AE2001 4-6

What is a population

A group of potentially interbreeding individuals of the same species occupying a defined area

Why do most species consist of multiple populations

Because geographic and ecological barriers limit interaction between groups

What is a hybrid zone

An area where individuals from genetically distinct populations interbreed

What type of organism is difficult to define as an individual

Modular organisms

What is a genet

A genet is a group of genetically identical individuals (like plants or fungi) that all originated from a single ancestor (usually a seed) through asexual reproduction.

What are ramets

Physically separate but genetically identical units of a genet

What defines a unitary organism

An organism that develops from a single zygote with predictable form

What are the five key population characteristics

Spatial distribution temporal distribution density age structure and sex ratio

What is a species range

The total geographic area where a species occurs

What distribution pattern results from antagonistic interactions

Regular distribution

What distribution pattern results from mutualistic interactions

Clumped distribution

What do random distributions indicate

Lack of strong attraction or repulsion between individuals

How does variance compare to the mean in clumped distributions

Variance is greater than the mean

Why do carnivores occur at lower densities than herbivores

Because energy is lost at each trophic level

What is age structure

The relative proportion of individuals in different age classes

What age classes are commonly used Pre‑reproductive reproductive and post‑reproductive

What age structure indicates a growing population

A wide base of pre‑reproductive individuals

What age structure indicates a declining population

A high proportion of older individuals

Why are human populations typically female‑biased at older ages

Because females have lower mortality and longer lifespan

What is sex ratio

The proportion of males to females in a population

What is a life history strategy

The lifetime pattern of growth development and reproduction of an organism

Why do life history trade‑offs exist

Because energy and time are limited resources

What is a Darwinian Demon

A hypothetical organism that maximizes all aspects of fitness simultaneously

Why do Darwinian Demons not exist

Because evolution is constrained by trade‑offs

What trade‑off links growth and reproduction

Energy allocated to growth cannot be used for reproduction

How does predation risk affect reproductive timing

High predation favors earlier reproduction

What life history trait is favored in unpredictable environments

Early reproduction with high fecundity

What is bet‑hedging in life histories

Spreading reproductive effort across strategies or time

What does the soma disposal theory predict

That increased reproduction accelerates aging by reducing somatic maintenance

What trade‑off is seen in dairy cattle

High milk production reduces fertility and longevity

What trade‑off explains reduced immunity in commercial chickens

Energy allocated to growth limits immune function

What characterizes r‑selected species

High reproductive output early maturity and low parental care

What characterizes K‑selected species

Low reproductive output delayed maturity and high parental care

What survivorship curve is typical of K‑selected species

Type I survivorship

What environmental condition favors r‑selection

Highly variable or disturbed environments

What type of life history strategy is described as fast

Early maturation short lifespan and high reproductive effort

How does early life stress influence human life history strategy

It promotes faster life history strategies

What is semelparity

Reproduction occurring in a single reproductive event

What is iteroparity

Reproduction occurring over multiple breeding events

Why is iteroparity favored when adult survival is high

Because reproduction can be spread over time

Why is semelparity favored when adult survival is low

Because future reproduction is uncertain

Which mammals show rare semelparity

Some dasyurid marsupials

What causes male die‑off in semelparous marsupials

Stress‑induced hormonal collapse after mating

What is Fisher’s principle

Sex ratios evolve toward 1:1 frequency

What is the primary sex ratio

Sex ratio at conception

What is the secondary sex ratio

Sex ratio at birth or hatching

What is the tertiary sex ratio

Sex ratio at maturity or reproductive age

At which stage are sex ratios most often skewed

Tertiary sex ratio

Why are mammal tertiary sex ratios often female‑biased

Higher male mortality

What mating system involves exclusive pairs

Monogamy

What mating system involves one male and multiple females

Polygyny

What mating system involves one female and multiple males

Polyandry

Why is monogamy common in birds

Because biparental care increases offspring survival

What is a harem mating system

One male defending access to many grouped females

What is a lek

A communal display ground where females choose mates

Why does polyandry evolve in some species

When male parental care limits female reproduction

What mating system best describes humans

Mildly polygynous with cultural monogamy

Why can skewed sex ratios affect social stability

Because unmet mating opportunities increase competition