Rule

Genes for altruism can increase in frequency if  

rB - C > 0.

Where r is the coefficient of the  

????

relationship of the atruist

Mating system

???? B is the fitness benefit to the recipient ???? C is the fitness cost to the altruist

May enhance inclusive fitness, kin selection, and altruism ◆ Diploid

Haplodiploid

May make altruism and eusociality more likely,  

but is not essential  

Chapter 7 textbook notes Thursday, October 5, 2017 6:57 PM

I.

What are the patterns of local environmental variation?

a.

How does the environment vary across space?

i.

Spatial variation in the environment is the result of discontinuities  in physical and biological factors from place to place

1)

Physical factors (temperature, soil salinity) vary, sometimes  abruptly, sometimes gradually  

2)

Biological components like predators, grazers, pollinators, or  parasites also vary spatially

ii.

Intraspecific variation = genetic or phenotypic variation within a  species

1)

Magnitude of the differences between patches

a)

Determines the selective pressure exerted  on the  organism

b) Ecotones are boundaries between habitat types 2)

Degree to which the patches are isolated  

a)

Determine the potential adaptive response of the  organism  

b)

Coarse-grained variation = spatial variation in the  environment that is large relative to the mobility of the  organism  

i)

Organism tends to experience just one or a few  different environments because its movement is  small compared to the scale of spatial variation in  the environment

c)

Fine-grained information = spatial variation in the  environment that is small relative to the mobility of the  organism  

i)

These individuals will experience many  environments

3) The relative  sizes

b.

How does the environment vary in time?

i. Temporal change occurs over many time scales

ii.

Unpredictability poses greater challenge  than a constant  environment  

iii. Spatial variation interacts with temporal variation II.

What are the adaptive responses to local environment variation?

b.

How does the environment vary in time?

i. Temporal change occurs over many time scales

ii.

Unpredictability poses greater challenge  than a constant  environment  

iii. Spatial variation interacts with temporal variation II.

What are the adaptive responses to local environment variation?

a.

Species = a group of populations that can interbreed with one another  and produce fertile  offspring  

b.

Subspecies = a local, phenotypically distinct form. Race and subspecies  are synonymous.  

c.

Essential feature of intraspecific variation is that the phenotype varies  with the patterns of environmental variation

i.

Genetically  distinct populations adapted to the local environmental  conditions are known as ecotypes

ii.

Nongenetic changes that arise as a developmental response to a  particular environment constitutes phenotypic plasticity

1)

Phenotypic plasticity = the ability of an organism to produce  different phenotypes in different environments  

d.

How do ecotypes arise?

i.

Adaptations arise by natural selection operating on the species'  genetic variation

1)

Directional, disruptive, and stabilizing selection eliminate  some variants and favor others

2)

Amount of variation on which these processes can act is  important to the process

a)

Specifically, the amount of genetic variation in the  population may limit the adaptive process  

b)

Fischer's Fundamental Theorem = the principle that the  rate of change in fitness by natural selection is equal to  the additive genetic variance in the population c)

Additive genetic variation is the combined effects of all  the different genes that affect a trait

3)

Intensity of selection also determines whether a local ecotype  will arise  

a) This is a direct result of the ecological  conditions

ii.

Ecotypic differentiation is more likely  to occur if the spatial  variation in the environment also includes barriers to gene flow  among populations  

1) Gene flow tends to oppose natural selection  

e.

What factors favor phenotypic plasticity?

i.

We can distinguish between phenotypic differences, which arise  due to the direct detrimental effect of the environment, and  phenotypic plasticity, in which the phenotype shifts in adaptive  ways in different environments

         e.

What factors favor phenotypic plasticity?

i.

We can distinguish between phenotypic differences, which arise  due to the direct detrimental effect of the environment, and  phenotypic plasticity, in which the phenotype shifts in adaptive  ways in different environments

1)

Adaptive phenotypic plasticity requires a mechanism that not  only detects environmental change but alters the  developmental pathways so as to produce the optimal  phenotype  

a)

Both an advantage and disadvantage of phenotypic  plasticity

i)

The organism can respond to its environment,  but the developmental complexity and energetic  requirements for phenotypic changes may be a  burden  

ii.

What determines whether the adaptive response to the  environment is genetic or phenotypic?  

1)

Determined by temporal and spatial pattern of variation in  the environment  

a)

In environments in which variation is fine-grained, the  organism typically experiences many ecological  conditions  

i)

In this case, phenotypic plasticity may be the  optimal response - a single genotype can develop  more than 1 phenotype depending on the  environment it encounters

b)

Plasticity is also advantageous if the pattern of  temporal variation includes rapid shifts or highly  unpredictable conditions for which a genetic response  would be too slow

III.

What factors determine the amount of intraspecific variation?

a.

What mechanisms increase genetic variation?

i. Ultimate source of all genetic variation = mutations  

ii.

Importance of sexual reproduction as source of new gene  combinations  

iii.

Disruptive selection maintains genetic variation in the population  because more than one phenotype is adaptive and selection  ensures that each persists

iv.

Frequency-dependent selection = a form of natural selection in  which the fitness of a gene is determined by its frequency in the  population  

1) Maintains variation by favoring rare genes  

b.

What mechanisms decrease variation?

iv.

Frequency-dependent selection = a form of natural selection in  which the fitness of a gene is determined by its frequency in the  population  

1) Maintains variation by favoring rare genes  

b.

What mechanisms decrease variation?

i.

Stabilizing selection eliminates extreme  phenotypes and their  genotypes

ii.

Directional selection favors phenotypes in one tail of the bell curve  and eliminates those at the other extreme  

iii.

Inbreeding  

1)

Increase the frequency of homozygotes and decrease the  frequency of heterozygotes  

a) Heterozygotes are a component of variation

b)

Increase in homozygosity exposes recessive alleles  to  natural selection. Variation is reduced as selection  eliminates recessive alleles  that otherwise would be  protected in heterozygous form

iv. Genetic drift  

c.

How do we measure genetic variation in populations?

i.

Common garden experiment = an experimental  design that  distinguishes between genetic variation and phenotypic plasticity.  Phenotypically different plants from different environments are  grown in a common garden. Differences that persist are genetic;  similar phenotypes in the common garden indicate phenotypic  plasticity.  

ii. Statistical models

iii.

Molecular techniques

1) DNA fingerprinting

2) Direct sequencing of DNA

3)

Measure variation in a much larger  proportion of the genome  than specific traits such as the shell color patterns  

a)

But do not necessarily measure the amount of adaptive  variation among populations  

4)

Genetic similarity = the measure of the proportion of alleles  shared by 2 populations

Study guide

Saturday, October  7, 2017 3:41 PMDefinitions

Coarse-grained environmental variation = patch size is larger than the  

-

organism's mobility, an organism experiences  few environments over its  lifetime

Fine-grained environmental variation = patch size is smaller than the organism's  

-

mobility range, an organism is exposed to many environments

Biological species = in sexually reproducing organisms, a species is a group of  

-

populations that can interbreed and produce fertile  offspring

Ecotype = genetically distinct populations adapted to local environment via  

-

natural selection

Subspecies/race = a local, distinct form that is distinctly different in phenotype  

-

(may rarely interbreed)

Phenotypic plasticity = development of different phenotypes in different  

-

environments by the same genotype

Common garden experiments = individuals with different phenotypes in the  

-

field are grown under similar conditions

Muller's ratchet = process by which the genomes of an asexual population  

-

accumulate deleterious mutations in an irreversible manner

Population bottlenecks = persistence of drift and inbreeding AFTER population  

-

re-expansion, caused by burden of ongoing homozygosity and expression of  deleterious alleles

Effective population size = the size of "an ideal population" of organisms (ideal  

-

refers to a hypothetical population in Hardy-Weinberg sense with constant  population size, equal sex ratio, and no immigration, emigration, mutation, or  selection) that would experience  the effects of drift or inbreeding to the same  degree as the population we are studying

Concepts

Aspects of environmental patchiness

-

○ The magnitude of the difference between patches ○ The degree to which patches are isolated ○ The relative  size of patches

Effects of temporal variability

-

Ecological effects of temporal variation depend on

▪ Amplitude of the change

        ○ The degree to which patches are isolated ○ The relative  size of patches

Effects of temporal variability

-

Ecological effects of temporal variation depend on

▪ Amplitude of the change

▪ Speed of the change

▪ Predictability

○ Unpredictable variation poses the greatest challenge - Adaptations to the local environment

- Subspecies and ecotypes CAN interbreed  

- Subspecies and race are synonymous

Variation within species driven by environmental variation -

Genetically  determined differences between populations inhabiting  

different environments give rise to ecotypes

○ Non-genetic changes give rise to phenotypic plasticity  Factors favoring the evolution of ecotypes

-

Existence of genetic variation in the trait ○

Fischer's fundamental theorem = the rate at which the mean fitness  

of a population increases by natural selection is equal to the  additive genetic variation in fitness (Ie, the combined effects of all  the different genes that affect fitness)

○ Intensity of natural selection

○ Geographical barriers to gene flow Phenotypic plasticity

-

Reaction norms

The range of all possible phenotypes that one genotype can  

produce

If you see a slope, your genotype is showing a different phenotype  

in a different environment -> phenotypic plasticity  

Spatially (and temporally) fine-grained environments favor phenotypic plasticity  

-

because it is the optimal response under variable ecological  conditions Coarse-grained environments lead to more predictable selective pressures that  

-

favor fixed genetic adaptations

- Genetic adaptations leads to differences in frequencies of the melanistic forms

Measuring genetic variation in populations -

Common garden experiments ○

If the field phenotypes persist in the common garden, the  

differences among populations are likely genetically  controlled  If the phenotypes in the common garden are similar, the variation in  

the field is due to phenotypic plasticity

Factors that influence genetic variation

-

○ Mutations are the ultimate source of all genetic mutation

Once mutations arise, their frequencies and combinations change due to ○

         

If the phenotypes in the common garden are similar, the variation in  

the field is due to phenotypic plasticity

Factors that influence genetic variation

-

○ Mutations are the ultimate source of all genetic mutation

Once mutations arise, their frequencies and combinations change due to

▪ Meiosis

▪ Natural selection

▪ Genetic drift

▪ Breeding system

▪ Etc

Mechanisms that decrease genetic variation

-

○ Stabilizing selection

○ Directional selection

○ Inbreeding

○ Genetic drift

Mechanisms that increase or maintain genetic variation  -

Overdominant selection (heterozygotes' phenotype different than either  

homozygous phenotype and heterozygotes have higher fitness)

○ Disruptive selection

Negative frequency-dependent selection (fitness depends on whether  

genotype is rare/common, highest fitness when your genotype is rare

○ Outcrossing (breeding with distantly related individuals) ○ Migration/gene flow

Two-fold cost of sex

-

Asexual individuals pass on twice as many genes to their offspring as  

sexual individuals

Sex is not an evolutionarily stable strategy (ESS) = an adaptation that increases  

-

in frequency when rare

Red Queen Hypothesis

-

Selection in a constantly changing environment favors sex

▪ Sex increases the variability of offspring via new combos of alleles

Measuring genetic variation: Wright's F-statistic -

The total variation (�"#) is due to the summed effects of variation within  

populations (�"$) and that between populations (�$#)

The higher the value of �$#, the larger the proportion of the total genetic  

variation is due to the differences among populations ( and the more  genetically differentiated populations)  

Chapter 8 textbook notes

Friday, October 6, 2017 9:46 AM

Demography = the quantitative description of a population and its characteristics  

I.

Population = a group of individuals of a single species inhabiting a particular  area

a.

What defines the boundaries of a Population?

i.

Individuals are not homogeneously distributed across the landscape

1)

Differences in demographic parameters like number of  individuals, their spacing in the habitat, and their  reproductive rate, distinguish local groups

ii.

Population boundaries are largely defined by the movement of  individuals

iii.

Connectivity = the link between 2 or more populations by dispersal  of individuals

1)

The movement of individuals among a set of populations  makes them more similar or homogeneous

2)

Demography of groups that are isolated from other groups by  habitat barriers or great distances is more likely to exhibit  distinct patterns  

iv.

Spatial scaling is more important to populations of sessile organisms  

1)

Genets = a genetically  distinct individual in a plant population.  Genets may comprise many individuals, especially when  reproduction is by cloning  

2)

Ramet = a physiologically distinct individual in a plant  population

3)

Unitary organisms = organisms that exist as separate and  distinct individuals

4)

Modular organism = an organism that develops by repetitive  patterns of growth of body parts

b.

Relationship between the ecological and evolutionary population

i.

Genetic change in a population occurs by evolution results from  combination of 4 processes:

1) Natural selection

2) Genetic drift

3) Gene flow

4) Mutation pressure

.

           combination of 4 processes:

1) Natural selection

2) Genetic drift

3) Gene flow

4) Mutation pressure

ii.

Deme = the evolutionary population unit; a group of randomly  mating individuals

1)

For evolutionary biologists, this is the relevant population  concept  

iii.

The discontinuities that define the ecological and evolutionary  populations often coincide

II.

What are key quantitative characteristics  of a population?

a.

How do we quantify the number of individuals in a population?

i.

�" = the total number of individuals in the population at a  particular time

1)

In terms of population density = the number of individuals per  unit area or volume  

a)

Individuals in dense populations may face more intense  competition for resources and thus may interact more  frequently  

ii.

Lincoln Index = a method for determining population size by  marking and recapturing portions of a population  

�% = sample of the population captured and marked at time t 1)

Represents a portion of the population  

a)

i) �%/N

2) Marked individuals are released back into the population

3)

At a later time, (�'), we capture another sample of the  population

a)

4)

Second sample will contain some individuals previously  captured and marked (�%), as well as some unmarked  individuals (�(%)

We can calculate total population size N with the equation                    � = �%* ∗,-.

⎯⎯⎯

,./ 

iii.

Index of relative abundance = a quantitative measure of the relative  size of a population using indirect evidence of the presence or  absence of individuals  

1)

Transects = a sampling method of measuring the presence or  absence of individuals along symmetric paths through the  habitat

b.

How do we measure spatial distribution of individuals in a population?

i.

Dispersion = the pattern of spatial distribution of species in a  habitat

1)

Potential patterns:

asence o nvuas aong symmerc pas roug e  habitat

b.

How do we measure spatial distribution of individuals in a population?

i.

Dispersion = the pattern of spatial distribution of species in a  habitat

1)

Potential patterns:

a) Randomly distributed

b) Clumped dispersion

c) Evenly distributed at regular intervals  

2)

Poisson Distribution = a statistical distribution in which rare  events occur at random. It can be used to analyze dispersion.  

a)

We compare the actual pattern of distribution to this  theoretical random dispersion. If they match, the  dispersion pattern is random. If not, the dispersion  pattern is either clumped or regular

b)

A grid is laid over the dispersion pattern of the  population such that the mean number of individuals in  each grid square is small

c)

The expected proportion of squares with x individuals is  calculated with the formula  

�2 = �2�56 

�! ⎯⎯⎯⎯⎯⎯

i) X is the number of occurrences

ii)

A is the mean number of occurrences per grid  square

iii) E is the base of the natural logarithms

iv)

X! is x factorial. This means we multiply the value  of x times the values x-1, x-2, x-3, and so on until  the remaining term is 1.  

v)

Ex: the expected proportion of squares with 2  individuals is  

�' = 0.51'�5=.>* 

2! ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯= 0.078

vi)

We can now calculate the expected number of  squares containing 2 individuals by multiplying  the expected proportion by the total number of  squares, in this example 100:  

One. 0.078 * 100 = 7.8  

d)

How do we determine if the population distribution is  clumped or random if it's not random?  

i)

Mean occurrence of the variance in occurrence  are equal

One.

If the mean/variance ratio = 1, the  dispersion is random

clumped or random if it's not random?  

i)

Mean occurrence of the variance in occurrence  are equal

One.

Two. Three.

If the mean/variance ratio = 1, the  dispersion is random

If the mean/variance ratio > 1, the variation  among squares is small, indicating a regular  dispersion pattern

If the man/variance ratio < 1 indicates a  clumped distribution

ii.

Key demographic characteristics of a population

1)

Age structure = the distribution of individuals according to  their ages

a)

Life table = a table showing the numbers of individuals  of different ages and their age-specific mortality and  reproductive rates

i)

Cohort life table = a life table based on following a  single cohort from birth to the death of the last  individual

ii)

Static life table = a life table based on a sample of  the population and the distribution of individuals  of different age

b)

Survivorship curve = a plot of the log lx as a function of  age

i)

Graphically represents the pattern of age-specific  survival

ii)

Patterns

One.

Type I survivorship curves are characterized  by low survival in young ages, then high  survival until old age, when mortality  increases rapidly

First.

Humans have this type of survivorship  curve

Two. Three.

Type II survivorship curves, survivorship is  constant across ages, leading to a linear  relationship between  

�2 and age.

First. Common among some birds Type III survivorship curves are  

characterized by very high early mortality  but decreases in older ages

First.

Many invertebrates have curves of  this form

iii)

Can provide useful comparative information

Three.

Type III survivorship curves are  

characterized by very high early mortality  but decreases in older ages

First.

Many invertebrates have curves of  this form

iii)

Can provide useful comparative information

One.

In polygynous mammals, the age-specific  survivorship of males and females often  differs  

First.

Male-male competition leads to  higher age-specific mortality for  males

Two.

Differences in habitat quality may be  reflected in the survivorship curve as well

c)

Life expectancy (�2) = the mean expectation of further  life for an individual of age x  

i) We calculate a new column  

�2 = �2 + �2E* 

2 ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

�2 = �2 

ii) ⎯⎯⎯

�2 

d)

Life span = the maximum age to which an individual can  live

e)

Reproductive rate (�=)= the average number of  individuals produced by a female in her life span

i)

ii) iii)

�2= the expected reproductive output of an  individual that has reached age x  

�2�2 measures the realized  production by  including the probability that an individual  survives to that age

Net reproductive rate is the sum of the �2�2 column

Sex ratio = the proportions of males and females in a  

f)

population  

May differ among populations of the same  

i)

species

Can change within a population for groups of  

ii)

individuals of different ages  

One. 1° sex ratio = sex ratio at fertilization

Two. Three. Four.

2° sex ratio = sex ratio at birth or  hatching

3° sex ratio = sex ratio at sexual  maturity

4° sex ratio = sex ratio of the adult  

        

Two. Three. Four.

2° sex ratio = sex ratio at birth or  hatching

3° sex ratio = sex ratio at sexual  maturity

4° sex ratio = sex ratio of the adult  population

iii) iv)

Monoecious = describes a plant in which male  and female function occur in the same  individual  

Dioecious = describes a plant in which male  and female function occur in separate  individuals

III.

How do populations  change in time and space?

Factors that determine dynamics of a population a.

The change in the number of individuals in a population  is a  

i.

result of 4 processes:

1) Immigration to the population  (I)

2) Emigration from the population  ( E)

3) Additions  to  the population  via births (B)

4) Losses from the population via deaths (D)  

ii.

The change in population size (N) from time t to  t+1 is thus  determined by the equation:  

�"E* = �" + � − � + � − �

b.

What determines the movement of individuals within and among  populations?

i.

Dispersal allows individuals to exploit spatial variation in key  resources  

ii. Dispersal maintains connections  between distinct populations c.

How do birth and death rates determine growth rate of a  population?

i. Discrete/overlapping generations

d.

How do populations  with discrete generations grow?

i.

Multiplicative growth rate = the factor by which the current  population size increases in each time period

ii.

If �= > 1, each female is more than replacing herself; the  population is growing

iii. If �= < 1, the population is in decline

e.

How do populations  with overlapping generations grow?

i.

Instantaneous  growth rate (aka intrinsic rate of increase) = the  potential growth rate of a population  based on  the difference  

population is growing

iii. If �= < 1, the population is in decline

e.

How do populations  with overlapping generations grow?

i.

Instantaneous  growth rate (aka intrinsic rate of increase) = the  potential growth rate of a population  based on  the difference  between  the per capita birth and death rates, measured at  small population size

ii.

General equation  to calculate the population  size at time t if  we know initial population size and the reproductive rate:  �" = �=�P" 

iii.

Transition matrix (aka Leslie matrix) = a method of predicting  population growth  from the probailities of transition from  each age class to  the next and the age-specific reproductive  rate

Study guide

Saturday, October  7, 2017 4:16 PMDefinitions:

Demography = the quantitative description of the structure of populations,  

-

includes size, age structure, sex ratios, and growth rate

Population = group of individuals of a single species inhabiting a particular area -

Ecological population = a group of individuals of a species that occupy a  

particular area, its boundaries are determined by an ecologically relevant  change in the environment

Evolutionary population = a local group of individuals that mate at  

random (a deme), its boundaries are determined by the barriers to mating  and gene flow

Connectivity = the link between 2 or more populations by dispersal of  

-

individuals

Abundance, �" = number of individuals in a population (NOT number of species  

-

in a community)

- Density = number of individuals per unit area or volume

- Genet = a genetically distinct individual or clonal colony in a plant population - Ramet = a physiologically distinct individual within a plant genet - Unitary organism = exist as separate and distinct individuals - Modular organisms = develop repetitive  patterns of growth of body parts - Cohort life table = follows a group of individuals over time

- Static life table = based on a sample of the population at one moment in time - Survivorship curve = graphically represents the pattern of age-specific survival  

Life expectancy (�$) = the mean expectation for further life of an individual of  

-

age x  

Life span = the maximum number of years an individual in the population could  

-

potentially live

Net reproductive rate (�&)  = the average number of offspring produced by an  

-

individual during their lifetime

Equations:

Lincoln (mark-recapture) methods

-

� = �+ ∗ �- 

○ ⎯⎯⎯⎯⎯⎯⎯

�. 

○ Where N = total population size

�+ = number of individuals marked and released in the population at time  ○

 

Lincoln (mark-recapture) methods

-

� = �+ ∗ �- 

○ ⎯⎯⎯⎯⎯⎯⎯

�. 

○ Where N = total population size

�+ = number of individuals marked and released in the population at time  

t1

○ �- = number of individuals captured in the population at time t2 ○ �. = number of marked individuals at time t2

Poisson distribution

-

�$ = �$�23 

○ ⎯⎯⎯⎯⎯⎯

�!

        where X is the number of occurrences

i. A is the mean number of occurrences per grid square ii. E is the base of the natural logarithms

iii.

X! is x factorial. This means we multiply the value of x times the  values x-1, x-2, x-3, and so on until the remaining term is 1.  

Life expectancy

-

�$ = �$ + �$8+ 

○ ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

2

○ �$ = �$ + �$8+ + �$8- + ⋯ + �< 

�$ = �$ 

○ ⎯⎯⎯

�$ 

Net reproductive rate (�&)

-

○ �$ = �������� ������������ ������ ��� �� ���������� �� ��� �

�$�$ = realized population determined by probability an individual will live  

to age x

○ �& = sum  �$�$ 

For exponentially growing populations with discrete generations: -

�" = �& + �& 

▪ Where �& = number of individuals at time 0 (now) ▪ �" = number of individuals at time t  

For exponentially growing populations with overlapping generations -

r is the instantaneous growth rate, or the intrinsic rate of increase

▪ � = �& − �& 

�" = �&�K" ○

Concepts:

Population boundaries are determined by the differences in demography  

-

○ Number of individuals

○ Spatial distribution

○ Reroductive rate

Concepts:

Population boundaries are determined by the differences in demography  

-

○ Number of individuals

○ Spatial distribution

○ Reproductive rate

○ Isolation vs connectivity  

How to quantify population size

-

Total census

▪ For large animals, trees, human populations

Lincoln (mark-recapture) methods

▪ For small, mobile organisms

Quadrat or transect methods

▪ For sessile or relatively immobile organisms

▪ Indirect, relative measure of the abundance, but can be scaled up

Spatial distribution of individuals -

Random - individuals distributed without regard to others ○

Processes: neutral or little interaction between individuals and  

between individuals and local environment

Clumped - individuals in discrete groups, positive interactions ○

Processes: attraction between individuals or to a common  

reassurance or little  dispersal far from parent

Regular - individuals maintain minimum distance between themselves and  

their neighbors

Processes: antagonistic interactions between individuals or local  

depletion of resources  

- Poisson distribution = random distribution

- Age structure provides insight into the ecology and history of populations  

Types of survivorship curves -

Type I - low survival in young ages, then high survival until old age, when  

mortality increases rapidly

▪ Many mammals, including humans

Type II - survivorship is constant across ages

▪ Common in small mammals, lizards, birds

Type III - early mortality is very high, but deceresaes with older ages

▪ Many marine fishes, invertebrates, and plants

- Habitat quality may affect survivorship curves - Survivorship curves can differ between the sexes

Net reproductive rate

-

○ If �& > 1 the population is increasing ○ If �& =  1 then population size is stable ○ If �& < 1, then population is decreasing  Sex ratio

-

○ 1° sex ratio = sex ratio at fertilization

Net reproductive rate

-

○ If �& > 1 the population is increasing

○ If �& =  1 then population size is stable

○ If �& < 1, then population is decreasing  

Sex ratio

-

○ 1° sex ratio = sex ratio at fertilization

○ 2° sex ratio = sex ratio at birth or hatching

○ 3° sex ratio = sex ratio at sexual maturity

○ 4° sex ratio = sex ratio of the adult population

-

Populations  change in time and space

1) Immigration to the population  (I)

2) Emigration from the population  ( E)

3) Additions  to  the population  via births (B)

4) Losses from the population via deaths (D)  

-

For exponentially growing populations with overlapping generations ○ If r >0, population declines

○ If r = 0, population stable

○ If r < 0 , population grows

-

A transition matrix tracks

○ The probabilities of transition from one age to another

○ The corresponding reproductive output that accumulates in the process

For newborn individuals, �& at time t+1 is calculated by the number of  individuals born at time t to individuals of different ages at time t ▪ This is the contribution from �&,�+, �- and so on of all age classes ○

For all other age classes, the number of individuals at time t+1 is the  result of survivorship from previous ages

▪ Given by the terms in the �$ column

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