BIOL 2140

Life History

The schedule of an organism's life, including age of reproduction and survival.

Fecundity

The number of offspring produced per reproductive episode.

Parity

The number of reproductive episodes an organism experiences in its lifetime.

Parental Investment

The amount of time and energy devoted to caring for offspring.

Longevity

The expected lifespan of an organism.

r-Selected Species Traits

Rapid development, early reproduction, semelparity, large clutches, small offspring, short lifespan.

K-Selected Species Traits

Slow development, delayed reproduction, iteroparity, small clutches, high parental care, long lifespan.

Grime's Ruderals

Plants adapted to high disturbance; they grow fast and devote energy to reproduction.

Grime's Stress Tolerators

Plants adapted to high stress; characterized by slow growth and vegetative reproduction.

Principle of Allocation

Energy devoted to one trait cannot be allocated to another trait.

Offspring Size vs. Number Trade-off

Producing more offspring generally results in smaller individual offspring size.

Determinate Growth

A growth pattern where an individual stops growing after initiating reproduction.

Indeterminate Growth

A growth pattern where an individual continues growing after reproduction begins.

Semelparity

A reproductive strategy where an organism breeds once and then dies.

Iteroparity

A reproductive strategy where an organism breeds multiple times throughout life.

Charnov and Schaffer Model

Semelparity is favored when adult survival is low relative to juvenile survival.

Senescence

A gradual decrease in fecundity accompanied by an increase in mortality probability.

Photoperiod

The daily amount of light that serves as an environmental cue.

Effects of predatiom

Has a strong affect many life history traits. (time to hatching, size at hatching, metamorphosis, sexual maturity)

Trade off

Hatch at a smaller size; more vulnerable to aquatic predators

Sexual Reproduction

Progeny inherit DNA from 2 parents

Gonads

Primary sexual Organs

Gametes produced through Meiosis

into haploid cells (a single set of chromosomes)

haploid Gametes fuse

diploid zygote

vegetative reproduction

An individual is produced from the nonsexual tissues of a parent

Clones

Individuals that descend asexually from the same parents (identical genotype)

Binary Fission

Duplication of genes followed by division of the cell into 2 identical cells

Parthenogenesis

Embryo is produced without fertilazation

Animals that undergo parthenogenesis are typically

all female

Clones result when germ cells

develop directly to egg cells

Genetically variable offspring result when germ cells undergo

partial meiosis

Cost pf Meiosis

50% reduction in the number of a parents genes passed in to the next generation

Hermaphroditism

A condition in which an individual has both female and male gonads and functions as both a male and female in sexual reproduction by producing both sperm and eggs.

Purging Mutations

Sexually reproducing organisms can lose deleterious mutations during meiosis

Random assortment

many gametes will not contain mutations

Red Queen Hypothesis

Sexual selection allows hosts to evolve at faster rate that counters the rapid evolution of parasites

Perfect flowers

Flowers that contain both male and female structures

simultaneous hermaphrodites

Possess Male and Female reproductive functions at the same time

Sequential hermaphrodites

Possess Male and Female reproductive functions and switch

Monoecious

Plants that have separate Male and Female flowers on the same individual

Dioecious

Plants that contain either only Male flowers or only Female flowers on a single individual

Comparing sexual strategy

Natural selection should favor the strategy with the highest fitness. If a Male can invest in a Female function while giving up only a little male fitness, or vice versa, selection should favor hermaphroditism

Self-fertilization

occurs when an individual's Male gametes fertilize its own female gametes

Costs

Inbreeding depression and less genetic diversity

Selection should favor individuals that occurs when possible

Sequential Hermaphroditism

Avoids selfing by separating sexual functions in time

Outcross

When mates are available

When mates are unavailable

Self-fertilize, not as many viable offspring, but it is better than nothing

Mixed mating can be in response to

a lack of resources in the environment

The ratio of Male to Female offspring

1:1

Female chromosomes

XX

Male chromosomes

XY

Environmental sex determination

Process in which sex is determined largely by the environment = Phenotypic plasticity

Temperature-dependent sex determination

sex of an individual is determined by the temperature

Fisher: sex ratio of clutch

Each individual had one mother and one father

-On average, producing one son should give her as

great a chance of leaving future descendants as

producing one daughter

- RV of average son = RV of average daughter

- Reproductive value = contribution in terms of # of

young that an individual animal will make to the

future population

- Specific prediction from Fisher: investment in sons

& daughters should be equal

- Fitness value of son or daughter depends on the population sex ration

Frequency dependent selection

When the rarer phenotype in a population is favored by natural

selection

In a population with an uneven sex ratio, the rarer sex will compete with fewer individuals for breeding

the rarer sex will gain higher fitness

Trivers and Willard (1973)

"Prediction" is not assumed to require conscious

thought or motivation

-How can the female "predict" that sons will be

more successful?

- Female in good condition ("fat") will result in

offspring in good condition (large, well-fed!)

- A healthy son will have a much better probability

to compete successfully for mates

A son in good condition will yield higher

fitness payoffs than a daughter in good

condition

- A daughter will always mate; whether in

good or poor condition

-A son will only mate if in good condition!

Offspring sex ratio

Females can influence the sex ratios of their offspring

Bednarz & Hayden 1991: Conclusions

Overall sex ratio biased toward males

- Consistent with Fisher's Equilibrium

hypothesis

- Suggest that female-male broods are

maladaptive

- Brood reduction: large females kill males

- Parents loose on 2 ways:

- Fledge fewer young

- Skew sex ratio in wrong direction: toward females

To avoid disadvantage of maladaptive

brood reduction

- Females might "purposely" skew the sex

ratio toward (~70%) in the first laid egg

- Results in overall skew in sex ratio toward Males 57%

- Adaptive following Fisher's Model

According to Fisher's equilibrium hypothesis

what is the primary factor that would cause a

skew in the sex ratio toward females at birth?

B.) When mature females are substantially larger

than males

According to the Trivers & Willard

hypothesis, when should females skew the

sex ratio of their offspring toward males?

E.) When a female's mate is dominant, healthy, &

likely to sire many offspring

Based on the research done by Bednarz &

Hayden, why do Harris's Hawks skew the sex

ratio of their 1 st -hatched young toward males?

B.) Because males grow slower than females & need a head

start

Mating systems

-Monogamy

-Polygyny

-Polygamy

-Polyandry

Promiscuity

Member of one sex has near equal opportunity of

mating with every individual of the opposite sex

-No mating system?

- Unlikely to occur in nature for almost all animals

- May occur with some outcrossing plants and

sedentary aquatic organisms that release

gametes in H2O

What do females need to fertilize all their eggs?

One or a few matings

What do males provide in most species?

Sperm

What limits females in mating systems?

Resources

How does the availability of resources affect female reproductive success?

The more resources a female can gather, the more offspring she can produce.

What do males tend to do in mating systems?

Initiate courtship, search for females, and fight with other males for access to females.

Monogamy

Social bond between a male & female persists

through the period that is required for them to

rear offspring

Extra-pair copulations

Females may use this strategy to obtain

1) Produce offspring with better genes

2) Increase the genetic diversity of brood

3) Fertility insurance

4) Induce sperm competition

Sexual Selection

Selection related to mating, Related to the advantage in which

certain individuals have over other individuals of the same sex and species. Related to reproduction

Female choice

individuals selecting

"attractive"

characters

Male-male competition

Characters that allow males to compete with other males for

mates

sexual dimorphism

Differences in physical characteristics between males and females of the same species.

Parental Investment

the time and energy parents expend for their offspring's benefit

runaway sexual selection

Sexual selection by female choice that results in elaborate and costly secondary sexual characteristics in males.

Zahavi handicap principle

states that only traits that are true and honest indicators of male genetic quality should be used by females when choosing mates

Good genes hypothesis

Females select males on basis of trait that indicates viability or beneficial adaptation

Good health hypothesis

Females select the healthiest males

Sexy son hypothesis (fashion icon

hypothesis)

Females only receive genes that will provide their male offspring with sexy trait favored by females.

-Trait provides no adaptive benefit

Social behaviors

interactions with members of one's own species

Dilution effect

Reduced probability of predation to a single animal when in a group

More individuals watching for predators

each individual spends less time watching & more time feeding

Group benefits

Many individuals searching for food may be able to find rare food more easily

-Probability of prey capture may increase in a group

Being social makes it easier to find potential mates

attract the attention of females

Lek

Location of an aggregation displaying males that attract the opposite sex

Group costs

Groups of animals are more conspicuous to predators

The risk of parasitic infection increases in groups

High densities can

Up the rate at which diseases spread

Larger the group

the more inter-individual agonistic interactions and larger groups are better able to locate food, but that food must be

shared

Territory

Area defended by one or more individuals against the intrusion of others and defending a high-quality territory often assures greater resources.

Territories

Can be temporary or relatively permanent

Examples

Migratory bird species will establish territories though out the breeding season (e.g., Swainson's Warbler)

Swainson's Warbler Territory & Home Range

defend small, localized breeding territories in dense wetland vegetation, with home ranges that can extend several hundred meters depending on habitat quality and food availability

Dominance hierarchy

Social ranking among individuals in a group, typically determined through contests such as fighting, displays, or contests over food and occurs when conspecific density is relatively high & not feasible to defend resources against all conspecifics

Types of social interactions

donor, recipient, cooperation, selfishness, spitefulness, altruism

Donor

Individual who directs a behavior toward another individual

Recipient

the individual who receives the behavior of a donor in a social interaction

Cooperation

Donor & recipient of a social behavior both experience increased fitness from interaction (e.g., pride of lions kills prey)

Selfishness

Donor experiences increased fitness & recipient experiences

decreased fitness (e.g., competition for food)