BIOL 3301 ch 7 8

Life history

organism’s lifetime pattern of growth, development, and reproduction

Organisms’ life history plays with

reproduction, survival, development

Fecundity

number of offspring produced by an organism per reproductive episode

Parity

number of reproductive episodes that an organism experiences

Parental investment

amount of time and energy given to an offspring by its parents

Longevity

life span of an organism, know as life expectancy

Grimes

proposed two most important variables exerting selective pressure in plants

Intensity of disturbance

any process limiting plants by destroying biomass

Intensity of stress

external constraints limiting rate of dry matter production

Competition factors in as well

influenced by stress and disturbance

Life history characteristics

fecundity, parity, parental investment, longevity

Ruderals

highly disturbed habitats, grow rapidly and produce seeds quickly

Stress tolerant

highs stress and grows slowly, grow slowly to conserve resources

Competitive

low disturbance equals low stress, grow well but eventually compete with others for resources

Macarthur and Wilson R selection

characteristic high population growth rate

Macarthur and Wilson K selection

characteristic efficient resource use

Pianka

r and k are ends of a continuum

Pianka r selection

unpredictable environments

Pianka k selection

predictable environment

Intrinsic rate of increase

highest in r selected species

Competitive ability

highest in k selected species

Reproduction r

numerous individuals rapidly produced

Reproduction k

fewer, larger individuals slowly produced

Principle of allocation

organisms use energy for one function, the amount of energy available for other functions is reduced

Principle of allocation leads to

trade offs between functions

Trade offs include

mode of reproduction, age of first reproduction, allocation to reproduction, number of size of eggs, young or seeds, timing of reproduction

Recruitment success

additions of new, breeding indibiduals into population through reproduction

Role of competition and disturbance

plants must become established in environment

Small plants producing large # of small seeds

advantage in areas of high disturbance

Plants producing large seedlings

more capable of surviving environmental hazards and competition

Probability of future survival can be reduced by

mate acquisition, defense of a breeding territory, feeding and protection of young

Costs of tradeoffs

allocation to reproduction reduces allocation to growth in many plant and animal species

Determinate growth

individual does not grow any more once it initiates reproduction

Indeterminate growth

individual continues to grow after initiating reproduction

Before sexual maturity

maintenance or growth

After sexual maturity

maintenance, growth, or reproduction

Individuals delaying reproduction will

grow faster and reach a larger size

Increased reproduction rate

reduces reproductive lifespan

Species with higher mortality show

higher relative reproductive rate

Iteroparous

organisms reproduce more than once, include most vertebrate animals, shrubs, trees, and perennial plants

Semelparous reproduce

once

Semelparous energy investeerment in

growth, development, and energy storage, one large reproductive effort, organism dies sacrificing all future reproduction

What animals are included in semelparous

most insects, annual and biennial plants, some fish

Some semelparous are short lived

mainly small plants that live in disturbed or ephermeral habitat, future reproduction is uncertain

Some semelparous are long lived and

many insects spend years as larvae, some plants live many years before a reproductive event

Optimal reproductive effort

balance between current and future reproduction, maximizes parental fitness

Semelparity

one large reproductive event followed by death is optimal

Iteroparity

less than maximum effort is optimal on the first attempt, organism survives to reproduce again

Senescence

gradual decrease in fecundity and an increase in the probability of mortality

Function of fecundity

increases with body size at maturity

Function of reproductive lifespan

shortened by delaying maturity

If organism can increase R0 by delaying maturity

then juvenile period should be extended

Life histories change based on conditions

food availability, predation, precipitation, photoperiod, temperature

Sexual reproduction

increases variability, costly to individual, offspring contribute to ½ fitness, finding mates a copulation

Asexual reproduction

mutation only variability, offspring contribute wholly to fitness of parent

Types of asexual reproduction

vegetative, clones, binary fission, parthenogenesis

Vegetative reproduction

individuals is produced from the nonsexual tissues of a parent

Clones

individuals descend asexually from the same parent, bare same genotype

Binary fission

reproduction through duplication of genes, followed by division of the cell into two identical cells

Parthenogenesis

embryo is produced without fertilization

Sexual steps

begin with one male and one female, each pair can only have two offspring per generation

Asexual steps

single asexually reproducing individual, each individual can only have two offspring per generation

Advantages of sex

recombination, good for population, bad for individulas

Disadvantages for sex

expensive and risky

Novelty hypothesis

sex allows new combinations of genotypes to be formed and keeps the genome clean

Without recombination deletions mutations would

accumulate by hitchhiking

Parasite hypothesis (red queen)

sex allows organisms to stay ahead in the evolutionary arms race against their parasites

Hermaphroditic individuals

can choose either self fertilization (asexual), or outcross with another individual(sexual)

Parasite/ red quens hypothesis was proposed by

van valen in 1973

Heterochromatic

male, having opposite chromosomes

Females produce

larger more energetically costly gametes

Males produce

smaller, less energetically costly gametes

Female reproduction limited by

resource access

Male reproduction limited by

mate access

Hermaphrodism

both sets of gametes and gonads, start as male and switch to female

Simultaneous

both sexual organs present at all times

Examples of simultaneous

snails and worms

Sequential

one sexual function occurs followed by the second

Example of sequential

mollusks, echinoderms, some fishes

Good environment cause animals to switch to

female

Bad environment cause animals to switch to

male

Dioecious plants

separate male and female individuals

Hermaphroditic plants

individuals with perfect flwoers, male and female reproductive organs in the same flower

Monoecious

individuals with imperfect flowers, separate male and female flowers on the same plant

Hermaphroditic and monoecious plants have

more self fertilization

Genetic sex determination

sex is determined by inheritance of sex specific chromosomes, mammals brids and many other organisms

Environmental sex determination

sex is determined largely by the environment, many reptiles and insects

Local mate competition in unbalanced sex ration

competition for mates by males, few males may fertilize all females

Female fitness in unbalanced sex ratios

may increase by producing more female offspring

What are the evolutionary consequences of sex

diversity

Sexual selection evolves when

there is assymety in reproductive success or investment

Intrasexual selection

members of the sex subject to strong sexual selection will compete over access to the other sex

Intersexual selection

members of the sex subject to weak sexual selection will be choose

Mating system

pattern of mating between males and females in a population

Polygamy

females

Poluandry

males

Promiscuous

strong but short pair bond

In polyandry females have what

weaker paired

In polygyny males are what

weakly paired